Fatal disseminated toxoplasmosis in captive red kangaroo (Macropus rufus) and Parma wallaby (Macropus parma): pathological and immunohistochemical investigations

Abstract

Toxoplasmosis is a protozoan zoonosis caused by Toxoplasma gondii. Marsupials are considered a susceptible intermediate host. T. gondii is mainly transmitted to intermediate hosts via the fecal-oral route. A captive red kangaroo was diagnosed with disseminated toxoplasmosis based on clinicopathological and immunohistochemical (IHC) investigations. Two years later, a five-year-old Parma wallaby was kept in the same area as the red kangaroo and showed clinical signs of depression, withdrawal from the troop, and weakness. The wallaby died within two days after showing the clinical signs. Pathological findings in this wallaby were compatible with disseminated toxoplasmosis. Tachyzoites and tissue cysts of T. gondii were demonstrated in the brain, striated and myocardial muscles, and lungs of these marsupials using periodic acid Schiff (PAS) staining and IHC. Stray cats were considered the most likely source of infectious oocysts for these marsupials. Taken together, we report fatal disseminated toxoplasmosis in a captive red kangaroo and Parma wallaby in Thailand. Controlling the population of stray cats should be implemented to reduce the exposure rate of T. gondii to zoo staff, animals, and visitors.