Tropical Health Matters

The recently concluded climate change summit on Copenhagen did not stress health, let alone malaria, as much as other consequences of climate change.  The Inter-governmental Panel on Climate Change has let us know a reason why attention to malaria in the climate debate may be somewhat confused:

Climate change may “have mixed effects on malaria; in some places the geographical range will contract, elsewhere the geographical range will expand and the transmission season may be changed.”

Kenya is one of those areas that has been reporting increases in the geographical range of malaria – particularly into the highlands.

Li and colleagues have been examining the Western Highlands over the period 2003-05 and documented variability of mosquito breeding sites by season and year.  Their findings point to ways to improve larval habitat modifications as an important part of integrated vector management in such areas of seasonal and focal mosquito breeding.

An integrated approach to malaria control also is credited for a “pronounced reduction and possible interruption of malaria transmission in 2 highland areas of Kenya for a 1-year period and provides evidence that interruption of transmission was related to widespread annual IRS insecticide treatment and use of ACT as first-line treatment for uncomplicated malaria. Although both areas remain at risk for recurrence of malaria epidemics, our study provides evidence that interruption and eventual elimination of malaria in areas of unstable transmission may be achievable.”

The Mount Kenya highlands have been studied by Chen et al. who were concerned about possible increases in malaria cases reported over the past 10-20 years there. They found that, “Local malaria transmission on the Mount Kenya highlands is possible due to the presence of An. arabiensis. Land use pattern and land cover might be the key factors affecting the vector population dynamics and the highland malaria transmission in the region.” Human factors appear to play an important role –

On the Mount Kenyan highlands, the population has increased at least 25% over the past 20 years. Population density in Karatina and Naro Moru areas is estimated at 530 persons per square km, much higher than those in the further north areas, e.g., only 81 persons per square km in Nanyuki. With the increasing population on the highlands, enhanced human activities including deforestation, farming and livestock rearing could create more vector habitats. For example, at the site northwest to Karatina, hundreds of anopheline larvae were found in ditches holding spring water for crops in a field. The vectors emerging from this kind of habitat can play an important role in local malaria transmission.

More recently researchers from the Kenya Medical Research Institute with support from DfID “found that the average temperature in the Kenyan Central Highlands had risen from 17C in 1989 to 19C today.” Specifically the group reported that …

Before the 1990s malaria was absent from the region because the parasite that causes it can mature only above 18C. However, malaria epidemics began among the population as average temperatures went over the 18C tipping point. The number of people contracting malaria during these epidemics has increased seven-fold in the past decade. In 2005, malaria-carrying anopheles mosquitoes were discovered in Naru Moro, more than 6,175ft (1,900m) above sea level.

Climate change may partly explain malaria increases in Kenya’s highlands, as may more local human activities. The important lesson is that such epidemic-prone areas need to be closely monitored. A timely mix of control interventions can then be judiciously applied. As Noor and colleagues recommend:

As malaria interventions go to scale effectively tracking epidemiological changes of risk demands a rigorous effort to document infection prevalence intime and space to remodel risks and redefine intervention priorities over the next 10-15 years .

Copenhagen is ready for the United Nations Climate Change Conference, which opens tomorrow for two weeks. Live webcasts and archived versions will enable people with adequate bandwidth to feel part of the deliberations. At present the main consequences of climate change that are attracting global attention include –

• More droughts and more flooding
• Less ice and snow
• More extreme weather incidents
• Rising sea level

These physical changes will have major social, political, economic and health consequences.  Implications for malaria specifically, require some interpretation. This is where reports of the Intergovernmental Panel on Climate Change may help.

Projected trends in climate-change-related exposures of importance to human health will have mixed effects on malaria; in some places the geographical range will contract, elsewhere the geographical range will expand and the transmission season may be changed.

The IPCC Report also acknowledges “the difficulty of generalizing health outcomes from one setting to another, when many diseases (such as malaria) have important local transmission dynamics that cannot easily be represented in simple relationships.” Examples of individual country assessments follow:

• Australia may see potential change in the geographical range of dengue and malaria
• Bolivia expects intensification of malaria and leishmaniasis transmission. Indigenous
  populations may be most affected by increases in infectious diseases
• Bhutan might experience spread of vector-borne diseases into higher elevations
• India projects that Malaria could to move to higher latitudes and altitudes

The IPCC report sees that drought would have a limiting effect on malaria.

