Survey of Microbiology of Parasitic Diseases

Parasitic Diseases of Wildlife

Helminths = worms

Arthropods (lice, mites, ticks)

Parasitic Diseases of Wildlife

Helminths - Multicellular eukaryotic animals w/ organ systems

Platyhelminthes = flatworms - flattened from front to back

Nematodes = roundworms – tapered at both ends

Helminths

Distinguishing characteristics of parasitic helminths1. May lack a digestive system

2. Nervous system is reduced

3. Means of locomotion is reduced or completely lacking

4. Reproductive system is complex, produce large numbers of fertilized eggs

Helminths

Generalized Life CycleCan be very complex, succession of intermediate hosts for

completion of each larval (developmental) stage of the parasite and a definitive host for the adult parasite.

Adults may be dioecious – male and female reproductive systems in separate individuals

Adults may be monoecious or hermaphroditic – male and female systems in the same individual

Platyhelminthes = flatworms

Trematodes = flukesFlat, leaf-shaped bodies,

ventral and oral suckersCommon names based on

tissue of the definitive host where adult lives – blood fluke, liver fluke, lung fluke…

Platyhelminthes = flatworms

Cestodes = tapewormsHead with suckers, flat body,

no digestive system

Nematodes = roundworms

Complete digestive systems

Most species dioecious

2 main categories

eggs are infective

larva are infective

Nematodes = roundworms

Meningeal (brain) worm - Parelaphostrongylus tenuis

Raccoon roundworm - Baylisascaris procyonis

Meningeal worm - Parelaphostrongylus tenuis

Meningeal worm - Parelaphostrongylus tenuis

Definitive Host

Meningeal worm - Parelaphostrongylus tenuis

A – Adult worms in meninges lay eggs

Meningeal worm - Parelaphostrongylus tenuis

B - Eggs go into circulation, reach lungs (C), hatch into larvae L1.

Meningeal worm - Parelaphostrongylus tenuis

The L1 migrate up bronchial tree (D) to pharynx, coughed, swallowed feces (E)

Meningeal worm - Parelaphostrongylus tenuis

L1 infects snails or slugs thru foot L3, takes ~3 wks.

Intermediate Host

Meningeal worm - Parelaphostrongylus tenuis

F – S with L3 are ingested abomasum

Intermediate Host

Meningeal worm - Parelaphostrongylus tenuis

Intermediate Host

Spinal nerves spinal cord mature 20-30 days to adults

Meningeal worm - Parelaphostrongylus tenuis

Intermediate Host

Adults migrate to subdural space brain

Meningeal worm - Parelaphostrongylus tenuis

Intermediate Host

From ingestion to exit of eggs in feces = prepatent period

Meningeal worm - Parelaphostrongylus tenuis

• If infected snails or slugs are ingested by susceptible incidental hosts, the L3 are released in the digestive tract.

• L3 migrate to the spinal cord and continue to migrate aimlessly within the CNS causing neurologic disease.

• Do not develop into adults.

Raccoon roundworm - Baylisascaris procyonis

Raccoon roundworm - Baylisascaris procyonis

Definitive host

Raccoon roundworm - Baylisascaris procyonis

Adults in intestines lay eggs

Raccoon roundworm - Baylisascaris procyonis

Eggs are shed with feces

Raccoon roundworm - Baylisascaris procyonis

Over 2-4 weeks the eggs develop larvae

Raccoon roundworm - Baylisascaris procyonis

Embryonated egg with larvae is ingested by raccoon

Raccoon roundworm - Baylisascaris procyonis

Larvae in intestines develop into egg-laying adults

Infection rates in raccoons are high – as high as 70% of adults and over 90% of juveniles

Raccoon roundworm - Baylisascaris procyonis

Embryonated egg with larvae are ingested by intermediate hosts

Raccoon roundworm - Baylisascaris procyonis

Eggs hatch and release larvae into intestines gut wall migrate thru the various tissue causing considerable damage and then encyst

Raccoon roundworm - Baylisascaris procyonis

In the eye blindness

Raccoon roundworm - Baylisascaris procyonis

5-7% CNS disease

Raccoon roundworm - Baylisascaris procyonis

Dead intermediate is scavenged by raccoon.

Emerging zoonotic disease

Dogs may be reservoir hosts, can shed eggs.

Infective eggs found in aging feces. Can remain in the environment for years.

Resistant to all common disinfectants

http://www.maniacworld.com/raccoon-encounter-with-dog-and-cat.html

Raccoon roundworm - Baylisascaris procyonis

Arthropds

Crustacea

Insecta - lice

Arachnids - mites and ticks