Background: Mosquitoes are well known vectors for transmission of vector-borne diseases affecting human beings, particularly malaria and lymphatic filariasis. Use of synthetic insecticides is one of the major methods of vector control. However, synthetic insecticides are associated with a number of problems including toxicity, mosquito resistance, environmental pollution, high operational cost and limited number of effective synthetic insecticides. These problems call for search and development of environmentally safe, biodegradable and low cost insecticides using natural sources. This study was undertaken to evaluate the larvicidal efficacy of clove and cinnamon essential oils against anopheles gambiae sensu stricto
Methods: The essential oils were collected from local market at Market Street in Mwanza. These oils were screened for larvicidal activity using WHO standardized procedures and guidelines for larvicidal test method under laboratory conditions using third instar mosquito larvae of Anopheles gambiae s.s. Lethal concentrations causing 50% and 95% mortality, LC50 and LC95 were determined by probit analysis using statistical programmed for social scientists version 17.0 (SPSS 17.0)
Results: The finding of the evaluated essential oils have shown a very great larvicidal activity against wild and laboratory reared larvae of A. gambiae s.s despite of different chemical compositions they have. The chemical composition of clove and cinnamon essential oils evaluated were found to have one common chemical Eugenol. The mortality caused by cinnamon was found to be higher this probable due to linalool compound. Mortality in susceptible laboratory larvae was higher than wild collected larvae due to reported resistance gene dominance in wild population. The mortality of larvae caused by the two blends of cinnamon and clove in both laboratory reared and wild larvae had the same trend with blend having higher proportion of cinnamon causing more mortality than one with higher proportion of clove.
Conclusion and Recommendations; The essential oils of clove and cinnamon shown to have larvicidal effect which was concentration dependent for both laboratories reared and wild collected larvae. The active ingredient compositions have caused different responses in mortality. I recommend further studies to be done on evaluating the each active ingredient of both essential oils to realize which particular active ingredient was a cause of high mortality in each essential oil.
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