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United States Department of Agriculture

Agricultural Research Service


Location: Animal Parasitic Diseases

Title: Detection and survival of Toxoplasma gondii in milk and cheese from experimentally infected goats

item Dubey, Jitender
item Verma, Shiv -
item Ferreira, Leandra -
item Cassinelli, Anna -
item Yuging, Ying -
item Kwok, Oliver
item Chiesa, Oscar -
item Jones, Jeffery -

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 28, 2014
Publication Date: N/A

Interpretive Summary: Toxoplasmosis is a parasitic infection of humans and animals and it continues to be public health and food safety problem. Among the many ways this infection is acquired, the consumption of unpasteurized goat cheese and milk has been suggested as a risk factor for human toxoplasmosis. Although pasteurization of milk is mandatory in many US states, many Americans consume products labeled as “Only for pet consumption” or as participants in food cooperatives. In the present study, scientists at ARS, in collaboration with CDC and FDA, tested excretion of Toxoplasma parasites in milk of experimentally infected goats. They found that live Toxoplasma can be transmitted through goat milk. Furthermore, Toxoplasma survived the cheese making process using the renin treatment. To prevent infection milk should be boiled or pasteurized before human consumption. These results will be useful for parasitologists, physicians and veterinarians.

Technical Abstract: The consumption of unpasteurized goat cheese and milk has been suggested as a risk factor for toxoplasmosis in humans. In the present study, detection and survival of Toxoplasma gondii in milk and cheese was studied. Eight goats were inoculated orally with 300-10000 oocysts of T. gondii strain TgGoatUS26. Milk samples were collected daily up to 30 days post infection (p.i.) and bioassayed in mice and cats. For mouse bioassay, 50 ml of milk samples were centrifuged and the sediment was inoculated subcutaneously into mice. By mouse bioassay, T. gondii was detected in milk from all eight goats. The T. gondii excretion in milk was intermittent. For cat bioassay, 400 ml (100 ml or more from each goat) of milk from 4 goats from 6 to 27 days p.i. were pooled, and cheese was made using renin. Ten grams of cheese was fed daily to 4 cats and cat feces were examined for oocyst shedding. One cat fed cheese shed oocysts 7-11 days after consuming cheese. Attempts were made to detect T. gondii DNA in milk of 4 goats; T. gondii was detected by PCR more consistently but there was no correlation between detection of viable T. gondii by bioassay in mice and T. gondii DNA by PCR. Results indicate that T. gondii can be excreted in goat milk, and can survive in fresh cheese made by cold-enzyme treatment. To prevent transmission to humans or animals, milk should not be consumed raw.

Last Modified: 9/22/2014
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