Abstract
BackgroundMalaria, one of the leading causes of death in Africa, is transmitted by the bite of an infected female Anopheles mosquito. Problems associated with the development of resistance to chemical insecticides and concerns about the non-target effects and persistence of chemical insecticides have prompted the development of environmentally friendly mosquito control agents. The aim of this study was to evaluate the larvicidal activity of a genetically engineered cyanobacterium, Anabaena PCC 7120#11, against five African Anopheles species in laboratory bioassays.FindingsThere were significant differences in the susceptibility of the anopheline species to PCC 7120#11. The ranking of the larvicidal activity of PCC 7120#11 against species in the An. gambiae complex was: An. merus <An. arabiensis <An. gambiae <An. quadriannulatus, where < indicates a statistically lower LC50. The LC50 of PCC 7120#11 against the important malaria vectors An. gambiae and An. arabiensis was 12.3 × 105 cells/ml and 8.10 × 105 cells/ml, respectively. PCC 7120#11 was not effective against An. funestus, with less than 50% mortality obtained at concentrations as high as 3.20 × 107 cells/ml.ConclusionsPCC 7120#11 exhibited good larvicidal activity against larvae of the An. gambiae complex, but relatively weak larvicidal activity against An. funestus. The study has highlighted the importance of evaluating a novel mosquitocidal agent against a range of malaria vectors so as to obtain a clear understanding of the agent’s spectrum of activity and potential as a vector control agent.
Highlights
Malaria, one of the leading causes of death in Africa, is transmitted by the bite of an infected female Anopheles mosquito
The study has highlighted the importance of evaluating a novel mosquitocidal agent against a range of malaria vectors so as to obtain a clear understanding of the agent’s spectrum of activity and potential as a vector control agent
Chemical insecticides have been used successfully in integrated vector control programs [3], many malaria vector control programs are hampered by the development of resistance of the vectors to chemical insecticides [4,5,6]
Summary
One of the leading causes of death in Africa, is transmitted by the bite of an infected female Anopheles mosquito. Problems associated with the development of resistance to chemical insecticides and concerns about the non-target effects and persistence of chemical insecticides have prompted the development of environmentally friendly mosquito control agents. In addition to development of resistance, concerns about the non-target effects and persistence of the chemical insecticides have prompted the development of environmentally friendly control agents and control programs [7]. There is low risk of resistance being developed to Bti [10], there are several disadvantages to using Bti as a control agent [11,12] These include its low persistence in the field due to inactivation by UV, ingestion of Bti by other aquatic organisms, and the settling of Bti from the mosquito larval feeding zone [11,12,13]. One strategy to overcome some of the disadvantages of Bti is to clone the cry genes of Bti into aquatic microorganisms that: (1) are not toxic to other organisms, (2) inhabit and persist in the larval feeding zone, (3) are used by mosquito larvae as a food source, (4) express Cry proteins at levels that are mosquito larvicidal, and (5) have cell walls that reduce inactivation of the Cry proteins by UV [13,14,15]
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