Detection of Deltamethrin resistance level and association between sodium channel domain III gene mutation sites and drug resistance of Rhipicephalus microplus.

To investigate the level of Deltamethrin resistance and mutation sites in the sodium iron channel gene in Rhipicephalus microplus (R. microplus) in Huaihua City, Hunan Province, and to examine the correlation between Deltamethrin resistance and mutation sites in the sodium iron channel gene of R. microplus. A total of 600 R. microplus were 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 R. microplus using PCR assay. Following sequencing and sequence alignment, mutation sites were detected in bases. The sodium iron channel domain III gene in R. 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 R. microplus were deduced and compared, and the association between mutation sites in bases and resistance to Deltamethrin was examined in R. microplus according the level of Deltamethrin resistance, sequence alignment and protein tertiary structure. The median (LC50) and 95 % lethal concentrations (LC95) of Deltamethrin were 121.39 mg/L and 952.61 mg/L against R. 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 R. microplus. Although no signal peptides were found in the sodium iron channel domain III protein of Deltamethrin-resistant or wild-type R. microplus, 6 trans-membrane domains, 42 phosphorylation sites and 8 glycosylation sites were identified, with a significant difference in the tertiary structure of the sodium iron.