The resistance of nematode parasites in sheep against anthelmintic drugs widely used in Western Turkey.

This study was carried out in seven sheep herds infected by gastro-intestinal nematodes in the Afyonkarahisar district (Western Turkey) from June to July 2005. Sixty sheep in each herd were distributed into 3 groups as anthelmintic treatment groups along with a control group containing 15 animals. The anthelmintic groups were treated with albendazole (7.5 mg/kg BW), oxfendazole (7.5 mg/kg BW)-oxyclosanide (15 mg/kg BW) combination and ivermectin (0.2 mg/kg BW-injectable). The faecal samples were collected before treatment and after 10 days of treatment. Nematode egg counts per gram of faeces (EPG) were examined in the faecal samples using the McMaster technique. To identify the genus, the faecal samples were cultured. The faecal egg count reduction test (FECR) was employed to determine the resistance. In ivermectin treated groups, the FECR% values and the lower confidence limits were estimated as A: 68.57(14.77), B: 46.42(22.47), C: 84.41(35.38), D: 95.23(61.64), E: 97.14(76.94), F: 65.21(80.46) and G: 91.66(31.69), respectively. In the A, B, C, F and G herds, statistical analysis showed that the FECR% values were less then 95% and the estimated lower confidence limits were less then 90%. In all herds, albendazole treated, oxfendazole-oxyclosanide treated and control group, there were no eggs in the feacal samples. In these groups, the FECR% values were 100. In ivermectin treated groups, the third stage larvae from the genera Haemonchus, Oesophagostomum, Trichostrongylus, Cooperia, Nematodirus and Ostertagia were detected in coprocultures before treatment and the larvae from the genera Haemonchus and Oesophagostomum were detected in post-treatment coprocultures in the resistant herds. In conclusion, there was no evidence of resistance in sheep gastro-intestinal nematodes against albendazole and oxfendazole-oxyclosanide; in contrast, the resistance against ivermectin was detected in five sheep herds in the Afyonkarahisar district.