Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2001
Publication Date: N/A
Interpretive Summary: Neospora caninum is a single-celled parasite of livestock and companion animals. It causes abortion in livestock. It is a major cause of abortion in dairy cattle in the United States. The source of Neospora infection in cattle is not fully known. Scientists at the Beltsville Agricultural Research Center and the University in La Plata, Argentina have demonstrated the resistant stage (oocysts) of N. caninum in the feces of a naturally- infected dog for the first time. These results will be of interest to biologists, parasitologists, veterinarians and farmers.
Neospora caninum is a major cause of abortion in cattle worldwide. Cattle become infected with N. caninum by ingesting oocysts from the environment or transplacentally from dam to fetus. Experimentally, dogs can act as definitive hosts, but dogs excrete few oocysts after ingesting tissue cysts. A natural definitive host was unknown until now. In the present study, N. caninum was isolated from the feces of a dog. Gerbils (Meriones unguiculatus) fed feces from the dog developed antibodies to N. caninum in the Neospora caninum-agglutination test and tissue cysts were found in their brains. Neospora caninum was isolated in cell culture and in gamma interferon gene knockout mice inoculated with brain homogenates of infected gerbils. The DNA obtained from feces of the dog, from the brains of gerbils fed dog feces, and from organisms isolated in cell cultures inoculated with gerbil brains, was confirmed as N. caninum. The identification of N. caninum oocyst by bioassay and PCR demonstrates that the dog is a natural definitive host for N. caninum.