Toxoplasma gondii Prevalence in Farm Animals in the United States

Toxoplasmosis is a significant public health problem in the US with more than one million people newly infected each year, according to new research from the USDA. Seroprevalence in pigs and chickens from non-biosecure management systems is high. Clinical disease and high seroprevalence occur in sheep and goats, while beef cattle do not appear to be important in the epidemiology of Toxoplasma or in transmission to humans.
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Toxoplasmosis, caused by Toxoplasma gondii, is one of the most common parasitic infections of humans and other warm-blooded animals, according to D.E. Hill and J.P. Dubey of the USDA ARS Beltsville Agricultural Research Center's Animal Parasitic Diseases Laboratory in Beltsville, Maryland. In their paper published online in International Journal for Parasitology, they say that the infection has been found worldwide and nearly one-third of humans have been exposed to the parasite.

Congenital infection occurs when a woman becomes infected during pregnancy and transmits the parasite to the foetus. Besides congenital infection, humans become infected by ingesting food or water contaminated with sporulated oocysts from infected cat faeces or through ingestion of tissue cysts in undercooked or uncooked meat.

Food animals (pigs, chickens, lambs and goats) become infected by the same routes, resulting in meat products containing tissue cysts, which can then infect consumers.

Toxoplasma infection is common in food animals in the United States. Type II and Type III clonal lineages and atypical genotypes predominate in food animals there.

Implementation of management factors such as biosecure confinement housing are important in reducing the levels of infection in animals destined for human consumption, concluded Hill and Dubey.


Hill D.E. and J.P. Dubey. 2012. Toxoplasma gondii prevalence in farm animals in the United States. International Journal for Parasitology. Available online 27 November 2012 [in press].

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December 2012
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