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Open Access Highly Accessed Research article

Evidence of man-vector contact in torn long-lasting insecticide-treated nets

Virgile Gnanguenon12*, Roseric Azondekon13, Frederic Oke-Agbo1, Arthur Sovi12, Razaki Ossè12, Gil Padonou12, Rock Aïkpon12 and Martin C Akogbeto12

Author affiliations

1 Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin

2 Faculte des Sciences et Techniques de l’Université d’Abomey-Calavi, Abomey-Calavi, Benin

3 University of Massachusetts Amherst, Amherst, USA

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Citation and License

BMC Public Health 2013, 13:751  doi:10.1186/1471-2458-13-751

Published: 14 August 2013

Abstract

Background

Studies indicate that physical damage to long-lasting insecticide-treated nets (LLINs) occurs at a surprisingly rapid rate following net distribution. To what extent does such damage affect the impact of LLINs? Can vectors pass a compromised LLIN barrier to bite? Do more resistant vectors enter the insecticide-treated nets (ITNs) through holes?

Methods

The study was carried out in three geo-locations. Two types of LLINs (polyester and polyethylene) with ‘standardized’ physical damage were compared with similarly damaged, but non-insecticidal (control) nets. The proportionate Holes Index (pHI) of each net was 276. Mosquitoes were captured inside the nets, identified taxonomically, and subjected to molecular analysis to estimate Knock-down resistance (Kdr) frequency.

Results

The most commonly observed species was Anopheles gambiae, accounting for approximately 70% (1,076/1,550) of the total mosquitoes collected both in LLINs and non-insecticidal nets. When compared with controls, number of vectors captured in torn LLINs was significantly reduced. Nonetheless in a night, an average of 5 An. gambiae s.l could enter the damaged LLINs to bite. Similar numbers of resistant mosquitoes were collected in both LLINs and non-insecticidal (control) nets (p > 0.05).

Conclusions

At a pHI of 276, man-vector contact was observed in torn LLINs. The insecticide at the surface of LLINs could only reduce the number of vectors. Resistant mosquitoes have opportunity to enter both non-insecticidal (control) nets and LLINs to bite.

Keywords:
Long-lasting insecticidal nets; Man-vector contact; Anopheles gambiae