Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 7, 1999
Publication Date: N/A
Interpretive Summary: Toxoplasma gondii is a protozoan parasite which causes clinical disease and birth defects in humans. Infection is acquired by accidental ingestion of parasite stages passed in cat feces or by eating raw or undercooked meat containing tissue cysts. The occurrence of Toxoplasma in pork varies, but can range as high as 50% in some parts of the U.S. To effectively control this parasite, through better animal management, it is necessary to have available simple and accurate detection methods. Current methods are slow and cannot be used easily on the farm or at slaughter plants. In this study, ARS scientists, in cooperation with scientists in the Food Safety and Inspection Service and at Palo Alto Research Institute, have tested several recombinant antigens in an enzyme immunoassay for their potential use in a rapid detection method for Toxoplasma infection in pigs. Several antigens appeared to have potential for use in parasite detection and will serve as a basis for further evaluation in larger groups of pigs. These results will be of interest to commodity groups, meat packers, regulatory agencies and scientists working with Toxoplasma.
Five recombinant Toxoplasma gondii antigens, designated B427, C51, C55, V22 and MBP30 were assessed for their potential use in an enzyme-linked immunoassay (EIA) for detection of T. gondii infection in swine. The antigens were evaluated with sera from young pigs which had been fed 1 to 10,000 T. gondii oocysts of the VEG or GT-1 stains. Results were compared with an EIA using a native T. gondii antigen extract. All 5 recombinant antigens, as well as native antigen, detected antibody responses as soon as 3 wks after infection in pigs inoculated with 1 or 10 oocysts of the VEG strain. This antibody response persisted, at varying levels, for 14 wks when the experiment was terminated. All antigens also detected antibody responses in pigs 4 wks after inoculation with 10,000 oocysts of the GT-1 strain. The antibody response recognized by native antigen remained high through 51 wks after inoculation. However, there was considerable animal to oanimal variation in responses to the individual recombinant antigens. Only antigens C51 and MBP30 consistently detected a positive antibody response over the entire 51 wk course of the experiment. These results suggest that these antigens might be useful for the serological detection of T. gondii infection in pigs.