Abstract
BackgroundAttractive toxic sugar bait (ATSB) sprayed onto vegetation has been successful in controlling Anopheles mosquitoes outdoors. Indoor application of ATSB has yet to be explored. The purpose of this study was to determine whether ATSB stations positioned indoors have the potential to kill host-seeking mosquitoes and constitute a new approach to control of mosquito-borne diseases.MethodsInsecticides were mixed with dyed sugar solution and tested as toxic baits against Anopheles arabiensis, An. Gambiae s.s. and Culex quinquefasciatus in feeding bioassay tests to identify suitable attractant-insecticide combinations. The most promising ATSB candidates were then trialed in experimental huts in Moshi, Tanzania. ATSB stations were hung in huts next to untreated mosquito nets occupied by human volunteers. The proportions of mosquitoes killed in huts with ATSB treatments relative to huts with non-insecticide control treatments huts were recorded, noting evidence of dye in mosquito abdomens. ResultsIn feeding bioassays, chlorfenapyr 0.5% v/v, boric acid 2% w/v, and tolfenpyrad 1% v/v, mixed in a guava juice-based bait, each killed more than 90% of pyrethroid-susceptible An. Gambiae s.s. and pyrethroid-resistant An. arabiensis and Cx. quinquefasciatus. In the hut trial, mortality rates of the three ATSB treatments ranged from 41-48% against An. arabiensis and 36-43% against Cx. quinquefasciatus and all were significantly greater than the control mortalities: 18% for An. arabiensis, 7% for Cx. quinquefasciatus (p<0.05). Mortality rates with ATSB were comparable to those with long lasting insecticidal nets previously tested against the same species in this area. ConclusionsIndoor ATSB shows promise as a supplement to mosquito nets for controlling mosquitoes. Indoor ATSB constitute a novel application method for insecticide classes that act as stomach poisons and have not hitherto been exploited for mosquito control. Combined with LLIN, indoor use of ATSB has the potential to serve as a strategy for managing insecticide resistance.
Highlights
Increased coverage of insecticide-treated nets (ITN) and indoor residual spraying (IRS) has been successful in reducing the malaria burden of many African countries
The negative impact of pyrethroid resistance on ITN effectiveness has been demonstrated in experimental hut trials [6] and household trials [7], the point at which pyrethroid resistance translates to diminished control of malaria transmission has yet to be demonstrated [8,9]
Attractive toxic sugar bait (ATSB) laboratory bioassays All ATSB insecticide treatments resulted in high mortality rates of female An. gambiae s.s., An. arabiensis and Cx. quinquefasciatus (Table 1)
Summary
Increased coverage of insecticide-treated nets (ITN) and indoor residual spraying (IRS) has been successful in reducing the malaria burden of many African countries. Despite this public health success there is concern with the overdependency on the pyrethroid class of insecticides, and the implications of wide-scale selection of pyrethroid resistance on the future control of malaria [1]. If a suitable delivery system could be developed for such insecticides against adult mosquitoes, this could provide an important new method for disease transmission control, supplementary to pyrethroid-treated nets, against mixed populations of susceptible and resistant mosquitoes. Methods: Insecticides were mixed with dyed sugar solution and tested as toxic baits against Anopheles arabiensis, An. Gambiae s.s. and Culex quinquefasciatus in feeding bioassay tests to identify suitable attractant-insecticide combinations. Combined with LLIN, indoor use of ATSB has the potential to serve as a strategy for managing insecticide resistance
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