Anthelmintic efficacy against gastrointestinal nematodes in goats raised under mountain farming conditions in northern Italy

BACKGROUND: This study aimed to evaluate the efficacy of anthelmintics in goats raised under mountain farming conditions in northern Italy. On 8 goat farms (n = 143 animals), a faecal egg count reduction (FECR) test was done after farmers conducted their routine anthelmintic treatments. Furthermore, on 5 goat farms (n = 135 animals) a FECR test was done under controlled conditions applying oral formulations of a macrocyclic lactone (ML), benzimidazole (BZ) (partly in combination with salicylanilide (SA)) or a combination of imidazothiazole (IT) and SA on the same farm. AR was assumed if FECR and the upper confidence interval (CI) was < 95% and the lower 95% CI was < 90%. RESULTS: Underdosing was found in 6 of the 8 farms tested after routine treatments. Out of the 6 routinely ML-treated goat flocks, only three were found where ML showed adequate efficacy. FECR in all others ranged between 64 and 93%. In one flock Trichostrongylus spp. and in one Haemonchus spp. larvae were identified after treatment. BZ-treated flocks had an efficacy of 99 and 37%. Larvae identified after treatment were Trichostrongylus spp. in one and Haemonchus spp. in the other flock. Under controlled conditions, ML had an adequate efficacy on 4 farms and a FECR of 88% on another one. BZ was effective on all farms. The combination of BZ and SA had a FECR of 99% on the farm it was tested. IT + SA in combination was effective on 2 farms and had a FECR of 91% on a third farm. Larvae identified after treatment were composed of Haemonchus spp. (ML and BZ), Trichostrongylus spp. (BZ) and Teladorsagia spp. (BZ and SA). CONCLUSIONS: This first report on the prevalence of AR in goats in the mountainous region of South Tyrol reveals a low efficacy of the most commonly used anthelmintics after routine treatments. This might be explained by a high level of underdosing as observed in the farms. However, results from the controlled FECR tests suggest that the observed level of AR was lower but cannot be solely explained by underdosing.