Identification of a mutation in the para-sodium channel gene of the cattle tick Rhipicephalus (Boophilus) microplus associated with resistance to synthetic pyrethroid acaricides

Abstract

Accepted ManuscriptIdentification of a mutation in the para sodium channel gene of the cattle tick Rhipicephalus (Boophilus) microplus associated with resistance to synthetic pyrethroid acaricides This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Resistance against synthetic pyrethroid (SP) products for the control of cattle 20 ticks in Australia was detected in the field in 1984, within a very short time of 21 commercial introduction. We have identified a mutation in the domain II S4-5 linker 22 of the para-sodium channel that is associated with resistance to SPs in the cattle tick 23 ACCEPTED MANUSCRIPTRhipicephalus (Boophilus) microplus from Australia. The cytosine to adenine 24 mutation at position 190 in the R. microplus sequence AF134216, results in an amino 25 acid substitution from leucine in the susceptible strain to isoleucine in the resistant 26 strain. A similar mutation has been shown to confer SP resistance in the whitefly, 27Bemisia tabaci, but has not been described previously in ticks. A diagnostic 28 quantitative PCR assay has been developed using allele-specific Taqman® minor 29 groove-binding (MGB) probes. Using the assay to screen field and laboratory 30 populations of ticks showed that homozygote allelic frequencies correlated highly 31 with the survival percentage at the discriminating concentration of cypermethrin. 32

Acaricide resistance mechanisms in Rhipicephalus (Boophilus) microplus

“…Molecular studies did not find the Domain III sodium channel mutation of Guerrero et al (2001), thus suggesting a novel sodium channel mutation was present in the Santa Luiza strain. We have now confirmed that Santa Luiza contains the Morgan et al (2009) Domain II mutation and this likely leads to the permethrin resistance phenotype of this Brazilian strain (F. GUERRERO, unpublished data).…”

“…The Domain II mutations are reported to convey lesser levels of resistance. The leucine to isoleucine change reported by Morgan et al (2009) conveys moderate levels (100-400-fold estimates) of resistance to permethrin, cypermethrin, and flumethrin, while the glycine to valine change was flumethrin resistance-specific and seemed to provide lower levels of resistance (JONSSON et al, 2010). Thus there are at least three target site mechanisms for pyrethroid resistance in R.…”

“…Our own survey, although limited in scope, also has not found the Domain III sodium channel mutation in either Brazilian or Australian tick populations (Table 1). However, recently Morgan et al (2009) andJonnson et al (2010) have reported nucleotide differences in the Domain II region of the R. (B.)…”

“…These nucleotide differences in the Australian cattle tick sodium channel gene led to amino acid changes that correlated with pyrethroid resistance. In the case of the Morgan et al (2009) report, the amino acid change is from leucine to isoleucine, while the change in the Jonsson et al (2010) report is a glycine to valine.…”

“…microplus. The Domain III mutation seems to be localized to North America, the Morgan et al (2009) mutation was discovered in Australia but has been seen outside of Australia (Table 1) Li et al (2008) had reported genetic and synergist studies on the 93-fold permethrin resistance of Santa Luiza. Metabolic resistance was ruled out by the lack of significant synergism of pyrethroid resistance by PBO, DEM, or TPP.…”