Insecticidal activities of ricinus communis extracts on phlebotomus duboscqi adults

Sand flies are small haematophagous insects that transmit Leishmania parasites through the bite of infected female phlebotomine sand flies. Roots, leaves and seeds of Ricinus communis are extensively used in different ways especially in the treatment of rheumatic arthritis, paralysis, epilepsy and distension of the uterus. This study sought to determine the adulticidal effects of Ricinus communis (Euphorbiaceae) leaf extracts on Phlebotomus duboscqi in the laboratory. A comparative experimental design using extracts obtained from the leaf and bark of Ricinus communis plant was used. The study was carried out at the Kenya Medical Research Institute, Centre for Biotechnology Research and Development, Kenya. Aqueous, methanol and ethyl acetate extracts were prepared from Ricinus communis plant. Thirty-five day old adult Phlebotomus duboscqi flies were aspirated into plastic rearing jars partially filled with plaster of Paris and fitted with screen tops. They were fed on R. communis extract laced with 10% sucrose. Sand flies that fed on 10% sucrose solution soaked in cotton wool pads and placed onto the screen tops were used as controls. There was no significant difference when bark and leaf extracts were compared (P=0.061). R. communis extracts from Narok showed insecticidal effects against adults. At 48 hours post treatment, the LC50 was 121.15 μg/ml and 126.21 μg/ml for bark and leaf extracts respectively. P. duboscqi adults were found to be highly susceptible to methanol extracts. Therefore, R. communis extracts have insecticidal effects on adult P. duboscqi; hence R. communis should be used against sand flies and Leishmania in situ.