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Pyrethroid-sprayed tents for malaria control: an entomological evaluation in Pakistan
S Hewitt1, M Rowland, N Muhammad
1Medecins Sans Frontières-Holland/HealthNet International, University Town, Peshawar, North West Frontier Province, Pakistan.
Medical and Veterinary Entomology
|October 1, 1995
Summary
Pyrethroid-sprayed tents significantly reduced mosquito biting rates and increased mortality, offering potential protection against malaria transmission for tent dwellers. Outer fly-sheets extended the insecticide
Area of Science:
- Medical Entomology
- Vector Control
- Public Health
Background:
- Endophilic mosquitoes pose a significant threat to malaria transmission, particularly in regions where inhabitants rely on tents for shelter.
- Traditional untreated tents offer limited protection against nocturnal mosquito bites.
- Pyrethroid insecticides are widely used for vector control due to their efficacy and residual activity.
Purpose of the Study:
- To evaluate the effectiveness of pyrethroid-treated tents in reducing mosquito feeding success, biting rates, and mortality.
- To assess the impact of permethrin and deltamethrin on wild mosquito populations attracted to bait cows.
- To determine the residual efficacy of pyrethroid treatments on tent materials over time.
Main Methods:
- Field trials were conducted in Pakistan using bait cows confined within untreated and pyrethroid-sprayed tents (permethrin or deltamethrin).
- Mosquito biting rates, feeding success, and mortality were monitored under natural conditions.
- Bioassays were performed to assess the insecticidal efficacy of treated tent surfaces over time, with and without outer fly-sheets.
Main Results:
- Pyrethroid-sprayed tents reduced the biting rate of Anopheles stephensi by approximately 40%.
- High mortality rates were observed for bloodfed Anopheles stephensi (75%) and Anopheles subpictus (65%) in treated tents, with lower efficacy against culicines (10%).
- Outer fly-sheets prolonged the insecticidal efficacy of the treatments, maintaining high efficacy for over a year, whereas efficacy declined rapidly without fly-sheets.
Conclusions:
- Tent spraying with fast-acting, photostable, residual pyrethroid insecticides offers a promising method for malaria transmission control.
- This approach is particularly effective in areas with endophilic and pyrethroid-susceptible vector mosquitoes.
- The use of outer fly-sheets is crucial for maintaining the long-term residual efficacy of pyrethroid treatments on tents.