Neospora caninum parasite’s link to equine abortion explored


A parasite that causes abortion in cattle is the subject of a study in Canada to determine if it is the cause of the same problem in broodmares.

Abortions in horses continues to be a very frustrating problem for breeders and veterinarians. So much time and effort is put into producing quality horses and it is heartbreaking when it does not work out; even more so when the cause is undetermined.

Dr Tracey Chenier, of the Ontario Veterinary College (OVC), said about 40% of abortions in horses that are submitted to the lab come back with no diagnosis, and an unknown cause.

“This means we are missing a significant number of potentially infectious and potentially preventable abortions in horses,” she said.

Dr Tracey Chenier
Dr Tracey Chenier

In the new study partly funded by Equine Guelph starting in September, Chenier will investigate the exposure rate or the seroprevalence of the parasite Neospora caninum and its potential link to equine abortions.

Neospora caninum is a coccidian parasite that was identified as a species in 1988. Before this, it was misclassified as Toxoplasma gondii due to structural similarities. Coccidian parasites infect the intestinal tracts of animals, and can infect all mammals. Until recently, the only known definitive host of Neospora caninum was the domestic dog, but new research has determined that other canids such as coyotes, gray wolves, and Australian dingos are also definitive hosts. Eggs passed in the feces of the host are ingested by an intermediate host, such as cattle. A second route of transmission is the congenital transmission from mother to offspring. Transplacental transmission has been shown to occur in dogs, cats, sheep, and cattle. If the intermediate host acquires the disease during pregnancy, cysts formed as an immune response can cause infection, often leading to spontaneous abortion.

Recently, Neospora caninum was found in an aborted equine fetus in Israel. This discovery sparked the interest of researchers in Israel who then reached out to Chenier to conduct a collaborative study. The team of researchers includes Dr David Pearl and Dr Robert Foster from the OVC who have special expertise in disease surveillance and Neospora caninum in cattle, as well as Dr Amir Steinman and his lab in Israel who are familiar with the detection of this parasite.

The collaborative study will be the first of its kind in horses in Canada, and will be focusing on Ontario broodmares. It will place over the course of three years thanks to industry partners and the Ontario Ministry of Agriculture, Food and Rural Affairs.

Neospora caninum is the single most important cause of abortions in cattle in Ontario and has a significant impact across North America. Previous studies have looked at the seroprevalence of this parasite in Europe and the United States but no studies have been conducted in Canada. This latest study will provide insight into the unknowns surrounding the parasite’s seroprevalence in Ontario broodmares, risk factors for exposure, and if it plays a role in equine abortions.

The first step is to collect blood samples from broodmares on randomly selected breeding farms across Ontario. The owners will be involved in a comprehensive survey, so researchers can have a full understanding of the horses’ history, farm management practices, and risk factors such as dogs and coyotes on or near the farm (known to increase risk levels in cattle). Next, the researchers will be looking at aborted fetuses for the presence of the Neospora caninum parasite.

Chenier has been a researcher in equine reproduction at the OVC for almost 18 years, investigating equine infertility, reproductive efficiency, and embryo freezing.

Additional reporting:

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