Práticas de controle e perfil de suscetibilidade de Haematobia irritans irritans (Linnaeus, 1758) (Diptera: Muscidae) e Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Acari: Ixodidae) à cipermetrina e clorpirifós na mesorregião do Triângulo Mineiro e Alto Paranaíba, MG, 2010

Abstract

This study aimed to characterize control practices adopted for controlling the horn fly, Haematobia irritans, and the cattle tick, Rhipicephalus (Boophilus) microplus, in cattle ranches in the regions of Triângulo Mineiro and Alto Paranaíba, Minas Gerais state, as well as to evaluate the susceptibility of these parasites to the pyrethroid cypermethrin and the organophosphate chlorpyrifos, and verify the occurrence of the mechanism of resistance to pyrethroids - target site insensitivity mediated by the T2134A substitution in the segment S6 domain III of the sodium channel, in R. (B.) microplus populations. Twenty-three ranches were visited on April/2010 and structured interviews were conducted to characterize parasite control practices. Insecticide susceptibility of horn flies to cypermethrin and chlorpyrifos was assessed in nine and two ranches, respectively, by the impregnated filter paper bioassay. Susceptibility of cattle tick populations to both active ingredients was evaluated by the Larval Packet Test, in individuals from seven ranches. Mutation occurrence was evaluated by an allele specific PCR in larvae of R. (B.) microplus from 10 ranches. Most of the interviewees were aware of characteristics regarding the epidemiology of parasites, but control of parasites was made without technical criteria. Despite recognizing the importance of H. irritans, its control was not a routine practice in 82.61% ranches. All horn fly populations were resistant to cypermethrin (47.3 < RF < 400.6) and susceptible to chlorpyrifos (RF < 0.01), while all R. (B.) microplus populations were resistant to cypermethrin (16.0 < RF < 25.0) and 85.71% to chlorpyrifos (2.2 < RF < 15.6). All cattle tick larvae were homozygous susceptible to the studied mutation.