Prevalence, Isolation, and Genetic Characterization of Toxoplasma gondii in Chicken from the United States

Introduction: Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of all deaths attributed to foodborne pathogens in the U.S. with an estimated 327 deaths per year, thus making this parasite as a serious food safety concern.  Consumption of raw or undercooked meat is the primary infection route for T. gondii. Chickens are important vehicles for T. gondii and as they are generally fed from the ground, they are used as good indicators for the environmental T. gondii oocysts contamination.

Purpose: In this study, we sought to investigate the safety of free-range chickens that are available to purchase by consumers in the U.S.

Methods: Chicken hearts were sampled from the local markets in Maryland and from farms in Maryland and Amish community in Chicago. Each seropositive (modified agglutination test (MAT) positive) heart was bioassayed using Swiss Webster (SW) mice and examined for T. gondii infection. In addition, thirteen cryopreserved isolations from previous studies were revived and ten PCR-RFLP markers were used to genotype those isolates.

Results: One hundred fifty from a total of 997 samples (15.0%) were found seropositive for T. gondii. No viable T. gondii was isolated from chicken hearts that were sampled. All seropositive (150) samples were from a total of 912 samples purchased from local markets.

Significance: The results suggest that T. gondii oocysts could present in the environment and infect the food animals. T. gondii prevalence in chicken hearts could reflect the environmental contamination of T. gondii and prevalence information can be used to manage T. gondii infection risk.