The damage caused by cyathostomins at the gut level may be assessed by measuring the levels of the LDH activity. The topical application of a 1 mg/kg BW IVM dose provides very effective results against the intestinal parasites infecting grazing horses. By taking into account the ease and safety of administration, this formulation is strongly advised for deworming of horses under an extensive regime or in cases when their correct immobilization is not possible