Impact of insecticide-treated nets on wild pyrethroid resistant Anopheles epiroticus population from southern Vietnam tested in experimental huts.
BACKGROUND
In this study, the efficacy of insecticide-treated nets was evaluated in terms of deterrence, blood-feeding inhibition, induced exophily and mortality on a wild resistant population of Anopheles epiroticus in southern Vietnam, in order to gain insight into the operational consequences of the insecticide resistance observed in this malaria vector in the Mekong delta.


METHODS
An experimental station, based on the model of West Africa and adapted to the behaviour of the target species, was built in southern Vietnam. The study design was adapted from the WHO phase 2 guidelines. The study arms included a conventionally treated polyester net (CTN) with deltamethrin washed just before exhaustion, the WHO recommended long-lasting insecticidal net (LLIN) PermaNet 2.0 unwashed and 20 times washed and PermaNet 3.0, designed for the control of pyrethroid resistant vectors, unwashed and 20 times washed.


RESULTS
The nets still provided personal protection against the resistant An. epiroticus population. The personal protection ranged from 67% for deltamethrin CTN to 85% for unwashed PermaNet 3.0. Insecticide resistance in the An. epiroticus mosquitoes did not seem to alter the deterrent effect of pyrethroids. A significant higher mortality was still observed among the treatment arms despite the fact that the An. epiroticus population is resistant against the tested insecticides.


CONCLUSIONS
This study shows that CTN and LLINs still protect individuals against a pyrethroid resistant malaria vector from the Mekong region, where insecticide resistance is caused by a metabolic mechanism. In the light of a possible elimination of malaria from the Mekong region these insights in operational consequences of the insecticide resistance on control tools is of upmost importance.
Van Bortel
Wim
W
Institute of Tropical Medicine, Dept Parasitology, Nationalestraat 155, B-2000 Antwerpen, Belgium. wvbortel@itg.be
Chinh
Vu Duc
VD
Berkvens
Dirk
D
Speybroeck
Niko
N
Trung
Ho Dinh
HD
Coosemans
Marc
M
D000818:Animals; D000852:Anopheles / Q000187:drug effects*; D005247:Feeding Behavior; D006801:Humans; D007303:Insect Vectors / Q000187:drug effects* / Q000469:parasitology; D007305:Insecticide Resistance; D057148:Insecticide-Treated Bednets; D007306:Insecticides / Q000494:pharmacology; D007846:Laundering; D008288:Malaria / Q000517:prevention & control*; D009032:Mosquito Control / Q000379:methods; D011157:Population Dynamics; D011722:Pyrethrins / Q000494:pharmacology*; D014744:Vietnam
D007306:Insecticides; D011722:Pyrethrins