Tropical Health Matters

In Nairobi’s Korogocho slum Yazoume Ye and colleagues looked for evidence of malaria parasites among 1,069 residents. Among those with data, 16.9% had a recent fever episode. Half were treated, primarily with sulphadoxine-pyrimethamine or amodiaquine, while four received artemether-lumefantrine. Ironically, “Three were positive for Plasmodium falciparum using RDT; however, all were confirmed negative on microscopy. Microscopic examination of all 953 readable slides showed zero prevalence.”

These results were similar to a study we did in low income neighborhoods of Lagos in 1998 screening only children between 6 months and 5 years of age [Afr. J. Med. med Sci (2001) 30, suppl. 7-15].  Blood film investigation of 916 children yielded a parasite prevalence of 0.9%.  Knockdown and night landing collections of mosquitoes in houses in these neighborhoods found no anopheles species. Very low densities of A. gambiae larvae were found in breeding sites.

These findings should not have surprised us since as far back as 1946, researchers had found that urban Lagos was too dirty to host the more finicky anopheles (Muirhead Thomson RC. Studies on Anopheles gambiae and A. melas in and around Lagos. Bulletin of Entomological Research. 1946; 38: 527-558).  Those cases we did find may have resulted from Lagosians visiting their relatives in the village during a recent wedding or funeral ceremony.

We do know that urban environments are not free from malaria, but one needs to identify anopheles-friendly sites and then look for focal transmission sites around those.  Urban agriculture (see photo from Bamako), flower gardens in higher income areas and some of the less dense urban peripheral settlements might be places to look.  This shows the need to plan urban malaria control with full understanding of the micro-ecologies of an urban setting.

The growing problem of urban hunger and urban food insecurity was featured in the Wall Street Journal today. In Monrovia, Liberia, “The cost of a cup of rice has risen to nearly 50 cents from 20 cents, a huge leap for many families who live on less than $1 per day.” The result: “Escalating hunger in African cities is forcing aid agencies accustomed to tackling food shortages in rural areas to scramble for strategies to address the more complex hunger problems in sprawling slums.”

One of these strategies, according to IDRC is urban agriculture:

Urban agriculture (UA) is wrongly considered an oxymoron. Despite its critical role in producing food for city dwellers around the world, urban food production has largely been ignored by scholars and agricultural planners; government officials and policymakers at best dismiss the activity as peripheral and at worst burn crops and evict farmers, claiming that urban farms are not only unsightly but also promote pollution and illness. Contradicting this image, recent studies document the commercial value of food produced in the urban area while underscoring the importance of urban farming as a survival strategy among the urban poor, especially women heads of households.

Urban farming requires water. The International Water Management Institute reports that, “Manual water fetching with watering cans is most common.” They often get water from “polluted streams or they do farming along storm water drains and gutters.” This sometimes leads to “wastewater irrigation.”

Of course malaria vectors need water. In urban Accra, Ghana, Klinkenberg and collaegues found that Anopheles and Culex “outdoor biting rates were respectively three and four times higher in areas around agricultural sites (UA) than in areas far from agriculture.”

The solution to the problem of urban malaria is not to stop urban agriculture, but to intensify integrated vector management interventions.  We certainly don’t want to protect people from malaria and then have then suffer from food insecurity.