The effects of Mundulea sericea (Fabales: Fabaceae) water extracts on Phlebotomus duboscqi (Diptera: Psychodidae) eggs and larvae

Abstract

Background: The sand fly, Phlebotomus duboscqi is the vector for zoonotic cutaneous leishmaniasis caused by Leishmania major. No definite control method for P. duboscqi is known. Of the plants known for entomocidal properties, Mundulea sericea is one, with the toxic principle being rotenone. Dried crude M. sericea powder extract mixed with water is used by the Giriama people of Coastal region, Kenya, to kill cat fleas and bedbugs. A recent laboratory study using M. sericea non-polar and polar extracts displayed remarkable entomicidal potential. Against this backdrop, M. sericea was chosen for this study.

Objective: To evaluate water extracts of Mundulea sericea leaves for efficacy against P. duboscqi eggs and larvae.

Methodology: The plant leaves were ground into fine powder and extracted using water. 1 g leaf powder was extracted using 100 ml distilled water, and then filtered. The eggs were then exposed to 1 ml of the filtered extract.  Further, 0.001 g of leaf powder was mixed with 1 g of larval food and fed to larvae. The eggs were incubated at 25 ⁰C and 80% relative humidity and observed for eclosion, and larvae for hatching to adult stage.

Results: The filtered extracts did not inhibit eggs from hatching. Additionally, all the larvae that were fed on food mixed with ground M. sericea leaves survived.

Conclusion: These findings suggest that suggest that M. sericea water extracts do not penetrate the egg chorion, thus the lack of activity. Moreover, the inability of P. duboscqi to digest the chlorophyll of M. sericea so as to release rotenone could be responsible for absence of entomocidal effect.

Key words: Mundulea sericea; Phlebotomus duboscqi; Leishmania major.