Situation of benzimidazole resistance in Haemonchus contortus in southwestern Hungary
Among the gastrointestinal nematodes of small ruminants Haemonchus contortus has almost the most overwhelming importance. This abomasal bloodsucking parasite has been presented all over the world, and it causes enormous economic and health problems in the sheep sector. A total of 189 adult male H. contortus worms were collected from sheep, bred southwestern Transdanubian region of Hungary, for monitoring whether the long-term usage of benzimidazoles could affect their effectiveness. The summarised allele frequencies, analyzed by RFLP-PCR, were 36.24% and 63.76% in case of susceptible and resistant ones, respectively. The proportion of homozygous susceptible (23.28%) and heterozygous (25.93%) worms were similar and the portion of homozygous resistant was about twice as much (50.79%). The correlation was pronouncedly significant between resistance allele frequency and the usage of benzimidazoles. According to our results, it seems the BZ resistance has appeared and extended within Haemonchus contortus in Hungarian sheep flocks.