An egg hatch assay using albendazole for in vitro detection of resistance of sheep and goat nematodes to anthelmintics

To detect resistance of nematodes in sheep and goats to benzimidazoles(BZS) by albendazole(ALB),25 samples collected from 23 farms were examined simultaneously by ALB and thiabendazole(TBZ) in egg hatch assay(EHA),and the comparison of resistance-to-BZs was carried out between faecal egg count reduction test(FECRT)and EHA.The mean LD50 of ALB and TBZ in all samples were 0.050 1 μg/mL and 0.054 0 μg/mL,respectively,and there was no significant difference between them.On 4 farms where resistance-to-BZs was detected by FECRT,the mean LD50 values were over 0.1 μg/mL in 75% of samples for ALB and TBZ,and the LD50 values were 0.068 9 μg/mL for ALB and 0.071 2 μg/mL for TBZ on 1 farm out of the 4 farms.On another 2 farms where the suspected isolates were detected by FECRT,and the LD50 values ranged from 0.04 to 0.07 μg/mL.In worm populations which were susceptible to BZs in FECRT,the LD50 values were lower than 0.04 μg/mL.In addition,the effect of DMSO-dissolved ALB solution which had been stored at 4 ℃ for 7 days on the LD50 values in vitro was not significant,indicating that the efficacy of ALB in solvent was steady,but its efficacy declined after 14 days of storage.