Unusual disseminated toxoplasmosis in an adult backyard chicken

A female, adult chicken was presented at the Veterinary Teaching Hospital and Clinic with a one-week history of blindness and ataxia. Postmortem examination revealed that the right eye was covered with mucus and the cornea was cloudy. Histopathological examination revealed variable sized Toxoplasma gondii-like tissue cysts and tachyzoites in various tissues including brain, spinal cord, right eye, optic nerve and heart, along with necrosis and mixed inflammatory infiltration of lymphocytes, plasma cells and macrophages. The maximum numbers of parasites were observed in the brain section. Immunohistochemistry with Toxoplasma-specific antibodies confirmed the diagnosis. Limited genetic typing, using the DNA extracted from the paraffin-embedded brain section of the chicken and six PCR-restriction fragment length polymorphism (RFLP) genetic markers, revealed mixed type I and type III genotypes at SAG2, alt.SAG2, SAG3, GRA6, c22-8 and L358 loci. No apparent concurrent viral, bacterial or parasitic infections were detected.