Wash-resistance and field efficacy of Olyset net, a permethrin-incorporated long-lasting insecticidal netting, against Anopheles minimus-transmitted malaria in Assam, Northeastern India.
BACKGROUND
The long-lasting insecticidal nets are ready-to-use, pretreated nets, which do not require retreatment for 4-5 years. Olyset nets that are made of high-density polyethylene monofilament yarn with 2% w/w permethrin incorporated (corresponding to 1 g/m(2)) are type-2 in which insecticide is incorporated into the polymers and are wash resistant. In these, insecticide migrates to the surface of the netting fiber to be bioavailable against mosquitoes and other insect pests. STUDY SITE AND OBJECTIVES: The present study was a village scale, field-based trial that was conducted in Plasmodium falciparum predominant area of Assam to assess feasibility, acceptability, and sustainability of this intervention against vector populations and disease transmission. We here report the research findings of Olyset net as an intervention against Anopheles minimus-transmitted malaria in foothill area of Assam for the first year of observations beginning July 2005 till June 2006.


RESULTS
An. minimus, the mosquito vector species, was observed to be fully susceptible to permethrin. Follow-up investigations revealed that An. minimus mosquitoes had virtually disappeared in Olyset net villages, which was corroborated by data on human bait mosquito-landing catches. There was a consistent decline in the malarial incidence in Olyset net intervention villages, and the overall impact on the malarial transmission was significant compared to untreated net and no-net control villages for the corresponding study period. The bioavailability of insecticide on Olyset netting fiber was consistent (100% kill effect) up to 10 months of monitoring, and was observed to be wash resistant even after the 20th wash at fortnightly intervals.


CONCLUSIONS
The Olyset nets were safe to use, wash resistant, and assessed to be operationally feasible, community-based intervention for sustainable management of disease vectors against malaria. Community compliance and acceptance was high, and users reported decreased nuisance due to biting mosquitoes.
Dev
Vas
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National Institute of Malaria Research (Field Station), Chachal, Guwahati, India. mrcassam@hotmail.com
Raghavendra
K
K
Barman
K
K
Phookan
S
S
Dash
A P
AP
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000852:Anopheles / Q000469:parasitology*; D002648:Child; D002675:Child, Preschool; D004777:Environment; D006801:Humans; D007194:India / Q000453:epidemiology; D007299:Insect Bites and Stings; D057148:Insecticide-Treated Bednets; D007306:Insecticides / Q000737:chemistry* / Q000494:pharmacology; D007846:Laundering; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000517:prevention & control; D008875:Middle Aged; D009032:Mosquito Control / Q000379:methods / Q000592:standards; D026023:Permethrin / Q000737:chemistry* / Q000494:pharmacology; D013997:Time Factors; D055815:Young Adult
D007306:Insecticides; D026023:Permethrin