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

Yvonne Geissbühler¹^,2 , Prosper Chaki²^,3^,5 , Basiliana Emidi³^,4 , Nicodemus J Govella²^,3^,5 , Rudolf Shirima³ , Valeliana Mayagaya² , Deo Mtasiwa³ , Hassan Mshinda² , Ulrike Fillinger⁵ , Steven W Lindsay⁵ , Khadija Kannady³ , Marcia Caldas de Castro⁶ , Marcel Tanner¹ and Gerry F Killeen¹^,2^,5

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

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

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

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

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

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

author email corresponding author email

Malaria Journal 2007, 6:126doi: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.