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Other Names: Raccoon Roundworm Infection, Visceral Larval Migrans

Baylisascaris is a type of roundworm parasite that is commonly found in raccoons and shed from their feces into the environment. Baylisascaris can also colonize within domestic dogs(B. procyonis), European badgers (B. melis), and skunks (B. columnaris).

Baylisascaris produces very large numbers of eggs; each nematode is estimated to lay up to 179,000 eggs per day, and raccoons carry an average of 43-52 worms. The eggs are also very resistant to environmental conditions, and can survive in the soil through harsh conditions for long periods of time. Clinical signs vary widely depending on where the larvae migrate once in the chicken's digestive system; Baylisascaris can affect the brain and spinal cord, organs and eye.

Baylisascaris eggs are shed in the feces of infected animals, into the surrounding environment. Chickens become infected if they accidently ingest infective eggs in the soil, water or objects that have been contaminated with raccoon feces.

Incubation Period
The incubation period is estimated to be between a week to 4 weeks, possibly longer.

Clinical Signs

Rough hair coat
Ruffled feathers
Progressive weakness
Difficulty perching
Unable to fly


  • History
  • Clinical signs
  • Physical exam
  • Fecal test
  • Tissue biopsy


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Piperazine100-500 mg/kg administered orally q2wK Marx
Pyrantel Pamoate4.5-25 mg/kg administered orally, q2wK Marx
Moxidectin0.2-0.8 mg/kg administered orally, onceK Marx



Discouraging raccoons, skunks, or badgers from entering area where poultry forage.

Scientific References

Risk Factors

  • Raccoons or domestic dogs living near the premises of where chickens are kept.