Urban Malaria or Urban Myth?

Debate has gone back and forth as to whether malaria is a serious urban health problem or not. This issue itself is important to consider since the world’s population continues to urbanize, making it very necessary to understand the nature of urban health problems for better planning.

The key issue is the anopheles mosquito, which likes relatively clean collections of water, like puddles, exposed to sunlight. The crowding and pollution characteristic of urban areas does not favor anopheles mosquitoes, and yet studies continue to document some degree of malaria prevalence in urban communities of endemic countries.dscn4191.JPG

Lagos, Nigeria represents anopheles scarcity. As far back as 1946 Muirhead Thomson observed an inhospitable environment for the breeding of anopheles. USAID partners revisited three neighborhoods in Lagos in 1998 and found malaria parasites in only 0.9% of over 900 children between 6 and 60 months of age. A. gambiae mosquitoes were not found in knockdown and human baiting studies, and a larval breeding density of only 0.3 was detected. The predominant mosquitoes were culex. Ironically in these neighborhoods, local shops were selling over US$ 3,000 per week in antimalarial drugs. Residents still perceived that they had ‘malaria’ and expressed similar cultural beliefs and perceptions as the outlying rural communities from where they had emigrated.

farm-to-market-jalokere-sm.jpgClearly some level of malaria prevalence in the cities arises from traveling back and forth between rural and urban areas for economic and social obligations, for example the traders who travel back and forth guaranteeing food supplies for the cities. Urban health services therefore do need some stocks of antimalarial drugs to treat people coming in from the rural areas who are incubating a malaria infection.

A more complex issue is the nature and extent of urban malaria transmission. A recent study in Ghana found that malaria in urban areas displayed a heterogeneity and complexity that differed from the rural environment. Marked intra-city variation indicated the need for targeting specific areas, especially neighborhoods of the urban poor. A major contributory factor to malaria prevalence in many cities is urban agriculture, an informal economic activity of the urban poor.

Urban areas present a special challenge for ITN distribution. Epidemiological and entomological studies are recommended to map each city to determine target areas, and yet such targeting may be seen as discrimination by the general population who do not distinguish among types of mosquitoes and febrile illnesses. It may be politically necessary to provide ITNs in all poor neighborhoods regardless of mosquito ecology. In the area of treatment, health providers can be a bit more focused through using laboratory or rapid diagnostic tests to reduce inappropriate use of expensive antimalarials. As cities grow, are urban planners and health policy makers ready for the problem of urban malaria?

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