In the long term, the incidence of mosquito-borne diseases such as malaria decreases because the mosquito vector lacks the necessary humidity and water for breeding. The northern limit of Plasmodium falciparum malaria in Africa is the Sahel, where rainfall is an important limiting factor in disease transmission. Malaria has decreased in association with long-term decreases in annual rainfall in Senegal and Niger.

We certainly do not hope that drought provides a ‘solution’ for malaria elimination in endemic countries.  What these climate proceedings should remind us of is the need for strong surveillance systems that can detect and respond to trends.

Countries therefore, need to be ready to adapt their malaria control efforts not only to the positive results of universal coverage but also to the negative spread and shifts in malaria transmission that could come from climate change.

The Americas have the lowest rates of malaria among the major endemic areas of the world. So when concerns are raised that Guyana may not be able to keep its total cases in 2009 below 10,000, countries like Nigeria, Tanzania and DRC may wonder what the fuss is all about. We must remember therefore, that for malaria eradication to succeed, the disease must be eliminated in EACH endmic country, no matter how few the number of current cases appears to be.

Success in Guyana has been mixed, with great reduction in some target communities, but now “There are areas in the country which did not have a problem now, but are not recording measurable and or moderate levels of malaria.” In the Omai area, “hundreds of small miners have appeared on the scene.” They are not paying attention to environmental control, but instead are responding to the increasing price of gold on the world market.

Guyana has received Global Fund grants from Round 3 and 7 for malaria control. Though the country has around three-quarters of a million people, the proposals focused on the more endemic regions. For example, Regions 7 and 8 are populated mostly by a little over 20,000 Native American peoples. These regions have also been inundated by another 20,000 informal miners and loggers.

The GFATM performance report on case management in the Round 3 grant shows that while appropriate malaria drugs are available in all target communities, actual appropriate treatment of vivax and falciparum malaria hovers around only 60% of cases. (Round 7 was signed only in May 2009 so a detailed progress report is not yet available.)

Community participation indicators also show high marks, but then one needs to consider that the non-indigenous miners and loggers may not really be part of a community.

The 2006 Multiple Indicator Cluster Survey found that sleeping under bednets by children under five years of age increased from 6.5% to 70% between 2000 and 2006. Of course this leaves open the question of whether adult migrant miners are using nets and are harboring the disease. Palmer and colleagues describe one typical mining camp in this region –

The mining camp … was approximately 400 km inland from Georgetown, the capital of Guyana, in the heart of the Amazon region of the country. It was typical of many of the mining camps in the jungle. Men sleep in rows of 20 to 40 hammocks strung underneath a large tarp-like covering. The tarp coverings are not enclosed, but the men usually sleep under mosquito netting, as malaria infection is a constant problem.

If Guyana is to meet its 2012 target of only 8,000 annual cases of malaria some serious thinking is needed about strategies to reach the diverse populations in the endemic regions.  The indigenous peoples have their community structures, and it appears that these have been reached.

The challenge then is to distinguish the other residents of these endemic regions and organize malaria control activities that will be appropriate to their social context, recognizing at the same time that their mining practices may be detrimental to the environment and the elimination of malaria.

The Los Angeles Times has reported on “Scientists have discovered that chimpanzees in Tanzania are falling ill and dying from an AIDS-like disease.” Researchers have known of simian immunodeficiency virus (SIV) for some time now, but had discounted its virulence.  The group in Tanzania has changed that by finding that chimps with SIV “died 10 to 16 times more frequently than uninfected chimps during a nine-year study.”

Not only are the researchers looking “into the origins of HIV and how it jumped from chimps to humans.”  They are also exploring the implications for HIV therapy and vaccines for humans.  A pathologist who examined the tissue in one dead chimp said it “looked just like a sample from a human patient who has died of AIDS.”

Reports are of shared malaria parasites between simians and humans are also becoming more common.  Here are some of the recent findings.

• Researchers at Duke University found some similarity in genetic response to P. vivax between yellow baboons in Kenya’s Amboseli National Park and humans
• Researchers based in Gabon and France report the discovery of a new malaria agent infecting chimpanzees in Central Africa. This new species, named Plasmodium gaboni, is a close relative of the most virulent human agent P. falciparum
• Ulf Bronner and colleagues document a human case of P. Knowlesi in a Swedish traveler returning from Malarian Borneo, while readers of Mayo Clinic Proceedings are reminded to “keep in mind a broad differential diagnosis. P knowlesi is transmitted from human to human or from the macaque monkeys.” in Southeast Asia
• In Brazil Ana Maria Ribeiro de Castro Duartea and colleagues explored the possibility arising from the parasitological prevalence of P. vivax and P. malariae in wild monkeys from Atlantic forest that monkeys could be a potential reservoir of these parasites for humans

In our efforts to control both HIV and malaria we must look at the broader environment and consider direct and indirect human interaction with wildlife.  It will not be enough to reduce and eliminate disease transmission among humans, if an animal reservoir remains.

