Background: Malaria control faces several threats. Alternative strategies to complement Long Lasting Insecticide-treated Nets and antimalarial therapy are therefore mandatory. This study evaluated the effectiveness of improved housing on indoor residual mosquito density and exposure to malaria-carrying Anophelines in Minkoameyos, a rural community in the center region of Cameroon.
Methods: Following the identification of housing factors affecting malaria prevalence in 2013, 218 houses were improved (screening of doors and windows, installing plywood ceilings on open eaves, closing holes on the walls and doors). Quarterly surveys were conducted in a sample of 21 improved and 21 non-improved houses from November 2014 to October 2015. Mosquitoes sampled by night collections on human volunteers were identified morphologically. Their parity status determined. Mosquito infectivity was verified through Plasmodium falciparum CSP ELISA. The average entomological inoculation rates were determined. A Reduction Factor (RF), defined as the ratio of the values for mosquitoes collected outdoor to those collected indoor was calculated in improved houses (RFI) and non-improved houses (RFN). An Intervention Effect (IE=RFI/RFU) measured the true effect of the intervention. Chi-square test was used to determine variable significance. The threshold for statistical significance was set at P < 0.05.
Results: A total of 1113 mosquitoes were collected comprising: Anopheles (58.6%), Culex (36.4%), Aedes (2.5%), Mansonia (2.4%) and Coquillettidia (0.2%). Amongst the anophelines were An. gambiae s.l. (95.2%), An. funestus (2.9%), An. ziemanni (0.2%), An. brohieri (1.2%) and An. paludis (0.5%). An gambiae s.s. was the only Anopheles gambiae sibling found. The intervention reduced the indoor Anopheles density by 1.8 fold (RFI=3.99; RFN=2.21; P=0.001 ). The indoor density of parous Anopheles was reduced by 1.7 fold (RFI=3.99; RFN=2.21; P=0.04 ) and that of infected Anopheles by 1.8 fold (RFI=3.26; RFN=1.78; P=0.04 ). Indoor peak biting rates were observed between 02am to 04am in non improved houses and from 02am to 06am in improved houses.
Conclusion: Housing improvement reduced indoor residual anopheline density and malaria transmission. This highlights the need for Standardization and promotion of similar interventions to prevent malaria in comparable contexts.