Susceptibility profile and associated factors analysis of Rhipicephalus microplus for 5 chemical groups on 47 populations from the north of Uruguay.

Abstract

Acaricide resistance of Rhipicephalus microplus tick in Uruguay means a serious problem that has been worsening through years hitting a high point with the detection of multiresistant populations on 2009. Therefore, the aim of this study was to analyze resistance for cypermethrin, ethion, amitraz, fipronil, ivermectin and flumethrin on 47 populations between years 2017 and 2018 by using the Larval Packet Test and a quiz made to the responsible for the farm. Results show that 46 from the 47 populations analyzed were resistant to pyrethroids. This chemical group also showed the largest number of resistant populations with a high grade of resistance. Every population showed to be resistant to at least one chemical group furthermore the 68,1% of the populations were resistant to at least 3 chemical groups simultaneously but no population was diagnosed resistant to the 5 chemical groups analyzed neither to be susceptible to all 5 chemical groups. It stands out that there were populations resistant to some chemical groups that the farms of origin had never used. There were registered a higher number of treatments done per year to control R. microplus, than the one recommended for a generational treatment. For every active ingredient evaluated, there were suspicions of resistance that the Larval Packet Test could not confirm. This reflects the complex situation of these farms in what refers to acaricide resistance of R. microplus. This may be related to the way, frequency and time acaricides had been used on these farms, as well as using them for other purposes and also due to the impact of the income of animals infested with R. microplus from other origins.