Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 1998
Publication Date: N/A
Interpretive Summary: Neosporosis is a protozoan (single-celled) parasite infection of livestock and companion animals. The etiologic agent, Neospora caninum causes abortion and neonatal mortality in livestock. Its life cycle and sources of infection are unknown. Transmission from the dam to the fetus is the only recognized mode of transmission. Scientists at the Beltsville Agricultural Research Center, in collaboration with University of Wyoming and Virginia-Maryland College of Veterinary Medicine have found that dogs are the definitive (reservoir) host for Neospora caninum. Dairy farmers should consider preventing dogs from defecating in cow feed. These findings will be of interest to dairy farmers, veterinarians, and parasitologists.
Dogs were investigated to determine if they are definitive hosts of Neospora caninum. Four dogs were fed N. caninum tissue cysts in infected mouse tissue, and 2 negative control dogs were fed uninfected mouse tissue. Dog faeces were examined daily for 30 days using a sucrose flotation technique. Three principal dogs shed spherical to subspherical unsporulated oocysts, measuring 10 to 11 æm in diameter. Oocysts sporulated within 3 days and contained 2 sporocysts, each with 4 sporozoites. Outbred, inbred, and gamma-interferon knockout mice were inoculated with dog faecal extracts and monitored for evidence of neosporosis using a variety of morphologic, immunohistologic, serologic, and genetic analyses. Mice that received faeces from each dog observed to shed oocysts were demonstrated to have neosporosis by 2 or more techniques. One mouse was demonstrated to be infected with N. caninum by immunohistochemistry, ultrastructural analysis, and polymerase chain reaction using a species-specific DNA sequence. No evidence of neosporosis was observed in control animals. Based on this study, dogs are a definitive host for Neospora caninum.