Development of resistance to anthelmintics is a threat to equine welfare. As with antibiotics, restrictive use with anthelmintics in order to retain the effect is essential. Current recommendation for deworming is targeted selective treatment to individuals shedding a certain amount of parasite eggs. Clinic veterinarians and pathologists have in recent years observed an increase in parasite-related injuries. In parallel, data from the SVA indicate an increase in the frequency of the large bloodworm. The aim of this Norwegian-Swedish collaboration is to investigate whether selective deworming can be linked to an increase in the prevalence of the parasite and parasite-related damages, and to develop a PCR-based test for rapid diagnostic and lastly to validate the effect of grazing hygienic measures as a complement to deworming. It is vital for the horse industry to apply sustainable practices for parasite control in order to minimize the negative health impact of parasitic infections.