Abstract
The mosquito Anopheles not only cause nuisance by their bites but also transmit deadly diseases like malaria in Sub-Saharan Africa, where most of the malaria deaths occur in the world. In Ethiopia, despite the use of native plants in traditional combat against mosquitoes, use in a modern way has remained scanty. The present study, being based on an initial ethno botanical survey, carried out screening experiments on five indigenous ethno botanical species (Aloe pirottae Berger, Aloaceae; Acokanthera schimperi (A.DC) Schweinf, Appocynaceae; Brassica nigra L. Koch, Brassicaceae; Oreosyce africana Hook.f., Cucurbitaceae and Piper capense L.f., Piperaceae). The larvicidal activity of 80% methanol extracts of the first two plant species against the fourth instars of Anopheles arabiensis Patton, and adulticidal activity with the same solvent extracts of the latter four species against Anopheles arabiensis adults, gave positive results upon evaluation under laboratory condition. The 80% methanol extract of the gel of A. pirottae had more activity within 24 hours on the larvae than the leaf extract of Acokanthera schimperi. The highest (100%) mortality in the fourth instars occurred on treatment with 160 ppm extract of Aloe pirottae and 480 ppm extract of Acokanthera schimperi. The maximum adult mortality was detected in the leaf extract of Oreosyce africana (LC50 18.74 and LC90 39.66 ppm) followed by fruit extract of Piper capense (LC50 24.30 and LC90 46.32 ppm), while no mortality was noticed in the control groups. Phytochemical screening of the methanol extracts of the leaves of Oreosyce africana and the fruits of Piper capense had key secondary metabolites (alkaloids, saponins, flavonoids, cardiac glycosides), further corroborating their adulticidal properties. These findings announce the first evidence that Aloe pirottae is a promising mosquito larvicide while Oreosyce africana and Piper capense carry huge potentials as mosquito adulticides contributing to integrated malaria control through proper mosquito management.
Highlights
Vector borne diseases are among the major causes of illness and death in many developing countries
The approach to combat this disease largely relied on interruption of the disease transmission cycle by either targeting the mosquito larvae through spraying of stagnant waters that serve as breeding sites or by killing the adult mosquitoes using insecticides
Mean percent mortalities of the adult An. arabiensis that were treated with crude methanol leaf extracts were determined by one-way Analysis Of Variance (ANOVA) using the SPSS for windows version 16.0, SPSS software 2007 [32]
Summary
Vector borne diseases are among the major causes of illness and death in many developing countries. Mosquitoes (Diptera: Culicidae) are responsible for transmitting the most important vector borne diseases including malaria, lymphatic filariasis, Japanese encephalitis, and dengue as well as yellow fever and other forms of encephalitis [1]. The abbreviation for Anopheles arabiensis is An. arabiensis [3], which is the most important vector associated with the transmission of malaria disease. Anopheles arabiensis is the major malaria vector in Ethiopia [4,5,6]. The malaria control strategies in Ethiopia include the combination of insecticide treated nets and indoor residual spraying that was found to be effective as a control measure [7]
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