Implementation of the Tick GenerationalTreatment in the Eradication of a Multiresistant Population of Rhipicephalus (Boophilus) microplus in Uruguay

Abstract

A methodology to eradicate a multiresistantRhipicephalus (Boophilus) microplus tick population is described based on Tick Generation Treatment concept. The active ingredient used (Ivermectin, Fipronil and Fluazuron), were selected as a result of the bioassay performed on adult tick (Drummond test) and in larvae (Stone & Haydock test). In vitro tests led to the first official diagnostic of resistance to Amitraz in Uruguay. The bovines presented high tick infestation and were in enzootic stability to Babesia bovis, Babesia bigemina and Anaplasma sp. (more than 85% positive serology). The frequency of treatments and the moment to rotate the active ingredient were based on previous knowledge of the efficacy and residual period of the acaricide. Calves were artificially immunized due to the high risk of getting blood parasites when decreasing burden of ticks. Animals were monthly inspected to determine efficacy treatment, number and tick stage. Calves were serologically followed prior to immunization. This strategy assures suppressive treatment using a different molecule of acaricide in each generation of ticks per year, optimizing the use of molecules effective and in turn to minimize selection pressure expands the emergence of resistance. Time needed to eradicate tick was 28 months,  involving 2 tick periods. Operative mistakes and adverse weather conditions were responsible of maintaining the non-parasitic cycle. Field treatment evaluations were monthly performed.