Strongylus vulgaris, commonly known as the bloodworm, is considered the most pathogenic parasite infecting horses worldwide. But scientists have until now not been able to develop a reliable diagnostic method for detecting migrating larvae of S. vulgaris.

A group of scientists from the University of Kentucky Gluck Equine Research Center and the Department of Large Animal Sciences at the University of Copenhagen in Denmark have developed a novel, reliable assay for detection of S. vulgaris in the bloodstream.

Martin Nielsen, DVM, PhD, Dipl. EVPC, assistant professor at the Gluck Equine Research Center, described S. vulgaris as the most dangerous of all equine parasites, largely due to its extensive larval migrations in the horse’s arterial system. The larvae make their way to the horse’s bloodstream and spend about four months there before returning to the intestine. During their migration the larvae cause a pronounced inflammation in the arterial wall and cause large blood clots to form. Smaller clots can detach and travel down larger blood vessels until they block smaller vessels. This can deprive parts of the intestinal tract from oxygen and nutrients and cause life-threatening colic.

Currently, detection of S. vulgaris infection is based on a time-consuming larval culture with subsequent microscopic examination or a recently developed PCR detecting DNA extracted from parasite eggs. No diagnostic method has been proven useful for detecting migrating larvae of S. vulgaris while still in the blood, Nielsen said. The larval culture and PCR assay both detect the adult worms present in t