Evaluation of larvicidal potential of Eritrean medicinal plants against Aedes aegypti.

Larvicidal activity of three Eritrean medicinal plants was evaluated against Aedes aegypti by conducting the bioassay using WHO methods. Efficacy of the plant extracts of O. hadiense, R. officinalis and C. spinarum was evaluated against 3rd instar Aedes aegypti larvae and mortality was recorded. LC₅₀ and LC₉₀ of the various plant extracts were also calculated using probit analysis. The morphological analysis of treated larvae was also performed. Extracts of O. hadiense, C. spinarium and R. officinalis were prepared using different solvents viz chloroform, 70% ethanol and water. Of the screened extracts, the chloroform extracts of O. hadiense exhibited the highest larvicidal activities and has the minimum LC₅₀ and LC₉₀ (24 mg/ml and 198.411 mg/ml respectively). Chloroform extract of C. spinarium exhibited the least larvicidal activity with maximum LC₅₀ and LC₉₀ (736.883 mg/ml and 1188.699 mg/ml respectively). Microscopic analysis confirmed the changes in the Aedes aegypti larvae caused by various plants extracts. An accumulation of dark pigmentation was observed in abdominal region and in the anal papillae after contact and also showed major structural damage such as destruction of the gut.