Screening mosquito house entry points as a potential method for integrated control of endophagic filariasis, arbovirus and malaria vectors.

BACKGROUND: Partial mosquito-proofing of houses with screens and ceilings has the potential to reduce indoor densities of malaria mosquitoes. We wish to measure whether it will also reduce indoor densities of vectors of neglected tropical diseases. METHODOLOGY: The main house entry points preferred by anopheline and culicine vectors were determined through controlled experiments using specially designed experimental huts and village houses in Lupiro village, southern Tanzania. The benefit of screening different entry points (eaves, windows and doors) using PVC-coated fibre glass netting material in terms of reduced indoor densities of mosquitoes was evaluated compared to the control. FINDINGS: 23,027 mosquitoes were caught with CDC light traps; 77.9% (17,929) were Anopheles gambiae sensu lato, of which 66.2% were An. arabiensis and 33.8% An. gambiae sensu stricto. The remainder comprised 0.2% (50) An. funestus, 10.2% (2359) Culex spp. and 11.6% (2664) Mansonia spp. Screening eaves reduced densities of Anopheles gambiae s. l. (Relative ratio (RR) = 0.91; 95% CI = 0.84, 0.98; P = 0.01); Mansonia africana (RR = 0.43; 95% CI = 0.26, 0.76; P<0.001) and Mansonia uniformis (RR = 0.37; 95% CI = 0.25, 0.56; P<0.001) but not Culex quinquefasciatus, Cx. univittatus or Cx. theileri. Numbers of these species were reduced by screening windows and doors but this was not significant. SIGNIFICANCE: This study confirms that across Africa, screening eaves protects households against important mosquito vectors of filariasis, Rift Valley Fever and O'Nyong nyong as well as malaria. While full house screening is required to exclude Culex species mosquitoes, screening of eaves alone or fitting ceilings has considerable potential for integrated control of other vectors of filariasis, arbovirus and malaria

Screening Mosquito House Entry Points as a Potential Method for Integrated Control of Endophagic Filariasis, Arbovirus and Malaria Vectors

Background Partial mosquito-proofing of houses with screens and ceilings has the potential to reduce indoor densities of malaria mosquitoes. We wish to measure whether it will also reduce indoor densities of vectors of neglected tropical diseases. Methodology The main house entry points preferred by anopheline and culicine vectors were determined through controlled experiments using specially designed experimental huts and village houses in Lupiro village, southern Tanzania. The benefit of screening different entry points (eaves, windows and doors) using PVC-coated fibre glass netting material in terms of reduced indoor densities of mosquitoes was evaluated compared to the control. Findings 23,027 mosquitoes were caught with CDC light traps; 77.9% (17,929) were Anopheles gambiae sensu lato, of which 66.2% were An. arabiensis and 33.8% An. gambiae sensu stricto. The remainder comprised 0.2% (50) An. funestus, 10.2% (2359) Culex spp. and 11.6% (2664) Mansonia spp. Screening eaves reduced densities of Anopheles gambiae s. l. (Relative ratio (RR)  = 0.91; 95% CI = 0.84, 0.98; P = 0.01); Mansonia africana (RR = 0.43; 95% CI = 0.26, 0.76; P<0.001) and Mansonia uniformis (RR = 0.37; 95% CI = 0.25, 0.56; P<0.001) but not Culex quinquefasciatus, Cx. univittatus or Cx. theileri. Numbers of these species were reduced by screening windows and doors but this was not significant. Significance This study confirms that across Africa, screening eaves protects households against important mosquito vectors of filariasis, Rift Valley Fever and O'Nyong nyong as well as malaria. While full house screening is required to exclude Culex species mosquitoes, screening of eaves alone or fitting ceilings has considerable potential for integrated control of other vectors of filariasis, arbovirus and malaria

A local house.

<p>The local houses are made of mud walls and thatched roofs. They have one door and two windows and open eaves (open spaces between the roof and the wall).</p

Impact of screening various entry points upon indoor densities of different mosquito species caught with reference to indoor densities when no entry point was screened.

<p>The relative rates (RR), model estimated 95% confidence intervals (CI) and probability of equivalence (P) were all estimated by Generalized estimating equations as described in the <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000773#s2" target="_blank">Methods</a> section.</p>a<p> =  Reference group (No entry point was screened).</p

Median indoor densities of different mosquito species caught in experimental huts and local houses when different entry points were screened.

<p>N =  Number of hut nights of experimentation conducted for each treatment.</p><p>n = number of mosquitoes caught.</p>a<p>Reference group (No entry point was screened).</p>b<p>A CDC Light trap was attacked by ants on one of the nights, thus no data was recorded for that particular hut night so N = 23 rather than 24.IQR  =  Interquartile range</p

A wooden experimental hut.

<p>The experimental huts were designed to represent local housing in southern Tanzania An experimental hut had a corrugated roof and covered with grass thatch on the top, to simulate the temperature of local houses with thatched roofing. The outer walls were constructed from wooden planks or canvas. The inner walls were made of removable panels coated with mud. They had one door and two functional windows with open eaves (open spaces between the roof and the walls).</p