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Toxoplasmosis is a disease caused by the protozoan parasite Toxoplasma gondii (T. gondii). T. gondii is commonly found in backyard and 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.


Felids (wild and domestic cats, bobcats, ocelots, pumas, and Asian leopards) are an essential part of the life cycle of T. gondii. Therefore, domestic cats are frequently infected with the organism, and will shed it's eggs (called oocysts) in their feces (by the millions), contaminating the surrounding environment. T. gondii oocysts are very hardy and will remain in the environment for years---well after the cat's feces has decomposed. Chickens become infected by ingestion of these oocysts from the environment.

Documented Toxoplasmosis Outbreaks in Chickens

Three out of a flock of 14 backyard chickens were infected with T. gondii in Illinois. The observed clinical signs were: torticollis (wry neck), inability to stand and lateral recumbency prior to death. The remaining 11 flock members showed no signs of disease.

Clinical Signs

Loss of appetite
Torticollis (wry neck)
Weight loss
Pale comb
Muscle spasms
Inability to stand


  • History
  • Clinical signs
  • Laboratory tests


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



Don't allow cats access to areas where chickens roam.

Scientific References

Risk Factors

  • Cats, bobcats, or pumas living nearby or on the premises

Also Consider