Tropical Health Matters

The Times of India reports that, “Malaria is no longer restricted to just monsoon months as in the past. Spurred on by widespread construction activity and the resulting poor sanitation, the disease has becomes a round-the-year feature in Mumbai, killing less people but afflicting more.”

An increase was noted: “In all, 76,755 contracted the ailment in 2010, 74% more than the 2009’s figure of 44,035,” but with fewer deaths (better case management?), but it is not clear whether these cases were parasitologically diagnosed.

A member of the medical association attributes the increase, especially the off-season rise, to human activity – construction projects. The official stated that, “Construction sites have puddles of water in which mosquitoes breed. Since construction work goes on throughout the year, so does the breeding. This obviously increases the incidence of malaria.”

Worry was also expressed about, “resistance developed by the Anopheles albimanus mosquito that the civic body’s insecticide fumigation has no effect on it.” This has led the city to consider using “bacillus thuringiensis variety israelensis” for control.

Ironically, in pointing out that, “Another reason for the spread of malaria, which is caused by a parasite called plasmodium, during non-monsoon months is that plasmodium can stay in the body for a long period,” the article raises the possibility that the upswing may not be fully due to new transmission.

Aside from these possible limitations on the validity of the data,  the potential for increased transmission is worrisome, especially in a part of the world that has received less (but increasing) attention from the Roll Back Malaria Partnership. The map from the 2008 World Malaria Report shows the extent of the problem in Asia.

India has a double problem with malaria, hosting both P. vivax and P falciparum.  A recently published article reports that while the national control program has introduced artemisinin-based combination therapy for P. falciparum as a first-line treatment, the older drugs, chloroquine (CQ) and Sulphadoxine-Pyrimethamine (SP) are still available. Unfortunately Shrabanee Mullic and colleagues found that, “In Jalpaiguri District the overall failure rate of CQ was 61% and of SP 14%, which was well above the WHO recommended cut-off threshold level (10%) for change of drug policy.”

Other research in India examined vector control with positive effects. “A study was conducted to evaluate the preventive efficacy of insecticide-treated mosquito nets (ITMNs) and mosquito repellent (MR) in a malaria-endemic foothill area of Assam, India, with forest ecosystem.” The researchers found that, “The total vector population in the three intervention sectors decreased significantly compared with that of the non-intervention one.”

Overall, malaria in India is a complex phenomenon with different forms of the parasite, different ecological settings and different levels of government involved. More attention is needed to address this complex situation is malaria is ever to be eliminated.

Africa is one of the fastest urbanizing regions of the world. Estimates are that nearly 40% of Africans live in urban areas today. This number is expected to exceed 50% by 2030. UN Habitat reports in State of the World’s Cities that African urbanization is often focused on the major cities like the capital, with major slum development, not a place where anopheles mosquitoes are comfortable.

Studies have shown that malaria is not generally an urban disease because dense, congested and dirty urban settings do not favor the breeding of anopheles mosquitoes. When malaria occurs in urban areas, it is often found in very focal transmission sites, for example, in places where urban agriculture is practiced.

Luanda in Angola presents a good example of the urban phenomenon as seen in the chart.  Although much of the surrounding country to the north and east are highly endemic areas, Luanda itself was found to have a prevalence of only 3.5%.  There are variations as expected with the somewhat less dense suburbs having greater, but still not high levels of prevalence.

What is important is that this city contains up to half of the country’s 16+ million inhabitants and is growing. Ironically, while prevalence is low, national strategy documents cite malaria as a cause of nearly one-quarter of child deaths in Luanda.  Clearly there are diagnostic challenges.

Unfortunately the absence of malaria in urban areas does not preclude spending money on malaria treatment, as was documented in Nairobi. We documented a similar challenge in Lagos, Nigeria where prevalence among children aged 1-6 years was only 0.9%, but community members had spent thousands of dollars in preceding weeks on antimalarial medicines to treat fevers that they suspected as being malaria.

Moving forward toward malaria elimination will require countries to account for increasing urbanization.  Increased use of diagnostic tools will be required to ensure appropriate and targeted use of anti-malarial drugs.  Vector control activities will need to be strategic and focus specifically on anopheles’ verified breeding sites.

While increasing urbanization may result in proportionately fewer people at risk from malaria, population growth generally will unfortunately guarantee that large rural populations remain at risk.  National malaria strategies need to take these varying ecologies into account if they are going to eliminate malaria.

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.