Raccoon Roundworm

Introduction

1. What is it? → intestinal parasite found in the feces of raccoons

2. Scientific name –? Baylisascaris procyonis

3. Why is this important? → ? Important pathogen affecting wildlife and domestic animals, causing severe neurologic damage

Now considered common in Texas and can be found in central, eastern, and coastal areas

Parasite

1. B. procyonis is a large, tan colors parasitic nematode

2. Adult females are 20 to 22 cm long, and males are 9 to 11 cm long

3. Eggs → thick-shelled and golden brown

4. Typically found in the small intestines or tissues of animals

5. Definitive host → raccoons (can complete whole life cycle)

History

1. 1931 first isolated from raccoons in the New York Zoological Park

2. 1968 the genus Baylisascaris was defined and included eight recognized and two provisional species previously classified as mem

3. 1984

   1. First confirmed cases in humans

Hosts and reservoirs

1. Primary host → raccoons

   1. Parasite can complete its life cycle and breed within a raccoon host

2. Other host → domestic dogs, rodents, rabbits, primates, and birds

   1. Not common in livestock

   2. ZOONOTIC (rare)

3. Raccoons are well-adapted hosts for B. procyonis

   1. They exhibit a high susceptibility to infection, and they release a significant number of eggs into the environment each day, typically at latrines

How infection works

1. Two types of life cycles for B. procyonis, direct and indirect

2. Type of life cycle depends on the host

3. Direct (only in raccoon)

   1. Adult worms live in the small intestine

   2. Eggs laid by the female worms are passed in feces and reach the ground

   3. Takes a minimum of about 2 weeks for larvae to develop from first stage to third stage

   4. Once ingested by raccoon, larvae invade intestinal wall to complete development

   5. Male and female worms, mate, and start oviposition 50 to 76 days after infection

4. Indirect

   1. Eggs are passed in feces and ingested by paratenic hosts

   2. Larvae penetrate the intestinal wall and migrate through the bloodstream to reach other organ and tissues

   3. Two to four weeks after infection, the larvae grow in their third stage of development

   4. Become encapsulated in granulomas in various organs and tissues

   5. Remain dormant in granulomas in parentic hosts until ingestion by predatory racoons, then continue into adulthood

Transmission

1. Extremely effective, raccoons can shed millions of raccoon roundworm eggs per day in their feces

2. Average 20,000 to 26, 000 eggs per gram of feces

3. Optimal condition: 75F 100% humidity

4. Infant raccoons are directly infected within the first few months

   1. Ingest eggs from mother’s contaminated teats or fur, contaminated den, or from nearby raccoon latrine sites

5. Older raccoons may become infected indirectly by killing or scavenging infected prey

Clinical signs

1. Raccoons → often asymptomatic, causing no clinical signs

   1. Unless the parasite load is large enough to cause intestinal obstruction

2. Other hosts

   1. Lethargy

   2. Depression

   3. Unkept coat

   4. Seizure

   5. Blindness

   6. Death

   7. Can invade CNS and eyes, causing neurologic and ocular signs

Population effects

1. Highly common

   1. Infecting 40-60% of adult raccoons and up to 90-95% of juveniles in certain areas

   2. 80% of raccoons acting as carriers in Texas, creating significant environmental contaminations

2. Rarely causes mortality in raccoons

3. Mortality rate is high for those who develop severe symptoms (other hosts)

4. Population limiting factor for these prey species

Diagnosis

1. Definitive host (and dogs) → Fecal floatation

   1. Process of mixing stool with high density solution to make parasite eggs float

   2. Can also use PCR to confirm presence

2. Other hosts → clinical signs of neurologic impairment

   1. Diagnosis is challenging

   2. No eggs in feces for floatation

   3. Also confirmed post-mortem via histopathology

Prevention

1. Raccoons and other definitive hosts can be treated with common antiparasitic drugs used in domestic dogs and cats

2. How to avoid infection/spread:

   1. Avoid direct contact with raccoons and raccoon latrines

   2. Avoid using pet doors

   3. Do not use self-feeders for outside pets

   4. On a community level identification and evaluation of contaminated areas

3. Best method → combination of treatment and removal of contaminated raccoon latrines

Key takeaways

1. Cause → intestinal parasite

2. Location → in small intestines or tissues of host, eggs excreted via feces, larvae is ingested

3. Hosts → Raccoons (definitive) and domestic dogs, rodents, rabbits, primates, and birds

4. Clinical signs → lethargy, depression, unkempt hair coat, blindness, or death (raccoons asymptomatic)

5. Treatment → common antiparasitic drugs