2016, Number 4
Anthelmintic resistance status of gastrointestinal nematodes of sheep to the single or combined administration of benzimidazoles and closantel in three localities in Mexico
PDF size: 137.35 Kb.
ABSTRACTSheep production requires the constant assessment of parasitic burden and the efficacy of existing treatments for proper management. In this study, the administration of five different treatments was evaluated for the reduction of the percentage of eggs per gram of feces (EPG) shed by gastrointestinal nematodes (GIN) from sheep on three different sheep-breeding farms in Mexico (Texcoco, Estado de Mexico; Hueytamalco, Puebla; and Tlaltizapán de Zapata, Morelos). In these farms, ivermectin and benzimidazole derivatives had been routinely administered for two consecutive years. To determine whether drugs with different pharmacological properties decreased GIN fecal egg excretion, the treatments closantel (CLOS), albendazole (ABZ) and fenbendazole (FBZ) were administered alone and in combinations of CLOS + ABZ and CLOS + FBZ, to five groups of sheep, with an additional untreated control group on each farm (n = 28 per flock). Anthelmintic resistance was determined using Fecal Egg Count Reduction Tests (FECRT) as recommended in the guidelines of the World Association for the Advancement of Veterinary Parasitology. Fecal samples were collected 14 and 21 days after treatment. The anthelmintic resistance status was determined based on the reduction in the fecal egg count arithmetic mean and 95 % confidence limits. According to the FECRT, resistance developed to CLOS, ABZ, FBZ and CLOS + FBZ because the mean percentage of EPG reduction was ≤ 95 % with a lower confidence limit of ≤ 90 %. By contrast, nematode susceptibility was confirmed for the CLOS + ABZ combination, as it reduced the percentage of GIN fecal egg output by 96.46 ± 3.04 % (day 14) and 96.88 ± 3.04 % (day 21). Based on the morphometric identification of larvae, Haemonchus spp., Cooperia spp. and Teladorsagia spp. were the most abundant genera on all farms before the administration of these five treatments. In conclusion, the use of the anthelmintic combination of closantel plus albendazole may reduce the development of anthelmintic resistance in gastrointestinal nematodes.
Encalada-Mena L, Tuyub-Solis H, Ramirez-Vargas G, Mendoza-de-Gives P, Aguilar- Marcelino L, Lopez-Arellano ME. Phenotypic and genotypic characterisation of Haemonchus spp. and other gastrointestinal nematodes resistant to benzimidazole in infected calves from the tropical regions of Campeche State, Mexico. Vet Parasitol. 2014(1873-2550):246-54.
Höglund J, Gustafsson K, Ljungström BL, Engström A, Donnan A, Skuce P. Anthelmintic resistance in Swedish sheep flocks based on a comparison of the results from the faecal egg count reduction test and resistant allele frequencies of the beta-tubulin gene. Vet Parasitol. 2009;161(1-2):60-8. doi: 10.1016/j. vetpar.2008.12.001.
Torres-Acosta JF, Molento M, Mendoza de Gives P. Research and implementation of novel approaches for the control of nematode parasites in Latin America and the Caribbean: is there sufficient incentive for a greater extension effort? Vet Parasitol. 2012;186(1-2):132-42. doi: 10.1016/j.vetpar.2011.11.053.
Levecke B, Rinaldi L, Charlier J, Maurelli MP, Bosco A, Vercruysse J, et al. The bias, accuracy and precision of faecal egg count reduction test results in cattle using McMaster, Cornell-Wisconsin and FLOTAC egg counting methods. Vet Parasitol. 2012;188(1-2):194-9. doi: 10.1016/j.vetpar.2012.03.017.
Dobson RJ, Hosking BC, Jacobson CL, Cotter JL, Besier RB, Stein PA, et al. Preserving new anthelmintics: a simple method for estimating faecal egg count reduction test (FECRT) confidence limits when efficacy and/or nematode aggregation is high. Vet Parasitol. 2012;186(1-2):79-92. doi: 10.1016/j. vetpar.2011.11.049.
Torres-Acosta JFJ, Sandoval-Castro CA, Hoste H, Aguilar-Caballero AJ, Cámara-Sarmiento R, Alonso-Díaz MA. Nutritional manipulation of sheep and goats for the control of gastrointestinal nematodes under hot humid and subhumid tropical conditions. Small Rumin Res. 2012;103(1):28-40. doi: 10.1016/j. smallrumres.2011.10.016.