Raised houses reduce mosquito bites.

Area of Science:

• Medical Entomology
• Public Health
• Tropical Medicine

Background:

• Malaria transmission in continental Africa largely occurs indoors due to house construction and vector biting times.
• Houses in São Tomé are often elevated on stilts, a traditional method to avoid mosquito bites.
• The effectiveness of stilt houses against malaria vectors and its relation to biting times was largely untested.

Purpose of the Study:

• To investigate if house construction and time of night influence exposure to Anopheles gambiae, the sole malaria vector in São Tomé.
• To assess the efficacy of elevated housing (stilt houses) in reducing indoor vector exposure.

Main Methods:

• Conducted all-night outdoor and indoor landing collections at ground level and in stilt houses.
• Determined the gonotrophic age of host-seeking Anopheles gambiae females.
• Utilized 1,149 miniature light-trap collections across 125 houses to correlate vector density with house construction.

Main Results:

• Anopheles gambiae predominantly bit outdoors at ground level, with less than one-third of biting occurring indoors.
• Stilt houses contained half the number of Anopheles gambiae compared to ground-level houses.
• Houses with eaves gaps had higher Anopheles gambiae density than those without; gonotrophic age did not affect entry rates.

Conclusions:

• House construction is a critical factor in determining malaria vector exposure in São Tomé.
• Significant variations in exposure levels exist between neighboring houses.
• Findings support the use of elevated housing designs as a malaria vector control strategy.