Quantifying the Risk of Human Toxoplasma gondii Infection through Consumption of Domestically-produced Lamb in the United States

Introduction: Toxoplasma gondii is a widely prevalent protozoan parasite that is able to infect humans and animals worldwide. Human toxoplasmosis is responsible for considerable morbidity and mortality in the United States. Meat products have been identified as an important source of T. gondii infections in humans. Lamb, defined as a sheep less than one year old and without permanent teeth, is one of the meat animals that is frequently infected with T. gondii.

Purpose: The goal of this study was to develop a farm-to-table quantitative microbial risk assessment (QMRA) model to predict the public health burden in the United States associated with consumption of U.S. domestically-produced lamb.

Methods: T. gondii prevalence in market lambs was pooled from the 2011 National Animal Health monitoring system (NAHMS) survey, and the concentration of the infectious life stage (bradyzoites) was calculated. A log-linear regression and an exponential dose-response model was used to model the reduction of T. gondii during home cooking and to predict the probability of infection, respectively.

Results: The mean probability of infection per serving of lamb was estimated to be 1.5 cases per 100,000 servings, corresponding to approximately 6,300 new infections per year in the U.S. population. Based on the sensitivity analysis, cooking was identified as the most effective method to influence human health risk.

Significance: This study provides a QMRA framework for T. gondii infection through consumption of lamb. The infection risk and public health burden associated with lamb consumption were quantified, which could help in managing T. gondii infection risk.