Mutation in the sodium channel gene corresponds with phenotypic resistance of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) to pyrethroids

Authors: KLAFKE, GUILHERME - Desiderio Finamore Veterinary Research Institute (FEPAGRO); Miller, Robert; Tidwell, Jason; BARRETO, RAFAEL - Desiderio Finamore Veterinary Research Institute (FEPAGRO); Guerrero, Felicito; KAUFMAN, PHILLIP - University Of Florida; Perez De Leon, Adalberto - Beto

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2017
Publication Date: 11/7/2017
Citation: Klafke, G.M., Miller, R., Tidwell, J.P., Barreto, R., Guerrero, F., Kaufman, P., Perez De Leon, A.A. 2017. Mutation in the sodium channel gene corresponds with phenotypic resistance of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) to pyrethroids. Journal of Medical Entomology. 54(6):1639-1642.

Interpretive Summary: Rhipicephalus sanguineus, commonly known as the brown dog tick, is a parasite of domestic dogs that can transmit severe and lethal diseases to humans and animals. The use of chemical pesticides represents the most common practice to control tick populations. However, ticks can adapt and develop resistance to these compounds impairing control methods. Resistance to synthetic pyrethroids is common among different species of pests of medical, agricultural, and veterinary importance and can be conferred by a single nucleotide point mutation (SNP) in the voltage-sensitive sodium channel (vssc) gene, which is the target of this class of pesticides. In this study we present the discovery of a SNP in the vssc gene in a highly resistant isolate of R. sanguineus collected in Florida. This is the first description of a mutation associated with pesticide resistance in the brown dog tick. This SNP can be used as a molecular marker of resistance, and molecular assays based on this knowledge could be developed to diagnose the risk for pyrethroid resistance. All this knowledge can inform decisions on integrated brown dog tick management practices.

Technical Abstract: The brown dog tick, Rhipicephalus sanguineus sensu lato, is a cosmopolitan ectoparasite and vector of pathogens that kill humans and animals. Pyrethroids represent a class of synthetic acaricides that have been used intensely to try to control the brown dog tick and mitigate the risk of tick-borne disease transmission. However, acaricide resistance is an emerging problem in the management of the brown dog tick. Understanding the mechanism of resistance to acaricides, including pyrethroids, is important to adapt brown dog tick control strategies. The main objective of this study was to determine if target-site mutations associated with pyrethroid resistance in other pests could be associated with phenotypic resistance detected in a brown dog tick population from Florida. We amplified segment 6 of the domain III of the voltage-sensitive sodium channel protein using cDNAs synthesized from pyrethroid-susceptible and -resistant tick strains. A single nucleotide point mutation (SNP) identified in a highly conserved region of domain III S6 in the resistant ticks resulted in an amino acid change from phenylalanine to leucine. This mutation is characteristic of resistance phenotypes in other pest species, and is the first report of this mutation in R. sanguineus. Molecular assays based on this knowledge could be developed to diagnose the risk for pyrethroid resistance, and to inform decisions on integrated brown dog tick management practices.