Determination of Effects of Tarchonanthus camphoratus, Acalypha fruticosa and Tagetes minuta Crude Extracts on the Vectorial Capacity of Phlebotomus duboscqi Samuel Mong’are

Abstract

The drawbacks of synthetic chemical insecticides have necessitated the search for new therapies against Phlebotomus duboscqi. The effects of Tarchonanthus camphoratus (Asteraceae), Acalypha fruticosa (Fabacea) and Tagetes minuta (Asteraceae) crude extracts on the vectorial capacity of Phlebotomus duboscqi were investigated. These plants are traditionally used for controlling sand flies and leishmaniasis in endemic areas. This study evaluated the following objectives: effects of T. camphoratus, A. fruticosa, and T. minuta crude extracts on the fertility of P. duboscqi, effects of T. camphoratus, A. fruticosa, and T. minuta crude extracts on longevity of P. duboscqi and the effects of T. camphoratus, A. fruticosa, and T. minuta crude extracts on infectivity of P. duboscqi by Leishmania parasites. The extracts were prepared from the dried aerial parts of T. camphoratus, A. fruticosa, and T. minuta. After grinding into a fine powder, the plant material was soaked in methanol and ethyl acetate solvents for 48 hours then filtered and dried using rotary evaporation at 30°C. The extracts obtained were later prepared into appropriate concentration for bioassay. The study was carried out using a completely randomized design. One hundred and sixty P. duboscqi adult flies were used; they were randomly divided into two groups; test and control groups. The collected data on bioassays was stored in MS Excel and analyzed using analysis of variance (ANOVA) and Student’s t test. The extracts were found to reduce the fertility of P. duboscqi significantly by 73% (A. fruticosa), 53% (T. minuta) and 26% (T. camphoratus) (P< 0.05). The extracts also reduced the survival time of P. duboscqi significantly to: 7 days (A. fruticosa), 7 days (T. minuta) and 9 days (T. camphoratus). Development of L. major was greatly inhibited by the crude extracts at the nectomonad stage. Percentage inhibition of L. major development was highest in A. fruticosa crude extract (86%) followed by T. minuta (79%) and finally T. camphoratus (63%). The observation that A. fruticosa, T. minuta and T. camphoratus have effect on infectivity, egg development and longevity of P. duboscqi has important implications for vector control because the high level of their activities would potentially reduce the population of sand flies. This study shows that these medicinal plants have effects on the vectorial capacity of sand flies.