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Evaluation of PermaNet 3.0 a deltamethrin-PBO combination net against Anopheles gambiaeand pyrethroid resistant Culex quinquefasciatusmosquitoes: an experimental hut trial in Tanzania

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Combination mosquito nets incorporating two unrelated insecticides or insecticide plus synergist are designed to control insecticide resistant mosquitoes. PermaNet 3.0 is a long-lasting combination net incorporating deltamethrin on the side panels and a mixture of deltamethrin and synergist piperonyl butoxide (PBO) on the top panel. PBO is an inhibitor of mixed function oxidases implicated in pyrethroid resistance. Method An experimental hut trial comparing PermaNet 3.0, PermaNet 2.0 and a conventional deltamethrin-treated net was conducted in NE Tanzania using standard WHOPES procedures. The PermaNet arms included unwashed nets and nets washed 20 times. PermaNet 2.0 is a long-lasting insecticidal net incorporating deltamethrin as a single active. Results Against pyrethroid susceptible Anopheles gambiae the unwashed PermaNet 3.0 showed no difference to unwashed PermaNet 2.0 in terms of mortality (95% killed), but showed differences in blood-feeding rate (3% blood-fed with PermaNet 3.0 versus 10% with PermaNet 2.0). After 20 washes the two products showed no difference in feeding rate (10% with 3.0 and 9% with 2.0) but showed small differences in mortality (95% with 3.0 and 87% with 2.0). Against pyrethroid resistant Culex quinquefasciatus, mediated by elevated oxidase and kdr mechanisms, the unwashed PermaNet 3.0 killed 48% and PermaNet 2.0 killed 32% but after 20 washes there was no significant difference in mortality between the two products (32% killed by 3.0 and 30% by 2.0). For protecting against Culex PermaNet 3.0 showed no difference to PermaNet 2.0 when either unwashed or after 20 washes; both products were highly protective against biting. Laboratory tunnel bioassays confirmed the loss of biological activity of the PBO/deltamethrin-treated panel after washing. Conclusion Both PermaNet products were highly effective against susceptible Anopheles gambiae. As a long-lasting net to control or protect against pyrethroid resistant mosquitoes PermaNet 3.0 showed limited improvement over PermaNet 2.0 against Culex quinquefasciatus.
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Tunguet al.Malaria Journal2010,9:21 http://www.malariajournal.com/content/9/1/21
R E S E A R C HOpen Access Evaluation of PermaNet 3.0 a deltamethrinPBO combination net againstAnopheles gambiaeand pyrethroid resistantCulex quinquefasciatus mosquitoes: an experimental hut trial in Tanzania 1,2 1,21,2,4 1,21,2 1,2 Patrick Tungu, Stephen Magesa, Caroline Maxwell, Robert Malima, Dennis Masue, Wema Sudi, 1,2 32,4* Joseph Myamba, Olivier Pigeon , Mark Rowland
Abstract Background:Combination mosquito nets incorporating two unrelated insecticides or insecticide plus synergist are designed to control insecticide resistant mosquitoes. PermaNet 3.0 is a longlasting combination net incorporating deltamethrin on the side panels and a mixture of deltamethrin and synergist piperonyl butoxide (PBO) on the top panel. PBO is an inhibitor of mixed function oxidases implicated in pyrethroid resistance. Method:An experimental hut trial comparing PermaNet 3.0, PermaNet 2.0 and a conventional deltamethrin treated net was conducted in NE Tanzania using standard WHOPES procedures. The PermaNet arms included unwashed nets and nets washed 20 times. PermaNet 2.0 is a longlasting insecticidal net incorporating deltamethrin as a single active. Results:Against pyrethroid susceptible Anopheles gambiae the unwashed PermaNet 3.0 showed no difference to unwashed PermaNet 2.0 in terms of mortality (95% killed), but showed differences in bloodfeeding rate (3% bloodfed with PermaNet 3.0 versus 10% with PermaNet 2.0). After 20 washes the two products showed no difference in feeding rate (10% with 3.0 and 9% with 2.0) but showed small differences in mortality (95% with 3.0 and 87% with 2.0). Against pyrethroid resistant Culex quinquefasciatus, mediated by elevated oxidase and kdr mechanisms, the unwashed PermaNet 3.0 killed 48% and PermaNet 2.0 killed 32% but after 20 washes there was no significant difference in mortality between the two products (32% killed by 3.0 and 30% by 2.0). For protecting against Culex PermaNet 3.0 showed no difference to PermaNet 2.0 when either unwashed or after 20 washes; both products were highly protective against biting. Laboratory tunnel bioassays confirmed the loss of biological activity of the PBO/deltamethrintreated panel after washing. Conclusion:Both PermaNet products were highly effective against susceptible Anopheles gambiae. As a long lasting net to control or protect against pyrethroid resistant mosquitoes PermaNet 3.0 showed limited improvement over PermaNet 2.0 against Culex quinquefasciatus.
Background The development of insecticide resistance is probably the biggest threat to capacity to control malaria vectors or sustain any drive towards malaria elimination. The chemical agents that make malaria vector control feasi ble are the pyrethroids. The best tools for delivering pyrethroids are longlasting insecticidal nets (LLIN) and
* Correspondence: mark.rowland@lshtm.ac.uk 2 PanAfrican Malaria Vector Research Consortium, Tanzania
indoor residual spraying (IRS) [1]. Recent trends confirm that the scale up of these two tools is making inroads into the malaria burden in many African countries [26]. This has stimulated new discussion about malaria elimi nation which a few years ago seemed inconceivable [711]. But coinciding with the increased coverage of LLIN and IRS is the development and spread of resis tant mosquitoes that may ultimately undermine the effectiveness of the two tools [1216]. For elimination to
© 2010 Tungu et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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