The role of rodents and other wildlife in the epidemiology of swine toxoplasmosis

Two swine production units and their contiguous wildlife populations were used for this study. These herds were located 7 miles apart in the major swine producing area of south central Georgia. Herd A had a Toxoplasma gondii antibody prevalence of 27.6% in all ages of swine sampled, with an increased incidence of 13.6% over a 5-month period. This herd was maintained under a semi-range condition. The swine in Herd B were maintained exclusively in concrete floored, enclosed buildings. This herd had a 0.85% T. gondii prevalence. Rodents and a few other wildlife and domestic species were trapped in or around both herds. These animals were examined for Toxoplasma antibodies using the same test procedure utilized for swine sera, the indirect immunofluorescent (IIF) test. Additionally, rodent tissues were homogenized and suspensions prepared for interperitoneal (I/P) inoculation into CF₁ laboratory mice.Rodents and wildlife species examined were: Mus musculus, Peromyscus leucopus, Rattus norvegicus, Sigmodon hispidus, Procyon lotor, and Didelphis marsupalis. Feral and domestic animals other than swine that also were tested for the presence of T. gondii antibodies included two cats, two horses, and a dog. The overall prevalence of T. gondii antibodies in all non-porcine species examined was 67% for those animals in and around the premises of Herd A, and 63% for those in and around Herd B.Toxoplasma infectivity of rodents whose tissues were processed and inoculated into laboratory mice correlated well with the results of the IIF test on the serum of these wild rodents. No tachyzoites of T. gondii were found in the peritoneal exudate of laboratory mice post I/P inoculation with wild rodent tissue, with one exception.While there was no significant difference in Toxoplasma infectivity in non-porcine species on these two premises, management practices appeared to be the determining factor in swine infection with T. gondii. Excluding wildlife precluded infection.