Evidence of man-vector contact in torn long-lasting insecticide-treated nets.
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.
Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin. amerusangel@yahoo.fr
Virgile
V
Gnanguenon
Roseric
R
Azondekon
Frederic
F
Oke-Agbo
Arthur
A
Sovi
Razaki
R
Ossè
Gil
G
Padonou
Rock
R
Aïkpon
Martin C
MC
Akogbeto
D000818:Animals; D000852:Anopheles / Q000145:classification / Q000187:drug effects; D016022:Case-Control Studies; D006801:Humans; D007299:Insect Bites and Stings / Q000517:prevention & control*; D007303:Insect Vectors / Q000187:drug effects; D007305:Insecticide Resistance; D057148:Insecticide-Treated Bednets / Q000592:standards*; D007306:Insecticides / Q000494:pharmacology
D007306:Insecticides