Acaricidal Activity of Commiphora merkeri Bark Exudate against Two Species of Rhipicephalus Koch (Acari; Ixodidae) by Larval and Adult Immersion Test

Ticks pose a threat in the infestation of both wild and domestic animals, thereby causing an increase in chances for transmission of diseases. Despite of the wide use of Commiphora species in tick control, no acaricidal activity of Commiphora merkeri. Engl. Exudate have been scientifically assessed. The acaricidal activity of the exudate extract and its Petroleum ether (PE), Dichloromethane (DCM) and Ethyl acetate (ETOAC) fractions were carried out by using the larval immersion test (LIT) and adult immersion test (AIT), against Rhipicephalus appendiculatus and Rhipicephalus averts. The crude extracts of C. merkeri showed 80% and 70% mortality on the LIT bioassay at concentration of 1.0 mg/mL for R. averts and R. appendiculatus, respectively. There was no statistical difference (p≥0.05) in activity of petroleum ether and dichloromethane fractions exhibiting 100% mortality at concentration of 1.0 mg/mL for R. appendiculatus and R. averts, also at 0.8 mg/mL to R. averts species. R. averts was more susceptible that R. appendiculatus showing stable incremental mortality in all concentration levels. In the AIT, no statistical significant difference (p≥0.05) in reduction was observed for crude extract of C. merkeri and petroleum ether fractions by having no surviving R. averts above 0.025 mg/mL after 24 and 72 h. The same trend was observed for R. appendiculatus within 24 h of exposure. However, at lower concentrations the residual effect of treatments on the ticks continued to elicit the effect over time having few or no immediate effect of death after exposure, This was vivid for R. averts within 24 and after 72 h. Follow up of survived engorged adults indicated that, the ticks could lay eggs but the eggs were not viable for hatching. This justifies its uses as an alternative agent in an integrated approach in reducing tick infestation among Pastoralist.