A pilot study on the potency of injectable vs. oral moxidectin formulation to suppress strongyle egg excretion in horses at twice lower dose

The aim of present study was to examine the potency of moxidectin solution (Cydectin 1 %; Zoetis) and commercially available oral moxidectin gel (Equest®; Zoetis) to suppress the excretion of strongyle eggs in horses over a 6-week period. The horses naturally infected with strongyle nematodes (>500 eggs/g of feces) were divided into two comparable groups according age, sex and weight. On day 0 of the study, horses in Group OT (oral treatment; N=5) were dewormed with moxidectin gel (Equest®; Zoetis; 0.4 mg/kg of b.w.) according to the manufacturer’s instructions, and horses in Group IT (intramuscular treatment; N=4) were dewormed with moxidectin injectable solution (Cydectin 1 %; Zoetis; 0.2 mg/kg of b.w.). Stool samples were collected rectally, on day 0, 17, 28, 35, and 42 of the study and examined using a modifi ed McMaster technique (Roepstorff et al., 1998) with modifi cations. The mean strongyle egg excretion has signifi cantly decreased in Group IT (P<0.01) and Group OT (P<0.001) on day 17 post treatment as compared to those on day 0. The effi cacy of oral gel (99.43 %) and injectable moxidectin (99.32 %) formulations was therefore high and comparable and no resistance of strongylids to moxidectin was recorded. On day 35 (P<0.001) and 42 (P<0.05) post treatment, the mean effi cacy was signifi cantly higher in Group IT as compared to Group OT. The present study contributes to the existing knowledge and providing more information on the use of injectable MOX solution for the treatment of strongylid infection in horses.