Download - 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