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 helminths 1.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 Cycle Can 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 = flukes Flat, leaf-shaped bodies, ventral and oral suckers Common names based on tissue of the definitive host where adult lives – blood fluke, liver fluke, lung fluke…
Platyhelminthes = flatworms Cestodes = tapeworms Head with suckers, flat body, no digestive system
Nematodes = roundworms Complete digestive systems Most species dioecious 2 main categories eggs are infective larva are infective
Meningeal worm - Parelaphostrongylus tenuis F – S with L3 are ingested abomasum Intermediate Host
Meningeal worm - Parelaphostrongylus tenuis Intermediate Host Spinal nerves spinal cord mature 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 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 Raccoon roundworm - Baylisascaris procyonis