Anthelmintic control practices in large equine farms from Argentina

Abstract

Due to the global background of increasing anthelmintic resistance in horses in Argentina, knowledge about
parasite control practices and the use of drugs by veterinarians in the field is essential to formulate
sustainable strategies and programs for control of the main nematodes. In this context, a survey was carried
out interviewing 80 veterinarians specialized in equine medicine in personal interview or by telephone.
These veterinarians are responsible for the general health of 85 equine establishments that produce saddle
horses in the central and northern areas of Argentina. Parasite control was studied in 17,711 horses (with 48 to 1,860 animals per farm). In more than 65% of the farms, horses were treated with a frequency of 3
and 4 times a year. Ivermectin was the most widely used anthelmintic (99% of farms), followed by
benzimidazoles (44%), pyrantel (13%), and moxidectin/oxfendazole combinations (6%). Despite the
documented information in the country indicating the resistance of Parascaris spp to macrocyclic lactones
and of small strongyles to benzimidazoles (the latter being extremely widespread), the use of these drugs
to control these parasites continues in the region.Veterinary practitioners involved with horses must monitor
and know the efficacy of anthelmintics in each farm before carry out parasite control programs. This
information is critical since anthelmintic resistance should be considered as probable in foals and adults
and neither of the two most widely used chemical groups in the central area of Argentina, can be considered
as broad-spectrum anthelmintics without previous evidence of their efficacy.