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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Parasitic Diseases Laboratory » Research » Publications at this Location » Publication #378622

Research Project: Detection and Control of Foodborne Parasites for Food Safety

Location: Animal Parasitic Diseases Laboratory

Title: Systemic toxoplasmosis in a horse

item KIMBLE, KATELYN - Texas A&M University
item GOMEZ, GABRIEL - Texas A&M Veterinary Medical Diagnostic Laboratory
item SZULE, JOSEPH - Texas A&M University
item Dubey, Jitender
item BUCHANAN, BEN - Brazos Valley Equine Hospitals
item PORTER, BRIAN - Texas A&M University

Submitted to: Journal of Comparative Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2020
Publication Date: 12/9/2020
Citation: Kimble, K.M., Gomez, G., Szule, J., Dubey, J.P., Buchanan, B., Porter, B.F. 2020. Systemic toxoplasmosis in a horse. Journal of Comparative Pathology. 182:27-31.

Interpretive Summary: Food safety research is of paramount importance for agriculture and the public. Foodborne protozoon infections are a leading cause of death from foodborne illness in the United States, especially for individuals with weak immune systems such as children and HIV patients. USDA research in this area has borne undeniable results – including helping to cut the prevalence of Toxoplasma gondii by as much as 50 percent in the United States. The USDA provided the veterinary, clinical, and public health communities an indispensable resource by disseminating up to date scientific information on toxoplasmosis and its prevention. Humans become infected mostly by ingesting food and water contaminated with oocysts or by eating infected under cooked meat. Horse and donkey meat is eaten in several countries and humans in France have developed severe toxoplasmosis after ingesting raw horse meat. The authors report here first case of clinical toxoplasmosis in a horse and distinguish it from 2 related protozoans, Sarcocystis neurona and Neospora hughesi infections that cause clinical disease in horses. This information will be of interest to parasitologists and veterinarians. This work was completed before the closure of ARS research in 2019.

Technical Abstract: An adult American Quarter Horse gelding with a history of weight loss presented with an acute onset of colic, fever, soft feces, and elevated liver enzymes. At necropsy, there were gastric mucosal masses and evidence of cecal 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, lung, and liver. Necrotizing typhlitis was also evident. Immunohistochemical staining for Toxoplasma gondii was positive, and the ultrastructural appearance 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.