Distribution Patterns of Three Sodium Channel Mutations Associated with Pyrethroid Resistance in Rhipicephalus (Boophilus) Microplus Populations from North and South America, South Africa and Australia

Authors: LOVIS, LEONORE - University Of Switzerland; Guerrero, Felicito; Miller, Robert; Bodine, Deanna; BETSCHART, BRUNO - University Of Switzerland; SAGER, HEINZ - Novartis

Submitted to: International Journal for Parasitology: Drugs and Drug Resistance
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2012
Publication Date: 9/3/2012
Citation: Lovis, L., Guerrero, F., Miller, R., Bodine, D.L., Betschart, B., Sager, H. 2012. Distribution Pptterns of three sodium channel mutations associated with pyrethroid resistance in Rhipicephalus (Boophilus) microplus populations from North and South America, South Africa and Australia. International Journal for Parasitology: Drug and Drug Resistance. 2:216-224.

Interpretive Summary: Resistance to synthetic pyrethroids (SP) in the cattle tick Rhipicephalus (Boophilus) microplus is widespread throughout its distribution area. Mutations in the sodium channel gene of R. (B.) microplus are known to be associated with target site pyrethroid resistance. We developed a diagnostic PCR assay to detect the presence of 3 documented pyrethroid resistance-associated sodium channel mutations in the cattle tick. This assay was used to screen tick samples originating from Brazil, Argentina, Mexico, South Africa and Australia whose resistant phenotype to flumethrin and cypermethrin had been determined by various bioassay techniques. These mutations were found to have distinct geographical distributions and result in different resistance phenotypes. A C->A mutation in Domain II of the sodium channel conferring resistance to various SP compounds was found in all the Brazilian, Argentinean and Australian populations and in one South African population. In contrast, this mutation was not found in samples from Mexico, while a sodium channel mutation in the Domain III region was found exclusively in this country. Our global survey shows the widespread distribution of the C->A Domain II mutation and provides evidence of its geographic separation from the Domain III mutation.

Technical Abstract: Resistance to synthetic pyrethroids (SP) in the cattle tick Rhipicephalus (Boophilus) microplus is widespread throughout its distribution area. Three single nucleotide substitutions identified in the Domains II and III of the sodium channel gene of R. (B.) microplus are known to be associated with target site pyrethroid resistance. We developed a multiplex PCR using allele-specific primers to amplify wild type or mutated genotypes of the three mutations simultaneously. This assay was used to screen tick samples originating from Brazil, Argentina, Mexico, South Africa and Australia whose phenotype to flumethrin and cypermethrin had been determined by the use of the Larval Tarsal test (LTT) or the Larval Packet Test (LPT). These mutations were found to have distinct geographical distributions and result in different resistance phenotypes. The C->A Domain II mutation conferring resistance to various SP compounds was found in all the Brazilian, Argentinean and Australian populations and in one South African population, with frequencies between 38% and 100% in flumethrin and cypermethrin resistant populations. In contrast, this mutation was not found in samples from Mexico, while the Domain III mutation was found exclusively in this country. The Domain II flumethrin-specific mutation was found in a single Australian population, at a very low frequency (6%). The homozygous resistant RR genotype of the C->A Domain II mutation correlated significantly with the survival rates at the discriminating doses of flumethrin and cypermethrin. This survey shows the widespread distribution of the C->A Domain II mutation and provides evidence of its geographic separation from the Domain III mutation.