RESUMO
The present study demonstrated the efficacy of a pour-on formulation of fluazuron 2.5 % and flumethrin 1 % (Drastic Deadline eXtreme®) against Rhipicephalus decoloratus and Rhipicephalus microplus on cattle on pasture previously grazed by experimentally infested animals. Six tick-free cattle were placed on the pasture and treated 7 days later (Day 0) with the pour-on. They were retreated on Days 63, 126 and 189 and monthly tick counts were done. Mean numbers of adult R. decoloratus and/or R. microplus decreased from 53 and 14 on Days 56 and 112 respectively to 2 or less on all other occasions including Day 254. Compared to the numbers of R. decoloratus and/or R. microplus larvae collected from vegetation in the previous year, larval numbers declined by 40.7 % on Day 28, and thereafter reduction remained between 84 % and 100 %. Pairs of tracer calves placed on the pasture for 7 days each month were then held in pens and adult ticks that detached collected. Reduction in the numbers of R. decoloratus collected from tracer animals was 75 % on Day 56 and remained above 93 % except for Day 224 when it temporarily decreased to 78.5 %. Reduction in the numbers of R. microplus was 97.5 % on Day 28 and remained above 98 % until the conclusion of the study on Day 254. Treatment with the pour-on formulation of fluazuron and flumethrin resulted in a marked decrease in the numbers of R. decoloratus and/or R. microplus on treated cattle followed by a reduction in the numbers of larvae questing on the vegetation and ticks picked up by tracer calves. No other potential host species for R. decoloratus and/or R. microplus were present in the camps.