Prevalence of benzimidazole-resistant small strongyles in horses in a southeastern Pennsylvania practice.
A survey was conducted to determine the prevalence of benzimidazole (BZ)-resistant small strongyles in horses in a southeastern Pennsylvania practice. Resistant parasites were found in 291 of 342 horses surveyed. Anthelmintic practices and pasture management factors in use for 3 to 6 years did not correlate with the presence of resistant small strongyles. Benzimidazole-resistant small strongyles were recovered in horses that had been treated alternately with BZ and non-BZ products and in horses receiving BZ products as infrequently as twice a year. However, inasmuch as the horses may have been infected with resistant small strongyles before the various anthelmintic schedules were implemented, it was not possible to attribute BZ-resistance to any particular pattern of drug use. Fifty-one (14.9%) horses had BZ-susceptible small strongyles: these horses were on poor overall parasite control programs and had received BZ products no more than once a year. Benzimidazole-piperazine and non-BZ drugs were effective in herds infected with BZ-resistant small strongyles.
D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D001562:Benzimidazoles / Q000627:therapeutic use*; D002159:Cambendazole / Q000627:therapeutic use; D004351:Drug Resistance; D005243:Feces / Q000469:parasitology; D005273:Fenbendazole / Q000627:therapeutic use; D006736:Horses; D008463:Mebendazole / Q000627:therapeutic use; D010270:Parasite Egg Count / Q000662:veterinary; D010414:Pennsylvania; D000077489:Piperazine; D010879:Piperazines / Q000627:therapeutic use; D011716:Pyrantel Pamoate / Q000627:therapeutic use; D013319:Strongyle Infections, Equine / Q000188:drug therapy*; D013827:Thiabendazole / Q000627:therapeutic use
D000871:Anthelmintics; D001562:Benzimidazoles; D010879:Piperazines; D002159:Cambendazole; D000077489:Piperazine; D005273:Fenbendazole; D011716:Pyrantel Pamoate; D008463:Mebendazole; D013827:Thiabendazole; C011030:oxfendazole