Abstract:
Background: Simple modifications of typical rural house design can be an effective and relatively
inexpensive method of reducing indoor mosquito vector densities and consequently decreasing
malaria transmission. Public health scientists have shown the potential for house design to protect
people against malaria, yet this type of intervention remains virtually ignored. A randomized-
controlled study was, therefore, undertaken to determine the effects of this method of vector
control on the density of indoor resting malaria vectors in a rice irrigation scheme area in lowlands
of western Kenya.
Methods: Ten treatment houses were modified with ceilings of papyrus mats and insecticide-
treated netting (ITN) and tested against ten control houses without papyrus ceilings. To determine
densities of mosquitoes resting in homes, the pyrethrum spray method was used to simultaneously
collect indoor resting malaria vectors in intervention and control houses. Each house was sampled
a total of eight times over a period of four months, resulting in a total of 80 sampling efforts for
each treatment. Community response to such intervention was investigated by discussions with
residents.
Results: Papyrus mats ceiling modification reduced house entry by Anopheles gambiae s.l and
Anopheles funestus densities by between 78–80% and 86% respectively compared to unmodified
houses. Geometric mean density of Anopheles gambiae s.l. and Anopheles funestus in modified houses
were significantly lower (t18 = 7.174, P < 0.0001 and t 18 = 2.52, P = 0.02, respectively) compared to
controls. Unmodified houses were associated with relatively higher densities of malaria vectors.
There was a 84% (OR 0.16, 95% CI 0.07–0.39, P < 0.0001) and 87% (OR 0.13, 95% CI 0.03–0.5, P
= 0.0004) reduction in the odds of Anopheles gambiae s.l. and Anopheles funestus presence in
modified houses, respectively, compared with unmodified houses. Residents responded favourably
to this mode of vector control.
Conclusion: House modifications involving insect screen ceilings made from locally available
materials and small ITN incorporated in house construction have the potential to reduce human
exposure to malaria vectors, and thus parasite infection, in a rice irrigation scheme area of western
Kenya. Ceiling modification is likely to be acceptable and is expected to be of greatest benefit when
used in combination with other malaria control strategies
