Wildlife Parasitic Zoonoses

Question 1

Definitive host of Angiostrongylus cantonensis?

Answer 1

Rat

Question 2

Definitive host of Baylisascaris procyonis?

Answer 2

Raccoon

Oocysts in their feces//”latrines”

Question 3

How can humans contract Toxoplasma gondii from oocysts versus tissue cysts

Answer 3

Oocysts
- contaminated soil
- eating filter-feeding shellfish
- anyone handling wild/zoo felid animals

Tissue Cysts
- contact with any warm-blooded wildlife (white-tailed deer, black bear, wild pigs)
- necropsy of infected animals, handling of aborted feti from infected animals

Question 4

How are humans infected by Cryptosporidium via wildlife?

Answer 4

• C. parvum & C. hominis
• ingested of oocysts (contaminated run-off/soil, water)

oocysts are extremely hardy in environment

Question 5

How are humans infected by Giardia duodenalis?

Answer 5

water contaminated with oocysts
- vets: always assume feces is infected prior to fecal tests

Question 6

What 4 parasites 1º affect wildlife, but also can successfully infect domestic animals with zoonotic potential?

Answer 6

1. Echinococcus multiocularis
2. Baylisascaris procyonis
3. Trichinella
4. Angiostrongylus

Question 7

Life cycle of Echinococcus multiocularis

Answer 7

Adults = small tapeworms
- Fox/dog/canid +/- cat eats IMH (rodent) -> adults develop in SI -> eggs passed in feces -> eggs ingested by IMH or abberant host like humans

Question 8

Geographical occurrence and diagnosis of Echinococcus multiocularis

Answer 8

• Central & Eastern Europe; Eastern U.S., Alaska, artctic Canada
• Dx of adult tapeworms = difficult
• Always have on Ddx for abdominal (liver) mass in any Eastern U.S. dog

Echinococcus multilocularis affects the liver as a slow growing, destructive tumor, often with abdominal pain and biliary obstruction being the only manifestations evident in early infection.

Question 9

Pathogenesis of Baylisascaris procyonis in humans

Answer 9

human ingest contaminated eggs -> larvae continue to grow & undergo extensive migration -> acute eosinophilic meningoencephalitis

raccoon latrines loaded with eggs

Question 10

How can a human become infected with Trichinella?

Answer 10

Consumption of contaminated meat from wildlife (larvae in muscle)- bears, pigs, arctic mammals

Question 11

How can humans become infected with Angiostrongylus cantonensis?

Answer 11

Accidental ingestion of gastropod or larvae (e.g., on contaminated product)

Question 12

Difference in pathogenesis of Angiostrongylus cantonensis in rat vs humans

Answer 12

aka Rat Lungworm
- Rat: ingest IH (gastropod) infected with 3rd larval stage -> larvae migrate to brain & develop into young adults -> travel to heart & pulmonary aa. and become sexually mature & lay 1st larval stage -> 1st-stage larvae travel to pharynx, swallowed then passed in feces
- Human: ingested 3rd-stage larvae migrate to CNS -> cause severe/poss. fatal eosinophilic meningoencephalitis