Acaricidal effect of Citrullus colocynthis fruit extract on the camel tick Hyalomma dromedarii (Koch, 1844)

The hard tick Hyalomma dromedarii is one of the most injurious ectoparasites affecting camels in Egypt and several other areas of the world. Hyalomma dromedarii engorged females were dipped in alcoholic extract of Citrullus colocynthis fruits at concentrations of 25, 50, 100, 200 and 400 mg/mL and then observed over four weeks following treatment. There was a marked increase in dead females following single treatment with the above concentrations, particularly for the two highest which caused ≥ 90% mortality. In addition, the extract caused rapid blood digestion in ticks as well as obvious decrease in their oviposition (40% oviposition for the highest concentration compared to 100% for the control group), hatchability (40-45% egg hatching across concentrations compared to 78% for the control group) and fertility index (0.32 compared to 0.56 for the control group). As the estimated LC50 and LC95 were recorded 63.84 and 1046.11 mg/mL, respectively, the study also revealed that dipping in 200 mg/mL of C. colocynthis alcoholic extract is sufficient to control H. dromedarii as it recorded >85% acaricide efficacy, so it might be selected to be the effective dose. Moreover, gas chromatography-mass spectrometry (GC-MS) analysis was carried out on alcoholic extract of C. colocynthis fruits and detected its major constituents of decanoic, oleic, linoleic, carbamic and vaccenic acids which have acaricidal activities impacting tick feeding, digestion and survival. The combined effects of alcoholic extract of C. colocynthis fruits indicated by high mortality rate as well as decreased fecundity and reproductive efficacy supports its effectiveness as a promising management agent for the control of H. dromedarii.