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Research: Supplementary effect and durability of prototype insecticide-treated eave curtains on indoor resting mosquitoes in Kadibo division, Western Kenya

August 16, 2016 - 01:27 -- MalariaWorld Journal
Author(s): 
Martin T.O. Odhiambo, John M. Vulule, Yaw A. Afrane, Maurice Ombok, Rune Bosselmann, Ole Skovmand
Reference: 
MWJ 2016, 7, 11
Article type: 
Research
Abstract: 
 
A field trial was conducted to investigate the effect and longevity of prototypes of long lasting impregnated UV protected eave nets, curtains and door hangers (fully screened houses), compared to houses with bednets only, in traditional East African houses. A randomised controlled trial was carried out in the Ahero rice irrigation scheme in Nyando district, Western Kenya. Eighty houses with open eaves were randomly selected. Forty of these houses were fully screened (FSH+LLINs) with long lasting insecticide-treated nets/curtains used to screen the eaves, windows and doors. The FSH materials were produced with anti-UV additives. The other 40 houses served as controls. Long lasting insecticide-treated bednets (LLINs) were suspended over all sleeping areas in the control and intervention houses. Indoor resting Anopheles mosquitoes were collected using pyrethrum spray catches (PSC) during both dry and wet seasons. Indoor population densities of anophelines were compared between intervention (FSH+LLINs) and control (LLINs) houses. Loss of insecticide (deltamethrin) was compared after 12 and 24 months for both the FSH materials and LLINs through bioassays and chemical analyses. In the FSH+LLINs houses densities of indoor resting Anopheles funestus and An. arabiensis were reduced by 82% (RR=0.18, 95% CI 0.09-0.36, P<0.0001) and 70% (RR=0.30, 95% CI 0.15-0.58, P<0.0001), respectively. No significant difference was recorded for indoor resting Culex spp. (RR=0.95, 95% CI 0.48-1.86, P=0.8). The population of indoor resting bloodfed An. arabiensis and An. funestus was reduced by 72% (RR=0.22, 95% CI 0.09-0.51, P<0.0001) and 84% (RR=0.16, 95% CI 0.07-0.33, P<0.0001) in the FSH+LLINs houses and LLIN houses, respectively. Insecticide loss in eave nets did not depend on the side of the house where the nets were placed. The eave nets showed little loss of bio efficacy over the 12-24 months period. The study revealed that the use of insecticide-treated nets on the eaves and windows combined with door hangers largely impeded entrance of anopheline mosquitoes into houses and can be used to compliment LLINs for household protection. The eave nets were suspended from wood structures near the eave and remained in place when walls were re- plastered. The nets are therefore not depending on daily compliance behaviour and provide protection for the entire household.


 
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Comments

William Jobin's picture
Submitted by William Jobin on
Congratulations on exploration of a more effective protection of homes against malaria mosquitoes. I noted that the weakest link in the various treatment of openings in the house walls and eaves, seemed to be the door hangings. Without trying to redesign the study, would it not have been much more effective to use a good screen door - with metallic screens? This would also exclude house-flies, transmitters of many serious diarrheal diseases, and spoilers of food.

William Jobin Director of Blue Nile Associates

Submitted by Rune Bosselmann on
Dear William, the door hanger strips was basically the best option that could be rolled out as part of a campaign (as we imagined the solution would be). The door screens would require fairly uniform sized and, equivalently important, straight angled door frames in order to arrive pre-fitted and to close properly. In the intervention area neither were present. The door strips could be measured out and installed in about 2 min. We did not count fly entry but anecdotally people noted reduced entry of flies, wasps and other insects. In addition to the problem of (pre-)fitting the screens, a good well fitting door screen would also be much more expensive. If this was to be a market driven solution (vs campaign), I would agree that proper screen should be considered

Rune Bosselmann

 

Director

Tananetting

Part of NRS International