Neospora caninum is a major cause of abortions in cattle. First recognized in 1988, and linked to dogs in 1998, this parasite causes an infection called neosporosis. Studies have shown that at least half the dairy and beef herds in the United States have one or more animals that have been exposed. In an infected herd, up to 30 percent of the animals may test positive, and some cows may abort several times.
Neospora caninum is a protozoal parasite—a microscopic organism.
Cows congenitally infected with Neospora appear healthy, but about 20 percent will abort at least once in their lifetimes. Cows typically abort between the fourth and seventh months of gestation. If they do not abort, they are likely to pass the infection to their calves. Congenitally infected calves are usually born healthy and robust and develop normally, but pass the infection on to their offspring. In this way, Neospora caninum perpetuates itself in lines of cattle.
The second way that cattle become infected is through consuming feed or water contaminated with oocysts, or eggs, from the parasite, or grazing on contaminated pastures. These oocysts are shed in the feces of dogs, and probably of wild canines including coyotes, foxes and wolves. These animals become infected by eating infected animals, placentas or fetuses.