Efficacy of two extra-label anthelmintic formulations against equine strongyles in Cuba

Equine cyathostomin parasites are ubiquitous in grazing horses and have been shown to cause severe inflammatory disease in the large intestine of horses. Decades of intensive anthelmintic therapy have led to widespread anthelmintic resistance in cyathostomins across the world. In Cuba, no anthelmintic products are formulated and sold for equine usage and little is known about anthelmintic efficacy of ruminant and swine formulations used. A strongyle fecal egg count reduction test was used to assess the efficacy of a liquid formulation of ivermectin labelled for use in swine, ruminants and carnivores and a pelleted formulation of albendazole labelled for usage in ruminants. Nine farms in the province Camagüey were enrolled in the study comprising 149 horses in total. Albendazole efficacy was reduced on five farms and with the other four farms having no signs of reduced efficacy. Mean farm efficacies were ranging from 41.7% to 100% on the tested farms. Coprocultures found large strongyle larvae present on all farms, but all larvae identified post-treatment were cyathostomins. Ivermectin was found 100% efficacious on all studied farms. This study provided evidence of reduced albendazole efficacy in the study population. Further work is needed to evaluate whether these findings reflect true resistance or if they are due to pharmacokinetic or pharmacodynamic characteristics of the pelleted formulation tested here.