Submitted to: Journal of Comparative Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/12/2005
Publication Date: 6/6/2006
Citation: Dubey, J.P., Buxton, D., Wouda, W. 2006. Pathogenesis of bovine neosporosis. Journal of Comparative Pathology. 134:267-289. Interpretive Summary: Neospora caninum is a single-celled parasite. It causes abortion in cattle and paralysis in companion animals. It is the most important cause of abortion in dairy cattle. Dogs and coyotes are its definitive hosts and main reservoirs of infection. This parasite is transmitted efficiently from the cow to the calf transplacentally. Scientists at the Beltsville Agricultural Research Center and Moredon Institue in Scotland review pathogenesis of neospora abortion in cattle.The results will be of interest to biologists, parasitologists, and veterinarians.
Technical Abstract: The protozoan parasite Neospora caninum is a major pathogen of cattle and dogs, being a significant cause of abortion in cattle in many countries. It is one of the most efficiently transmitted parasites, with up to 90% of cattle infected in some herds. The pathogenesis of abortion due to Neospora is complex and only partially understood. Losses occur following a primary infection during pregnancy but more commonly as the result of recrudescence of a persistent infection during pregnancy. Following a parasitaemia the parasite invades the placenta and fetus. It is suggested that abortion may occur when primary parasite-induced placental damage jeopardises fetal survival directly or causes release of maternal prostaglandins that in turn cause luteolysis and abortion. Fetal damage may also occur due to primary tissue damage caused by the multiplication of N. caninum in the fetus or due to insufficient oxygen/nutrition, secondary to placental damage. In addition maternal immune expulsion of the fetus may occur associated with maternal placental inflammation and the release of maternal pro-inflammatory cytokines in the placenta. Thus N. caninum is a primary pathogen, capable of causing abortion either through maternal placental inflammation, maternal and fetal placental necrosis, fetal damage or a combination of all three. The question of how N. caninum kills the fetus exposes the complex and finely balanced biological processes that have evolved to permit bovine and other mammalian pregnancies to occur. Defining these immunological mechanisms will shed light on potential methods of control of bovine neosporosis and enrich our understanding of the continuity of mammalian and protozoal survival.