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Toxoplasmosis is a zoonotic disease caused by infection with the protozoan parasite Toxoplasma gondii. T. gondii is commonly isolated from free range chickens worldwide. However, clinical disease rarely occurs in chickens, and they are generally considered to be resistant to clinical toxoplasmosis. There have only been a few documented reports of clinical toxoplasmosis in chickens worldwide. Humans can become infected by eating chickens that are infected with T. gondii. Felids, especially domestic cats, are the most important life cycle host of T. gondii due to their ability to excrete environmentally resistant oocysts. Cats become infected from eating intermediate hosts that contain the parasite.

Three out of a flock of 14 backyard chickens that were infected with T. gondii in Illinois acutely demonstrated clinical signs of torticollis, inability to stand and lateral recumbency prior to death. The remaining 11 flock members showed no signs of disease.

Clinical Signs

No clinical signs
Loss of appetite
Weight loss
Pale combs
Muscle spasms


  • Modified agglutination test (MAT)
  • Complement fixation test (CFT)
  • Indirect haemagglutination test (IHAT)
  • Complement inhibition test
  • Fluorescent antibody test (IFAT)
  • Latex agglutination test (LAT)
  • Sabin-Feldman dye test (DT)


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.
Pyrimethamine0.5 mg/kg administered orally, twice a dayK Marx
Diclazuril0.5-1 mg/kg food in feed, dailyK Marx



Prevent exposure of flock to rodents and cats

Scientific References

Risk Factors

  • Cats on the premises
  • Predator attack by a bobcat or mountain lion