Parasitology Final Notes

INTRO & NEGLECTED TROPICAL DISEASESI. Ecology - study of life and interactions.

A. Symbiosis Association of organisms of different species. Participants are called symbionts. Tells us nothing about the nature of the relationship. Categories based on:

1. Trophic interactions (nutritional relationships); transfer of energy.2. Harm or benefit.3. How many hosts are involved.

SYMBIOSIS

No trophic interaction --> phoresis Indirect trophic interaction --> commensalism Direct trophic interaction --> 1) beneficial, mutualism; 2) harmful, exploitation

Expanding on EXPLOITATION

Always killed --> 1) many hosts --> predator; 2) one host --> parasitoid Seldom killed --> 1) many hosts --> micropredator; 2) one host --> parasite

B. Phoresis - "to carry"; two symbionts travel together.

No physiological or biochemical dependency that occurs between them. Phoront - smaller carried by larger (host). Example: butterfly dusted with pollen from a flower; carries pollen to next flower --> fertilization.

+/0 relationship: (+) refers to pollen benefits and (0) refers to no effect to the butterfly. No trophic interaction.

C. Commensalism Benefit - unidirectional; one partner benefits (+) while the other partner is not harmed or

benefited (0). Difference from phoresis: Commensal feeds on food not consumed by the host. Indirect trophic interaction. Both symbionts can survive independently. Example: remora - slender looking fish whose dorsal fin is modified into an adhesive organ to

attach to a large fish; receives the food that floats by that the larger fish drops. Derives energy from actions of host.

D. Mutualism +/+ relationship - both partners benefit; also obligatory -- cannot survive alone; physiological

dependence. Direct transfer of energy between mutualists. Example: Termites eat wood but can't digest but intestinal protists secrete cellulose that allow

them to digest wood. Intestinal protists can't get to wood without the termites.

Example: blood-sucking leeches; intestinal bacteria digest blood.E. Exploitation

+/- - one partner benefits and the other is harmed. Predator - attacks and kills many organisms in its lifetime.

Direct trophic interaction. Example: cat eating a mouse; lion eating a gazelle.

Parasitoid - only one host is attacked and killed. Example: hymenopterans (wasps & bees) and dipterans (flies). Example: adult female wasp that will deposit an egg either on or in another insect.

A larval parasitoid hatches and consumes the host.

3. Micropredator - the host is not necessarily going to die; attacks more than one organism, but seldom kills them.

Example: hematophagous organisms (like mosquitoes, some leeches & biting flies).4. Parasites - only one host is attacked, but the host is seldom killed.

One partner (parasite) benefits from the relationship and the other partner (host) CAN be harmed.

II. ParasitologyA. Definition:

1. Relationship of two organisms of different species. Smaller (parasite) has potential of harming the larger (host). Parasite relies on the host for nutrients and a place to live.

2. Parasite has a greater reproductive potential than the hostB. What is a parasite?

1. Parasite is: Helminth (worm)

i. Cestodes & trematodes (flatworms).ii. Hematodes (roundworms).

Protozoa - some, not all Arthropods

Parasite infection tends to be chronic and difficult to control.2. Not parasites:

Bacteria Viruses Fungi

C. Different types of parasites:1. Differ in location in/on a host.

Ectoparasite - lives or feeds on hosts surface. Examples: ticks, lice

Endoparasite - lives or feeds inside the host. Examples: tapeworm in intestines

2. Vary in dependency. Obligate - MUST be parasitic for at least part of life cycle.

Examples: tapeworm or tick Facultative - not normally parasitic; can survive if it is accidentally eaten or

enters a body orifice. Examples: women in commune as hosts who used moss as tampons;

nematodes on moss were presented with a beneficial environment within the women.

3. Duration of relationship with the host. Temporary Permanent - away from the host for only a short time; period away is when

parasite is transitioning to another host.

**Most of what we'll talk about are endoparasitic and obligate**

D. Types of hosts:1. Definitive host (DH) - parasite reaches sexual maturity.

In species with no sexual reproduction, the DH is the one that is most important to humans.

2. Intermediate host (IH) - required for parasite development. Parasite does not reach sexual maturity; most cases a larval stage until it reaches a DH.

**Host is defined by the state of the parasite**

E. Distribution of parasite populations : Overdispersed distribution within host population; graph of # of hosts vs. # of parasites/host.

Negative binomial A few hosts have many parasites heavily infected --> killed. Most hosts have few parasites --> not killed.

F. Life cycles1. Method of depicting the stages of a parasite and the host(s) that it infects.

Example: Opisthorchis felineus infects humans.--> Human = DH (parasite reached sexual maturity).--> Releases parasite eggs that shed in human feces.--> Eggs are ingested by snail (IH).--> Parasite undergoes larval development and asexual reproduction.--> Cercariae stage - larval stage that are released from the snail.--> Penetrate a fish host (2nd IH) - parasite still has not reached sexual maturity.--> Parasite encysts as metacercariae until the human ingests metacercariae.--> At this point, parasite reaches sexual maturity and the cycle begins again.

2. Types of life cyclesa. Direct - parasite passed from one host to another with no IH.

Through air, contaminated food/water, or fomite (object). Example: Tritrichomonas foetus transmitted by sexual intercourse. Example: Intestinal protists transmitted via food/water.

b. Indirect - parasite develops in an IH.

III. Health StatisticsA. CDC

Leading causes of death in U.S.:a. Heart diseaseb. Cancerc. Stroked. Lower respiratory disease (bacterial pneumonia)e. Accidentsf. Diabetes

B. WHO Leadings causes of death in underdeveloped countries:

a. Heart diseaseb. Lower respiratory infectionsc. HIV/AIDsd. Diarrheal disease

Leading cause of childhood death. Dehydration.

Bacteria, viruses, parasites.e. Tuberculosisf. Malariag. Measles

IV. World Actions

A. General Assembly of UN 2000 - UN Millenium Declaration

a. Sustainable development.b. Eradication of poverty.c. Eight specific MDGs (millenium development goals)

B. MDGs Eradicate extreme poverty and hunger. Achieve universal primary education. Promote gender equality and empower women. Reduce child mortality. Improve maternal health. Combat HIV/AIDs, malaria, and other diseases (see NTDs below). Ensure environmental sustainability. Develop global partnership for development. 2015 = target for accomplishment of these goals.

C. MDG 6 Funds directed toward Africa. Most funds go towards:

a. HIV/AIDs - retroviral medications.b. Malaria - drugs, bed nets.

D. Neglected Tropical Diseases (NTDs) STH Infections - soil transmitted helminthes (worms)

a. Ascariasis - 4.2 billion people at risk (over 50% of world's population)b. Hookworm infections - 3.2 billion people at risk.c. Trichiuriasis - 3.2 billion people at risk.

Other helminth infectionsa. Schistosomiasis - 779 x 10^6b. Lymphatic filariasis - 1.3 billionc. Anchoceriasis - 90 x 10^6d. Dracunculiasis

Protozoan infectionsa. Leishmaniasis - 350 x 10^6b. Chogas' disease - 25 x 10^6c. Human African trypanasomiasis - 60 x 10^6

Bacterial infectionsa. Trachomab. Buruli ulcerc. Leprosy

E. Features of NTDs High prevalence, but in the poorest people of developing countries. Rural poverty. They are ancient diseases as opposed to emerging diseases. Chronic - lasts years/decades, but doesn't have the mortality figure. Causes disability and disfigurement.

F. World population - 6.7 billion. 1 billion people live on < $1 per day. 2.7 billion people live on < $2 per day.

Of the above, 1 billion affected by one or more NTDs. NTDs have high disease burden but low mortality.

530,000 people die annually from NTDs which is much lower than HIV/AIDS and malaria, which cause 2.6 x 10^6 deaths.

G. Disability Adjusted Life Years (DALY) Measures health impact of NTDs. Using time instead of death. Numbers of healthy years lost from premature death or disability. DALY = YLL + YLD; YLL is the average # of years of life lost and YLD is years lived with the

disability. Japanese life expectancies - standard for measuring premature death, because they

have the highest.o According to WHO > 2 billion people travel by air (per day? -- ask prof.)

V. Class overview

o Parasitology Ecology Phylogeny Physiology/biochemistry Immunology

o Major human parasitic diseases: studying their identification, life cycles, diagnosis, and treatment.

TREMATODES - INTROI. Classification

A. Phylum Platyhelminthes - flatworms.1. Dorsalventrally flattened.2. Acoelomate - lack a coelom (body cavity).3. Bilaterally symmetrical.4. Lack skeletal, circulatory, and respiratory system.

B. Classes1. Turbellaria - free living.2. Monogenea - ectoparasites of fish.3. Cestoidea - tapeworms.4. Trematoda

a. Subclass Aspidogastrea - parasites of mollusks.b. Subclass Digenea ("Two beginnings") - at least 2 hosts in life cycle (DH + 1 or

more IH). One IH is always a mollusk.

II. Digenetic TrematodesA. Characteristics

Flukes. Causes economic losses in domestics animals. Human medical importance.

B. General life cycle Adult worms in DH produce eggs. Eggs are shed into external environment (water) and hatch. Miracidium swim until they find and penetrate snail (IH). Forms sporocyst that reproduces asexually. Forms redia that also reproduces asexually. Two paths:

a. Cercaria exits snail and infects DH, cycle returns to 1).

b. Metacercaria form and DH ingestion causes the cycle to return to 1).III. Egg stage (Figure 9-15a)

A. Structure1. Shell - protection.2. Embryo - develops into miracidium.3. Vitelline membrane protects miracidium.4. Operculum - opening through which miracidium will escape.5. Viscuous cushion inside egg that contains mucopolysaccharides; plays role in hatching.

B. Hatching1. Response to stimuli that trigger the behavior - precise conditions that are different from

conditions inside the host. Example: light tember < 37 degrees C.

2. Activity Miracidium's eyespot (sensory) is triggered by light; releases enzyme.

Enzyme alters permeability of membrane around viscuous cushion. Viscuous cushion becomes hydrated and expands in volume. Miracidium releases leucine aminopeptidase; digests shell from inside. Operculum pops open and miracidium escapes to outside.

 TREMATODES - HOST-PARASITE INTERACTIONS & LARVAL STAGESI. Host-parasite Interactions

A. Host As environment1. Able to respond to the presence of parasites.2. Complex interactions that have evolved between host and parasite.3. Two sets of mechanisms in animals which provide them with resistance.

a. Innate resistance - natural immunity in all animal groups.b. Specific immunity - higher animal phyla vertebrates.

B. Innate resistance - nonspecific responses; regardless of what the invader it is, the body is going to respond in the same way.1. External surface

a. Feathers, hair, scales, etc. - provide some sort of physical barrier. Mainly a deterrent to ectoparasites.

b. Skin - example: mammals. Compacted layer of dead cells that is difficult to penetrate. Salts in perspiration and organic acids and fatty acids; chemical barrier.

2. Internal defenses Most parasites release substances that trigger the host's body; substances that

act as chemo-reactants. Phagocytic cells like neutrophils and macrophages are attracted to site

of infection.C. Specific immunity

1. Antibody response - specific protein is produced in response to a specific parasite epitope.

Epitope - very small part of a parasite macromolecule; often a polysaccharide or protein associated with that parasite.

Antibody combines with epitope; antibody neutralizes parasite's ability to enter cell or inhbits toxic parasite products.

Can combine with macrophages (phagocytic cells) to increase phagocytosis.2. Cellular immunity - T-cells combine with specific epitopes and can directly kill parasite.

II. Miracidium stage - emerges from the egg.A. Intro

~100 micrometers in length, non-feeding stage. Its mission is to find and infect snail host.

B. Structure Ciliated epidermal plates that allow the organism to swim; ~2mm/sec. Cephalic ganglion - concentration of nervous tissue kind of like a brain.

Nerve fibers.3. Apical papilla that cover the anterior end (no cilia).

a. Has sensory nerve endings from the cephalic ganglion; detects environmental stimuli. Photoreceptors, georeceptors (detects gravity, position to the earth),

chemoreceptors.b. Glands - 1 apical gland and 2 lateral glands; secrete enzymes that help

miracidium adhere to and penetrate snail.4. Germinal cells - develop into next larval generation.

C. Miracidial behavior1. Host-finding

a. Responds to environmental cues. Sensory endings in apical papilla come into play. (+) or (-) response to light, gravity, and temperature; similar to

behavioral responses of snail host to the same cues. Example: shcistosoma mansoni

Miracidia and snail hosts are both geonegative (move away from earth) and photopositive (toward light).

b. Responding to host cues. Miraxone - Substances of snail origin that attract miracidia; amino

acids, fatty acids, ammonia. Attraction can be measured by the rate of change of direction (RCD)

and swimming speed. Miracidium far from snail: low RCD (covers more distance) &

fast swimming. Miracidium close to snail: high RCD (less distance) & slow

swimming so that it stays close and doesn't exit the active space of the host.

2. Infection of snail. Respond to the specific components of snail mucus.

Incorrect cues causes miracidium to leave. Correct cues causes it to release enzymes from apical papilla. Cytolysis of snail tissue --> penetrates.

III. Sporocyst stage (Fig 9-19)A. Structrual changes

1. Loss of cilia - no need to swim.2. Formation of new tegument (outer surface) with many microvilli (increase in surface

area).B. Morphology

1. No mouth or digestive system; absorbs nutrients from host tissue through tegument.2. Germinal sac with embryos developing inside.

C. Development Depending on species - daughter (secondary) sporocysts; redia and cercaria.

D. Effect on snail host Example: Leuchocloridium pardoxum (not human parasite)

Causes tentacle to enlarge, become brightly colored, and pulsate. Birds notice the snail; they are the next host in the life cycle of this parasite.

E. Snail defenses - innate resistance called internal defense system (IDS).

Allows snail to distinguish between self and non-self. Haemocytes - main defense against trematode larvae; motile and encapsulating.

Surrounds larval trematode and releases cytotoxic superoxides; leads to phagocytosis.

IV. Rediao Exit sporocyst - can burst out (may kill sporocyst) or exit through a birth pore.o Morphology (Fig 9-20)

1. Digestive system - rudimentary (simple, but functional). Mouth, muscular pharynx that pumps food into gut of redia. Gut is short and unbranched. Tegument also absorbs nutrients.

2. Ambulatory bud - outgrowth on posterior end of body. Allows redia to move around.

3. Germ balls - Depending on species, develops into daughter rediae or cercariae. Exits through birth pore.

o Effect on snail host Example: parasitic castration

Redia move to snail reproductive tissue (good food resource), feed on and destroy it.

No longer able to reproduce. Snail no longer allocating resources to reproduction, so instead, puts those

resources toward growth; bigger snail means more space and tissue resources for parasite.

V. CercariaA. Morphology (Fig 9-21 and 9-25)

Head and tail. Mouth - surrounded by oral sucker. Pharynx. Forked intestine. Glands in the head.

B. Behavior Exit the snail

Uses escape glands - produces enzymes that breaks down snail tissue (cytolysis).

External environment 1-3 days. Swims or crawls to find either a place to encyst or to find the next host.

3. Development - depends on species.a. Cercaria encysts on vegetation and develops into metacercaria.

Attach to plant; result of post-acetabular glands that produce mucus used in adherence.

