关键词: 微小扇头蜱, 溴氰菊酯, 钠离子通道结构域III基因, 成虫浸渍法, 突变位点, 抗药性

Abstract: Objective　To investigate the level of deltamethrin resistance and mutation sites in the sodium iron channel gene in Rhipicephalus microplus in Huaihua City, Hunan Province, and to examine the correlation between deltamethrin resistance and mutation sites in the sodium iron channel gene in Rh. microplus. Methods　Rh. microplus was sampled from multiple yellow cattle farms in Huaihua City, Hunan Province from June to September 2022, and the level of resistance to deltamethrin was determined in ticks using the adult immersion test. The sodium iron channel domain III gene was amplified in deltamethrin⁃resistant and wild⁃type Rh. microplus using PCR assay. Following sequencing and sequence alignment, mutation sites were detected in bases. The sodium iron channel domain III gene in Rh. microplus was translated, and the signal peptide, transmembrane domain, and phosphorylation and glycosylation sites were detected in amino acid sequences. The tertiary structures of the sodium iron channel domain III protein of deltamethrin⁃resistant and wild⁃type Rh. microplus were deduced and compared, and the association between mutation sites in bases and resistance to deltamethrin was examined in Rh. microplus according the level of deltamethrin resistance, sequence alignment and protein tertiary structure. Results　The median (LC50) and 95% lethal concentrations (LC95) of deltamethrin were 121.39 mg/L and 952.61 mg/L against Rh. microplus, with a resistance factor of 9.24 and level II resistance. The sequence of the sodium ion channel domain III gene was 1 010 bp in size, and mutation sites were detected in two neighboring bases in the sequence of the sodium ion channel domain III gene in deltamethrin⁃resistant Rh. microplus. Although no signal peptides were found in the sodium iron channel domain III protein of deltamethrin⁃resistant or wild⁃type Rh. microplus, 6 transmembrane domains, 42 phosphorylation sites and 8 glycosylation sites were identified, with a significant difference in the tertiary structure of the sodium iron channel domain III protein between deltamethrin⁃resistant and wild⁃type Rh. microplus. Conclusions　Level II resistance to deltamethrin is detected in Rh. microplus in Huaihua City, Hunan Province, and two mutation sites that correlate with the emergence of deltamethrin resistance are identified in the sequence of the sodium iron channel domain III gene in deltamethrin⁃resistant Rh. microplus.

Key words: Rhipicephalus microplus, Deltamethrin, Sodium ion channel domain III gene, Adult immersion test, Mutation site, Drug resistance