First report of anthelmintic resistance among sheep in six farms from three governorates in Jordan.

This study aimed to identify the presence of gastrointestinal nematode populations resistant to albendazole, levamisole, and ivermectin in six farms located in three regions of Jordan (Irbid, Mafraq, and Ma'an). Infected sheep (40 per farm) with at least 100 eggs per gram were randomly divided into four groups (10 animals per group). Three groups were treated with ivermectin, albendazole, or levamisole while the fourth group was used as a negative control group. The standard faecal egg count reduction test (FECRT) was used to assess the drugs' efficacy. Resistance to ivermectin and albendazole was detected in all studied farms while resistance to levamisole was detected in four of the sampled farms. FECRT ranged from 55.6 % (90 % Confidence Intervals (CI): 29.6 % - 79.6 %) to 80.3 % (CI: 48.3 % - 92.1 %) for ivermectin, 77.4 % (CI: 53.2-86.7 %) to 95 % (CI: 85.8-97.6 %) for albendazole, and 86 % (CI: 46.1-95.6 %) to 99.4 % (CI: 97.6-99.7 %) for levamisole. Post-treatment copro-cultures, faecal floatation and/or Baermann technique indicated the presence of larvae of Haemonchus spp. in all of the sampled farms, followed by Nematodirus spp. in four farms, Trichostrongylus spp. in three farms, then Marshallagia spp. in one farm. This is the first study of its kind in Jordan that shows widespread anthelmintic resistance for gastrointestinal nematodes in geographically distant sheep farms in Jordan. Such widespread resistance to anthelmintics imposes a risk of failure to the present control programs and urges for changing the methodology of selecting effective anthelmintic treatments in local farms.