Sheds tail and cystogenous glands kick in to produce a cyst that develops into larval metacercaria.

b. Cercaria penetrates 2nd IH and develops into metacercaria.c. Cercaria penetratrates DH and develops into an adult worm.

BOTH B & C. Spatial location - light, gravity, temperature, host cues. Temporal location - circadian release of cercariae.

Released from snail only at certain times of the day. Corresponds to time host may be present.

c. Infection of host Post-acetabular glands release mucus used for adherence.

Sheds tail and pre-acetabular (penetration) glands release enzymes.

d. Inside host B - species that infects 2nd IH cystogenous glands -->

metacercaria. C - species that infect DH and migrate in host; develop to the

adult worm.4. Cercarial success

Example: Schistosomes - many species, each infects a particular host species. Bird schistosomes - cercariae seeking birds.

Bird cues: movement, shadow, warmth, skin chemicals. Human in water: movement, shadow, warmth, skin

chemicals. Cercariae might penetrate human instead of bird; wrong

host, cercariae dies, and human experiences allergic reaction (itchy rash called swimmer's itch).

VI. Metacercaria (Fig 9-22) - In most species - transmission stage.A. Structure

1. Cyst wall - multi-layered. In species that encyst on vegetation - cyst wall tends to be thick and complex. In species that encyst in 2nd IH - thin and simple due to constant internal

environment that requires less need for protection.B. Effect on host (in species that encyst in 2nd IH).

Trophic levels - Different levels of food chain/web (i.e. - prey and predator). Metacercariae in prey item (IH) move up a trophic level when IH is ingested. Parasite-increased trophic transmission (PITT) - effect of parasite on a host which

increases the chances of a host being ingested. Site of infection

Example: muscles, CNS, eyes - areas in which, if compromised, may influence behavior or physical characteristic of host. Predisposes that host to predation.

Example: Microphallus papillorobustus - infects amphipods (2nd IH) and get into the brain. Swim closer to surface of the water; increases vulnerability to birds

(DH). Not restricted to just metacercariae; similar to snail.

C. Development to adult stage (inside DH). Respond to stimuli inside host; affects body temperature, digestive enzymes, and

carbon dioxide. Excysts and develops into adult.

TREMATODES - ADULT MORPHOLOGYI. Morphology

A. Tegument (Fig 9-3) For absorption and defense. Syncystium - multinucleated tissue with no cell boundaries Glycocalyx - surface coat.

Comprised of glycoproteins. Many invaginations - increases surface area. Hydrolytic enzymes - break things down; increases uptake of molecules. Protective - shields tegument from antibodies and digestive enzymes.

Distal cytoplasm

Anucleate (no nucleus). Vesicles - substances which maintain glycocalyx; damage repair, etc. Spines - projections that help parasite attach; also important in storage.

3. Muscle layer - comprised of circular and longitudinal muscle.4. Proximal cytoplasm (cyton region)

Nuclei and organelles. Produces material to maintain distal cytoplasm. Connected to distal cytoplasm by internuncial processes.

B. Muscular system1. Subtegumental - comprised of longitudinal, circular, and diagonal muscle.2. Gastrodermal - helps move food in intestine.

C. Nervous system Flatworms are among the first organisms with a clearly defined CNS.

1. Cerebral ganglion - like a brain; at the anterior end and has nerves that branch off. Nerves that branch off to anterior to oral sucker.

2. 3 pairs of longitudinal nerve cords from cerebral ganglion. Supplies posterior end.

3. Transverse ring commisures - bands of nerve tissue that connect the longitudinal nerve cords at intervals. Branches go to muscles and tegument; provides motor and sensory endings.

Orthogon - like a ladder. Sensory endings

Chemoreceptors - response to chemical environment. Tangoreceptors - response to touch.

5. Neurotransmittersa. 5-HT (5-hydroxytryptomine) - serotonin; excitatory.b. Acetylcholine (Ach); inhibitory.

D. Digestive Tract

Incomplete - opening at top, none at the bottom; 2 way.E. Reproductive system

Hermaphroditic - monoecious; both male and female parts (exception: schistosomes). Self fertilization or cross-fertilization. Male (Fig 9-10)

2. Female

a. Ovary - produces oocytes.b. Ovicapt - sphincter that controls passage of oocytes.c. Oviduct - leads from ovary.d. Seminal receptacle - stores sperm.e. Vitelline cells - produces yolk and shell materials.f. Ootype - expanded area of oviduct.g. Mehlis' gland - produces secretions involved in shell formation.h. Uterus - shelled eggs move through here up to and out of genital pore while sperm

move down to seminal vesicle.i. Metraterm - muscular distal end of uterus that propels eggs out of uterus; role of

copulation.II. Egg development

A. Oocytes leave ovary.B. Move down oviduct.C. Ootype - oocytes, sperm, vitelline secretions, Mehlis' gland cells; produces egg.D. Egg moves through uterus.E. Out the metraterm.

III. Polyembryony - ensures continuation of life cycle.o Asexual reproduction that results in multiple offspring from 1 embryo.o 1 egg --> 1 miracidium --> 1 sporocyst --> many rediae --> many many cercariae --> many many

metacercariae.IV. Habitats in human body

A. DiagramB. Human trematodes

Habitat Species

Intestine 1. Fasciolopsis buski2. Metagonimus

yokagawai3. Heterophyes

heterophyes

Liver/Bile duct 1. Fasciola hepatica2. Clonorchis sineusis

Lung 1. Paragonimus westernami

Blood 1. Schistosoma mansoni2. S. japonicum3. S. haematobium

TREMATODES - INTESTINAL1. Fasciolopsis buski (Large intestinal fluke)

o Parasite of humans and pigs; uses hosts as definitive hosts.o Pig is a reservoir host - non-human animal that can be DH.

Serve as a source of infection for humans.o Life cycle (Fig. 10-6)

Adult worm that lives in small intestine of DH. Produce eggs that are shed in the feces. Hatches, and miracidium emerges and swims around in the water. Finds a snail and penetrates the IH; undergoes larval development. The sporocyst leads to redia I and then redia II. Redia II develop into cercariae and they exit the snail. Develops into metacercariae on water vegetation and is ingested by DH.

o Morphology Adult is 75mm x 20mm. Has an unbranched cecum. Branched testes. Ventral sucker (acetabulum) - another adhesive organ a little further down from the oral

sucker and on the outer surface; much larger than oral sucker. No cephalic cone

C. Pathology Adults attach to intestinal mucosa and feed on host tissue. Light infection - adult worms in duodenum and gejunum; few symptoms. Heavy infection - adult worms living throughout small intestine.

Inflammation, ulceration, abscesses. Will experience abdominal pain and malabsorption which can lead to diarrhea;

bowel obstruction is possible.D. Diagnosis

Look for eggs in feces; eggs are large and operculated. Each worm deposits about 25,000 eggs/day; massive environmental contamination. Direct wet smear - ~2 mg feces + drop of saline; slide --> microscope.

If infection low -- may not find eggs. Formalin-ethyl acetate sedimentation concetration technique.

Allows for detection of small numbers of eggs. Formalin preserves specimen.

Ethyl acetate extracts debris and fat from feces. Method:

~4g feces + formalin then strain through gauze. Add saline and centrifuge. Discard supernatant (stuff that's at the top). Add formalin + ethyl acetate, centrifuge again. Analyze sediment for parasite eggs.

E. Treatment Praziquantel (PZQ) or Biltricide. Platyhelminthes. Very safe. Precise mode of action is still unclear. Upon exposure to PZQ, there are 2 main effects on worm:

Rapid, sustained, muscular contraction; paralysis and gets flushed out of intestine.

Tegumental (outer surface) disruption - exposure of parasite to host attack. PZQ disrupts voltage-gated Ca2+ channels.

Results in rapid influx of Ca2+ of worm and disrupts functions.F. Control

Kill adult worms using PZQ. Do not use night soil - human feces as fertilizer. Snail control.

Physically remove snails. Molluscicides - chemicals that kill molluscs.

Copper sulfate and sodium pentachlorophenate. Problem: ecotoxicity; toxic effects on other organisms.

c. Difficulties Recolonization - snails carried downstream. Self-fertilizing.

Boil vegetables that could potentially have metacercariae attached to them. In particular, watercress (Nastrutium officinale) - grows in water.

Peppery leaves - used in salads.2. Metagonimus yokagawai and Heterophyes heterophyes

A. Life cycle (key features) 1st IH - snail; develops into sporocyst then to 2 rediae generations. 2nd IH - fish; develops into metacercaria. DH - human; reservoirs --> fish-eating mammals (cats and dogs).

B. Morphology (Fig. 10-8) Adult is 1.4mm x 0.5mm; among smallest trematodes found in humans. Hh - has structure called gonotyl - sucker surrounding the genital pore. My - gonotyl and ventral sucker are fused and off-center; genito-acetabulum.

C. Pathology Adults - because they are so small, they are generally not a problem.

However, in large numbers, you may experience inflammation and ulceration in the small intestines.

Eggs Because adults are so small, they burrow into mucosa; erode tissue. Eggs can enter host's circulatory system. Can be carried to ectopic sites.

Heart --> heart failure. Brain & spinal cord --> neurological disorders.

D. Diagnosis - eggs in feces. Formalin-ethyl acetate sedimentation concentration.

E. Treatment - PZQ.F. Control

Cook the fish properly.

TREMATODES - LIVER/BILE DUCT & LUNGS1. Fasciola hepatica (sheep liver fluke)

o Sheep and cattle - reservoir hosts.o Liver rot.o Humans - 2-17 x 10^6 cases worldwide.A. Life cycle (Fig. 10-2)

IH - snail; parasite goes through sporocyst larval stage, 2 generations of rediae, and cercariae emerge.

Metacercariae encyst on plants (focus: watercress). Plants are NOT hosts. Inside the host:

A. Metacercaria excysts in SI.B. Migrates through abdominal cavity.C. Juvenile penetrates Glissais capsule and gets into liver.

Those that taste diaphragm reject it and prefer Glissais capsule and enter liver.4. Juveniles develop in liver, migrate, feed, and grow --> liver rot.5. Migrate to bile duct and develop into adult; final habitat.

B. Adult morphology1. 30 mm x 13 mm.2. Cephalic cone - widening at anterior end.

C. Oral and ventral suckers are same size.D. Cacae are highly branched (as opposed to Fasciolopsis buski).E. Testes - highly branched (just like Fasciolopsis buski).

C. Pathology1. Juveniles

a. Ulcers in ectopic sites. Example: eyes, brain, skin, lungs, etc.

b. Acute fascioliasis Necrosis of liver tissue. Liver swells --> hepatomegaly; capsule may rupture ~8 weeks.

2. Chronic fascioliasis Adults; >12 weeks. Occurs in bile duct - blockage and inflammation. Secretes proline and stimulates host collagen deposition. Collagen and fibrous tissue in walls of bile duct; hardening of tube is called

pipstem fibrosis. Unable to handle as much bile coming through.

Back pressure --> liver atrophy, jaundice, and eventually cirrhosis - chronic disease in which normal tissue is replaced with fibrous tissue.

D. Diagnosis - eggs in feces Formalin-ethyl acetate sedimentation concentration.

E. Treatment11 PZQ does NOT work.11 Triclabendazole (TCBZ)

a. Highly active against juvenile stages.b. Variety of effects.

Tegument swelling - drug damages ion pumps in tegument. Disruption of spines (involved in attachment and storage). Stimulates blebbing - parasite mechanism for shedding damaged

tegument Swelling of mitochondria. Microtubule inhibiter - disrupts formation of cytoskeleton; disrupts

movement of vesicles to distal cytoplasm3. Bithionol

F. Control1 Fascioliasis - emergin/re-emerging parasite disease.1 Related to environmental changes and human-made modifications to the environment.

Changes generally have something to do with snail habitats. Sewage disposal (important in all fecal-borne infections).

Control reservoir hosts. Domestic - sheep and cattle. Wild animals - rats.

2. Clonorchis sinensis (Oriental liver fluke)o 19 x 10^6 cases.A. Life cycle (Fig.10-3)

Egg is eaten by snail. 1st IH - snail; egg develops into miracidium, then sporocyst with one redia generation --

> cercaria. 2nd IH - fish; develops into metacercariae. DH - human; reservoir host - fish-eating mammals. Metacercaria excysts in duodenum; instead of penetrating in intestinal wall, juveniles

migrate directly to bile duct.B. Pathology

Adults found in bile duct - presence erodes epithelial lining of duct. Host response - production of fibrotic tissue; thickening of bile duct and can't handle

bile as well and causes blockage of the duct --> hepatomegaly - englargement of bile duct. On average, if there are <100 worms in individual - asymptomatic. 100-1000 worms - nausea, diarrhea, pain. >1000 worms - jaundice, a lot of abdominal pain, and fever.

C. Diagnosis - eggs in feces.

D. Treatment - PraziquantelE. Control

1. No night soil use to fertilize fish farming ponds.2. Fish preparation is critical.

Metacercariae can survive salting, pickling, smoking, drying. Raw fish - delicacy. In some parts of the world, cooking fuel is limited.

3. Reservoir hosts3. Paragonimus westernami (Oriental lung fluke)

A. Life cycle1. Microcercous cercaria

1st IH - snail; develops into sporocyst and then 2 rediae generations and microcercous cercaria - tail is extremely small and knob-like (crawls instead of swims).

Crawls over rocks in environment. 2nd IH - crabs and crayfish; develops into metacercaria. DH - humans; many reservoir hosts.

2. Inside host

Metacercaria excysts in SI. Burrows through intestinal wall.

Embed in abdominal wall for ~1 week. Migrate in abdominal cavity. Penetrate diaphragm. Enter lungs - develop to adult stage.

Fibrous tissue surrounds worms --> cysts; very often forms distoma cysts - 2 worms inside.

B. Pathology1. Necrosis of lung tissue.

2. Symptoms Cough, blood-tinged sputum, chest pain.

3. Ectopic sites Example: brain, heart, abdominal wall.

C. Diagnosis Eggs in sputum and feces (when you cough and swallow the eggs, they travel through to

the feces). Formalin-ethyl acetate sedimentation concentration.

D. Treatment - PZQE. Control

Major emphasis on properly cooking food (crabs and crayfish). "Drunken crab" (delicacy in certain countries) - emmersed in rice wine for about 12

hours and then eaten; not cooked. Crab juices used for medicinal purposes.

TREMTATODES - BLOOD FLUKESI. Introduction -

A. Schistosoma - blood fluke - live in veins of DH. Cause a disease called Schistosomiasis (bilharziasis or snail fever).

B. 3 species in humans. Schistosoma mansoni S. haematobium S. japonicum

C. About 250 x 10^6 people infected worldwide; 2nd only to malaria.D. Major differences between schistosomes and other trematodes.

Schistosomes are dioecious - males and females are separate individuals. Live in blood vessels. Non-operculated eggs. No redia stage. No metacercarial stage. The only human trematode that is not food-borne.

II. Life CycleA. Egg - no operculum

S. haematobium has a terminal spine. S. mansoni has a lateral spine. S. japonicum has a lateral knob.

Hatching - fresh H2O stimulates miracidium to start beating cilia rapidly.

Miracidium starts spinning inside the egg; causes a friction that leads the suture (line along eggshell) to rupture and allows miracidium to escape.

