Low prevalence of viable Toxoplasma gondii in fresh, unfrozen, American pasture-raised pork and lamb from retail meat stores in the United States

Authors: Dubey, Jitender; HILL, DOLORES - Retired ARS Employee; Fournet, Valsin; Hawkins Cooper, Diane; CERQUEIRA-CEZAR, CAMILA - Non ARS Employee; MURATA, FERNANDO - Non ARS Employee; VERMA, SHIV - Non ARS Employee; Kwok, Oliver; RANI, SURABHI - University Of Maryland; Fredericks, Jorrell; ADAMS, BRANDON - Non ARS Employee; JONES, JEFFREY - Centers For Disease Control And Prevention (CDC) - United States; WEIGAND, RYAN - Centers For Disease Control And Prevention (CDC) - United States; YING, YUQING - University Of Maryland; GUO, MIAO - University Of Maryland; SU, CHUNLEI - University Of Tennessee; PRADHAN, ABANI - University Of Maryland

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2019
Publication Date: 10/22/2019
Citation: Dubey, J.P., Hill, D., Fournet, V.M., Hawkins Cooper, D.S., Cerqueira-Cezar, C.K., Murata, F.H., Verma, S.K., Kwok, O.C., Rani, S., Fredericks, J.N., Adams, B., Jones, J., Weigand, R., Ying, Y., Guo, M., Su, C., Pradhan, A.K. 2019. Low prevalence of viable Toxoplasma gondii in fresh, unfrozen, American pasture-raised pork and lamb from retail meat stores in the United States. Food Control. 109:106961. https://doi.org/10.1016/j.foodcont.2019.106961.
DOI: https://doi.org/10.1016/j.foodcont.2019.106961

Interpretive Summary: Among zoonotic pathogens, the protozoan parasite T. gondii is perhaps the most ubiquitous, having been identified in the tissues of a variety of animal hosts, including both mammalian and avian species. Toxoplasma gondii is estimated to chronically infect one third of the world’s human population, causing ocular toxoplasmosis in immunocompetent individuals and often-fatal encephalitis in the immunocompromised, as well as birth defects and mortality following vertical transmission to developing fetuses. Humans become infected postnatally by eating undercooked meat infected with T. gondii tissue cysts or by ingesting oocysts from the environment. In America, pigs are considered the main meat source of Toxoplasma because beef and poultry are rarely infected with this parasite. While T. gondii infection has decreased in US confinement-raised market pigs (typically used for fresh, unprocessed pork products) over the last 30 years, infection levels in pigs with access to the outdoors can be quite high. An upsurge in consumer demand for ‘organically raised’, ‘humanely raised’ and ‘free range’ pork products has resulted in increasing numbers of hogs being raised in non-confinement systems. Given suspicions that animals raised with outdoor access might contribute appreciably to the public health burden of toxoplasmosis, we therefore conducted a nationwide survey of organically raised pork and lamb in USA, and found reassuringly low rates of viable toxoplasma parasites. The results will be of interest to farmers, public health workers, consumers, biologists, parasitologists, and those responsible for the oversight and marketing of the USDA Organic production standard.

Technical Abstract: In a national survey of organic lamb and pork, the prevalence of viable Toxoplasma gondii was determined in 1500 samples (750 pork, 750 lamb) obtained from 250 retail meat stores from 10 major geographic areas of USA. Each sample consisted of a minimum of 500g of meat purchased from the retail meat case. To detect viable T. gondii, 50g meat samples of each of 1500 samples were bioassayed in mice. Viable T. gondii was isolated from 2 of 750 lambs and 1 of 750 pork samples. Overall, the prevalence of viable T. gondii in these retail meats was very low. Nevertheless, consumers, especially pregnant women, should be aware that they can acquire T. gondii infection from ingestion of undercooked meat. Cooking meat to an internal temperature of 660C kills T. gondii.