Neospora caninum is a coccidian parasite that was identified as a species in 1988. Prior to this, it was misclassified as Toxoplasma gondii due to structural similarities. The genome sequence of Neospora caninum is determined by the Wellcome Trust Sanger Institute. Neospora caninum is an important cause of spontaneous abortion in infected livestock.
Neospora caninum has a heteroxenous life cycle, with the sexually reproductive stage occurring in the intestine of a definitive host. Until recently, the only known definitive host was the domestic dog. New research has determined that coyotes and gray wolves are also definitive hosts.  Oocysts passed in the feces of the definitive host are ingested by an intermediate host, such as cattle. These become permanently infected, and form tissue cysts. Pregnancy activates these cysts, and active infection often causes spontaneous abortion. If the aborted foetus and membranes are then eaten by the definitive host, they cause further infection and the cycle is complete. Transplacental transmission (passage from mother to offspring during pregnancy) has also been shown to occur in dogs, cats, sheep and cattle. Other carnivores, for example the red fox (Vulpes vulpes), may also be intermediate hosts, but they are not known to be definitive hosts. Neospora caninum does not appear to be infectious to humans. In dogs, Neospora caninum can cause neurological signs, especially in congenitally infected puppies, where it can form cysts in the central nervous system.
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