Seroprevalence of Toxoplasma gondii in market hogs collected from United States slaugherhouses

Authors: Fredericks, Jorrell; Hill, Dolores; Hawkins Cooper, Diane; Fournet, Valsin; CALERO-LANDA, JONATHAN - Non ARS Employee; Adams, Brandon; Johnson, Alexis; BARROW, MARWA - Non ARS Employee; Aquino, Jovan; MAHMOUD, TALATHA - Non ARS Employee; MURPHY, VICTORIA - Non ARS Employee; BARLOW, ALEC - Non ARS Employee; PATEL, PRIYAL - Non ARS Employee; GEORGE, MEGAN - Non ARS Employee; Chehab, Nadya; Kramer, Matthew; BAUER, NATE - Food Safety Inspection Service (FSIS)

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2021
Publication Date: 5/19/2021
Citation: Fredericks, J.N., Hill, D.E., Hawkins Cooper, D.S., Fournet, V.M., Calero-Landa, J., Adams, B.T., Johnson, A.N., Barrow, M., Aquino, J.F., Mahmoud, T., Murphy, V., Barlow, A., Patel, P., George, M., Chehab, N.L., Kramer, M.H., Bauer, N. 2021. Seroprevalence of Toxoplasma gondii in market hogs collected from United States slaugherhouses. Journal of Parasitology. 107(3):404-410. https://doi.org/10.1645/20-142.
DOI: https://doi.org/10.1645/20-142

Interpretive Summary: While the production of safe and healthy products is one of the main objectives of the food industry worldwide, food products continue to be responsible for important outbreaks of disease in consumers. For example, toxoplasmosis has historically been linked to the consumption of raw or undercook pork. Toxoplasmosis is a zoonotic disease that occurs worldwide and is caused by the protozoan Toxoplasma gondii. In this study, we have investigated the seroprevalence of Toxoplasma gondii in market hogs and sows from United States slaughterhouses and found 0% seroprevalence for market hogs while sows from geographically similar but separate slaughter facilities demonstrated a seroprevalence of 1.03%. This study demonstrated that continued adherence to stringent biosecurity and management practices on US swine farms is resulting in a low prevalence of infection with T. gondii in US market hogs and sows. This research was completed in 2019, before closure of Toxoplasma research at USDA.

Technical Abstract: Foodborne pathogens continue to pose a public health risk, and can cause serious illness and significant outbreaks of disease in consumers. The consumption of raw or undercooked infected meat, including pork containing infectious stages of Toxoplasma gondii, may be a major route of transmission to humans. Given the occasional presence of T. gondii in pork meat and the frequent use of pork for products not intended to be cooked, such as dry-cured ham, a potential risk exists for T. gondii transmission to consumers of these products. The purpose of this study was to determine the seroprevalence of T. gondii in US market hogs and sows at slaughter. A total of 20,209 sera samples collected from 22 US slaughterhouses, which include 15 of the top 25 largest slaughter plants in the United States, were tested for T. gondii antibodies using a commercial ELISA assay. Seroprevalence in this study, as determined by ELISA, was 0.74%, with a herd prevalence of 10.86%. Further analysis was done to compare seroprevalence of T. gondii in market hogs vs. sows from a separate but geographically similar set of slaughterhouse locations. Serum samples were screened with the T. gondii modified agglutination test (MAT). Results showed that this set of market hogs demonstrated 0 % seroprevalence for T. gondii, while sows from geographically similar but separate slaughter facilities demonstrated a seroprevalence of 1.03%. Overall, both analyses show low seroprevalence of T. gondii in U.S market hogs and sows, respectively, and a significant drop in prevalence in market hogs and sows as compared to previous studies. Current biosecurity, management, and production practices in place have reduced the risk of T. gondii infection in pigs, thus reducing the likelihood of human infection from consumption of infected pork.