Detection of pyrethroids resistance alleles in goat biting louse Bovicola caprae (Phthiraptera: Trichodectidae) in west and northwest of Iran

Pyrethroid insecticides target voltage-gated sodium channels (VGSCs) that are essential for electrical signaling in the nervous system of insects. Three-point mutations at the corresponding amino acid sequence positions M۸۱۵I, T۹۱۷I, and L۹۲۰F located in domain II conferring the knockdown resistance (kdr) are the most important mutations in pyrethroid-resistant lice worldwide. In addition, six new mutations have been reported in the extracellular loops IIS۱-۲ (H۸۱۳P) and IIS۵ (I۹۲۷F, L۹۲۸A, R۹۲۹V, L۹۳۰M, L۹۳۲M) in the α- subunit of the sodium channel in lice. The aim of this study was to detect alleles resistant to pyrethroids in the domain II (S۵-S۶) of the VGSC gene in goat biting louse. Goat biting lice were collected from five provinces in the west and northwest of Iran. Genomic DNA was extracted from goat biting lice and Bovicola (Damalinia) caprae species was confirmed by amplifying the cytochrome oxidase subunit I (COXI) gene. A fragment in the domain II (S۵-S۶) of the VGSC gene was amplified using the specific primers and the resultant polymerase chain reaction products were sequenced. Substitutions T۹۱۷I, L۹۲۰F, I۹۲۷F, L۹۲۸A, R۹۲۹V and L۹۳۰M were identified in the examined sequences. The results showed that all the examined lice had at least one mutation in their VGSC gene associated with pyrethroid resistance or new mutations. The presence of these mutated alleles in the VGSC gene may be due to the long-term and multiple use of pyrethroids against arthropods. Thus, the molecular detection of resistance to pyrethroid insecticides in goat chewing lice can help plot a kdr frequency map to enact effective policies to control caprine pediculosis.

Keywords:

Bovicola caprae , Goat , knockdown resistance , VGSC gene