In the past, malaria has generally been associated with swampy, rural areas, explains Guy Barnish, a parasitologist at the LSTM. When people in cities went down with malaria it was thought that they had contracted it by going into rural areas. But our research in west Africa has produced more and more evidence to show that malaria is now actually being transmitted in cities.
What we are keen to get across is that this is a potentially avertable crisis, says Martin Donnelly, a vector biologist at LSTM. In Ghana, he supervised the first study to assess malaria in large numbers of children in cities. Its not just a health sector problem - it involves all municipal authorities, government and environmental planning.
Part of the problem is thought to stem from more vegetables and crops being grown within city boundaries, as more of the worlds population moves into urban areas. By watering crops, people are inadvertently creating a suitable habitat for the deadly, malaria-carrying mosquito, says
This idea gets some support from Donnellys study. His student, Eveline Klinkenberg, surveyed urban Ghanaian communities in Accra - a dry, coastal city - and Kumasi - a wetter forest city.
She surveyed about 1800 children under five in each city for malaria prevalence, and questioned parents or caregivers on factors such as socioeconomic status and recent travel. GPS (global positioning system) technology was used to record locations.
Mapping distances between communities and urban agriculture sites showed in some cases that the closer you were to agricultural sites, the higher the risk of malaria, says Donnelly. Though he emphasises that this was not a universal finding.
Urban agriculture is a problem, agrees Marcia Caldas de Castro, now at the University of South Carolina, US, who worked on an eight-year project to control urban malaria in Dar es Salaam, Tanzania. But she adds: For some families, urban agriculture is a food security issue. So it is not feasible to come up with policies that remove agriculture.
The Ghanaian study revealed surprisingly high rates of urban malaria, Donnelly told New Scientist, as well as high variations in prevalence within the two cities
Of the children surveyed in Accra, between 8% and 20% had contracted malaria. The general prevalence was lower in sites at Kumasi - contrary to the researchers expectations of the wetter city - at around 5% to 6%, says Donnelly. But one site in Kumasi showed that 33% of the children had malaria, despite there having been no recent history of travel in most cases, suggesting the infection had been caught in the city.
These rates are still lower than in rural areas, but with the United Nations forecasting that by 2025 over 800 million people will live in African cities, urban malaria could become a major problem.
The next stage of the study will look at the use of interventions, such as insecticide treatments and bednets. Caldas de Castro agrees that community education and better agricultural practices may also help.
The Ghanaian study was conducted in collaboration with the International Water Management Institute and was funded by the UK Department for International Development. An international workshop on urban malaria will take place in Pretoria, South Africa from 2 to 4 December.
( Source: NewScientist.com news service , 30 November 04)