Resistance of the tick Boophilus microplus to organophosphate and synthetic pyrethroid acaricides in the department of Huila

Abstract

40 samples of Boophilus microplus ticks collected in farms in the department of Hui­la were evaluated using the larval packet test (FAO kit) to determine their level of susceptibility to the acaricides: diazinon, coumaphos, cypermethrin, deltamethrin, and dieldrin. Laboratory results showed the presence of resistance to the synthetic pyrethroids on 25 farms; whilst, marked resistance to the organophosphates evaluated was found on 4 farms. Dieldrin showed intermediate resistance on all samples. The association between acaricide management and the presence of resistance was established by means of a questionary applied on each farm. A significative association (p-0.04) was found between resistance to dieldrin and continuous grazing; with a relative risk (R.R) of 2.3. Likewise, significative associations were detected between resistance to cypermethrin and the risk factors: type of production (milk and dual-purpose, p=0.01, R.R=2.7) and the frequency of treatments (more than 12 dips/year, p=0.01, R. R1.7)