Evaluation of Ocimum suave essential oil against anthropophilic malaria vector Anopheles gambiae s.s after ten years of storage

Interruption of vector-human contact is of priority in breaking the transmission chain of malaria parasites. The use of plant extracts as repellents against malaria vectors have been advocated in different studies. The objective of this study was to evaluate the protective efficacy of freshly distilled and ten years old essential oil of Ocimum suave against Anopheles gambiae s.s. The feeding inhibition of old and freshly prepared O. suave extracts in liquid paraffin or glycerine were compared with N,N-diethyl-3-methylbenzamide (DEET) using mosquito cage evaluation. There was no significant difference between the ten years stored and freshly prepared O. suave extract in either glycerine (t = 0.578, df = 58, P = 0.566) or liquid paraffin (t = 0.148, df = 58, P = 0.883). Neither ten years old ( P = 0.423 in glycerine and P =0.423 in liquid paraffin) or freshly prepared ( P =0.427 in glycerine and P = 0.412 in liquid paraffin) O. suave extracts had significant difference against DEET in protection efficacy. Comparison of the mean between O. suave in glycerine and in paraffin had no difference (t= 1.445, df = 24, P = 0.161). Therefore, promotion of plant extracts for commercialization is of priority in rural Tanzania where whole plants are currently used as repellents against malaria vectors