Immunization of cattle with synthetic peptides derived from the Boophilus microplus gut protein (Bm86)

Survey of pyrethroids resistance in Indian isolates of Rhipicephalus (Boophilus) microplus: Identification of C190A mutation in the domain II of the para-sodium channel gene

Applicability of in vitro bioassays for the diagnosis of ivermectin resistance in Rhipicephalus microplus (Acari: Ixodidae).

ATP-binding cassette (ABC) transporters are responsible for pumping drugs across membranes and are an important drug detoxification mechanism. Since ABC transporters act on a wide spectrum of chemical compounds, they have been associated with multidrug resistance phenotype in various parasites and cancer cells. Here, we document the presence of a Rhipicephalus (Boophilus) microplus tick population (Jaguar) resistant to four acaricide classes (organophosphates (OP), synthetic pyrethroids (SP), amitraz and macrocyclic lactones (ML)) and reveal that the cattle tick has a multidrug detoxification mechanism based on ABC transporter proteins. Acaricide toxicity was assessed using the larval packet test (LPT), and mortality data were subjected to probit analysis using a susceptible strain (POA) as reference. Larvae were pre-exposed to sub-lethal doses of the ABC-transporter inhibitors, cyclosporin A (CsA) and MK571, and subsequently treated with ivermectin, abamectin, moxidectin, chlorpyriphos, cypermethrin, or amitraz in LPT. Results show that lethal concentrations 50 % (LC50) of ivermectin, abamectin, moxidectin (MLs), and chlorpyriphos (OP) were significantly reduced in larvae exposed to CsA and MK571 inhibitors in the Jaguar resistant population, but LC50 did not change in POA susceptible strain larvae. LC50 of cypermetrin (SP) and amitraz remained unchanged in inhibitor-exposed larvae, compared to larvae from Jaguar and POA strains not exposed to inhibitor. These results suggest that ABC transporter proteins can protect ticks against a wide range of acaricides and have an important implication in drug resistance development as a multidrug detoxification mechanism.

ABC transporters as a multidrug detoxification mechanism in Rhipicephalus ( Boophilus ) microplus

Survey of pyrethroid and organophosphate resistance in Brazilian field populations of Rhipicephalus (Boophilus) microplus: detection of C190A mutation in domain II of the para-type sodium channel gene.

This paper describes the susceptibility of various samples ofBoophilus microplus from the southern region of Minas Gerais State in Brazil to the 4 commonest organophosphorus acaricides employed in the area. All samples showed some degree of resistance to each of the compounds used. The resistance factor varied from 1.42 to 132.90, being less in the case of dicrotophos and fenthion than with chlorpyrifos and coumaphos.

J. O. Costa

Papers

Susceptibility of Brazilian samples of Boophilus microplus to organophosphorus acaricides.