1a.Objectives (from AD-416):
The objective of the research is to establish a baseline prevalence of oocyst-transmitted Toxoplasma in the U.S. population. These data will support science-based decisions on the most effective methods to reduce or eliminate Toxoplasma transmission to humans in the U.S. Additionally, development of current Trichinella prevalence data in humans will inform policy makers on the effectiveness of farm level controls of this zoonotic parasite for reduction of risk in the human population.
1b.Approach (from AD-416):
Sera will be acquired from a sample of the NHANES III participants aged 6 and over, and tested for Toxoplasma in duplicate by ELISA using an in-house developed test using an 11 kDa sporozoite protein related to embryogenesis (TgERP). Trichinella seroprevalence will be determined using a commercially available test kit which uses T. spiralis excretory/secretory proteins (E/S) as the antigen in an ELISA format. The collected prevalence data for Toxoplasma will be used to determine the predominant route of infection (oocyst versus tissue cysts in meat) from a representative sampling of the U.S. population and ascribe demographic features to those found to be infected. The collected prevalence data for Trichinella will be used to measure the impact of the elimination of Trichinella from the U.S. swine herd on human health and the prevalence of Trichinella infection in the U.S. population.
The ARS laboratory is conducting a serological survey of Toxoplasma infection using sera and demographic data collected during the National Health and Nutrition Examination Survey (NHANES) from 2007-2010, in an ELISA based on a Toxoplasma sporozoite-specific antigen which differentiates oocyst (cat) vs tissue cyst (meat borne) transmission. The survey will provide, for the first time, a measure of the proportion of Toxoplasma infections in humans which result from consumption of T. gondii oocysts (from cat feces) versus consumption of tissue cysts (contained within infected meat). In addition, we will test these and an additional 2000 randomly selected NHANES sera to determine seroprevalence to Trichinella spiralis in the U.S. population in the face of recent evidence that Trichinella has been virtually eliminated from the domestic hog population, the major source of Trichinella infection for people in the U.S. This project relates to the parent project Objective #1 on the impact of changing management and production practices on the incidence of Trichinella in swine as it relates to foodborne risk.