Quantitative risk assessment of meat-borne Toxoplasma gondii infection in the mainland of China

Abstract

Toxoplasma gondii, a protozoan zoonotic parasite, has a worldwide distribution. It can cause severe pathological damage to the fetus in primary infected pregnant women and life-threatening encephalitis in immunocompromised patients. One of the main transmission routes to humans is consumption of raw or undercooked meat containing viable T. gondii tissue cysts. In China, the lack of quantitative information on the risk and incidence of infection due to consumption of meat hampers the development of prevention strategies to reduce the burden of toxoplasmosis. The aim of this study was to set up a quantitative microbial risk assessment (QMRA) model to estimate the relative attribution of different types of meat (i.e., pork, beef, lamb and mutton, chicken and duck) to human T. gondii infections in China. The model was built based on the structure of the first meat-borne T. gondii infection QMRA model developed in the Netherlands and applied for seven regions of mainland China. Data on the prevalence of T. gondii in livestock and consumption were obtained from China, however information on preparation habits was lacking. Consumption data were available as average consumption amounts per day collected over three days. The results calculated from the QMRA model were at least thousand-fold higher compared to the incidence rate obtained from an epidemiological susceptible-infected (SI) type model. In general, pork and chicken meat contributed more to the estimated number of infections than beef, small ruminant and duck meat. Cooking temperature was identified as one of the parameters that most strongly affected the estimated incidence rate in the QMRA model. Sensitivity analysis showed that the estimated incidence rate from the QMRA model would be comparable to the results obtained from the SI model if final cooking temperatures are around 1.7 times higher than the temperatures based on a dataset for American consumers. Scenario analysis demonstrated that it is important to know portion size and frequency of consumption in addition to total consumed amounts to calculate incidence of infection. Due to uncertainties present in the input data and the at least thousand-fold overestimated incidence rates, the results merely give an indication of the relative importance of different types of meat. However, the QMRA model clearly identified the key knowledge gaps for future research and can subsequently support cost-effective decisions to reduce the disease burden of human toxoplasmosis.