While there have been some doubts that climate change will cause more malaria, there is little doubt expressed that deforestation is one of the major contributors to the malaria problem.  Actually a link is found between deforestation and malaria.

Yasuoka and Levins looked at anophelene ecology changes in relation to deforestation. They learned that, “Although niche width of anopheline species was not associated with density changes, sun preference was significantly associated with an increase in density. This study suggests the possibility of predicting potential impacts of future deforestation on vector density by using information on types of planned agricultural development and the ecology of local anopheline species.”

Their review of reports from across the malaria-endemic parts of the would found that although the mechanisms that link malaria and deforestation are complex, there were clearly examples of direct effects on some anopheline species either because of habitat changes or because of land use changes, particularly agriculture.

Vittor and colleagues have recently examined deforestation and malaria in the Peruvian Amazon.  Their study concluded that, “Multivariate analysis identified seasonality, algae, water body size, presence of human populations, and the amount of forest and secondary growth as significant determinants of A. darlingi presence. We conclude that deforestation and associated ecologic alterations are conducive to A. darlingi larval presence, and thereby increase malaria risk.”

Ultimately the elimination of malaria will require our links with broader development and environment partners.

We know at the global level that malaria currently clusters in countries that are relatively closer to the equator rather than in temperate or colder regions.  A study out of Papua New Guinea (PNG) emphasizes the need to learn about local variations in malaria distribution as an aid to proper planning and intervention.

Meyers and colleagues found that, “malarial infection is significantly and independently associated with lower elevation and greater distance from administrative centre in a rural area in PNG.” They considered that higher elevations would be hillier with less opportunity for water collection, and locations on the outskirts of villagers may be closer to swampy or agricultural lands where mosquito breeding would be greater.

Local geography also plays a role in the distribution of urban malaria. A recent study in Ouagadougou, Burkina Faso found that malaria was “focused in areas which are irregularly or sparsely built-up or near the hydrographic network” such as urban gardens as well as in poorer neighborhoods. The solutions to urban areas are multi-sectoral according to Donnelly et al. : “Urban malaria is uniquely amenable to prevention and control as the existing health, urban planning, agricultural and governance structures present opportunities for collaborative approaches that can include both the community and the substantial private sector.”

The East African Highlands are another example of geographical variations of malaria distribution in a country.  These are areas where malaria is seasonal.  Recent investigation has shown how climate change may actually be changing the seasonal distribution of rain, vector and thus malaria. Deforestation can also create geographical variations in malaria distribution.

Natural and man-made variations in geography within countries and even communities have important implications for the planning, targeting and timing of malaria control activities.  Clinics in certain areas may need more stocks of ACTs. Supplies of drugs, nets and spray should be timed in advance of known seasonal onset of malaria in other areas.  As elimination comes closer to reality this micro-planning for micro-geographical areas will be the only way to keep the disease under control. It will also require a multi-sector approach.

Kenya is facing at least two major and seemingly opposing changes in its malaria epidemiological profile.  SciDev.net reports on an article from The Lancet that confirms, “An analysis of data collected over 18 years from malaria-infected children at Kilifi District Hospital, on Kenya’s Indian Ocean coast, found that paediatric admissions for malaria had fallen by 75 per cent over a period of just five years.”

At the same time, “In recent years malaria has also appeared in the highland areas where it was previously unheard of,” according to Inter Press Service (Johannesburg).  Keeping pace with these changes is essential if the national malaria control services and its malaria donor partners are to provide appropriate interventions for each part of the country.

In the highlands where people are less used to malaria, Sumba and colleagues found that. “A significant proportion of this highland population chooses local shops for initial malaria treatment and receives inappropriate medication at these local shops, resulting in delay of effective treatment.”

Because highland residents, for example those in Kibera, Nairobi, travel back to their home villages in malaria endemic areas, they bring the parasites back. With the potential of global warming making the highlands more favorable to malaria transmitting mosquitoes, the highlands will face increasing risk, according to an IRIN news release. Furthermore, “As 20 percent of Kenya’s population — eight million people — living in the highland areas are now exposed to malaria, new plans for preparing and responding to an epidemic are needed” (Inter Press Service News).

