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

Abstract

BackgroundPartial 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.MethodologyThe 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.Findings23,027 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.SignificanceThis 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.

Risk factors for <i>Anopheles</i> mosquitoes in rural and urban areas of Blantyre District, southern Malawi

“…funestus-like mosquito, described as a new species within this group of mosquitoes. 25,26 We did not assess the presence of ceilings, but these have also been shown to reduce mosquito entry in houses in urban areas 27 and could have contributed to the absence of anopheline mosquitoes in urban areas of Blantyre as well. Ownership of ITNs was not associated with a reduced number of mosquitoes in either survey.…”

Eave Screening and Push-Pull Tactics to Reduce House Entry by Vectors of Malaria

“…are not vectors of malaria, they are able to transmit lymphatic filariasis and they are nuisance biters, which makes their control important both from a medical viewpoint and for the social acceptability of the intervention. [50][51][52] Conducting both experiments simultaneously would have allowed for comparison of wire mesh screening with fabric screening under the same conditions. Unfortunately logistical limitations meant that a simultaneous comparison was not possible during this study, but this could be addressed in future experiments.…”

“…Several later studies confirmed that screening the house entry points of mosquitoes can significantly reduce the entry of malaria vectors and other mosquitoes, although the effect size differs per species and according to the method of screening used. 21,51 The method of screening that was used in field experiment I (wire mesh, see section Materials and Methods for details on the application technique) yielded house entry reductions between 87% and 99%, whereas the method that was used in field experiment II (cotton net fabric, see the section "Materials and Methods") resulted in reductions of between 61% and 74%. In part, this difference may be explained by the application of cotton wool to close gaps between the house's structure and the wire mesh in field experiment I.…”

The impact of host species and vector control measures on the fitness of African malaria vectors

“…Mosquitoes could enter and exit the hut through its open eaves as they do in nature [21], or exit via the six windows. Mosquitoes leaving the hut were caught outside or in window exit traps.…”