Quantifying the risk of human Toxoplasma gondii infection due to consumption of fresh pork in the United States

Toxoplasma gondii is one of the leading foodborne pathogens in the United States. The Centers for Disease Control and Prevention (CDC) reported that T. gondii accounts for 24% of deaths due to foodborne illness in the United States. Consumption of undercooked pork products in which T. gondii has encysted has been identified as an important route of human exposure. However, little quantitative evaluation of risk due to different pork products as a function of microbial quality at the abattoir, during the production process, and due to consumer handling practices is available to inform risk management actions. The goal of this study was to develop a farm-to-table quantitative microbial risk assessment (QMRA) model to predict the public health risk associated with consumption of fresh pork in the United States. T. gondii prevalence in pigs was derived through a meta-analysis of existing data, and the concentration of the infectious life stage (bradyzoites) was calculated for each pork cut from an infected pig. Logistic regression and log-linear regression models were developed to predict the reduction of T. gondii during further processing and consumer preparation, respectively. A mouse-derived exponential dose-response model was used to predict infection risk in humans. The estimated mean probability of infection per serving of fresh pork products ranges from 3.2 × 10−7 to 9.5 × 10−6, corresponding to a predicted approximately 94,600 new infections annually in the U.S. population due to fresh pork ingestion. Approximately 957 new infections per year were estimated to occur in pregnant women, corresponding to 277 cases of congenital toxoplasmosis per year due to fresh pork ingestion. In the context of available data, sensitivity analysis suggested that cooking is the most important parameter impacting human health risk. This study provides a scientific basis for risk management and also could serve as a baseline model to quantify infection risk from T. gondii and other parasites associated with meat products.