In The Lancet article O’Meara and colleagues believe that the reduction in transmission in coastal Kilifi is multi-factorial and could be related to bednet use and changes in malaria drug policy among others. They conclude that, “Our results are consistent with comparisons between multiple sites and provide further evidence that reduction of trans mission leads to a change in pattern of severe disease but might not lead to immediate reductions in disease burden.” This means that …

Emphasis on use of insecticide-treated bednets, early treatment, and other control measures must be increased to maintain reductions in disease burden and prevent a potential resurgence of malaria in a population with far less immunity than before.

The experience in Kenya shows that changing climatic conditions and increasing effectiveness of malaria control interventions may in the short run put more people at risk of severe malaria due to reduced immunity levels.  The need for sustaining efforts in some parts of the country and focusing new interventions on others makes the elimination of malaria a challenging and ever shifting target.

Malaria “vectorial capacity was estimated to be 77.7% higher in the deforested site than in the forested site” in western Kenya according to a new study by Afrane and colleagues. Deforestation created micro-climates and micro-habitats. They concluded that “deforestation in the western Kenyan highlands could potentially increase malaria risk,” and unfortunately, “In African highlands where temperature is an important driving factor for malaria and the human population generally has little functional immunity.”

Generally, “Kenya’s forests are rapidly declining due to pressure from increased population and other land uses,” as explained by the World Rainforest Movement (WFM). The process has been long standing from including early establishment of large agricultural plantations in the last Century to continued agricultural expansion based on population growth and logging. WFM advocates for community involvement in forest conservation.

Kenya is making progress on reducing malaria deaths through successful LLIN and treatment efforts, but this may be offset if communities do not see the connection between malaria and their environment.  Intersectoral collaboration in malaria control is crucial so that gains in malaria intervention coverage are not counteracted through expanding endemic areas.

Malaria is a disease with strong links to the environment. Here are a few thoughts on malaria in observance of Earth Day.

• Washing Long Lasting Insecticide-treated Nets infrequently will not only preserve their effectiveness longer but might save water
• Integrating agriculture – e.g. coffee production – into existing forest ecology saves trees, whose clearing would have opened more mosquito breeding sites
• Appropriate and safe use of insecticides during indoor residual spraying can prevent environmental contamination

People alter the environment in many ways that make mosquito breeding possible and in the process create other environmental problems. We may thereby make the environment less economically viable – as people lose income they are less able to afford malaria treatment and preventive interventions or buy or build housing that protects them from disease. We need to look beyond medicines and nets and think about the broader social, economic and environmental factors that contribute to the spread or control of malaria.

Please feel free to add your own ideas and help celebrate Earth Day.

The Cape Times has issues a warning that greatr than normal malaria transmission is expected during the current rainy season in southern Africa. They quote a WHO official as syaing, “Malaria transmission from November 2007 to May 2008 is expected to be above normal in most parts of southern Africa. In East Africa, October to May is an important part of the rainy season, when malaria transmission and epidemics can occur. In southern Africa, the heavy rains and likelihood of flooding in certain areas from December may lead to an increase in malaria transmission.” This prediction links with US Weather Service reports for early December that state, “In southern Africa, consistent with the current moderate La Nina episode, rainfall was overall above average across much of southern Africa.”

Jones et al., (2007) tested a model for understanding forecasting malaria in the highlands of Tanzania, Such highland areas, like much of southern Africa are subject to epidemics as opposed to the year round transmission found in the lowlands of much of Africa. They addressed the issue of Malaria Early Warning Systems (MEWS) based on climate variations that have been proposed to warn ministries of health of the potential of increased risk of malaria epidemics and drew attention to the The El Niño Southern Oscillation cycle. this builds on suggestions for creating such a system by Thomson and Connor (2001).

Jones et al., found that “malaria incidence is positively correlated with rainfall during the first season (Oct-Mar). For the second season (Apr-Sep), high malaria incidence was associated with increased rainfall, but also with high maximum temperature during the first rainy season.” Chaves and Pascual (2007) built on the malaria early warning experience to propose and discuss early warning systems for other neglected tropical diseases. They concluded that, “EWS are a feasible ecological application for neglected tropical diseases,” and recommended that “Forecasts can be useful in planning services for the populations affected, allowing estimates of approximate number of hospital beds, vaccine shots, drug doses and vector control measures.”

The increasing ability to understand weather and climate and their effects on malaria, especially in epidemic regions of the world is extremely helpful for planning timely deployment of malaria treatment and prevention interventions. This presents a big challenge to countries dependent on large scale donor project funds, which are not always dispersed in a timely manner or on a regular schedule and are thus, not always in tune with general national health and development planning cycles.