Comparative efficacy of synthetic acaricides against tick infestations in goats

Abstract

Four commercial synthetic compounds, pyrethroid, organophosphates, macrocyclic lactones and phenylpyrazole have been used for tick control worldwide. However, periodic monitoring of the effectiveness of acaricides has not been fully explored, although such information could contribute to a more effective application, economic analysis and harmful impact on other organisms and environmental contamination. This study investigates the effect of cypermethrine (CYM), deltamethrin, trichlorphon + dimethylester, ivermectin (IVM) and fipronil on natural infestations of ticks in goats. The in vivo quantitative assessment of four tick genera i.e. Hyalomma, Rhipicephalus, Ixodes and Haemaphysalis revealed that both CYM and IVM treated groups resulted in significantly lower (P<0.05) tick counts relative to other compounds and controls on all post-treated days. The maximum reduction in the mean number of ticks in the CYM and IVM treated group was recorded from days 3 to 4, followed by complete shedding of ticks on day 5. However, deltamethrin, trichlorphon + dimethylester and fipronil showed 100% efficacy on the sixth day. In-vitro efficacy trials showed a 100% tick’s mortality based upon the use of fipronil (0.25 g/100 mL) within the 18th h in the post-treated group, while deltamethrin, trichlorphon + dimethylester and CYM were ranked 2nd, 3rd and 5th based on their 100% efficacy within 24-33 h, 33-42 h and 39-48 h, respectively. The investigation has shown that tested acaricides varied in their efficacy to reduce the tick infestation and further experiments on different formulations of the other members of the major acaricidal classes need to be standardized.