Efficacy of a formulation of chlorfenvinphos and dichlorvos on Rhipicephalus microplus in vivo test in Bahia, Brazil.

This study aimed to evaluate the efficacy of a commercial formulation containing the combination of chlorfenvinphos and dichlorvos on Rhipicephalus microplus in a field test in northeastern Brazil. Adult crossbred cattle naturally infested with R. microplus were restrained in a trunk to count partially engorged female ticks between 4.5 and 8.0 mm in length on days -7, -3, and -1 before the acaricide was applied. The animals were divided into two groups containing ten animals each and with similar tick infestations (P > 0.05). In the control group, the animals were sprayed with drinking water. In contrast, in the treated group, the animals were sprayed with the acaricide formulation containing chlorfenvinphos and dichlorvos diluted following the manufacturer's instructions using 1 L of water/product for every 100 kg of the animal. To assess treatment efficacy, partially engorged female tick counts were carried out, by individually inspecting each animal on the left side of the body every seven days for 28 days. The results showed that the combination of chlorfenvinphos and dichlorvos was highly effective, especially on days + 7 and + 14, with tick reductions of 96.6% and 95.9%, with an overall average decrease in ticks of the four counts of 92.4%. Formulation containing chlorfenvinphos and dichlorvos was effective in the field test on the population of R. microplus in cattle in the northeast of Brazil. These results are significant because they enable producers to use a formulation considered to be low-cost and have a short waiting period of action, which will contribute to the control of cattle ticks.