Chemical Composition and Repellent Activities of Formulated Creams from Essential Oils of Three Tropical Plants Against Adults of Simulium damnosum Sensu Lato

Abstract

Simulium damnosum sensu lato (Diptera: Simuliidae) commonly known as black fly transmits Onchocerca volvulus, the parasite which causes onchocerciasis (river blindness) in Africa. The medical and socio-economic importance associated with the biting of this fly is enormous, hence, the need to devise effective means of breaking man-fly contact. The present study examined repellent activities of formulated topical creams prepared from white soft paraffin and two concentrations (5.0% and 7.5%) of essential oils of three plants, namely Monodora myristica, Eugenia caryophyllus and Xylopia aethiopica against Simulium damnosum s.l. vectors of human onchocerciasis in Nigeria. The chemical characterization of the oils was determined using gas chromatography and mass spectrometry. Fly collectors that applied the formulated creams at both concentrations caught lower numbers of black flies compared with the control. The difference in the number of flies caught between each of the three essential oils and the control was statistically significant at 7.5% concentration, whereas only E. caryophyllus was significantly different from the control at 5.0% concentration. Eugenia caryophyllus had the highest repellent activities, with the protection of 47.1% and 50.6%, followed by X. aethiopica (37.1% and 36.1%), whereas M. myristica had the least (28.7% and 34.1%) for concentrations of 5.0% and 7.5%, respectively. Trans-13-octadecenoic acid, Eugenol and Alpha-pinene were found to be the principal chemical constituents in M. myristica, E. caryophyllus and X. aethiopica, respectively. The active agents in the essential oils could be useful in providing low-cost repellents to prevent human-vector contact in black fly-infested communities.