Study of the Drug Resistance Function of Ivermectin-Resistance-Related miRNAs in Haemonchus contortus

Haemonchus contortus has caused significant economic losses in many regions. The emergence of drug resistance has created new difficulties for the prevention and control of parasitic diseases in cattle and sheep. The mechanism of drug resistance to ivermectin in H. contortus is not clear; therefore, it is of great significance to study it. Non-coding RNAs, especially microRNAs (miRNAs), play important roles in drug resistance in some human tumors and insects. However, few studies have investigated whether miRNAs are involved in the regulation of drug resistance to ivermectin. In the early stages of this study, four miRNAs that may be involved in the regulation of ivermectin resistance in H. contortus were identified by high-throughput sequencing analysis of ivermectin-sensitive and -resistant strains of H. contortus. To verify whether these miRNAs are indeed related to ivermectin resistance in H. contortus, RNA interference (RNAi) experiments were performed on these miRNAs. The expression of candidate drug-resistance-related miRNA target genes before and after RNAi was detected by quantitative polymerase chain reaction. The resistance of the third-stage larvae (L3s) of H. contortus before and after RNAi was detected using 0.5% dimethyl sulfoxide and 100 µg/mL ivermectin treatment. The locomotion behavior of the L3s of H. contortus before and after RNAi was detected by counting the frequency of head thrashes and body bending. Finally, we confirmed that miR-10,025-y, miR-5960-z, miR-27-y, and miR-276-y were involved in and regulate ivermectin resistance in H. contortus.