B. Miracidium Either male or female infects snail.

C. Sporocyst - produce daughter sporocysts. Parasitic castration. Peptide called schistosomin - normally produced by snail.

When snail is infected, parasite causes it to over-produce it; imbalance interferes with snail's neuroendocrine system.

Reproductive organs of snail are affected; decreased egg production by snail.D. No redia stage.E. Daughter sporocysts produce cercaria.

1. Morphologya. Head

Mouth Digestive tract Glands

Escape glands allow them to exit snail. Post-acetabular glands produce mucus important for attachment. Pre-acetabular glands produce enzymes that allow for penetration of

host skin. Head glands function in the adjustment of parasite after penetrating

the DH.b. Tail - used for swimming.

2. Once cercaria has penetrated DH: Loses tail. Loses glycocalyx - was important in protecting against hypo-osmotic environment of

fresh H2O. Now called a Schistosomulum(a) - previous cercaria that has now penetrated a DH.

F. Schistosomula Inside DH - gets into bloodstream; migrates to lungs.

Lives in pulmonary capillaries and feeds on red blood cells (RBCs). At young adult stage, they migrate into systemic circulation.

G. Adults1. Migrate to hepatic portal veins in liver; reach sexual maturity and mate.

Pairs migrate to venules of mesentery - membrane suspending organs. Life span - 10-30 years.

2. Morphology Oral sucker that surrounds the mouth. Ventral sucker. No pharynx. Cecum - bifurcates but then joins together in the posterior part of the worm to form a

single cecum.

e. Dioecious.f. Sexually dimorphic.

Male is shorter and stouter than female.

g. Male Gynecophoral canal - groove that goes down the entire length of the body. Schisto = split and soma = body. Thinner female - held in canal; continuous mating Unpaired females do not become sexually mature.

3. Major differences between 3 species.a. Size

Species Male Female

S. japonicum 20mm 26mm

S. mansoni 10mm 14mm

S. haemotobium 15mm 20mm

b. Male tegument Sj - smooth. Sm and Sh - tubercles (bumps) on surface.

c. Females - egg production Sh - 30 eggs per day (epd). Sm - 200-300 epd. Sh - 3500 epd.

d. Habitat of adults in DH. Sh - lives in veins of urinary bladder. Sm - lives in veins of large intestine. Sj - veins of small intestine.

4. Avoidance of immune attack; involves molecular mimicry. Absorb lipoproteins that come from host serum onto tegument. Worm looks like host. Resistant to re-infection.

1. Schistosomulum in body.2. Host antibody is produced, kills some schistosomula.3. Adults develop.

Molecular mimicry. Host antibodies present, but do not attack adults.

4. Any new schistosomula are destroyed by antibodies.H. Exit of eggs from DH

1. Pair works its way upstream into smaller vessels.2. Female - by herself into smaller vessels.3. Lays eggs.4. Male - blocks blood flow.5. Female migrates back to male.6. Eggs must get out of vessel and into intestinal/bladder lumen.

a. Endothelial cells that line the vessels and veins are capable of moving; will actively move over and sequester the eggs.

Excludes egg from vein lumen.b. Miracidium - releases SEA (soluble egg antigen).

Enzymes, proteins, carbs. SEA leaves through pores in eggshell.

c. SEA stimulates granuloma to form around the egg. Motile cells; eosinophils and macrophages.

d. Granuloma moves across wall to gut/bladder lumen and carries eggs.e. Granuloma cells disperse and egg is shed either in the feces or urine.

2/3 eggs don't make it out.

III. PathologyA. Cercarial dermatitis - penetration by cercariae into skin; allergic reaction, itchy rash.B. Acute disease - development of Katayama Fever - associated with Sm and Sj infection; heavy

infection and initiation of egg production. Symptoms - high fever, muscle pain, hepatosplenomegaly (enlarged liver and spleen). Immunology not understood.

C. Main pathology is due to the eggs. Egg entrapment either in the gut or bladder wall; calcify.

Other eggs go to the bloodstream and are trapped in the liver and spleen. Granulomatous response - eggs are antigenic (SEA).

Granuloma - protection from toxic substances but are costly in terms of pathology. Examples:

a. Liver - Symmer's pipestem fibrosis - liver becomes fibrotic and does not function properly; causes extra load on the heart.

b. Sh - fibrosis of ureters and bladder; allows back pressure of urine to reach kidney and causes kidney failure.

c. Schistosome infection may cause cancer. Sh infections - increases chances of bladder cancer. Sm infection - increases chances of colon cancer.

IV. Diagnosiso Sh - eggs in urine and feces.

Hematuria - blood in urine; male menstruation.V. Treatment

A. Praziquantel damages tegument of the adult - makes worm vulnerable to the immune response; resistance.

B. Arthemether - damages tegument, cecum and vitelline glands.VI. Vaccine development

o Chemotherapy and vaccination.o Most candidate vaccine antigens are parasite muscle proteins and enzymes.o Glutathione-S-transferase (GST) - parasite enzyme.

Antioxidant for the parasite - defense mechanism against reactive oxygen species. 40-60% reduction in worm burden. Inhibitory effect on egg production. No cross reactivity with human GST. In phase II clinical trials - about 100-300 humans are being used for the testing of safety

and efficacy of the vaccine.VII. Control

A. DrugB. Sewage treatmentC. Snail controlD. Boots and rubber glovesE. Education

F. VaccineG. Schistosomiasis Control Initiative

Bill and Melinda Gates Foundation. Providing massive amounts of PZQ in sub-Saharan Africa.

------------------------------------------------- END OF FIRST EXAM MATERIAL -------------------------------------------------

CESTODES - INTRO & ADULTSI. Introduction

A. Phylum Platyhelminthes.1. Class Cestoidia2. Order Cyclophyllidea and Pseudophyllidea.

B. Common name - tapeworm.C. All parasitic.

Found somewhere in digestive tract of some vertebrate hosts.II. Morphology of adult tapeworm (Fig 12-1)

o Scolex - anterior end.o Neck - immediately posterior to scolex.o Strobila - rest of body.

A. Scolex1. Nervous structures.

a. Neural ganglia.b. Sensory endings on surface - detect chemical and physical stimuli.

2. Attachment structures. Help attach to host intestinal wall. Suckers - prominent in many tapeworm species.a. Acetabulate; 4 muscular cups on scolex of Cyclophyllidean tapeworms.

Hooks - May have accessory holdfast structures. Rostellum - muscular and protrusible; an armed rostellum is one with hooks.

b. Bothriate - found in Pseudophyllidea and has 2, 4, or 6 bothria, or shallow grooves; Fig 13-3a.

B. Neck Posterior to scolex. Contains stem cells; undifferentiated zone - has not developed into any specific tissue.

Gives rise to proglottids. Strobilation - process by which proglottids form at the neck. Praziquantel - treatment for many adult tapeworm infections.

Acts preferentially at the tegument of the neck.C. Strobila

Each segment is a proglottid; varying degrees of development.

Each proglottid develops male and female organs; monoecius.D. Mature proglottids

Male organs form first; protandry. Produce sperm which is stored in proglottid. Female organs develop next.

Self-fertilization and cross-fertilization.

CESTODES - INTRO & ADULTS (CONT.)D. Mature proglottids (cont.)

1. Reproductive structuresa. Male

b. Female Oogenatope - entire female reproductive complex.

2. Egg Developmenta. Ovary produces oocytes.b. Oocapt - regulates passage of oocytes into oviduct.c. Sperm - fertilizes oocytes in oviduct; zygote.d. Vitelline gland produces vitelline cells.

i. Important for yolk and shell material.ii. Vitelline gland morphology

In cyclophyllidea - single, compact gland; like the drawn diagram. In pseudophyllidea - scattered throughout proglottid.

e. Zygote - passes into ootype.f. Mehlis' gland surrounds ootype.

Secretes thin membrane that surrounds zygote and vitelline cells; critical in formation of egg shell.

g. Pass into uterus. In cyclophyillidea - uterus ends blindly; see diagram. In psuedophyllidea - uterus ends in uterine pore.

3. Release of eggsa. Apolysis - gravid proglottid released and shed in feces; occurs in cyclophyllidea.b. Anapolysis - eggs released through uterine pore; occurs in pseudophyllidea.

4. Egg stage Oncosphere - larva in egg.

6 hooks - hexacanth embryo; -canth means "hooks."

Many protective layers surrounding oncosphere to protect from external environment (temp, light, chemicals, etc.).

Cyclophyllideans Psuedophyllideans

E. Adult tegument (Fig 12-3)o Syncytium - no cell boundaries.o Glycocalyx - outermost layer.

A lot of carbohydrates. Functions

a. Able to bind host enzymes. Example: Amylose - allows them to break down starch into sugar for

the worm; contact digestion - worm digests meal outside its body and absorbing the molecules.

b. Inhibits host enzymes (trypsin, chymotrypsin, and pancreatic lipase) that are threatening to the worm.

Microtriches (microtrix) - microvilli that completely cover worm surface. Increases surface area 10-50 times; key feature for absorption. Orientation is pointed posteriorly.

o Distal cytoplasm Help maintain glycocalyx; vesicles used for maintenance are produced by cyton layer are

held here.3. Tegumental muscle layer4. Cyton layer

Where the nuclei and organelles are located.5. Cytoplasmic connectives

Channels through tegumental muscle - connect distal cytoplasm and the cyton layer.F. Tegumental activity

1. Diffusion - net flow of nutrients from region of high concentration (host gut) to low concentration (in worm).

No metabolic energy required. Example: Pyroxidine (B vitamin)

2. Active transport - allows worm to move substances against concentration gradient. Requires metabolic energy. Example: Glucose uptake - most important nutrient for worm.

3. Intrinsic enzymes - actively produced by tapeworm. Embedded in tegument. Digest molecules in host gut and smaller molecules are taken in by active transport. Example: Phosphohydrolase - hydrolyzes glucose-6-phosphate to glucose and brings it into the

worm.G. Parenchyma

1. Loosely arranged mass of fibers, cells, and fluid. Internal organs embedded. Glycogen synthesis and storage.

2. Calcareous corpuscles embedded in parenchyma. Source of calcium, magnesium, phosphorus, DNA, RNA, protein, sugars, and enzymes. Function is unknown; there are theories.

a. Supply of ions.b. Excretory product.c. Buffers worm tissue against organic acids produced in energy metabolism.

CESTODES - DEVELOPMENT & PSEUDOPHYLLIDEAI. Development

A. At least 2 hosts; in all species. Oncosphere develops inside egg --> egg hatches and larva is eaten by IH OR egg eaten

by IH and then hatches --> penetrates through gut and migrates to parenteral site (not in intestine) --> develops to metacestode (juvenile).**Type of metacestode depends on species; many varieties.** (Fig 12-12)

IH - can be vertebrate or invertebrates.B. Pseudophyllidean life cycle

1. Egg released through uterine pore (anapolysis). Ciliated coracidium hatches from egg into water.

2. Swims rapidly. 1st IH - arthropod - more specifically, copepod (microcrustacean), eats coracidium.

3. Oncosphere - uses 6 hooks to penetrate host gut. In hemocoel, it metamorphoses into procercoid - forms cercomer for attachment. Impairs copepod's ability to move; more vulnerable to predation - example of PITT.

4. 1st IH consumed by 2nd IH (fish) - procercoid stage. Penetrates fish gut and goes into skeletal muscle.

5. Develops into plerocercoid - metacestode stage. Scolex - bothria. Strobila - short, undifferentiated. "Miniature adult." Either:

a. 2nd IH (fish) --> eaten by another fish - paratenic host (transport host) --> plerocercoid penetrates gut and goes into skeletal muscle.

No development takes place.b. 2nd IH (fish) --> eaten by mammal (DH); fish from a. can be eaten by DH.

6. DH eats 2nd IH (paratenic host) Plerocercoid develops into adult in gastrointestinal tract

CESTODES - DEVELOPMENT & PSEUDOPHYLLIDEA (CONT.)

C. Cyclophyllidean life cycle Terrestrial hosts. No cilia on larval stages. Invertebrate IH (arthropod)

Egg is ingested by IH. Hatches inside in the digestive tract. Larva - oncosphere with 6 hooks that are used to enter the hemocoel - body cavity of

arthropod. Oncosphere develops into cysticercoid.

Scolex - fully developed and invaginated - set inside the solid body. Example: Hymenolepis nana.

2. Three other types of development - occur in vertebrate IH. Egg is ingested by IH. Hatches in the intestine. Oncosphere uses its hooks to penetrate through intestinal wall and gets into the

circulatory system. Travels throughout the body and ends up in a parenteral site - not in the intestine. Develops into metacestode. Cysticercus

Example: Taenia solium.b. Coenurus

Protoscolex can develop into an adult worm in DH; potential for the development of worms.

Example: Taenia multiceps.c. Hydatid

Occurs only in the genus Echinococcus; two types.

i. Unilocular cyst Endogenous budding. Millions of protoscolices. Several quarts of fluid. Found in E. granulosis.

ii. Multilocular (alveolar) cyst Exogenous budding - secondary cyst comes off towards the outside

of the cyst. Cyst infiltrates host tissue due to budding; common in liver. Found only in E. multilocularis.

D. Development of all metacestodes in DH Gastrointestinal tract of DH. Stimulated by host digestive enzymes to excyst, evaginate, etc. Begins to grow until it becomes a mature adult.

II. Diphyllobothrium latumo Pseudophyllidea commonly known as Broad Fish Tapeworm.o Life cycle

1st IH - Copepod. Parasite develops into procercoid.

2nd IH - Fish. Develops into plerocercoid. Possibly paratenic hosts involved - other fish eating other fish.

DH - wide range of piscivores - fish eaters. Develops into plerocercoid - noticeable white mass in uncooked fish,

unnoticeable in cooked fish but it is not infective.o Egg morphology

C. Adult morphology Can be up to 10m long (33 feet). Produces 10^6 eggs per day. Scolex - bothria - 2. Proglottids - wider than long.

Numerous, scattered testes and vitelline glands. Female and male genital pores open midventrally. Uterus - opens to midventral uterine pore.

D. Who is infected? Areas where sewage drains into lakes and rivers and fish host is present.

Example: Scandanavia and U.S. Great Lakes region.E. Pathology

1. Many cases are asymptomatic.2. Vague symptoms.

Diarrhea, nausea, abdominal discomfort. Reaction to waste products of the parasite and intestinal irritation.

3. Pernicious anemia - general medical term that refers to a disease state in which the host is unable to absorb vitamin B12.

B12 - hemoglobin synthesis. Worm - absorbs large amounts (80-100% of total) vitamin B12 --> anemia.

F. Diagnosis - eggs in feces.

G. Treatment PZQ Niclosamide - inhibits e- transport in mitochondria of worm.

Minimally absorbed by host intestine. Vitamin B12.

III. Larval Pseudophyllideans in humanso Sparganosis - plerocercoid is in human; mainly caused by pseudophyllideans of the genus

Spirometrao Mode of infection

1. Drink H2O - infected copepods (procercoids). Penetrates intestinal wall and develops into plerocercoid in the tissue.

2. Ingests uncooked animal containing plerocercoid. Example: frog, snake, bird, etc. Migrates through intestinal wall and into tissue. Remains a plerocercoid because it is still considered to be in the IH; human

considered a paratenic host.3. Physical contact with flesh of infected IH (plerocercoid).

