An epidemiologic study of Toxoplasma gondii in swine in Tennessee

The reliability of the Modified Agglutination Test (MAT) to detect infection with Toxoplasma gondii was evaluated in a murine model. Thirty-five mice (ICR) were infected with bradyzoites of (UT-1 strain) and all acquired the infection. IgM and IgG titers were measured every two days in the twenty-five infected mice. IgM and IgG appeared seven days postinfection (PI). IgM peaked from 11-15 days PI and remained throughout the experiment (45 days). The presence of T. gondiiwas confirmed post-mortem in all infected mice by impression smear, hematoxylin and eosin and/or immunoperoxidase straining of brain sections. The MAT was proven a reliable test for seroprevalence studies.

The seroprevalence of T. gondii in finishing pigs at the University of Tennessee (UT) Crossville Experiment Station was studied for period of two years, 1991-92. The seroprevalence both years was 0.6%. At another UT experiment station, the Ames Plantation, the seroprevalence was evaluated in swine of all ages raised in three different types of management systems. The pigs of all ages in partial confinement had the highest Seropositivity (POf 3,841 sow serum samples received from the TN State Diagnostic Laboratory in 1991-92, 1130 were positive for T. gondii antibody. The total number of farms sampled was 343. The true prevalence was 36% for both years. A survey was mailed to 303 swine farmers concerning their management practices; 107 responses were returned and analyzed. There was no significant difference between the respondents and nonrespondents. From the analysis of the survey sows associated with cats were 2.6 times more likely to be seropositive for T. gondii than sows that were not associated with cats. Sows kept outdoors at any time were 23 times more likely to be seropositive than sows that were kept indoors. Sows on small farms (≤ 29 sows) were 4.47 times more likely to be seropositive than sows on large farms.