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Systemic Toxoplasmosis in a Horse

Katelyn M. Kimble, Gabriel Gomez, Joseph A. Szule, Jitender P. Dubey, Ben Buchanan, Brian F. Porter
Journal of comparative pathology 2021 v.182 pp. 27-31
Quarter Horse, Toxoplasma gondii, case studies, cecum, gastric mucosa, geldings, histopathology, horse diseases, inflammation, liver, lungs, lymph nodes, necrosis, new host records, seroprevalence, signs and symptoms (animals and humans), spleen, tachyzoites, toxoplasmosis, ultrastructure
An adult American Quarter Horse gelding with a history of weight loss presented with an acute onset of colic, fever, soft faeces and elevated liver enzymes. At necropsy, there were gastric mucosal masses and evidence of caecal necrosis. Histologically, the masses were lymph nodes with granulomatous inflammation and areas of liquefactive necrosis. Within and surrounding necrotic areas were free and intrahistiocytic clusters of protozoal tachyzoites. Similar but milder inflammation was evident in the spleen, lungs and liver. Necrotizing typhlitis was also evident. Immunolabelling for Toxoplasma gondii was positive and the ultrastructural morphology of the protozoa was compatible with T. gondii. Although studies have shown seropositivity to T. gondii in horses throughout the world, this is the first report of clinical toxoplasmosis in this species.