Phylum nematoda

The Roundworms

Phylum Nematoda

Genus Trichinella All are parasitic

11 known species compromise the genus

2 main clades1. Encapsulated

species in which the host muscle cells they invade become surrounded by a collagen capsule

2. Non-encapsulated no encapsulation occurs in the host muscle

Genus Trichinella The five species (and three genotypes yet to be

defined taxonomically) that comprise the encapsulated clade parasitize only mammals

Three species comprise the non-capsulated clade One infects mammals and birds Other two species infects mammals and reptiles There are only two of these parasites, T.

papuae and T. zimbabwensis, known to complete their entire life cycle independently of whether the host is warm-blooded or cold-blooded

Genus Trichinella

Trichinella papuae Trichinella zimbabwensis

Trichinella spiralis Greek: trichinos = of hair, -ella = diminutive Latin: Trichinella spiralis means spira, which is a

reference to how this organism coils up in its host Well known for its parasitic lifestyle Belongs to the first clade Main hosts are meat eating animals Resides within skeletal muscles Disease caused is “trichinosis”

T. spiralis - adaptation Buccal cavity

one of the most important structures for adaptation developed

Has a very similar function to our mouth Contains teeth to help the organism to adhere to

the substrate Supplies the organism with a place to take up

nutrients from its surroundings

T. spiralis - adaptation

Hydrostatic skeleton Helps with movement

Tail Helps in locomotion Supplies a place for claudal glands

responsible for secreting an adhesive mucus that helps this organism stick to the substrate of interest

Amphids Specialized sensing structures Located on the lateral sides of the head Gives the organism the ability to sense and then

adapt to their surroundings

T. spiralis - adaptation

Simple nervous system Consists of dorsal and ventral nerve cords allows them to interpret information coming from

their sensory organs such as the amphids Enables them to react to their environment better

and have an increased chance of survival Cuticle

located on the external aspect of the worm is shed off to allow these organisms to grow and

develop  larger body size all results in a discount

metabolic rate per gram of tissue

T. spiralis – life cycle

T. spiralis - reproduction

Encysted nematode is ingested Travel to the stomach to be digested digestive functions of the stomach allow the

nematodes to change from their encysted to their active forms

Molts four times for the first 34 hours Female releases pheromones to attract the male Male coils itself around the females genitals Male then inserts its spicule/s into female’s genitals

where the amoeboid sperms will crawl When eggs are fertilized, the mother will not release

the eggs unless they have hatched within its uterus Usually the 5th or 6th day of infection

T. spiralis - reproduction

Enterobius vermicularis

Greek: enteron = intestine, bios = life Has the broadest geographic range of any helminth Small, white, and thread-like Females: ranging between 8-13 mm x 0.3-0.5 mm

Possess a long pin-shape posterior end Males: ranging between 2-5 mm x 0.1-0.2 mm Dwells primarily in the cecum of the large intestine Females migrate at night to lay 15,000 eggs on the

perineum

Enterobius vermicularis

E. vermicularis - eggs

Flattened asymmetrically on one side Ovoid Approximately 55 mm x 25 mm in size Embryonate in six hours Can remain viable for about twenty days in a moist

environment Viable eggs and larvae were found in the sludge of

sewage treatment plants in Czechoslovakia in 1992

E. vermicularis - epidemiology

High prevalence in countries with a temperate climate

approximately 200 million people are infected internationally

The most common intestinal parasite Serves as an exception to the general rule that

intestinal parasites are uncommon in affluent societies

Does not need to rely on a vector for transmission Infection usually occurs via ingestion of infectious

eggs by direct anus-to-mouth transfer by fingers

E. vermicularis – life cycle

E. vermicularis–diagnostic test

Scotch tape test Most common test A clear adhesive cellulose tape is applied to the

anal area early in the morning before bathing or defecation

It is then observed under the microscope for the presence of eggs

These eggs may also be stained blue with lactophenol cotton blue, which aids in detection and identification

Sensitivity of this test when performed for three consecutive mornings is 90%

E. vermicularis - prevention

Bathe when you wake up to help reduce the egg contamination

Change and wash your underwear each day. Frequent changing of night clothes are recommended

Change underwear, night clothes, and sheets after each treatment. Because the eggs are sensitive to sunlight, open blinds or curtains in bedrooms during the day

Personal hygiene should include washing hands after going to the toilet, before eating and after changing diapers

Trim fingernails short Discourage nail-biting and scratching bare anal areas.

These practices help reduce the risk of continuous self reinfection

Wuchereria bancrofti

Filial nematode that is a thread-like worm Female: 10 cm long and 0.2 mm wide Male: about 4 cm long Adults reside and mate at the lymphatic system Can produce up to 50 000 microfilaria per day microfilaria are 250-300 µm long, 8 µm wide and

circulate in the peripheral blood and can live as is up to 12 months

Adult s take 6 to 12 months to develop from the larval stage and can live between 4 and 6 years

Wuchereria bancrofti

W. bancrofti - epidemiology

Interactions are with humans and mosquitoes Mosquitoes are intermediate hosts Humans are definitive hosts Microfilariae inhabits the mosquito and the mosquito

then transfers the microfilariae to humans when it takes a blood meal

Some of the common vectors are the Culex, Anopheles, and Aedes mosquito

CULEX ANOPHELES AEDES

W. bancrofti - epidemiology

RED: EndemicPINK: UnknownGREEN: Unaffected

Lymphatic filariasis

This disease is transferred by mosquitoes and is found mainly in the tropics and sub-tropics

Very rarely found in Western countries Onset of symptoms is usually slow, but after a couple

of years, the lymphatic system will no longer work like it should

Lymph nodes become enlarged and clogged Swelling, discoloration, and thickening of the skin

occurs Without treatment, the tissue infected with Lymphatic

filariasis develops into Elephantiasis

Elephantiasis

The thickening of skin and other tissues to produce huge growths on a person’s body

Growths result from the blocking of lymphatic vessels by the parasite

Usually found in the lower regions of the body W. Bancrofti can affect the arms, legs, and breasts

Filarial worms