The results of this randomized trial show that screening doors and windows, and closing openings on walls and eves by mud reduced the overall indoor densities of An. arabiensis by 40%. Although screening intervention reduced indoor density of An. arabiensis at all abdominal stages, the reduction was substantially higher against unfed An. arabiensis. The intervention was based on locally bought materials, and was affordable.
The houses we assessed were grass thatched, and doors and windows were not well-suited for screenings. The incompatible of doors for screening might reduce the efficacy in such house types. The roofs of grass thatched local houses prevent opening of screened doors outward; consequently, the screened doors were not permanently fixed and people might not used them constantly during the nights before collection.
A house screening study from The Gambia resulted in 43% reduction of house entry of An. gambiae which is comparable to the current study
. Although the incidence of malaria infection was not assessed, the previous studies have shown less malaria cases in screened houses than in controls
. Moreover, the association between the incidence of malaria and the accessibility of a population to mosquitoes was observed with the highest incidence in the population most accessible for mosquito bites
. In The Gambia, screening doors, windows and eves resulted in 59% reduction of indoors density of An. gambiae, and reduced the prevalence of anaemia
. Screening houses by plastic insect-screen resulted 80% protection from indoor bites of An. gambiae in The Gambia
The likely explanation for moderate efficacy the current intervention is that people may not use screened doors in the nights before collection because the screened doors were not permanently fixed as windows. Moreover, An. arabiensis could enter houses when the people open the doors during earlier hours of the night
. The small gaps left in the door and windows could also contribute for the moderate reduction of mosquitoes in the intervention houses. Maximum reduction in number of An. arabiensis might be achieved if the screened doors were constantly used by home owner’s, and the doors were compatible for screening. The likely reason for the overall lower number of mosquitoes sampled during intervention (October/November 2011) compared to the pre-intervention period (April/May 2011) was presumably due to the seasonal variation of the area. Study from the same area shows the highest density of mosquitoes in April and May; the months with the highest rainfall than the October and November; the months with short and small rains
The intervention was cheap, and simple to implement and hence, it can be incorporated into an integrated vector management strategy, and combined with IRS and LLITNs. The cost for screening doors and windows and closing openings on eves and walls (7.3 USD per house) was lower than that was used for fully screening houses (9.98 USD per person) and for screening ceilings (8.69 USD per person) in The Gambia
. However, improving doors and windows fitness for screening should be considered during house construction to increase the efficacy of screenings.