Veterinarians once considered Strongylus vulgaris (the bloodworm) to be the main cause of colic in horses. We now know many other factors cause colic more frequently than this parasite, but it still poses a risk to horses' gastrointestinal tracts. But how big a risk, exactly? Thanks to a recently developed blood test, researchers were able to investigate the link between S. vulgaris and colic.
Once ingested by a horse, S. vulgaris spends four months migrating through the horse’s blood vessels before returning to the intestines. During this migration they can cause serious damage to the blood vessels and in extreme cases kill the intestinal tissue.
Previously, veterinarians did not have diagnostic tests that could evaluate the stages of the parasite’s migration. But recently, researchers developed a test to measure the level of bloodworm antibodies in a horse's blood.
“We developed the serum ELISA test for detection of larval stages present in the blood, and this enabled us to study the correlation between S. vulgaris and certain types of colic,” said Martin K. Nielsen, DVM, PhD, Dipl. EVPC, ACVM, a parasitologist at the University of Kentucky's Gluck Equine Research Center, in Lexington.
While the test is effective at determining the level of antibodies present in the blood, it is not necessarily an accurate indicator of a horse’s colic risk.
Nielsen and his team examined serum samples from a large number of colic patients at a Danish teaching hospital and compared these to a control group consisting of horses referred to the hospital for reasons unrelated to the gastrointestinal tract.