Example: In East Asia where they take the flesh of frogs as poultice (mashed substance) and use it to treat medical conditions (skin wounds, sore eyes, vaginitis, etc.)

Plerocercoids migrate into human.o Diagnosis

Detection of plerocercoids in tissue.o Treatment - surgical removal.

CESTODES - CYCLOPHYLLIDEAI. Taenia solium (pork tapeworm)

A. Life cycle (Fig 13-5) IH - pig; ingests egg. DH - human; ingests improperly cooked pork that contains cysticerci.

B. Egg morphology

Not useful for ID of species.C. Adult morphology

1. Scolex (Fig 13-3a) Small and round. Acetabulate. Armed rostellum (2 circles of hooks).

2. Mature proglottid (Fig 13-4) Lateral genital pore. No uterine pore. Compact vitelline gland. Trilobed ovary. 150-200 testes.

3. Gravid proglottid (Fig 13-3b) Much longer than they are wide.

7-13 lateral uterine branches. Apolysis for egg release (breaks off). Useful for ID.

D. Clinical disease Severity depends on stage of development. Adult worm in human (DH) usually causes no problems.

Vague symptoms: discomfort, diarrhea, etc. Cysticercosis

Human (IH) ingested eggs. Hatch in intestinal tract. Eggs penetrate intestinal tract and cysticercus develops in a parenteral site. Cysticercus becomes encapsulated by host response; collagenous capsule. Can be asymptomatic.

Pathology Development of space occupying lesion. Pressure on adjacent tissue and interferes with function. Necrosis due to decreased circulation. Symptomatic cysticercosis.

i. Disseminated cysticercosis 35% of cases. In viscera, muscle, or subcutaneous areas.

ii. Ocular cysticercosis 3% of cases. May float in aqueous or vitreous fluids. May adhere to retina; affects vision and possibly leads to loss

of eye.iii. Neurocysticercosis

60% of cases. Lodged in brain or spinal cord. Example: headaches, seizures, dementia, paralysis. Most common cause of adult-onset epilepsy in the world.

iv. Racemose type Proliferating form. Growth of interconnected bladders through host tissue.

E. How does cysticercosis occur?a. Self-infection - hand to mouth infection.b. Environmental contamination - someone else is infected with the adult worm (they are the DH).c. Internal autoinfection - re-infection of individual by parasite without it leaving the host.

Human is DH. Adult worm in SI of human. Gravid proglottid detaches and rather than moving down the intestine and into the

feces, it moves forward; may be due to reverse peristalsis in the intestine - up the intestine.

It ends up going into the stomach, and it is as if it had been ingested. Goes into SI and eggs hatch - stomach environment stimulates the hatching. Penetrates intestine and goes to a parenteral site and develops into cysticercus.

F. Diagnosis1. Adult worm - gravid proglottids in feces.2. Cysticercosis - x-ray or surgical removal for identification.

G. Treatment1. Adult worms - PZQ or Niclosamide.2. Cysticercosis - PZQ or albendazole - inhibits glucose uptake.

Surgical removal since cyst will still be there.H. Control

1. Human waste management. No pig or human access to feces.

2. Meat inspection. If pig is infected, there may be cysticerci on the tongue; inspection of the pig's tongue

when slaughtered. Heavy infection - carcass destroyed. Light infection - may pass inspection.

3. Cook or freeze meat. Over 65 degrees C for ~30 min. Below 10 degrees C for ~14 days.

I. NTD of North America Common in Latin America. Issue in US due to immigration.

II. Taenia saginatao Common name is Beef Tapewormo Life cycle (Fig 13-5)

IH - cattle. DH - human; ingests cysticercus.

o Egg morphology Identical to Taenia solium.

C. Adult morphology1. Scolex (Fig 13-3a)

Cuboidal. Acetabulate. No rostellum. No hooks.

2. Mature proglottida. Lateral genital pore; no uterine pore.b. Compact vitelline gland.c. Bi-lobed ovary.d. 300-400 testes.

3. Gravid proglottida. 15-20 lateral uterine branches.

D. Pathology Most likely asymptomatic. Diarrhea, nausea. Intestinal obstruction. No cysticercosis.

E. Treatment1. PZQ2. Niclosamide

F. Control1. Human waste management.

No cattle or human access to feces.2. Cook/freeze meat.

Meat % Cysticerci killed

Rare 0

Medium 50-67

Well 100

III. EchinococcusA. Life cycle - hydatid cyst develops.

IH - herbivores, particularly sheep or cattle; ingest eggs. DH - dogs and canids (dog-like animals); ingesting IH containing hydatid cysts. Humas are never DH; significant if human becomes IH.

B. Morphology (Fig 14-4) Scolex, neck, and three proglottids. Scolex

4 suckers. Rostellum with double row of hooks.

3. Proglottids Immature. Mature. Gravid.

C. Pathology Echinococcosis (hydatidosis) occurs when human ingests eggs.

1. Cystic echinococcosis - caused by E. granulosus. Space-occupying lesion. Osseous cyst - in bone; too big can cause bone to break. Fluid leaks from cyst.

Host becomes hypersensitized. If cyst ruptures, fluid pours into host tissue; causes anaphylaxis -

sudden, severe allergic reaction that can cause death.2. Alveolar echinococcosis - caused by E. multiocularis.

Cysts are metastatic - spread through tissue.D. Diagnosis

1. X-rays.2. Ultrasound.

E. Treatment1. Surgery.2. Albendazole - disrupts glucose reuptake.

F. NTD in North America1 Primarily affects Inuit people - indigenous people of Artic regions.

Cystic echinococcosis - E. granulosus from wolves (natural DH). IH - moose, reindeer, and elk. Sled dogs are fed offal (organ meat) of moose, etc. Humans ingest eggs from feces of sled dogs.

IV. Hymenolepis nanaA. Dwarf tapeworm

Infects mice and humans. 40mm long x 1mm wide.

B. Life cycle Invertebrate IH optional. Egg eaten by beetle or flea (IH).

Develops into cysticercoid in hemocoel. Human or mouse (DH) becomes infected by ingesting infected beetle. Adult worm develops in DH.

Eggs ingested by human or mouse. Hatch in duodenum. Oncosphere that gets released penetrates mucosa. Enters lymph channel of villas. Develops into cysticercoid. Shed in feces and infective to humans or mice.

Facultative nature of life cycle - Cysticercoids can develop at higher temperatures.C. Pathology - rare.D. Treatement - PZQ.

NEMATODES - INTRO & MORPHOLOGYI. Introduction

o ~20,000 species described in all environments.o Free-living (terrestrial and aquatic nematodes).o Plant-parasitic; significant in agriculture because ~10% of all crops are destroyed.o Parasites of invertebrates.o Parasites of vertebrates.o Major medical importance

II. General Morphologyo Roundworms - generally elongate, cylindrical, tapered at both ends.

III. Body WallA. Cuticle - many layers and covers surface and lines openings.

Contains enzymes; capable of some metabolic activity but nothing like the tegument. ~80% collagen - fibrous protein. All openings are lined with cuticle.

B. Hypodermis - thin layer whose major function is formation of cuticle. Important in development of nematode. Small protrusions in hypodermis that contain longitudinal nerve cords and excretory

canals.

C. Muscle layer - underneath hypodermis and longitudinal.IV. Pseudocoel - fluid-filled cavity that is enclosed by the body wall.

o Filled with hemolymph1. Transport - solutes.2. Structural - acts as a hydrostatic skeleton; contributes to support of organism and its locomotion.

a. Locomotioni. Muscles on one side contract.

ii. Compresses cuticle on that side.iii. Force of contraction transmits fluid to the other side.iv. Cuticle on other side will be stretched due to extra fluid.v. Alternation of contraction and relaxation enables locomotion; series of curves

that causes S-shaped locomotion.V. Digestive tract

o Complete digestive tract - mouth --> gut --> anus; one direction.o Foregut lined with cuticle.

1. Mouth - circular and may be surrounded by lips.2. Buccal cavity - between the mouth and esophagus.

Good for identification because it is not present in all species. Size and shape varies among species. In some species there are teeth.

3. Esophagus - muscular and glandular components. Tri-radiate - in a cross-section, one radius is pointed ventrally and 2 of these

radii are pointed laterodorsally.

Glands - structures which produce digestive enzymes. Example: Amylase, proteolase, cellulase.

Pumping structure - forces food through esophago-intestinal valve into midgut.B. Midgut - simple, straight, and extends from esophagus to hindgut.

Simple columnar cells. Microvilli. Absorption. Non-muscular.

C. Hindgut - lined with cuticle.1. Female

Midgut empties into a short hindgut which opens into the anus.2. Male

Has structure called cloaca - receives products of reproductive system via vas deferens; posterior-most part of hindgut.

D. Food resources Metabolism - most do not completely oxidize all of their nutrients. Many degrade glucose incompletely and excrete high energy compounds.

E. Drugs interfere with metabolism Example: Albendazole and mebendazole - blocks glucose uptake. Drugs cause degenerative changes in nematode intestine. May also inhibit mitochondrial electron transport.

VI. Nervous systemA. 2 major nerve centers.

1. Circumesophogeal commisure - rings of nerve cell. Nerves that extend up from the commissure - innervates sense organs that are

at the anterior end of the worm. Nerve cords that run down from commissure - innervate the posterior end of

the worm. Largest of nerve cords is the ventral longitudinal nerve.

2. Rectal commissure Follow ventral longitudinal nerve to posterior end of worm. Nerve then branches and surrounds hindgut. Innervate posterior end of worm.

B. Sense organs1. Labial papillae - bumps on lips that function as mechanoreceptors.

Innervated by nerves from circumesophogeal commissure.2. Cephalic papillae - posterior to the lips; function as mechanoreceptors.

Nerves from circumesophogeal commissure.3. Amphids - chemoreceptors.

Same level as cephalic papillae.

Modified cilia innervated by nerves from circumesophogeal commissure.4. Phasmids - chemoreceptors near the tail.

Innervated by nerves from rectal commissure. Presence/absence is a prime character of taxonomic classification.

C. Neurotransmission Nerve fibers in nematode are either excitatory or inhibitory. Stimulation of excitatory fibers releases ACh at neuromuscular junctions.

ACh depolarizes the muscle membrane and produces an action potential. Inhibitory fibers releases GABA.

GABA hyperpolarizes the muscle membrane and reduces the rate of action potentials.D. Nervous system is major drug target

Paralysis - flaccid (limp) and spastic (rigid). Piperazine - blocks ACh and causes hyperpolarization of membrane.

Leads to flaccid paralysis. Ivermectin - stimulates GABA release.

GABA binds to receptors on muscles; inhibitory. Leads to flaccid paralysis.

3. Pyrantel - inhibits enzyme cholinesterase - required to break down ACh; increased levels of ACh. Excitatory; causes spastic paralysis.

VII. Reproductiono Dioecious organisms.o Male

1. Tests - 1 or 2.2. Vas deferens.3. Seminal vesicle.4. Ejaculatory duct.5. Accessory organs - located in cloaca.

Copulatory spicules keep gonopore open and help sperm enter the female. Guberuoculum guides spicules.

B. Female Didelphic - 2 ovaries and 2 uteri.

Oocytes produced in ovaries.

They move down oviducts and into seminal receptacles. Oocyte + sperm --> fertilization. During mating, sperm migrate up vagina and into seminal receptacle. Egg moves down uterus; uterine peristalsis and pressure from hemolymph helps it along. Down vagina and out the gonopore.

C. Eggshell formation Penetration of oocyte by sperm initiates process. Layers form around zygote and embryo. Most nematodes - eggshell has 3 layers:

Vitelline layer - outermost. Chitinous layer Lipid layer - innermost.

Some nematodes have a fourth layer - the outermost. Proteinaceous - forms from uterine secretions.

Sperm penetrates oocyte. Causes a new plasma membrane to form beneath the original oocyte plasma membrane.

The old plasma membrane becomes the vitelline layer.3. Chitinous layer contains protein chitin - forms beneath the vitelline layer.4. Refringent bodies (from sperm) migrate to the periphery right below the chitinous layer; they

expel all of their contents. Contents fuse together and form the lipid layer. Lipid layer confers resistance to desiccation (drying out) and penetration of water-

soluble substances.VIII. Nematode classification

A. Morphology Phylum Nematoda.

Class Adenophorea Class Secernentea

No plasmids.

Cellular hypodermis.

Have plasmids.

Syncytial hypodermis.

B. Routes of infection Oral - ingested by host.

In some species, ingestion of egg and in other species, ingestion of larva. Skin penetrator - larva. IH - vector - actively transmits the parasite.

IX. General life cycle of egg transmission1. Adult worms in DH.2. Eggs exit in feces.3. Inside egg, L1 (first stage larva) molts to L2.4. L2 molts to L3** (infective to host in most species).5. L3 ingested by host and hatches.6. Molts into L4 stage which molts into the adult worm.o Direct life cycle - only one host involved and there is no amplification.o Molting occurs as the nematode grows.

Larva secretes exsheathing fluid. Cuticle detaches from hypodermis. Hypodermis secretes a new and bigger cuticle. Old cuticle ruptures and larva escapes.

X. STH - soil transmitted helminthes

o Most common of the NTDs.o Infections acquired through contact with soil contaminated with either parasite eggs or larval

stages.o 3 major STH: Trichuris, Ascaris, hookworms; unholy trinity.

NEMATODES - TRICHURIS TRICHIURA Class Adenophorea. Common name: whipworm.

A. Life cycle Egg - exits in feces; thick shell.

Opercular knob at each end. Embryonation - develops to L3 inside egg.

External environment of moisture and shade. Swallowed by host and hatches in SI. L3 penetrates into internal villi. Molts 2 times; adult worm. Adult migrates back into lumen of SI. Migrates to cecum and LI. Anterior end burrows into mucosa.

**In males, posterior end has a noticeable coil (Fig 16-1)**B. Pathology

<100 worms - asymptomatic. Infections of 200-1000 worms; more common in young children because they play outside. Worms feed on cell contents and blood. Trauma to intestinal lining.

Leads to chronic hemorrhaging and anemia; ~0.005mL of blood per worm per day lost in feces.

200 worm infection increases daily iron needs of child by 4.25mg/day. Host inflammatory response.

Macrophages, IgE, Eosinophils; all increased levels. Colitis - inflammation of the colon.

3. Systemic effects - rest of body is affected. Occurs in heavy infections. Stunted growth and impaired cognitive function.

4. Increased peristalsis in LI. Can lead to rectal prolapse - part of intestine hanging out of the anus.

5. TDS (Trichuris dysentary syndrome). Heavy infections and diarrhea.

C. Diagnosis - eggs in feces.

D. Treatment - Albendazole and mebendazole.E. Who gets infected?

In U.S. - 2.2 x 10^6 in rural SE. In the world - 800 x 10^6 infected, 3.2 billion at risk. Poor standards of sanitation. Environment conditions favorable for embryonation to occur.

Warm climate, sufficient rainfall, humidity, moisture-retaining soil, and shade.

