In vitro acaricidal activity of Callistemon viminalis and Cupressus lusitanica leaf essential oil against Amblyomma variegatum tick

Abstract

Tick infestations are among the main constraints to livestock productivity in sub-Saharan Africa but their control is tedious. Thus, a study on the acaricidal effect of two indigenous plants extracts on Amblyomma variegatum tick was carried out in the western highland of Cameroon. The leaf essential oil (EO) of Callistemon viminalis and Cupressus lusitanica were obtained by hydrodistillation and incorporated into soap. Three concentrations (0.16, 0.22 and 0.27 μL per gram of soap) and a control (soap without EO) with three replications for each treatment were used for in vitro trial. Each replication consisted of 10 ticks put into contact with a filter paper impregnated with soap foam and placed at the bottom of a Petrie dish. The mortality rate was significantly higher (P<0.05) from day 2 up to the end of the trial for both EO compared with control for the highest concentration (0.27μL/g). On day 8, the mortality rate for control was 16,6±5,7% whereas the highest concentration of C. lusitanica EO killed 96.2±6.4% of ticks. In contrast, the highest concentration of C. viminalis killed 100% of ticks from the fourth day of exposure, suggesting that the speed of action was faster for C. viminalis EO than for C. lusitanica EO. The LC₅₀ for C. viminalis EO and C. lusitanica EO were 0.77 and 1.05 μL/g respectively, indicating that C. viminalis EO is more toxic than EO from C. lusitanica. The soap based on the EO from both plants is a promising alternative tool in tick control.

Keywords: acaricidal effect, essential oil; Callistemon viminalis; Cupressus lusitanica; Amblyomma variegatum