Survey of anthelmintic resistance in a Romanian horse stud using three different methods.

Resistance of cyathostomins to benzimidazole (BZ) anthelmintics is widespread in horses in many parts of the world. This study compared three methods for the determination of benzimidazole resistance of Cyathostominae in 18 horses from a stud farm in Romania. The horses were treated with Fenbendazole. The resistance test was performed by FECRT, ERP and PCR. On Day 0, larvae of species belonging to the Cyathostominae subfamily, types A, B, C, D and Gyalocephalus, as well as Strongylus vulgaris species of the Strongylinae subfamily, were identified. At 42 days post treatment with fenbendazole only larvae of Cyathostominae, types A and D were identified. Resistance to Fenbendazole was found in one horse, using the FECRT and ERP tests. Both genetic resistance and susceptibility to BZ anthelmintics was observed in 13 samples (72.22%) using the PCR test. However, three samples (16.67%) showed only the BZ-susceptibility gene. In 2 samples, (11.11%) only the resistance gene to BZ anthelmintics was identified. Several inconsistencies in the evidence of resistance to benzimidazole were observed between the PCR test and the other two methods, which indicates that several methods for determining and controlling the resistance should be used in practice.