NEMATODES - ASCARIS & HOOKWORMS1. Ascaris lumbricoides

o STH.o Class Secernentea.o Life cycle

Adult worms in SI. Eggs shed in feces. L1 inside egg molts. L2 inside egg; transmission stage. L2 ingested by the host and egg hatches in SI. They burrow through the intestinal wall and get into the circulatory system (blood and

lymph). End up in the lungs and undergo 2 molts; L4. L4 crawl up the trachea and into the mouth; host swallows them. Goes down esophagus and get to the SI. Molt into an adult worm.

o Egg - transmission stage. Mammillated - has a fourth layer.

a. Proteinaceous layer from uterine wall.b. Thick and bumpy outer shell.

o Golden brown color - from host bile.o Extremely resistant to external conditions.

2. Lipid layer of eggshell.a. Lipids, proteins, and ascarosides.b. Ascarosides - glycosides that are found specifically in the ascaris egg; compound in

which a sugar is bound to a non-sugar by a glycosidic bond. Don't let anything in; eggshell is impermeable to all substances other than

gases and lipid solvents.3. Pathology

a. Larva migration Juveniles get lost and die.

Example: spleen, liver, brain; sends out immune response that results in inflammation and a granuloma.

1b Pulmonary Damage to lung capillaries; blood pools in the lungs. White blood cells and tissue - congest lungs.

High risk of secondary bacterial infection; may lead to pneumonia. Loeffler's syndrome.

Increased eosinophils in lungs; they are attracted to the larva due to the protein on the surface.

Coughing, wheezing, chest pain.3. Intestinal

a. Abdominal pain.b. Allergic responses to worm waste products; rashes, asthma.c. Wander into bile/pancreatic ducts and out the mouth (distress!).d. Intestinal obstruction; children more susceptible because they are smaller.e. Pierce intestine; can lead to peritonitis and inflammation which can result in

death if not treated.4. Diagnosis - eggs in feces.5. Treatment

1 Mebendazole and albendazole.1 Piperazine and pyrantel.1 Surgery in some cases.

6. Infection1 Worldwide - ~1 billion.1 Most common helminth.1 In the U.S. - 4 x 10^6 in SE.1 Warm climates.1 Poor sanitation.1 Night soil.

2. Epidemiology1. Study of occurrence of a particular disease.2. Ascaris

1. Direct life cycle - one parasite and one host; no intermediate hosts.2. Parasite population:

A = adults. E = eggs. r = per capita reproductive rate (# eggs produced per worm). rA = net reproductive rate (# of eggs shed out of host into external environment) Beta = per capita transmission rate (likelihood an egg will get into a host and develop

into an adult). Contact rate; probability of contact with host and probability that this contact will

lead to establishment inside the host. Example: A = 10 worms; r = 20 eggs per worm produced; Beta = 0.5 (50% of eggs will

develop to the adult stage). E = 200 eggs. How many adults will develop from this batch of eggs? 100 worms. How many worms total? 110 worms. How many eggs will they produce? 2,200 eggs.

How many adults will develop from this batch of eggs? 1,100 eggs. How many worms total? 1,210 eggs.

3. What factors may affect the transmission rate, Beta? # of eggs. # of hosts.

Birth rate. Death rate. Immigration and emigration rates.

Behavior of host. Parasite's ability to survive in host; host immune status.

4. Other factors?

u1 = per capita death rate for adults. u2 = per capita death rate for eggs. Au1 = # adults removed from population. Eu2 = # eggs removed.

Use model to determine parasite survival. Parasite reproduction (rA) and transmission (Beta). Parasite elimination (Au1 and Eu2).

6. Get rid of Ascaris?a. Increase parasite elimination.

Au1 - increase by drug treatment. Eu2 - increase by killing eggs in external environment; not viable.

b. Decrease parasite transmission (decrease Beta) Decrease contact - don't use night soil and wash hands. Decrease # of eggs - not viable. Decrease # of hosts - not viable. Decrease rA - drugs.

3. Measuring model parameters; field data.a. Prevalence - % of host population that is infected.

Eggs in feces (Ascaris). In other species, serological assay (antibody to the parasite).

b. Intensity - average number of parasites in an individual. Determine number of eggs per gram of feces; enables us to extrapolate how

many adults are in the host.1c Presentation of data.

Look at different age classes. Presented as age-prevalence or age-intensity curves.

1 Age-prevalence curve - all ages have equal probability of encountering the parasite.

1 Age-intensity curve - immunity may be lower in children which explains high intensity of infection.

4. Ro = basic reproductive ratio. Number of eggs produced by a single adult that survive to produce adults which can

reproduce. Threshold level of Ro = 1; assumes that parasite survival occurs. To eradicate parasite: Ro < 1. Ro - naturally occurring; without human intervention.

Small pox = 2; eradicated. Ascaris = 5. Measles = 8. Malaria = 50.

3. Hookworms - STH.o Class Secernentea.1. Life cycle

Adults in SI. Mate and shed eggs in feces; hatch. L1 stage then molts. L2 stage molts. L3 = infective stage that penetrates skin. Gets into blood and lymph (circulatory) systems. Ends up in the lungs and then up the trachea and the molts.

Down the esophagus and to the SI where it molts into an adult.2. Life cycle stages

a. Adults Anterior end is curved dorsally.

2. Large buccal cavity - teeth/cutting plates.3. Male - has a copulatory bursa at posterior end; used to mate.

2. Egg Goes through embryonation.

Warm, moist, and shady environment; develop to L1 stage. Oval, thin shell. Hatches.

3. L1 and L2 stage Feed on fecal matter. Grow and molt.

4. L3 stage In contrast to L1 and L2, L3 is a non-feeding stage. Transmission stage.

Freezing and desiccation kills L3. When surface of ground is dry - L3 move down. Wet surface - L3 move up; extend up and nictate - wave back and forth to

maximize host contact. 2 primary species that infect humans.

Life cycle, egg, L1, L2, and L3 are identical. Adult morphology and geographical distribution differ. Necator americanus

American killer. SE U.S. and South America. Accounts for 95% of human hookworm infection. Buccal cavity (btwn mouth and esophagus).

Anterior - 4 cutting plates (wide thickening of cuticle). Posterior - 4 teeth (narrow and pointy parts of cuticle).

Ancylostoma duodenale

Europe, Asia, and Africa. Buccal cavity

2 cutting plates and each plate has 2 teeth.3. Pathology

a. Invasion - L3 enter skin. Ground itch - rash and irritation.

Inflammatory to bacteria.b. Migration

Lungs; damage capillaries and aveoli. Coughing, pneumonia.

c. Intestinal - most serious phase of pathology. Burrow into intestinal mucosa. Salivary secretions - anticoagulants that keeps the blood flowing. Blood loss

Necator americanus - ~0.03mL blood/worm/day; many worms and many days.

Ancylostoma duodenale - 0.2mL blood/worm/day; many worms and many days.

Adult survival = 2-14 years. ~1 billion infected worldwide (7 x 10^6 in U.S.); estimated ~7

x 10^6 liters blood/day. Anemia

Stunted growth and cognitive function.4. Hemoglobinolysis

Digestion of hemoglobin (Hb).a. Hemolysin - breaks apart blood cells; lyses erythrocytes.b. Aspartic and cysteine proteases - begins cleavage of Hb.

~280 x 10^6 Hb molecules in each RBC.c. Metalloproteases - cleavage fragments.d. Exopeptidases (amino- and carboxy-) - releases free amino acids.

5. Treatment Mebendazole. Iron therapy to increase iron levels.

6. Controla. Mass chemotherapy.b. Sanitation.c. Shoes.d. Iron and adequate protein in diet. Na - 5,000-10,000 eggs/worm/day. Ad - 10,000-30,000 eggs/worm/day.

7. Cutaneous larva migrans Caused by non-human hookworms. L3 penetrates human skin. Inflammation; noticeable tract.

Most commonly caused by Ancylostoma brazilieuse and A. caninum.4. Children Without Worms

Johnson & Johnson and The Task Force for Global Health.

Goal to decrease STH infections in children; focus on Trichuris, Ascaris, and hookworms. Goals

1. Donation of mebendazole.2. Health education; personal and environmental.3. Improved sanitation.

Access to clean water. Latrines.

NEMATODES - TOXOCARA, STRONGYLOIDES, ENTEROBIUS1. Toxocara canis

o Class Secernentea. Host is dog.

1. Ingest eggs.2. If pregnant dog becomes infected, larvae can cross into fetus.

If lactating dog becomes infected, larvae can pass into mammary tissue; transmammary infection.

Ingests prey item which itself ingested eggs and developed larvae.B. Humans can become accidental hosts by ingesting eggs (contain L2).

Eggs begin tissue migration but don't complete it because they are in the wrong host. Developmental arrest - do not continue development; wanders aimlessly. Damage to liver, lungs, and brain; visceral larva migrans. Some larvae enter the eye; causes inflammation.

Can lead to scarring and then blinding; ocular larva migrans.C. Infections

In U.S. - significant STH; 20% dogs infected.D. Symptoms

Fever, cough, abdominal pain, vision problems.E. Diagnosis

ELISA - looking for antibody produced by host against parasite antigen; Enzyme Linked Immunoabsorbant Assay.

Antigen (Ag) is bound to the bottom of a microtitre plate well.

1. Add serum from patient.2. Wash the serum/well out.

If antibody (Ab) against Ag is present in serum, it will bind.3. Anti-Ab + enzyme is added.4. Wash the well out.5. Add enzyme substrate; if an enzymatic reaction occurs, there will be a color change.

Color change means Ab is present and person is infected. If no color change, no Ab present and the person is not infected.

F. Treatment Often self-limiting. Mebendazole or albendazole.

2. Strongyloides stercoraliso Class Secernentea.A. Life cycle - parasite and free-living generations.

Inside host - only female adults. Parasitic females are protandrous - during development, had male reproductive organs

first, produces sperm. Male organs disappear and female organs develop second.

B. Pathology Strongyloidiasis - threadworm infections. Cutaneous - ground itch. Pulmonary. Intestinal - nausea and abdominal pain. ~90% of cases are asymptomatic. Occurs in immunosuppressed patients. Autoinfection is serious - increased population in the body; hyperinfection syndrome -

abnormal proliferation of parasite. Hematogenous spread of bacteria; piggyback transport.

Example: E. coli Can lead to septicemia, pneumonia, meningitis.

C. Diagnosis Fecal - look for larvae. ELISA.

D. Treatment Ivermectin. Thiabendazole.

E. Infections U.S. - STH. 30 x 10^6 cases worldwide; cosmopolitan. Warm and moist climates.

3. Enterobius vermiculariso Class Secernentea.o Common name: pinworm.A. Adults

Alae - found at anterior end of worm; little expansions of cuticle.

Female - posterior end has a very pointed tail.

Male - curved posterior end.

B. Life cycle (Fig 16-21) Adults in LI. Female to perianal area and oviposits. Egg embryonates.

Hatches (retroinfection) and wanders back; molts and migrates to LI. Migrates to external environment.

Ingested by human. Hatches in SI. Molts and migrates to LI

Retroinfection - Eggs hatch in perianal area and larva wanders back into intestine.

Autoinfection - Host ingests eggs from worms in that individual's body.C. Pathology

Large number of worms - damages in intestine and around anus. Inflammation and bacterial infection. Leads to sleeplessness and irritability.

D. Diagnosis Scotch tape test.

E. Treatment Pyrantel. Albendazole. Mebendazole.

F. Common in children

Hygiene habits. Sleeping - things itch, they scratch and put fingers in their mouth.

NEMATODES - TRICHINELLA, ANISAKIS, DRACUNCULUS

1. Ingestion of larvaeA. Trichinella spiralis

Class Adenophorea. Morphology

a. Esophagus Very long; ~2/3 body length. Anterior portion - thin wall, muscular. Posterior portion - tube surrounded by cells called stichocytes -

glandular cells that produce digestive secretions.b. Stichosome - the whole structure that includes the posterior esophagus and

stichocytes.c. Male

Posterior end has a pseudobursa - thickened cuticle; function unknown, ideal for identification.

Life cycle Same individual acts as DH and IH. Adults - live in SI; very small.

Females: ~3-4mm in length. Males: ~half the size. Enables them to inhabit a unique location in the SI: intramulticellular

habitat in the intestinal epithelium.

Mating - female is ovoviviparous - produces L1's, not eggs. L1 penetrates the intestinal wall and gets into the bloodstream. Destination is the skeletal muscles - penetrates individual fibers.

Trauma and immune response. Experience of muscle pain and fever.

L1 induces changes in muscle fiber cell; changes turn muscle cell into a nurse cell. Loses myofilaments (muscle can't carry out normal contractions). Nuclei hypertrophy. Mitochondria degenerate. Circulatory rete - network of very tiny blood vessels; surrounds nurse cell.

L1 - developmental arrest; remains in the L1 stage for months/years. Next host is infected by eating meat with L1 in the muscle. L1 gets released from the nurse cells into the SI of the new host; 4 molts and becomes an

adult.C. Very low host specificity; affects wide range of hosts.

Sylvatic trichinellosis - disease is cycling among wild carnivores and their prey. Urban trichinellosis - disease cycling among humans, rats, and pigs; tends to be in a farm

setting. Rats & pigs - infected when they feed on garbage that contains infected pork. Pigs can also eat infected rats.

Pigs also like to attack each other; tail area. Humans eat pigs.

D. Pathology Intestinal phase - mild penetration of worms into intestinal mucosa; inflammation.

Nausea, diarrhea, fever, abdominal pain; vague symptoms. Migration phase - severe.

Many L1's end up in the eye, tongue, diaphragm, and jaw. Muscle pain, difficulty breathing, chewing and swallowing.

c. Inflammatory phase - moderate. Nurse cells formed. Strong host immune reaction; heart damage and nervous disorders.

E. Diagnosisa. Clinical symptoms - cannot make a diagnosis just on clinical symptoms alone.b. Muscle biopsy - expensive and painful.c. Serology - ELISA; common method of determining diagnosis.

Looking for antibodies that were produced against the parasite. Ag (antigen). ESA - excretory secretory antigen from stichocytes.

F. Treatment Mebendazole. Thiabendazole - inhibits carbohydrate metabolism. Effective against adults. Treatment usually used is for relieving symptoms.

Bed rest. Corticosteroids - decreases inflammation. Oxygen administered if person is having difficulty breathing.

1G Infectionsa. Eastern Europe - 50% prevalence in swine herds.b. U.S. - worry about getting involved with the sylvatic cycle (wild animal sources); wild

bears and boars.H. Control

a. Cook meat - 170 degrees F.b. Freeze meat - 5 degrees F for 21 days.c. Inspection.d. Education.

B. Anisakis species Related to Ascaris. Most common in humans: Anisakis simplex.a. Life cycle

Marine mammals that act as DH. Crustaceans - 1st IH. Fish - 2nd IH --> L3.

1b Pathology Humans can be an accidental host if they ingest raw/undercooked fish with

L3's. Luminal form - L3's in the lumen.

They die and expel through the feces; asymptomatic. Some L3's invade the stomach or the intestinal wall.

Acute symptoms: intense abdominal pain, nausea, and vomiting. Chronic symptoms: abscesses - parasite peptidases destroy host

tissue. Granuloma's are produced - host immune response.

3. Diagnosis

a. Symptomsb. ELISA - circulating Ab not detected until 2-3 weeks after infection.

