Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 1999
Publication Date: N/A
Interpretive Summary: Infections by the protozoan (single-celled) parasite Toxoplasma gondii are widely prevalent in livestock and humans. They cause mental retardation and loss of vision in children and abortion in livestock. Toxoplasma infection in wild carnivores is a good indicator of the prevalence of the parasite in nature. Scientists at the Beltsville Agricultural Research Center and Purdue University found serum antibodies to T. gondii in 59% of 222 coyotes, 85% of 283 red foxes and 75% of 97 grey foxes. These findings indicate that T. gondii is widely prevalent in the environment in Indiana and the findings will be of interest to wildlife biologists and parasitologists.
Antibodies to Toxoplasma gondii were determined in sera from 222 coyotes (Canis latrans), 283 red foxes (Vulpes vulpes), and 97 gray foxes (Urocyon cinereoargenteus) from Indiana, Kentucky, Michigan, and Ohio during 1990- 1993. Sera were examined in 1:25, 1:100, and 1:500 dilutions by the modified direct agglutination test (MAT) using formalinized whole tachyzoites plus mercaptoethanol. Antibodies were found in 131 (59.0%) of 222 coyotes, 243 (85.8%) of 283 red foxes and 73 (75.3%) of 97 gray foxes. Antibodies were also measured by different serologic tests in 4 littermate T. gondii-free red foxes fed T. gondii tissue cysts or oocysts; the fifth littermate fox was not fed T. gondii. Antibodies were measured in fox sera obtained 0, 14, and 36-55 days after infection with T. gondii. All 4 foxes fed T. gondii developed MAT and dye test antibody titers of 1:400 or 1:800 14 days later. The latex agglutination test (LAT) and indirect hemagglutination test (IHAT) were less sensitive than MAT for the diagnosi of T. gondii infection in foxes. Antibodies were not detected by LAT (titer 1:64) in the 2 foxes fed tissue cysts, nor by IHAT in one of the foxes fed tissue cysts. Toxoplasma gondii was isolated by bioassay in mice from tissues of all 4 foxes fed T. gondii. The control fox had no T. gondii antibodies detectable by any of the serologic tests. Toxoplasma gondii infections in wild carnivores are good indicators of T. gondii infections in the environment (Dubey and Beattie, 1988). Therefore, we surveyed coyotes, red foxes, and gray foxes for the presence of antibodies to T. gondii. Because little is known about the diagnosis of toxoplasmosis in wild carnivores, antibodies were also measured by different serologic tests in experimentally infected red foxes.