Análise da susceptibilidade de Rhipicephalus (Boophilus) microplus aos acaricidas de contato na última década

Abstract

The countryside of Rio Grande do Sul, is in a traditional farm barn, cutting and milk, and in this context, the tick Rhipicephalus (Boophilus) microplus, is responsible for numerous losses, by their direct and indirect damages. Nowadays, resistance to acaricides, affects almost all active ingredients on the market, and there is a lack of data on this process in the region under study. The aim of this study was to understand the evolution of the susceptibility of populations Riphicephalus (Boophilus) microplus to active ingredients for use in immersion and sprinkling on the market during the last decade in the region. To do so, 439 samples of properties were analyzed in the region by tick immersion "in vitro" testing at the Veterinary Doctor s Office (CONSULVET) - Bage / RS. We evaluated the following active ingredients: amitraz, cypermethrin + ethion association, deltamethrin, and from the year 2003, a combination cypermethrin + chlorpyrifos + citronellal, yielding the following averages of efficiency: 64.3%, 83.2%, 43.3 and 82.4% respectively. Upon examining the percentages of samples with ≥ 95% efficiency, we obtained the following results: 1st five-year period (2001-2005) = 50.7%, 38.2%, 16.0% and 38.8%, as in 2 ° five-year period (2006-2010) = 24.2%, 41.7%, 4.5% and 48.9% respectively. The study showed that in the countryside of Rio Grande do Sul, there are populations of R. (B.) microplus resistant to all the principles available for application by dipping or spraying is more serious the situation of deltamethrin. It also found that associations of pyrethroid with phosphorated and citronellal are the most indicated formulations in the present, since there was a significant reduction in the efficiency levels of amitraz, over the five-year periods, especially in the last year, which may be due to the use intensity of this principle in the region and the slow selection of resistant populations. It is, therefore, evident the critical situation of tick resistance to acaricides, even in a region where the climate allows only three annual generations of the ectoparasite, and the need for measures that allow the rational and oriented use of acaricides, and management measures and knowledge about the epidemiology of the tick in the region to exert less selection pressure on populations, favoring the life of the active ingredients on the market.