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Interdependence of domestic malaria prevention measures and mosquito-human interactions in urban Dar es Salaam, Tanzania

Yvonne Geissbühler12*, Prosper Chaki235, Basiliana Emidi34, Nicodemus J Govella235, Rudolf Shirima3, Valeliana Mayagaya2, Deo Mtasiwa3, Hassan Mshinda2, Ulrike Fillinger5, Steven W Lindsay5, Khadija Kannady3, Marcia Caldas de Castro6, Marcel Tanner1 and Gerry F Killeen125

Author Affiliations

1 Swiss Tropical Institute, Department of Public Health and Epidemiology, Socinstrasse 57, PO Box, 4002 Basel, Switzerland

2 Ifakara Health Research and Development Centre, Co-ordination Office, Kiko Avenue, PO Box 78373, Dar es Salaam, Tanzania

3 Dar es Salaam City Council, Dar es Salaam, Tanzania

4 University of Dar es Salaam, Dar es Salaam, Tanzania

5 School of Biological and Biomedical Sciences, South Road, Durham DH1 3LE, UK

6 Department of Population and International Health, Harvard School of Public Health, 655 Huntington Avenue, Boston, MA 02115, USA

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Malaria Journal 2007, 6:126  doi:10.1186/1475-2875-6-126

Published: 19 September 2007

Abstract

Background

Successful malaria vector control depends on understanding behavioural interactions between mosquitoes and humans, which are highly setting-specific and may have characteristic features in urban environments. Here mosquito biting patterns in Dar es Salaam, Tanzania are examined and the protection against exposure to malaria transmission that is afforded to residents by using an insecticide-treated net (ITN) is estimated.

Methods

Mosquito biting activity over the course of the night was estimated by human landing catch in 216 houses and 1,064 residents were interviewed to determine usage of protection measures and the proportion of each hour of the night spent sleeping indoors, awake indoors, and outdoors.

Results

Hourly variations in biting activity by members of the Anopheles gambiae complex were consistent with classical reports but the proportion of these vectors caught outdoors in Dar es Salaam was almost double that of rural Tanzania. Overall, ITNs confer less protection against exophagic vectors in Dar es Salaam than in rural southern Tanzania (59% versus 70%). More alarmingly, a biting activity maximum that precedes 10 pm and much lower levels of ITN protection against exposure (38%) were observed for Anopheles arabiensis, a vector of modest importance locally, but which predominates transmission in large parts of Africa.

Conclusion

In a situation of changing mosquito and human behaviour, ITNs may confer lower, but still useful, levels of personal protection which can be complemented by communal transmission suppression at high coverage. Mosquito-proofing houses appeared to be the intervention of choice amongst residents and further options for preventing outdoor transmission include larviciding and environmental management.