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Mosquitoes and bednets: testing the spatial positioning of insecticide on nets and the rationale behind combination insecticide treatments

Oxborough, R. M., Mosha, F. W., Matowo, J., Mndeme, R., Feston, E., Hemingway, Janet ORCID: https://orcid.org/0000-0002-3200-7173 and Rowland, M. (2008) 'Mosquitoes and bednets: testing the spatial positioning of insecticide on nets and the rationale behind combination insecticide treatments'. Annals of Tropical Medicine and Parasitology, Vol 102, Issue 8, pp. 717-727.

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Abstract

The recent development of pyrethroid resistance of operational significance in Anopheles gambiae s.l. is a major threat to the control of malaria in West Africa. The so-called '2-in-1' bednet, in which the top of the net is treated with a non-pyrethroid insecticide and the sides with pyrethroid, has been proposed as a way of maintaining efficacy in the wake of such resistance. A host-seeking female Anopheles mosquito must contact both the top and sides of a '2-in-1' net, however, for such nets to be useful in resistance management.
In the present study, the interaction between mosquitoes and insecticide-treated bednets (ITN) was explored by restricting the insecticide to particular surfaces of the nets (top only or sides only) and then testing these nets, untreated nets and nets treated on all their surfaces in experimental huts, under simulated field conditions. Over the 6-week trial, there was no significant difference in An. arabiensis mortality between nets treated with pyrethroid on the top only (39.2%), sides only (39.6%) and all surfaces (39.7%), thus indicating that a female An. arabiensis usually contacts both the top and sides of a bednet during its host-seeking behaviour. The data on blood-feeding indicated, however, that the insecticide used on the sides of the net may be more important in preventing mosquito biting than that on the top.
These results support the rationale behind the '2-in-1' nets. Such nets may have advantages over the use of nets treated on all surfaces with a mixture of insecticides that includes a non-pyrethroid component. With the '2-in-1', the more toxic component can be deployed on the top of the net, away from human contact, while the more repellent pyrethroid can be restricted to the sides, to prevent blood-feeding.
With the scaling-up of ITN coverage and the need to preserve pyrethroid efficacy, more consideration should be given to switching from pyrethroid-only nets to 'combination' nets that have been treated with a pyrethroid and another insecticide. Since the mosquitoes that act as malarial vectors may contact all surfaces of a bednet during their host-seeking, spatial heterogeneity in insecticide levels over the surface of a net may not reduce that net's overall efficacy. Nets with a rather uneven distribution of insecticide (such as those that might be produced using home-treatment insecticide kits) may therefore be no less effective, prior to washing, than nets with a more even distribution of insecticide (such as long-lasting insecticidal nets produced under factory conditions).

Item Type: Article
Uncontrolled Keywords: resistant anopheles-gambiae experimental hut evaluation culex-quinquefasciatus pyrethroid resistance malaria vector treated nets impregnated bednets cote-divoire efficacy arabiensis
Subjects: WA Public Health > Preventive Medicine > WA 110 Prevention and control of communicable diseases. Transmission of infectious diseases
WA Public Health > Preventive Medicine > WA 240 Disinfection. Disinfestation. Pesticides (including diseases caused by)
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 765 Prevention and control
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 750 Malaria
QX Parasitology > Insects. Other Parasites > QX 650 Insect vectors
QX Parasitology > Insects. Other Parasites > QX 510 Mosquitoes
QX Parasitology > Insects. Other Parasites > QX 600 Insect control. Tick control
Faculty: Department: Groups (2002 - 2012) > Vector Group
Digital Object Identifer (DOI): https://doi.org/10.1179/136485908X337553
Depositing User: Users 183 not found.
Date Deposited: 05 Jul 2010 10:14
Last Modified: 06 Feb 2018 13:00
URI: http://archive.lstmed.ac.uk/id/eprint/890

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