Detects circulating Ag - secretions released by L3 during tissue invasion; diagnosis can be made in the acute phase.

4. Treatment Self-limiting. Surgery.

5. Prevention Cook/freeze. Candling - method of inspection where you take a light source and hold the fish

over the light and look through the fish to see if it is infected. Study of fish off the U.S. west coast - ~42% were infected.

2. Dracunculus medinensiso Class Secernentea.o Common names: Guinea worm, fiery serpent.o Transmission by IH.A. Life cycle

1. Adult female Lives in the skin of DH (human); often in the legs. Ovoviviparous - produces thousands of L1's. Uterus and body wall of adult female bursts open and L1's pour out and into

the skin.2. L1's stimulate a very strong immune reaction; painful blister in skin.

Cool water feels good, blister then ruptures. L1's exit to the water. Water increases muscular contractions of the uterus; parts of the worm and

uterus are going to protrude from the blister.3. L1 in water - get eaten by copepod (crustacean), usually cyclops species.4. The copepod = IH.

L1 penetrates into hemocoel. 2 molts and L3 in copepod.

5. DH (human) becomes infected by ingesting water with infected copepods.6. L3 in DH (human).

L3's released from copepod and penetrate duodenum. Migrate through abdominal muscles and get into subcutaneous tissue. Migrates to inguinal and axillary regions.

7. Molts to L4 then adult (female and male). Mating occurs. Males (2cm) die and are rarely found. Female migrates in skin - grows to 1m long.

B. Pathology1. Migration - allergic reactions to metabolic wastes.2. Blister - many occur on feet and legs.

Abscessed. Painful. Secondary bacterial infections - sepsis and death.

3. Non-emergent worms - don't make it to skin surface. Die and become calcified. Arthritis.

C. Diagnosis Blister with emerging worm.

D. Treatment

Winding the worm on a stick - caduceus - symbol of the medical profession. Surgery. Metronidazole - inhibits protein synthesis.

E. Infections Drought. Small bodies of water - concentration of activities. Example: step wells in India.

F. Eradication - projected to be the 1st parasite (and only 2nd disease) to be eradicated. 1986 - ~3.2 x 10^6 cases. 2001 - ~100,000 cases. 2008 - <10,000 cases.

G. Carter Center Jimmy Carter. Emory University in Atlanta, Georgia. Committed to human rights and relieving human suffering. 1987 - Pakistan and Ghana.

Educated the people to the biology of the parasite. Treated the water.

Temephos - kills copepods and decreases toxicity to fish and mammals.

Funding and political assistance. Construction of water wells - bore holes. People were given filter cloths and shown how to filter their water. Medical supplies: J&J donated Tylenol, forceps, and gauze.

H. Parasitologist's Dilemma If you accomplish the eradication of a parasite, it may lead to a lower death rate. If this is not matched with a lower birth rate, there may be a serious effect on the

quality of life. Increased population may not be supported by the available resources.

NEMATODES - FILARIAL WORMS I & II1. Filarial Diseases

6 genera in humans. Transmitted by a vector - an IH that is actively seeking out a host for its own purposes. Microfilaria (mf) - stage not as developed as L1; advanced embryo.

Covered by sheath/membrane. When stained, there is a particular pattern to the location of the nuclei; helps identify

the species.2. Wuchereria bancrofti

o Causes lymphatic filariasis, or elephantiasis.A. Life cycle

Adult female and male worms in major lymphatic ducts. Usually in lower half of the body.

Female produces mf that are released into the lymph, which eventually gets into the blood.

If blood sample of infected person is taken, mf can be found. Periodicity - mf in peripheral blood between 10pm and 2am.

Vector is a night-feeding mosquito. During all other times, mf are found in blood vessels of deep tissues, primarily

the lungs. Causes of periodicity:

Decreased body temperature, increased body acidity, and decrease in water secretion by kidneys during sleep.

Mosquito ingests mf during blood meal. Inside the mosquito, mf molts from L1, to L2, and then L3. L3 migrates up to proboscis. Mosquito's saliva is filled with lubricants and anticoagulants that are injected into the

host along with L3's. L3's migrate and enter the lymphatic ducts and molts to an adult.

B. Pathology1. Many cases asymptomatic.

No detectable microfilaremia - mf in blood. Only way to detect an infection is by ELISA; detect Ag in blood.

2. Acute infection - many symptoms. Inflammatory response to dying adult worms. Episodic adenolymphangitis (ADL) - attacks of fever, chills, and edema.

Associated with inflammation of inguinal lymph nodes.3. Chronic

10-20 years after initial exposure. Lymph tissue blocked by worms.

Granulomas formed. Infiltration by fibrous connective tissue. Impairs function of lymph tissue; causes lymphoedema - swelling in

lymph tissue of legs, arms, breasts, and genitals.a. Grade I - transient (comes and goes)and soft (application of

pressure causes a pit to form in the skin). Responds to rest and elevation of the limb.

b. Grade II - swelling is hard and permanent. Does not pit on pressure.

c. Grade III Subcutaneous thickening. Hyperkeratosis - increase in cell size on the outer

skin layer. Fissures (splits) in skin and development of nodules;

warty appearance. Elephatiasis can develop; lymphatic filariasis.

Repeated acute and chronic attacks. Chronic blockage of lymph. Fibrous tissue and fat. Common in legs, arms, and scrotum. Psychological impact and social impact.

C. Diagnosis1. mf in blood.

Because of periodicity, this method is unpopular. Also pricey.

2. CFA test - circulating filarial antigen test. Finger prick blood droplet any time of the day.

3. Ultrasonography - look for adult worms in lymphatics. Looking for the "filarial dance."

D. Treatment

1. Treating bacterial and fungal infections. Daily washing (2x a day) with soap and water. Clean nails. Wearing shoes. Antibiotic creams to treat abrasions. Raise and exercise limb.

2. Drug combination.a. DEC - diethylcarbamazine.

May increase immune response of host by disrupting the cuticle of the worm and causing the release of antigenic components.

b. Albendazole - disrupts metabolic function.c. Ivermectin - increases GABA.

E. Costs of the disease. Permanent long-term disability. Social loss. Decrease in economic productivity.

India - losses of $800 million - $100 billion per year.F. Costs of treatment

Albendazole - donated by Smith Kline Beecham. Administered as a single treatment.

Ivermectin - donated by Merck. Also a single dose.

DEC - single annual dose. Cost is 2 cents/person/year. Form of DEC in salt: DEC fortified salt - table salt.

Tasteless and survives cooking. Eliminates mf. 30 cents/person/year.

CFA test - $1 per test. Costs of treatment and diagnosis: $1.32/person/year.

G. Control of lymphatic filariasis 1 of 6 diseases targeted by WHO. Elimination - reduce incidence to 0 in a particular area. Eradication - reduce incidence to 0 worldwide. Why does WHO think eradication is possible?

Parasite does not reproduce in the vector; no amplification. No animal reservoir. Diagnostic test. Treatment - effective and inexpensive.

Large scale treatments possible. Drug combination - decreases likelihood of resistance developing. Collateral health benefits.

3. Loa loao Eye worm.A. Life cycle

Adults migrate freely in the subcutaneous tissue. Males and females mate and mf are produced.

Periodicity of mf; peripheral blood by day, lungs at night. Vector - deerfly (chrysops) tha tingests mf during the day. Molts to L1, then L2, and then L3. L3 infects next host when fly bites.

B. Pathology Adults - inflammatory reaction.

May stop in one location for a while. Host raection - localized and painful swelling - calabar swelling.

May migrate across the cornea and conjunctiva.C. Diagnosis

mf in blood sample or an ELISA.D. Treatment and Control

Ivermectin and DEC can kill mf. Surgery. Controlling deerflies - difficult because they like to breed in swampy areas and forests.

4. Dirofilaria immitiso Heartworm.A. Life cycle

Dog = DH. mf in the blood of the dog.

Produced by adult worms in heart and pulmonary arteries. Vector = mosquito.

B. Pathology Fatigue and general loss of condition. Decreased heart function. Coughing and respiratory problems.

C. Diagnosis mf in blood.

D. Treatment1. Immiticide - compound that contains arsenic.

Kills adult worms. Problems:

Arsenic toxicity - low margin of safety. Dead worms can obstruct vessels.

2. Surgery Caval syndrome - heavy infection of heartworm.

Treatment of immiticide is contra-indicated - not recommended. Risky and expensive.

3. Heartgard - combination of Ivermectin and Pyrantel; kills L3.

NEMATODES - FILARIAL WORMS I & II (cont.)5. Onchocerca Volvulus

o “River Blindness."o Life cycle

Adult female and males live in the onchocercoma - nodule in the skin. Female produces mf. Mf in skin, ingested by blackfly (Simulian species). Blackfly takes a bloodmeal.

Scarifies the skin, scratches away the skin, small amount of blood. Inside the blackfly - mf penetrate into hemocoel, molts from L1 to L2 to L3. Migrates to the mouth part. L3's infect next host through the skin. Molts into L4 and then adult.

o Pathology Onchocercoma

Distribution: Central American - above waist; Africa - below waist. Onchocerciasis – “River blindness."

Disease of the skin and eyes; caused by mf. Live in mf – little host immune response and therefore limited pathology. Dead mf - stimulate immune response.

Lesions Acute

Mf in skin causes persistent, itchy rash. Can lead to the secondary bacterial infection. Skin thickens. Enlargement of regional lymph nodes.

Chronic Long term, heavy infections. Skin thickened and discolored. Lizard appearance. Loss of skin elasticity. Femoral and inguinal lymph nodes. Enlarging - hanging groins.

c. Ocular Mf invade the eye and die, leading to an inflammation and blindness. Africa - 10-30% of adults blind.

o Host inflammatory response Response to bacterium inside mf. Wolbachia species.

Intracellular. Inherited. Found in many insects (75%) and crustaceans. Insects - wolbachia controls reproductive functions and sex determination. Endo-symbiont of many filarial worm species. Found in all developmental stages. Found in all developmental stages in hypodermis and reproductive tissue.

Antibiotic treatment? Experiments - animals treated with tetracycline.

The adult worms are stunted and mf development decreases. Penicilin and ciprofloxacin - ineffective. Wolbachia – cell wall LPS – lipopolysaccharide, endotoxin.

LPS stimulates the host inflammatory response.o Simulian

Lay eggs in water of fast flowing rivers. Mf taken up during bloodmeal. Mechanical - teeth in blackfly gut breaks up RBCs; also destroys mf. Bloodmeal may coagulate in blackfly gut - mf stuck. Immune molecules in hemocoel proteases.

E. Diagnosis1. Skin snip

Bit of skin raised up needle. Razor used to take skin slice. No blood. Skin snip on slide with saline and microscope.

F. Treatment1. Ivermectin - paralyzes mf; macrophages remove mf before they degenerate.2. Mectizan - may affect development of mf in female.3. Surgery - removal of nodules.

G. Control programs1. Ivermectin (large scale), insecticides, antibiotics.

2. Onchocerciasis Program of West Africa. 1974 - 11 west African countries. 20 million cases - today almost 0. December 2002 - program zero and ended the work.

3. Carter Center River Blindness Program 1996 - with Mectizan Distribution Program (MDP). 1988 - Merck.

PROTOZOA - INTRO & ENTAMOEBA HISTOLYTICA1. Introduction

A. Traditional parasites1. Helminthes - multicellular organisms; worms.

Platyhelminthes. Nematoda.

2. Protozoa - unicellular.B. Kingdom Protista

Single cell eukaryotes. ~45,000 species identified. Do more damage than any other group of disease organisms.

2. Classification of ProtozoaA. Phylum Sarcomastigophora

1. Subphylum Sarcodina - characterized by pseudopodia. Order Amoebida

i. Entamoebaii. Endolimax

iii. Iodamoebaiv. Acanthamoeba

Order Schizopyrenidai. Naegleria

2. Subphylum Mastigophora - characterized by 1+ flagellum. Order Retortamonadida

i. Chilomastix Order Diplomonadida

i. Giardia Order Trichomonadida

i. Trichomonas Order Kinetoplastida

i. Trypanosomaii. Leishmania

B. Phylum Ciliophora - characterized by cilia.1. Genus Balantidium

C. Phylum Apicomplexa - characterized by an apical complex.1. Genus Plasmodium

3. Cell StructureA. Locomotor organelles

1. Pseudopodia Found in amoebae. Involved in locomotion and food acquisition. Temporary extensions of the plasma membrane and the cytoplasm. Contain actin and myosin - contractile function. Substrate required.

2. Flagella

Found in Subphylum Mastigophora. Trophazoite stage - 1+ flagella. Enables organism to swim - liquid. Cytoplasmic extension that is surrounded by plasma membrane. Embedded in flagellum is an axoneme - provides support to flagellum. Basal body - also known as blepharoplast or kinetosome - anchor to the

flagellum.3. Cilia - shorter and more numerous than the flagella.

B. Mitochondria1. Present in some species.

Cristae - tubular shaped; different from multicellular eukaryotes.2. Absent in other species - anaerobic.

4. Order AmoebidaA. Habitat - most are free-living, but some are found in vertebrate and invertebrate intestinal tracts.B. Reproduction - asexual via binary fission.C. Symbiotic relationships with humans.

Most commensals (+/0). A few pathogenic (+/-).

D. 3 genera - parasites or commensals of humans.1. Entamoeba2. Endolimax3. Iodamoeba Size and nuclear structure used to differentiate.

5. Genus EntamoebaA. Nucleus

Chromatin distribution varies. Endosome - inside nucleus.

a. Contains RNA & genes involved in ribosome synthesis.b. Size and position in nucleus is significant for differentiation.

Position is centric or eccentric.

Small, centric endosome. Evenly distributed peripheral chromatin (PC).

Large, centric endosome. Unevenly clumped peripheral chromatin.

B. Life cycle - 2 stages. Trophozoite (troph) - feeding stage.

Cyst - passes out of host.a. Survives external environment.b. Transmission stage - what is going to be infective to the next host.c. Chromatoidal bars - useful in ID for some species - deposits of nucleic acids.

Morphology varies between species. Usually found only in young cysts. In old/mature cysts, the bars disintegrate.

6. Entamoeba histolytica - parasite.A. Amoebic dysentery, amoebic colitis, and liver abscesses.

3rd most common cause of parasitic death in the world. ~500 x 10^6 infected. ~110,000 deaths/year.

B. Morphology & Life cycle (Fig 4-2). Trophs

~25 micrometers in diameter. Live in the crypts of LI.

Feed on starch and mucus. Nucleus

Endosome - small & centric. PC - fine, evenly distributed.

Binary fission - nucleus divides. Daughter cells start to pull away from each other.

Cleavage furrow - thinning area between separating daughter cells. 1/3 of cells can't break apart.

Use a chemoattractant to attract a "midwife" cell - any Entamoeba histolytica troph in area.

Midwife travels and goes straight into the cleavage furrow and ruptures it.B. Encystment

Trophs in LI. Some carried posteriad with fecal material. Stimulated to encyst from drying out in LI.

Precyst - rich in glycogen. Secretes thin, rough wall; cyst resistant.

c. Cyst ~10-20 micrometers in diameter. Young - chromatoidal bars with rounded ends.

