Impact of urban agriculture on malaria vectors in Accra, Ghana

Host-Pathogen interactions, Malaria Infection cell biology. See complete image here.

Published in Malaria Journal, 4 August 2008
By Eveline Klinkenberg, PJ McCall, Michael D Wilson, Felix P Amerasinghe and Martin J Donnelly

To investigate the impact of urban agriculture on malaria transmission risk in urban Accra larval and adult stage mosquito surveys, were performed.

There has been a resurgence of interest in the problem of urban malaria in sub-Saharan Africa in recent years. Urban malaria is likely to increase in importance as rapid urbanization will result in the majority of Africa’s population living in cities in the near future. It is commonly assumed that urbanization leads to a decrease in malaria prevalence because it results in fewer Anopheles breeding sites, reduced biting rates due to the higher ratio of humans to mosquitoes, better access to treatment and better (mosquito-proof) housing.

However, there is a concern that areas with rapid, unplanned urbanization, typically associated with low income, poor education, poor health care and poor housing/sanitation, may not experience such marked decreases in malaria transmission.

Urban malaria epidemiology will pose different challenges to those in rural areas. One concern is that urban agriculture, promoted to increase food security and alleviate poverty might, especially when irrigated, increase the urban malaria risk by creating breeding sites for the Anopheles vector. Several studies have recorded breeding of Anopheles in urban agricultural sites, but few studies have investigated the impact of urban agriculture on entomological and epidemiological indicators. In urban Bouaké, Côte d’Ivoire, higher vector densities were found in rice growing areas than market garden areas, although sporozoite infection rates were lower and the impact on malaria epidemiology was not quantified.

Robert et al suggested that the market garden wells in urban Dakar, Senegal, might not be the most important mosquito breeding grounds as the presence of larvae in the wells did not coincide with the vector density peaks. Matthys et al found that urban farming created additional breeding sites for anophelines in the city environment and that malaria risk was affected by the type of farming present. However, in a recent study in two cities in Kenya, Keating et al found no association between household level farming and vector breeding sites. Entomological studies in Kumasi, Ghana, found higher Anopheles biting rates and significantly more reported malaria cases in urban areas with agriculture compared to urban areas without agriculture, though later epidemiological studies indicated that living near urban agriculture was not associated with malaria parasitaemia in young children in Kumasi.

Read the complete paper here in the Malaria Journal.