PCR-RFLP STUDY ON DRUG RESISTANCE OF HAEMONCHUS CONTORTUS TO BENZIMIDAZOLE IN SHEEP, NORTH REGION OF IRAN.

Haemonchosis is one of the most important parasitic diseases of the gastrointestinal tract of small ruminants in different parts of Iran and worldwide. While the disease poses major economic problems in the livestock industry, there are many reports on parasites' resistance to benzimidazoles necessitating to study of the level of this drug resistance in pathogens. The aim of this study was to evaluate the drug resistance of Haemonchus contortus to benzimidazole using molecular method in sheep from the North region of Iran. In this study, the resistance to benzimidazole was investigated using the PCR-RFLP method in the nematode Haemonchus contortus from sheep slaughtered in the northern region of Iran (Gilan and Mazandaran provinces). The samples examined in this study were evaluated between April 2020 and September 2021 from a total of 2400 sheep by determining the age groups of <2 years, 2>4 years, and >4 years. Three hundred Haemonchus contortus nematodes were randomly selected and investigated by means of PCR-RFLP and using TaaI endonuclease enzyme (SNP) in the beta-tubulin gene, responsible for drug resistance of Haemonchus contortus to benzimidazole. Haemonchus contortus was found in 66.8% and 60.5% of sheep in Gilan and Mazandaran. The results of the study showed that the drug sensitivity rate was 24% (72/300), the drug resistance rate was 54% (162/300) and 22% (66/300) of the samples had both resistant and sensitive alleles. Presented data showed a high level of prevalence of drug resistance in the nematode Haemonchus contortus in sheep in the northern region of Iran, which requires special attention to control the development of this resistance and the epidemic of haemonchosis in ruminants. [ABSTRACT FROM AUTHOR]