1 Metacyst - mature, 4 nuclei, no chromatoidal bars, transmission stage.1 Mechanical vector - no parasite development.

Ex. - Flies and cockroaches. Metacyst is ingested by host.

Resistant to stomach secretions (gastric acid). Excysts in SI; trypsin breaks down cyst wall. Cytoplasm and nuclei divide - 8 metacystic trophs. Move down to the LI.

D. Summary

C. Luminal amoebiasis Asymptomatic. Pass cysts. Carrier - main source of infection.

D. 2 major forms of pathology Hystolytica - tissue and lysis.a. Amoebic colitis

A. Trophs release a secretagogue - agent that stimulates secretions. Increases host mucus secretion until depleted.

B. Trophs have galactose binding lectins on their surface. Lectin - protein that has a high binding specificity for a particular carbohydrate. Troph binds to host cell surface; cytoadherence.

c. Troph secretes into host cell.i. Amebapores - small peptides that lyse the host cell.

Form pores in host cell lipid bilayer.ii. Cysteine proteases - cleave host cell structure.

d. Trophs move and destroy more cells. Forms ulcers into submucosa - under epithelial cells.

e. Circulation inadequte. Sheets of epilthelial tissue sloughs off. Results in bleeding and loss of electrolytes. Experience of diarrhea/dysentery - individual is passing trophs, not cysts.

2. Perforate intestinal wall - can lead to peritonitis. Trophs can enter circulatory system; brought to ectopic sites, frequently the liver and

lungs. Begin to form abscesses.

Lungs - secondary bacterial infections may occur; dead end for parasite.

E. Diagnosis Cysts in feces - stool sample; useful in luminal amoebiasis cases. ELISA - detect antibody; useful if abscesses are suspected in the lungs & liver.

F. Treatment Metronidazole - enters trophs and inhibits their nucleic acid synthesis. Antibiotics for secondary bacterial infections.

G. Control Sanitation. Emphasis on clean drinking water.

Sand filtration. Preventing food contamination. Treatment.

PROTOZOA - NPP, PAM, FLAGELLATES1. Non-Pathogenic Protozoa (NPP)

A. Introduction Commensals - live in humans but do not cause disease.

Why should we study them? Indication of oro-fecal contamination.

3. Why should we be able to identify them? So we don't undergo unnecessary treatment.

4. Order AmoebidaB. Entamoeba dispar

Troph and cyst - morphologically identical to E. histolytica. ELISA used for identification.

C. Entamoeba hartmani Same morphology as E. histolytica, but smaller. Trophs - 12-15 micrometers. Cysts - 5-9 micrometers.

D. Entamoeba coli1. Trophs

25 micrometers. Lives in LI. Do not feed on or invade host tissue. Nucleus has large eccentric endosome and irregularly dispersed PC.

2. Cysts 17 micrometers. Young

1, 2, or 4 nuclei. Chromatoidal bars have splintered ends.

C. Mature - 8 nuclei and have no chromatoidal bars.E. Entamoeba gingivalis

1. Trophs - on surfaces of teeth and gums.2. Unhealthy mouths - 95%.

Healthy mouths - 50%.C. Does not form cysts.

1 Trophs are the transmission stage. Directly - kissing. Indirectly - chewing gum, sharing utensils.

1D Nucleus - small, centric endosome and fine, evenly distributed PC. Similar to E. histolytica.

1F Endolimax nana1. Smallest amoeba found in humans.2. Trophs

8 micrometers - can be used for identification. Large, centric endosome. PC - thin layer. Move much slower than other species. "Dwarf, internal slug."

11 Cyst Very small; 4 nuclei.

G. Iodamoeba butschlii11 Troph

~10 micrometers.

Large nucleus. Eccentric endosome.

1 Chromatin - granues in a "halo" around the endosome.B. Cyst

Oval with large glycogen vacuole; stains with iodine.

2. Pathogenic Free-Living Amoebaeo Capable of facultative parasitism if they come in contact with humans - parasitism is an option,

but not necessary for the organism's survival.A. Naegleria fowleri

1. Order Schizopyrenida.2. Found worldwide - soil, fresh water, warm ponds and lakes, and heated swimming

pools.3. Enters nose when water is forced in.

Migrates along olfactory nerves to the brain. Secretes enzymes - necrosis and hemorrhage.

Results in meningitis/encephalitis. Left untreated - leads to a coma and death. Primary Amoebic Meningoencephalitis (PAM).

4. Rare - ~200 cases reported. U.S. - 6 cases (death) in 2007.

3 in Florida, 2 in Texas, and 1 in Arizona. High death rate.

Mortality rate - 95% within 72 hours.5. Symptoms

Stiff neck, headaches, light sensitivity, fever, and seizures.6. Diagnosis

Trophs in cerebrospinal fluid.7. Treatment

Combination of antibiotics and antifungals. Amphotericin B - antifungal that binds to trophs and disrupts the

membrane. Rifampin - antibiotic that disrupts transcription. Miconazole - antifungal; function unknown.

8. Control Chlorination in pools. Be careful in fresh water and lakes.

B. Acanthamoeba species. Order Amoebida. Found in soil and water.1. Pathology

GAE - granulomatous amoebic encephalitis - enters nose and into brain. Damage less severe than PAM.

Acanthamoebic keratitis - infection of skin resulting from soil contact. Acanthamoebic uveitis - infection of the eye; contact lenses.

2. Diagnosis Trophs in cerebrospinal fluid, skin, and eyes.

3. Treatment Amphotericin B. Kitamipin (sp?). Miconazole.

3. Subphylum Mastigophorao Flagella.A. Chilomastix mesnili (NPP)

1. Troph - 12 micrometers long

3 free flagella. Cytostome - used for ingestion; encloses a 4th flagellum called a recurrent flagellum (not

free).B. Cyst

Transmission stage. Lemon-shaped. 8 micrometers.

B. Giardia lamblia Wilderness camping; "backpacker's disease." Beaver is the reservoir host; Beaver Fever.1. Troph (Fig 5-1a)

2 adhesive discs. 2 nuclei. 4 pairs of flagella. 2 median support bodies.

B. Cyst (Fig 5-1b)

4 nuclei. Life cycle

Trophs - live in SI; duodenum and bile duct.

Binary longitudinal fission. Attach to epithelial cells with adhesive discs. Stimulated by trypsin. Trophs that move posteriad encyst in LI. Cysts out of host. Ingested by next host. Excyst in SI.

4. Pathologya. Diarrhea and malabsorption.b. Villi shortened, crypts inflamed, lesions.c. Malabsorption.

Inability to absorb fat soluble substances; steaterrhea (fat in feces).5. Diagnosis

Diarrhea - foul odor. Cysts in feces. Entero-Test Capsule - string test.

Capsule with string. Ingested and capsule dissolves. Recover string and check it for trophs.

11 Treatment Metronidazole (Flagyl) - inhibits DNA synthesis.

11 Prevention Drinking water should be treated - chlorination and sand filtration. Campers - be careful, avoid drinking water by beaver dams. Treatment.

C. Trichomonas1. General characteristics

a. Undulating membrane - recurrent flagellum pulls plasma membrane and cytoplasm away from cell body.

b. No mitochondria.c. Hydrogenosomes - involved in metabolism; end product = hydrogen gas.d. No cyst stage.

2. Trichomonas vaginalis (Fig 5-9b)a. Only pathogenic trichomonad.

Female - vagina and urethra. Male - urethra, prostate, seminal vesicles.

b. Pathology Male - asymptomatic. Female - trichomonad vaginitis

Normal pH of vagina - 4-4.5. Lactic acid producing bacteria. Trichomonas vaginalis feeds on bacteria. pH goes up; optimal pH for T. vaginalis is ~5-6.

Inflammation of vaginal epithelium; pain, itchiness, leucorrhoea - increased mucus.

c. Transmission Direct contact - sexual. Indirect - underwear, towels. Newborns.

d. Diagnosis Trophs

Females - vaginal smears and in urine. Males - secretions and in urine.

e. Treatment Metronidazole. Condoms.

3. Trichomonas tenax1 In mouth.1 NPP.1 ~10% people worldwide.1 Direct contact - kissing.1 Indirect - sharing utensils.1 Trophs - can live for several hours in drinking water.

PROTOZOA - TRYPANOSOMA Subphylum Mastigophora All have flagellum Order Kinetoplastida

I. Kinetoplastid infectionsA. 3 major human infections

1. HAT - human African trypanosomiasis2. Chagas' disease3. Leishmaniasis

B. NTD Estimated that they kill ~150,000 people/year.

C. Kinetoplastids1. Single-celled organisms.2. Have a flagellum.3. All have a kinetoplast (kinetoplastid) - organelle found within mitochondrion of the

organism. Contains DNA. May play a part in mitochondrial function and metamorphosis.

II. 4 morphological formsA. Amastigote (LD body) - "mastigote" means "whip" and "a" means "no"; no flagellum.

Kinetosome - basal body that gives rise to flagellum. Kinetosome and kinetoplast are usually in close proximity to each other.

B. Promastigote

Nucleus posterior to kinetosome/kinetoplast.

Flagellum - used for locomotion and attachment. Found only in insect vector and in culture.

C. Epimastigote

Kinetosome and kinetoplast migrate posterior and pull flagellum with it.D. Trypomastigote (tryp)

3 basic forms - differ biochemically and infectivity.1. Long, slender2. Stumpy3. Metacyclic

III. TrypanosomaA. Section Salivaria (anterior station development)

Parasite will develop in the anterior part of the vector's digestive tract.B. Section Stercoraria (posterior station development)

Parasite will develop in the vector's hindgut.IV. Section Salivaria

o Trypanosoma brucei - vector is Glassina.o Introduction

1. Life cycle Glossina injects metacyclic tryps. Slender tryps in blood. Blunt, posterior end multiply by binary fission. Stumpy tryps do not multiply; waiting to be picked up. Ingested by Glossina. Inside the fly, turns into an epinastigote. Then metacyclic tryps.

o Trypanosome brucei: 3 subspecies Morphologically indistinguishable. Vary in their host and in the pathology that they cause.

o Glossina - vector for all 3 subspecies; commonly known as the tsetse fly - "fly destructive to cattle."

"Meat cleaver" cell in wing.

Distribution - tropical Africa between 15N and 15S latitudes - fly belt - area of continental U.S.

D. Trypanosoma brucei brucei Causes a disease known as nagana. Infects antelope and livestock. Animals suffer from anemia and fever; undergo paralysis and eventually die.

E. HAT - human African trypanosomiasis - African Sleeping Sickness Caused by 2 subspecies of T. brucei.

T. Brucei gambiense (Tbg) T. b. rhodesiense (Tbr)

F. Similarities between Tbg and Tbr1. Chancre - small sore that develops at the site of the bite; lasts 1-2 days.2. Development into slender tryps - in blood and lymph.

Multiply by binary fission.3. Lymph nodes swell.

Base of neck. Winter bottom's sign . British officer. Recognized by slave traders as a sign of death.

G. Differences btween Tbg and Tbr1. Tbg - found in West and Central Africa.

Causes the chronic form of the disease; long-lasting. May be asymptomatic for a year or two. Eventually tryps invade CNS. Mental dullness. May be so severe that person lapses into a coma and dies from the infection.

2. Tbr - East Africa. Acute, virulent form. Becomes invasive much more quickly. Tryps invade the heart and other areas. Causes the host to die. Usually no nervous disorders because host dies quickly after becoming infected (2-6

months). Native game reservoir hosts.

H. Diagnosis - tryps in blood and cerebrospinal fluid.I. Treatment

Suramin sodium - found to be effective in the early stages of infection. Arsenic-based drugss - for later stages.

J. Control/Prevention1. Mass screenings of the population and treatment.2. Vector control.

a. Insecticide - DDT.b. Sterile insect technique (SIT).

Male Glossina - irradiated, which sterilizes them. 3-4 generations of SIT and insecticide spraying.

K. Antigenic variation - allows parasites to hide from the immune system. Slender tryps - specifically in blood.

Surface coat consists primarily of a single protein - variant surface glycoprotein (VSG). Host mounts an effective immune response against tryps with a specific VSG. <1% of tryps survive - possess variant VSG; temporarily unrecognizable.

Continues indefinitely. Each population is a variant antigenic type (VAT). ~1000 VSG genes.

V. Section Stercorariao Trypanosoma cruzi.o Causes American Trypanosomiasis, also known as Chagas' Disease.o Life cycle

Vector - Panstrongylus megistus - takes a blood meal. As it's taking the blood meal, it swells up and defecates on skin of host. Fecal droplet contains thousands of metacyclic tryps. Metacyclic tryps enter host when host scratches or rubs the bite. They enter the cells and transform into amastigotes.

Liver, spleen, lymphatics, muscle. Multiply by binary fission. Host cell lyses and amastigotes released. Most amastigotes invade other cells. Some amastigotes stay in blood and transform into tryps; tryps are ingested by the

vector (bug). Inside vector:

Epimastigotes - multiply in midgut then move to hindgut. Transform into metacyclic tryps.

o Trypomastigote in blood Has a very pointed posterior end. Very large kinetoplast. No variable surface antigen.

Destroyed by circulating antibodies; low #'s of tryps in blood.C. Pathology

1. Acute Chagoma - local inflammation at the site of the bite. Romaria's sign - metacyclic tryps have entered the eye.

Edema of eyelid and conjunctiva. Fatigue, fever, swollen glands. Parasite spreads - muscle, intestine, bone marrow. Pseudocysts - clumps of amastigotes found in the tissue.

80% of cases in the heart. Symptoms - anemia, nervous disorders, weakness, muscle pain. Children - death in 3-4 weeks.

2. If survive acute phase, then usually asymptomatic for many years.3. Chronic

Seen most often in adults. Long term decline in health. Heart and intestine. Toxins produced by amastigotes cause damage to the host.

Some are neurotoxins - affect conduction. Muscle cells lose their ability to contract.

Intestinal tract Smooth muscle - peristalsis is affected. Eventually, esophagus and colon lose tone.

Megaesophagus - diameter of esophagus increases. Megacolon - diameter of colon increases. Difficulty swallowing and voiding.

Heart Nerves destroyed by neurotoxins. Muscle fails to contract. Enlarged and flabby heart. Decreased pumping efficiency. Heart failure.

D. Diagnosis1. Examine blood or tissue fluid.

Tryps in blood. Amastigotes in tissue.

2. Xenodiagnosis. Lab-raised vectors. 40 vectors feed on patient. 30-60 days later - squeeze bugs or dissect them and examine for parasite.

E. Control1. Chemotherapy

Nifurtimox - has some effect on tryps and amastigotes. Extracellular types - present for only short time. Intracellular amastigotes - shielded.

2. Vector control - main method. Rural and poverty-stricken areas. Panstrongylous

Often underground. In the trees, houses. During the day, they live in hiding places. At night, come out for blood meal. Use bednets, patch up cracks in the house, use insecticides.

F. Distribution1 15 x 10^6 cases in Western hemisphere; South America.1 Urban areas - risk in blood transfusions.1 U.S.

1989 - 3 cases from contaminated blood. 2001 - 3 organ transplant recipients who developed Chagas' disease.

PROTOZOA - LEISHMANIA & CILIATESI. Leishmania

A. Introduction1. Phylum Sarcomastigophora

Order Kinetoplastida2. Many species

Wide range of hosts.3. Human (Table 6-1)

Leishmaniasis. Worldwide.

