Window screening, ceilings and closed eaves as sustainable ways to control malaria in Dar es Salaam, Tanzania

Abstract

Background: Malaria transmission in Africa occurs predominantly inside houses where the primary vectors prefer to feed. Human preference and investment in blocking of specific entry points for mosquitoes into houses was evaluated and compared with known entry point preferences of the mosquitoes themselves.

Methods: Cross-sectional household surveys were conducted in urban Dar es Salaam, Tanzania to estimate usage levels of available options for house proofing against mosquito entry, namely window screens, ceilings and blocking of eaves. These surveys also enabled evaluation of household expenditure on screens and ceilings and the motivation behind their installation.

Results: Over three quarters (82.8%) of the 579 houses surveyed in Dar es Salaam had window screens, while almost half (48.9%) had ceilings. Prevention of mosquito entry was cited as a reason for installation of window screens and ceilings by 91.4% (394/431) and 55.7% (127/228) of respondents, respectively, but prevention of malaria was rarely cited (4.3%, 22/508). The median cost of window screens was between US $ 21-30 while that of ceilings was between US $301-400. The market value of insecticide-treated nets, window screening and ceilings currently in use in the city was estimated as 2, 5 and 42 million US$. More than three quarters of the respondents that lacked them said it was too expensive to install ceilings (82.2%) or window screens (75.5%).

Conclusion: High coverage and spending on screens and ceilings implies that these techniques are highly acceptable and excellent uptake can be achieved in urban settings like Dar es Salaam. Effective models for promotion and subsidization should be developed and evaluated, particularly for installation of ceilings that prevent entry via the eaves, which are the most important entry point for mosquitoes that cause malaria, a variety of neglected tropical diseases and the nuisance which motivates uptake.

Figure 1

Time trends of protective measures and drug use in the survey areas of the urban malaria control program. The overall trends over time were calculated using a logistic regression model with the protection measures and drugs as an outcome. Except for ITN usage (P = 0.507), usage and other protective measures and drugs all significantly increased or decreased (P < 0.001) (Year 1: May 2004-March 2005; Year 2: April 2005-March 2006; Year 3: April 2006- March 2007). Reproduced from reference [18].

Figure 2

The proportion of houses with different types of screens and ceilings found in Dar es Salaam city.

Figure 3

Graphs showing the cost paid for and expected for ceilings and window screening by respondents. A: The amount of money that has already been spent on the installation of ceilings, B; The amount of money that the non-users expected to spend on ceilings, C; The amount of money that has already been spent on the installation of window screens, D; The amount of money that the nonusers expected to spend on window screens.

Figure 4

A photograph of different types of ceilings illustrating the stylish gypsum and tongue and groove types of ceiling.