Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 12, 1998
Publication Date: N/A
Interpretive Summary: Neosporosis is a newly recognized single-celled parasite infection. It causes abortion in livestock and paralysis in companion animals. Its life cycle and sources of infections are unknown. There is no vaccine for neosporosis. Until 1988, the parasite Neospora caninum, the cause of neosporosis, was misdiagnosed as Toxoplasma gondii because of structural similarities. Scientists at the Beltsville Agricultural Research Center and the Auburn University, Alabama examined cross protection between N. caninum and T. gondii and found that there was little protective effect of vaccination of mice with N. caninum against T. gondii infection. These results will be of interest to parasitologists, veterinarians, and public health workers.
Neospora caninum is a protozoan parasite that can cause severe disease in mammals. Two experiments were conducted to examine the effects of subcutaneous (s.c.) vaccination with Hanks balanced salt solution (HBSS), 1 x 100,000 N. caninum NC-1 strain tachyzoites or 1 x 100,000 Toxoplasma gondii TS-4 strain tachyzoites on challenge oral infections in mice with sporulated VEG strain T. gondii oocysts (1 x 1,000 oocysts Exp. 1 and 5 x 1,000 oocysts Exp. 2). No difference was observed in tissue cyst numbers in mice vaccinated with HBSS or NC-1 strain tachyzoites in Experiment 1. No HBSS vaccinated mice survived Experiment 2. Results of these experiments indicate that infection with N. caninum provides some protection against fatal oral infection with T. gondii oocysts of a moderately pathogenic strain but not tachyzoites of a highly pathogenic strain. The protection provided by N. caninum is much less than that provided by previous exposure eto T. gondii and the numbers of tissue cysts in the brains of mice are not significantly lowered.