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Background <p>Brown dog ticks, <i>Rhipicephalus sanguineus</i> sensu lato (s.l.), have spread globally and are an important vector of multiple pathogens affecting both dogs and humans. The control of these ticks on dogs and human dwellings often relies on synthetic pyrethroids, a chemical class of acaricides that targets the voltage-gated sodium channel (VGSC) protein of arthropod nerve cells, causing influxes of sodium and ultimately, paralysis. Invasive <i>Rhipicephalus sanguineus</i> s.l. ticks in the Americas can be broadly grouped into two main lineages: temperate and tropical (<i>Rh. sanguineus</i> sensu stricto (s.s.) and <i>Rh. linnaei</i>, respectively). Phenotypic resistance to synthetic pyrethroids in a verified <i>Rh. sanguineus</i> s.s. population has only been reported in the state of Rio Grande do Sul, Brazil. The objectives of our study were to 1) screen a small number (<i>n</i> = 10) of <i>Rh. sanguineus</i> s.s. from Brazil to check for <i>VGSC</i> gene mutations known to be associated with resistance to synthetic pyrethroids in ticks and other arthropods, and 2) provide molecular confirmation that all ticks were <i>Rh. sanguineus</i> s.s.</p> Methods <p>We used next-generation DNA sequencing methods to analyze the <i>VGSC</i> gene and mitochondrial loci (<i>12S</i>, <i>16S</i>, <i>COI</i>) of 10 brown dog ticks sampled from a stray dog in the Restinga sub-district of Porto Alegre, Rio Grande do Sul, Brazil. The progeny of other ticks from this animal had previously been shown to display a low level of resistance to deltamethrin.</p> Results <p>Analysis of mitochondrial genes confirmed these ticks were <i>Rh. sanguineus</i> s.s. We identified two known resistance mutations in domain II segments 4 and 5 of the <i>VGSC</i> gene (C190A and G215T). These specific mutations have not been reported previously in any brown dog tick lineages from the Americas, and this is the first case of <i>VGSC</i> mutations described from ticks confirmed to be <i>Rh. sanguineus</i> s.s. using genetic analyses.</p> Conclusions <p>The discovery of these mutations in <i>Rh. sanguineus</i> s.s. is important for the effective management of ticks on dogs in Brazil and other countries where brown dog tick infestations occur.</p> Graphical Abstract <p></p>

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First report of VGSC mutations for resistance to synthetic pyrethroids in brown dog ticks (Rhipicephalus sanguineus sensu stricto) from Brazil

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月21日

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  • Hayden Kleinschmidt,
  • Nathan E. Stone,
  • Rebecca Ballard,
  • Natalie B. Thornton,
  • Grant L. Pemberton,
  • Simone Becker,
  • Guilherme M. Klafke,
  • David M. Wagner,
  • Joseph D. Busch

摘要

Background

Brown dog ticks, Rhipicephalus sanguineus sensu lato (s.l.), have spread globally and are an important vector of multiple pathogens affecting both dogs and humans. The control of these ticks on dogs and human dwellings often relies on synthetic pyrethroids, a chemical class of acaricides that targets the voltage-gated sodium channel (VGSC) protein of arthropod nerve cells, causing influxes of sodium and ultimately, paralysis. Invasive Rhipicephalus sanguineus s.l. ticks in the Americas can be broadly grouped into two main lineages: temperate and tropical (Rh. sanguineus sensu stricto (s.s.) and Rh. linnaei, respectively). Phenotypic resistance to synthetic pyrethroids in a verified Rh. sanguineus s.s. population has only been reported in the state of Rio Grande do Sul, Brazil. The objectives of our study were to 1) screen a small number (n = 10) of Rh. sanguineus s.s. from Brazil to check for VGSC gene mutations known to be associated with resistance to synthetic pyrethroids in ticks and other arthropods, and 2) provide molecular confirmation that all ticks were Rh. sanguineus s.s.

Methods

We used next-generation DNA sequencing methods to analyze the VGSC gene and mitochondrial loci (12S, 16S, COI) of 10 brown dog ticks sampled from a stray dog in the Restinga sub-district of Porto Alegre, Rio Grande do Sul, Brazil. The progeny of other ticks from this animal had previously been shown to display a low level of resistance to deltamethrin.

Results

Analysis of mitochondrial genes confirmed these ticks were Rh. sanguineus s.s. We identified two known resistance mutations in domain II segments 4 and 5 of the VGSC gene (C190A and G215T). These specific mutations have not been reported previously in any brown dog tick lineages from the Americas, and this is the first case of VGSC mutations described from ticks confirmed to be Rh. sanguineus s.s. using genetic analyses.

Conclusions

The discovery of these mutations in Rh. sanguineus s.s. is important for the effective management of ticks on dogs in Brazil and other countries where brown dog tick infestations occur.

Graphical Abstract