Susceptibility of Laboratory Colonies of Members of the Anopheles Gambiae Complex to Entomopathogenic Fungi Beauveria Bassiana
Year: 2010
Type: dissertation
Abstract: Control of the major African malaria vectors of the Anopheles gambiae complex \ncontinues to rely heavily on the application of insecticides either by indoor residual \nhouse spraying (IRS) or bednet impregnation (ITNs). However, growing concerns \nabout their negative impact on human health, their potential impact on the \nenvironment, and the ever-increasing spread of insecticide resistance across sub- \nSaharan Africa has diverted attention to alternative strategies that are not based on \nchemicals. Therefore, alternatives such as vector control with biological agents may \nbe effective. Levels of susceptibility to the entomopathogenic fungus Beauveria \nbassiana were assessed against insecticide-resistant and insecticide-susceptible \nlaboratory colonies as well as a wild-caught sample of the An. gambiae complex of \nwhich most members are major or localised malaria vectors. \nInsecticide susceptibility tests against all four classes of insecticides recommended by \nWHO for vector control was performed according to the standard WHO bioassay \nprotocol. Fungal susceptibility tests using suspensors dusted with dry conidia of B. \nbassiana isolate IMI 391510 were performed on laboratory-reared colonies of An. \ngambiae complex members as well as on a sample of wild caught, insecticide \nsusceptible An. arabiensis from Malawi. \nOur data showed that there is no interaction between insecticide susceptibility and \nfungal susceptibility. Survival of both insecticide susceptible and insecticide resistant \ncolonies as well as wild mosquitoes was significantly affected (P< 0.001) by fungal \ninfection. All infected mosquitoes succumbed to fungal infection within 7-20 days \npost-exposure compared to control groups for which 70-85% of mosquitoes were still \nalive at that time. The evidence of fungal infection was confirmed with more than \n90% of the mosquito cadavers sporulating 3-5 days after incubation. These results provide hope for alternative control strategies for adult anopheline \nmosquitoes other than those that rely entirely on insecticides. There was evidence that \ninsecticide susceptible and resistant mosquitoes can be killed by the fungus B. \nbassiana within the 14 day period before they become infective with the malaria \nPlasmodium parasite. However, conidia formulations and concentrations as well as a \nsuitable delivery method for efficient coverage remain the areas of focus for field \nimplementation.
Author: Christophe K. Kikankie
Language: English
Subfield: Insect Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2101467965