RISK-FACTORS FOR TRANSMISSION OF TOXOPLASMA-GONDII ON SWINE FARMS IN ILLINOIS

Two epidemiologic studies of risk factors for transmission of Toxoplas ma gondii to swine were conducted for farms in Illinois. The first stu dy was a cross-sectional survey of swine farms from the state of Illin ois pseudorabies testing program, in which farm owners or managers wer e interviewed by telephone regarding presence of risk factors for tran smission of T. gondii on the farm. There were 123 farms surveyed that provided blood samples for at least 30 sows. The mean sow seroprevalen ce was 19.5% (median = 10.0%). Multiple regression analysis of the ass ociation of sow seroprevalence with outdoor housing of SOWS, cat acces s to sow areas, number of sows, open feed storage and water delivery, delayed removal of carcasses, and presence of rodents on the farm indi cated that higher sow seroprevalence was associated with cat access to sows (P = 0.009) and fewer sows in the herd (P = 0.05). The second st udy was a field investigation of 47 swine farms (37 from the cross-sec tional study). Data collection included obtaining blood samples from s wine, cats, and rodents, and fecal samples from cats, heart and brain tissue from rodents, and feed, water, and soil samples for T. gondii e xamination. The risk of T. gondii transmission from cats and rodents t o sows and finishing pigs was evaluated, taking into account housing c onditions and herd size. Multiple regression analysis indicated that T . gondii seroprevalence in finishing pigs increased with more seroposi tive juvenile cats on the farm (P < 0.0001) and higher seroprevalence in house mice (P = 0.0023). For sows, the only risk factor associated with increased T. gondii seroprevalence was a higher number of seropos itive juvenile cats on the farm (P = 0.0008). Housing swine outdoors w as not associated with a higher T. gandii seroprevalence. These result s identify T. gondii infection in cats (particularly juveniles) and ho use mice as indicators of increased risk of transmission to swine.