Recent study results showed that the presence of S. vulgaris was significantly associated with the time elapsed since the most recent deworming. | Photo: Kristen M. Janicki

Results from a recent study performed on American and Danish horses identified an association between selective treatment and occurrence of the most pathogenic (capable of producing disease) parasite, Strongylus vulgaris, said Martin Nielsen, DVM, PhD, EVPC, assistant professor in the Department of Veterinary Science at the Gluck Equine Research Center.

In the study, presence of S. vulgaris was significantly associated with the time elapsed since a horse’s most recent deworming. Frequent anthelmintic treatments tend to eliminate S. vulgaris completely.

The study involved 991 horses representing 53 different horse farms in Denmark and Central Kentucky. The data were subdivided based on whether farms used selective therapy as a treatment strategy and the time since the most recent deworming. The Danish results indicated a possible association between selective therapy use and S. vulgaris occurrence in both individual horses and at horse farms in Denmark