B. Life cycle1. Vector - sandfly.

General term that encompasses a variety of different genera. One is found in the Old World - what people knew of the world before

exploration. Europe, Asia, and Northern Africa. Primarily in the Genus Phlebotomus.

New World - Americas were found, Mexico and South America. Primarily in the Genus Lutzomyia.

Blood meal from infected host, sandfly ingest amastigotes. Parasite moves into the gut of the sandfly and transforms into promastigote. Attaches to gut wall and goes through binary fission. Promastigotes move into mouth parts of sandfly and clog it up. When sandfly takes its next blood meal, it clears out all of its mouth part and

infects the next host.2. In human.

Promastigote enters macrophage by phagocytosis. Parasite inside a parasitophorous vacuole from host cell membrane. Parsitophorous vacuole fuses with lysosomes; pH very low. Transforms into amastigote; acidophilic.

Metabolic activities are at an optimum between pH 4 and 5.5. Reproduces by binary fission.

Host cell ruptures and amastigotes are released. Amastigotes invade nearby macrophages; causes the spread of the infection

through the body.C. Reservoir hosts

Wild dogs, domestic dogs, and rodents can be infected by the same species that infect humans. Control very difficult.

D. Pathology1. Cutaneous leishmaniasis.2. Mucocutaneous leishmaniasis.3. Visceral leishmaniasis.

E. Treatment - for all Pentostam

II. Cutaneous Leishmaniasiso Mild skin disease.o Oriental sore.o Old World - Leishmania tropica.o New World - Leishmania mexicana.o Life cycle

Sandfly blood meal deposits promastigotes in skin. Promastigotes engulfed by macrophages at the site of the bite. Nodule forms on the skin. Amastigotes cannot grow at core body temperature. Nodule breaks open and amastigotes spread to macrophages in skin.

Sore enlarges. Secondary infections. Self-limiting infection - it will heal without treatment.

Disfiguring scar. Innoculate in less conspicuous location; develop immunity.

o Diagnosis

Look for amastigotes in margin of the lesion.III. Mucocutaneous Leishmaniasis

o Common in Western hemisphere.o Primary cause - Leishmania braziliensis.o Primary skin lesion that develops

Forms at site of the bite.o Secondary lesions

Formed by amastigotes that in macrophages at mucocutaneous junctions of the skin - areas where dry skin meets moist skin; around the lips, the nose, etc.

Different forms on secondary lesions.a. Chiclero ulcers

Mexico and Central America. Lesion on the ear; pinna.

Cartilage - poorly vascularized and the immune response is weak.

Infection remains for years; pinna erodes.b. Espundia

Rainforests of Central and South America. Long, chronic. Skin lesions spread and invade mucous membranes. Nose affected. Long term infection - cartilage of the nose and soft palate erode. Larynx and trachea - destroy voice.

IV. Visceral LeishmaniasisA. Leishmania donovani

Kala azar. William Leishman - 1900. Charles Donovan - 1903. Amastigotes - LD body.

B. Life cycle Broad host range - infects humans and canid and felid reservoir hosts. Amastigotes throughout the body and inside macrophages. Spleen and bone marrow affected; undergo compensatory macrophage production to

the detriment of RBC production. Hepatosplenamegaly - enlarged liver and spleen.

Anemic. Immature macrophages; ineffective. Emaciated.

C. Pathology Fever, progressive wasting, anemia, immune deficiencies. Death 2-3 years after infection if untreated, usually form secondary pathogen.

D. Diagnosis Amastigotes in tissues.

Blood/nasal smears. Spleen puncture. Bone marrow.

XenodiagnosisE. Control strategies

Vector control Sandflies have a short flight range. Insecticides - inside homes. Flies use low growing bushes as resting spots.

Protect humans against bites. Insect repellants. Clothing. Bed nets. Fly screens.

3. Eliminate reservoir hosts?F. Leishmania - HIV co-infection.

Emerging disease in many developing countries. Both decrease immune responses. Opportunistic infection.

V. Phylum Ciliophorao Possess cilia in at least one stage of life cycle.o 2 nuclei:

Marconucleus - controls trophic activities - normal everyday body functions. Micronucleus - controls reproductive functions.

o Balantidium coli is the only type that infects humans; also infects pigs (reservoir host). Largest protozoan parasite in humans.

o Trophozoite Lives in LI of host and reproduces by binary fission. Thousands of cilia on its surface

2 contractile vacuoles - osmoregulatory ability. Unique among parasitic protozoa.

Peristome - lined with coarse cilia. Leads into the cytostome.

Cytostome - actual area on cell membrane where all food material is ingested. Cytopyge - site on membrane through which wastes are eliminated.

B. Cyst Encystment stimulated by dehydration of feces. Transmission stage. Infects next host. Excysts in SI and then migrates to LI.

C. Pathology1. Many cases are asymptomatic; they are carriers.

Trophs are ingesting starch and cellular debri; not causing any tissue damage.2. Can produce hyaluronidase - enzyme that starts to ingest the host intestinal epithelium.

Causes flask-shaped ulcer. Necrosis and sloughing of tissue. Hemorrhage - diarrhea and dysentery. Secondary bacterial infection. Bilantidial dysentery.

3. Perforation of LI. Peritonitis. Death. Secondary foci in liver and lungs.

D. Treatment Metronidazole.

E. Control Sanitation.

PROTOZOA - MALARIA II. Phylum Apicomplexa

A. Characteristics1. All parasitic.2. Apical complex

a. Rhoptries and micronemes Secretory organelles. Penetrating host cells.

b. Conoid and subpellicular - structural microtubules.3. Complex life cycles.

B. Plasmodium Malaria. 500 x 10^6 infected. ~2 x 10^6 deaths/year - mostly children. Swamps and fever. "Mal" is "bad" and "aria" is "air." 4 species of Plasmodium that infect humans.

Plasmodium vivax. Plasmodium malariae. Plasmodium ovale. Plasmodium falciparum.

II. Life cycleA. Overview

B. Vertebrate phase1. Infected female Anopholes species mosquito takes a blood meal.

Probes skin for a capillary. Injects salivary gland secretions; prevents clotting. Sporozoites injected.

2. Sporozoites in bloodstream.3. Circumsporozoite protein on surface of sporozoite.

Binds specifically to receptors on hepatocytes.4. Secretions from apical complex; penetrate liver cell.5. Exoerythrocytic cycle.6. Metamorphoses into trophozoite.

Feeds on host cell cytoplasm. After ~1 week, the troph is mature. Begins schizogony - asexual reproduction.

a. Numerous daughter nuclei formed; schizont - cryptozoite.b. Cytoplasm divides.

7. Merozoites burst out of hepatocytes.8. Into blood; erythrocytic cycle.9. Random interaction between merozoite and RBC.

Merozoite surface protein-1 (MSP-1) - proteins bind specifically to proteins on RBC surface.

10. Apical complex orients toward the RBC membrane. Secretions from apical complex; invades RBC.

Merozoite pushes in and forms a parasitophorous vacuole.11. Transforms into trophozoite.

Ingests host cell cytoplasm; large food vacuole forms.

Signet ring stage.12. Trophozoite grows and food vacuole becomes less noticeable.

Hemozoin becomes apparent; end product of digestion of host hemoglobin.13. Schizogony

Blood schizont with numerous nuclei.14. Segmenter - parasite when it has undergone cytoplasmic division.

Merozoites produced.15. Mature merozoites.

Host cell ruptures and merozoites and their waste products are released.16. Merozoites invade other RBC's.

Synchrony - in an infected individual, merozoites develop at the same time. Release from host cells is synchronous. Massive release of merozoites and waste products. Stimulates host response; fever and chills. Periodicity of symptoms.

17. Some merozoites enter RBC and develop into either macrogametocytes or miccrogametocytes. Ingested by mosquito.

PROTOZOA - MALARIA II1. Invertebrate phase

o Genus Anopheles - mosquito.o Gametocytes are released from RBC's in stomach.

1. Macrogametocyte Shift of nucleus leads to a macrogamete (can be considered the female).

2. Microgametocyte Undergoes considerable development - exflagellation - nucleus divides and

forms 8 daughter nuclei. Each daughter nuclei develops its own flagellum. These 8 flagellated nuclei break apart.

Stimuli for exflagellation: Decreased temperature. Increased pH - dissolved CO2 from RBC's in the mosquito stomach.

oMicrogamete swims and will fertilize the macrogamete.oOokinete - mobile stage.

Penetration through the stomach wall. Attaches on the hemocoel side of the wall.

oOocyst Nucleus divides - results in sporoblasts. Sporoblasts develop into sporozoites.

>10,000 sporozoites in oocyst.oSporozoites break out of the oocyst and migrate through the body to the salivary glands.oInfected mosquitoes feed more frequently; PITT.

2. Plasmodium vivaxo Characteristics

1. Sporozoites Short-prepatent - when the parasite is in the liver but the person has no

symptoms. Invade hepatocytes. Develop into merozoites, which leave the hepatocytes and then

invade RBC's. Long-prepatent

Invade hepatocytes. Develop into merozoites. Rather than leaving the hepatocytes, they stay there. Hypnozoites.

Relapse - vivax malaria infection; recovers. Recurrence of the disease following initial infection do to

hypnozoites. Hypnozoites escape hepatocytes. Erythrocytic cycle.

2. Merozoites Can only penetrate RBC's with a Duffy antigen - receptor site on the surface of

the RBC, function unclear. Duffy antigens act as specific receptor sites on the RBC surface If the Fy^a or Fy^b Duffy antigen are present, the merozoite can

penetrate.

If Fy (Duffy negative), that means there are no receptors and the merozoite cannot penetrate.

Resistance to vivax malaria. Fy genotype is present in ~90% of West African natives and

~70% African Americans.3. Trophozoites

RBC enlarges. RBC develops stippling - dots caused by the development of little invaginations

on the surface; Schuffner's dots.4. Fevers - occur every 48 hours.

3. Plasmodium malariaeo Fever - every 72 hours.o Ring stage - when mature, it elongates; band form.

3. Recrudescence Let's say you are infected and you recover. Many years later, you are sick again even though you have not been infected again. Due to a sudden increase in a persistent low-level parasite population in the blood. Transfusion malaria possible.

4. Plasmodium ovaleo Very rare.o Fevers - every 48 hours; mild.o Mature schizont and RBC are oval in shape.

5. Plasmodium falciparumo Most common.1. Morphology

Ring stage Very small. Multiple infections - more than one ring stage inside a single RBC. Characterized by an applique form - appears that ring stage is attached to the

RBC membrane.

Infected RBC - develops irregular blotches - Maurer's clefts.2. Gametocytes

Crescent shape - stretches out the RBC.

2. Early ring stages and gametocytes in blood smears. After invasion of RBC, troph produces proteins deposited in RBC membrane.

Knob proteins bind to glycoproteins in endothelium of capillaries.

Infected RBC's are sequestered in capillaries.3. Falciparum pathology

Fevers - every 48 hours; severe. Cerebral malaria

Sticky RBCs (knobs) blocking capillaries. Tissues don't receive the oxygen that they need; hypoxia. Headaches --> coma --> high temperatures --> convulsions --> death.

3. Blackwater Fever Caused by an acute, massive lysis of RBC's (infected and uninfected). High levels of hemoglobin and hemozoin in blood. Kidney function impaired; urine becomes really dark and can lead to kidney

failure. Autoimmune problem.

6. Difference in pathology?

Species Type of RBC Level of Parasitemia

P. vivax Young <1%

P. malariae Old <1%

P. ovale Young <1%

P. falciparum All 5-50%

7. Arms Raceo Sickle Cell Disease

In the Beta-chain of hemoglobin, one of the glutamic acids is replaced by valine. Sickle cell hemoglobin is normal until stressed by low oxygen levels. Sickle shape loses flexibility. Blockage of capillaries decreases oxygen carrying capacity. Reluctance to release oxygen.

Heterozygous - NS. Sickle gene - incompletely recessive; some sickle Hb produced. ~60% RBC's normal, ~40% sickle for example. If infected with P. falciparum, 80-90% protection against Falciparum malaria. Sickle HB - needle-like and mechanically destroys parasite. Level of parasitemia is ~1% of the RBC's; similar to the other three species.

Homozygous - NN. You will die from P. falciparum.

Homozygous - SS. Die from sickle cell disease.

NS genotype is the preferable one; heterozygote advantage. Maintains both alleles in the population.

8. Antimalarial drugs1. Chloroquine

Builds up inside the parasite's food vacuole. Normally there is a heme polymerase (parasite enzyme).

Heme (toxic) converts to hemozoin (non-toxic). Drug blocks heme polymerase and parasite dies from increased heme. Resistance has developed; no longer recommended for use.

2. Pyrimethamine Inhibits dihydrofolate reductase, a parasite enzyme required for folic acid synthesis. Effective against the liver stage.

C. Mefloquine (common name Lariam) Introduced in 1984. Acts against blood schizonts. Adverse CNS events associated with use.

Nightmares. Insomnia. Severe depression. Anxiety. Paranoia. Aggression. Seizures. Birth defects.

D. ACT (Artemisinin-based combination therapies) Combines several antimalarial drugs. One is a derivative of artemisinin from Artemesia annua plant.

Most common are artesuate and artemether. The other component is a partner drug.

Example: mefloquine. Drugs with different modes of action.

Reduces the selection of any resistant mutants.9. Immunity

o Antibodies.o Premunition - resistance to superinfection.

Works as long person maintains a low parasite population.o In areas where there is year-round exposure to malaria, infants still breast-feeding are protected

by maternal antibodies.o Children are very vulnerable to malaria.

10. VaccineA. Most targets are circumsporozoite protein.

Problems: Circumsporozoites proteins spend only a short time in the blood. Lack of cross-protection between species. Lack of cross-protection between strains of the same species.

B. Sanaria - company located in Rockville, MD. Developed a vaccine called PfSPZ. Irradiate infected mosquitoes and then harvest the whole parasite and incorporate it

into a vaccine.11. Mosquito control

A. Destruction of breeding sites.B. Mosquito predators.

Example: fish - Gambusia affinis feed on mosquito larva. Problem - introduced species.

C. Insecticides DDT - ecotoxicity. Example: Asia.

Homes with thatched roofs. Thatch bugs destroy thatch.

Wasp - kills thatch bugs. Found that DDT is more toxic to wasps than to thatch bugs; destruction of

thatched roofs.12. Economic burden

o Every 30 seconds it is estimated that a child dies from malaria.o Causes billions of dollars of damage to economies.o Increase in incidence of malaria.

Population movement. Dams and irrigation systems. Decrease in public health systems. Drug and insecticide resistance.

13. Dr. Henry Heimlicho Idea of using malaria to cure AIDS and other diseases.o Malariotherapy

1918-1975 - malaria was used to treat neurosyphilis. Malaria used to induce high fevers. This would kill the syphilis, the bacteria.

o Heimlich says that the fevers will kill HIV. Let the fevers go for about 10-12 rounds; ~3 weeks. Treat malaria with drugs. Idea is that the fevers will kill HIV, and the drugs will treat malaria.

o In Africa, malaria/HIV co-infection is common; kind of disproves this idea.