By Andi Anderson
Neospora caninum, a protozoan parasite, has become the leading cause of bovine abortion across the United States. Most abortions occur between five and seven months of gestation, and infected cows often retain fetal membranes.
While some calves are born alive, they may suffer neurological issues ranging from poor balance to weakness. For cattle producers, the disease brings not only reproductive losses but also higher culling rates, longer calving intervals, and reduced breeding value.
The parasite’s life cycle involves both wildlife and domestic animals. Dogs and coyotes are the definitive hosts, shedding infectious oocysts in their feces after consuming contaminated tissues.
These oocysts can spread into feed, water, and pastures, infecting cattle that consume them. Once inside the cow, the parasite may remain dormant in muscle tissue for life. However, it can reactivate during pregnancy, crossing the placenta and infecting the developing calf. This transmission can occur repeatedly, causing scattered abortion losses within herds.
Three pregnancy outcomes are possible depending on the stage of infection. If infection occurs in early gestation, calves are often born healthy.
Mid-gestation, however, represents the highest risk window, with increased likelihood of abortion or neurologically impaired calves. Late gestation infections may still result in live births, but these calves are often persistently infected and carry the risk into future pregnancies.
Diagnosis relies on laboratory testing of fetal tissues, especially the brain and heart, or through PCR testing. Blood tests are available but are most reliable at the herd level rather than for single abortion cases.
Control remains difficult since no vaccine or treatment exists. Recommended strategies include culling females with repeated abortions, testing replacement heifers, and preventing environmental contamination by removing aborted tissues and restricting dog and coyote access to feed and water.
Guard dogs may help deter wildlife, but young dogs themselves pose the highest risk of spreading oocysts.
As the parasite continues to cycle in wildlife, it poses ongoing risks even for closed herds. Effective management depends on strict biosecurity, careful replacement selection, and close collaboration with veterinarians.
Neospora caninum is unlikely to disappear, but informed herd management can help limit its economic and reproductive impact.
Photo Credit: istock-simplycreativephotography
Categories: Ohio, Livestock