Abstract
BackgroundMosquitoes are well-known vectors of many diseases including malaria and lymphatic filariasis. Uses of synthetic insecticides are associated with high toxicity, resistance, environmental pollution and limited alternative, effective synthetic insecticides. This study was undertaken to evaluate the larvicidal efficacy of clove and cinnamon essential oils against laboratory Anopheles gambiae (sensu stricto) and wild An. arabiensis larvae.MethodsThe standard WHO guideline for larvicides evaluation was used, and the GC-MS machine was used for active compounds percentage composition analysis and structures identification. Probit regression analysis was used for LC50 and LC95 calculations while a t-test was used to test for significant differences between laboratory-reared and wild larvae populations in each concentration of plant extract.ResultsMortality effect of clove and cinnamon essential oils against wild and laboratory-reared larvae had variations indicated by their LC50 and LC95 values. The mortality at different concentrations of cinnamon and clove post-exposure for wild and laboratory-reared larvae were dosage-dependent and were higher for cinnamon than for clove essential oils. The mortality effect following exposure to a blend of the two essential oils was higher for blends containing a greater proportion of cinnamon oil. In the chemical analysis of the active ingredients of cinnamon essential oil, the main chemical content was Eugenol, and the rarest was β-Linalool while for clove essential oil, the main chemical content was Eugenol and the rarest was Bicyclo.ConclusionThe essential oils showed a larvicidal effect which was concentration-dependent for both laboratory and wild collected larvae. The active ingredient compositions triggered different responses in mortality. Further research in small-scale should be conducted with concentrated extracted compounds.
Highlights
Mosquitoes are well-known vectors of many diseases including malaria and lymphatic filariasis
The aim of this study was to determine the active ingredients, and larvicidal activities of clove (Family: Myrtaceae) and cinnamon (Family: Lauraceae) essential oils and their blend against insectary-reared Anopheles gambiae (s.s.) larvae and An. arabiensis larvae from wild populations
The larvicidal activity of essential oils of cloves and cinnamon against laboratory and wild collected larvae were found to be dosage-dependent with a higher mortality observed for cinnamon essential oils (Figs. 1, 2)
Summary
Mosquitoes are well-known vectors of many diseases including malaria and lymphatic filariasis. Tanzania spends a low share of its Thomas et al Parasites & Vectors (2017) 10:411 complex sibling species of An. gambiae which transmit malaria worldwide have been described [9]. All of these vector-borne diseases occur mainly in tropical countries where more than two billion people live in endemic regions [10]. The toxicity of the available chemical insecticides, their high operational cost and the subsequent environmental pollution have caused the need for developing alternative approaches to control vector-borne diseases [15]. Essential oils are composed of isoprenoid compounds, mainly monoterpene carriers of smell in the aromatic plants, such as sesquiterpenes alcohols identified from Chamaecyparis obtusa leaf oil and various monoterpene components derived from Thuja orientalis [18]
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