a complex disease

The Challenge | The Response | The Control

The Health Challenge

Malaria is a mosquito-transmitted parasitic disease that can be life-threatening. More than 200 million malaria infections are estimated to occur annually in over 100 countries. Of the nearly 900,000 malaria deaths estimated to occur annually, more than 90% are in African children less than 5 years old.

Plasmodium falciparum is the most threatening of the four malaria species that infect humans, because of its wide geographic range (covering most of sub-Saharan Africa) and its greater ability to cause severe or fatal disease.

Adults and older children living in areas where falciparum malaria is endemic are generally resistant to severe forms of malaria by virtue of having built up their immunity through repeated infections. Those most at risk of a severe or fatal outcome with falciparum malaria include young children (and others encountering malaria for the first time) who have essentially no immunity.

Pregnant women, whose natural malaria immunity is reduced during pregnancy, are also at greater risk of severe disease and death. Because malaria can have an impact on the placenta, pregnant women infected with falciparum malaria also face an increased risk of having a low birth weight baby.

The Responses to Global Malaria

Malaria infections are both preventable and treatable.

Prevention of new malaria infections:

There is currently no effective vaccine for malaria. The RTS,S pediatric malaria vaccine, under development by a consortium that includes the international nonprofit PATH and GlaxoSmithKline, has entered late stage human trials.

Currently, five key preventive measures are used in malaria-endemic areas:

• Use of insecticide-treated bed nets (ITNs). Distribution of bed nets has accelerated dramatically in recent years.
• Indoor residual spraying (IRS) with an effective insecticide. This approach requires high coverage of a community’s housing to be effective. DDT was reintroduced in 2006 and, because it is highly effective, it became the preferred insecticide. Opposition has formed, and because of continued uncertainty about DDT’s long term safety, WHO has recently begun to look for alternatives.
• Elimination of mosquito breeding sites. This aspect involves better management of standing water and improved controls over mosquito larvae.
• Intermittent preventive treatment of pregnant women (IPT) with anti-malarial drugs in the second and third trimesters of pregnancy.
• Ongoing malaria surveillance. For malaria control, the goal of surveillance is to detect changing malaria infection patterns in order allow control programs to respond rapidly.

Photo from Center for Disease Control

Treatment of malaria infections: If begun early enough the course of infection, treatment of falciparum malaria is almost always successful.

• For many years, chloroquine was the drug of choice for both treatment and prevention of malaria. As malaria organisms developed resistance to chloroquine, that drug was eventually replaced by a combination of sulfadoxine and pyrimethamine. Eventually, resistance to these latter two drugs also spread and falciparum malaria is today resistant to all three drugs nearly everywhere.
• The current recommendation for treatment of falciparum is a drug combination that always includes the drug artemisinin. These artemisinin-based combination therapies (ACTs) have high malaria cure rates in most situations and have the added benefit of reducing the parasite load in blood, thereby reducing the chance that subsequent mosquito bites can transmit malaria to others.
• Concern is increasing that malaria’s resistance to ACTs will eventually develop, especially if, as sometimes happens, artemisinin is used as the only anti-malarial drug (i.e., monotherapy) rather than as part of a multi-drug combination. Artemisinin is still relatively expensive although efforts are underway to lower its cost.
• The advent of accurate rapid diagnostic tests for falciparum malaria is helping increase the proportion of infected people who are correctly diagnosed and treated early in their infection.

The Control

Previous Malaria Control Efforts

Through coordinated U.S. domestic efforts directed by CDC (which was established in 1946 as a malaria control agency), malaria was eliminated from the United States in the early 1950s.

From 1955 to the early 1970s, the World Health Organization carried out a malaria eradication program that, paradoxically, did not include most countries of sub-Saharan Africa. In its early phases, that eradication program, reliant on insecticides, malaria treatment and malaria surveillance, significantly reduced malaria burdens in several countries.

However, growing resistance of falciparum malaria to chloroquine and of target mosquitoes to available insecticides eventually stymied progress. Further setbacks included unsustained donor funding and the spread of malaria through movements of large refugee populations. Many of the gains achieved in the 1960s and early 1970s were subsequently reversed and the goal of malaria eradication was abandoned.

WHO, World Malaria Report 2008: 33.

Renewed Interest in Global Malaria Control

In the 21st Century, malaria control has ceased to be a backwater issue and is emerging as a global health success story capable of attracting significant new resource flows and high-level political support from diverse sources.

In 2003, the aggregate investment in malaria in developing countries was approximately $50 million. By 2008, the amount had climbed to $1.1 billion. In part, this resource surge occurred as a spinoff effect of the global mobilization around HIV/AIDS.

No less important, the accelerating push on malaria stemmed from a perception that malaria was a neglected disease with considerable opportunity for rapid, measurable gains, and recognition that progress was possible through a small battery of relatively simple and cost-effective interventions in countries where reliable government partners existed.

In this decade, multiple interests have made malaria control a priority: the government of the United States and the UK; the Global Fund to Fight AIDS, TB and Malaria; the Bill and Melinda Gates Foundation; the World Bank; corporations such as ExxonMobil, GlaxoSmithKline, and Hershey, and independent U.S. implementers such as PATH, CARE, and Family Health International.

Dramatic and cost- effective gains have been achieved where the key interventions (ITNs, IRS, ACTs, preventive treatment of pregnant women, improved surveillance) were successfully coordinated in a few focal countries. In Zambia, for example, malaria prevalence fell by 53% between 2006 and 2008 and the prevalence of severe childhood anemia, a marker of malaria, fell by 68% n that period.

A major survey in Zambia in 2007 found a 29% reduction from earlier periods in overall mortality of children less than five years old. In Rwanda, a steep increase in the proportion of children sleeping under ITNs (from 15% to 58% between 2005 and 2008) was associated with a 32% decrease in mortality among children less than five. Similar promising results have been reported recently in Malawi, Mozambique and Zanzibar/Tanzania.

U.S. Government Malaria Control Activities

The U.S. government’s FY 2009 total funding to malaria control activities is $561million. In his May 5, 2009 statement on the U.S. Global Health Initiative, President Obama proposed that FY2010 funding for malaria be $762 million, a 35 percent increase.

Much of the U.S. government’s current malaria control effort is organized through the President’s Malaria Initiative (PMI), a five year (FY 2006-2010) $1.2 billion program launched in 2005. PMI is jointly implemented by USAID and CDC, with a core goal to reduce malaria-related deaths by 50% in 15 African focus countries. PMI-supported interventions include ITNs, IRS, IPT, rapid malaria diagnosis and treatment with ACTs. In addition, the Department of Defense has been involved in malaria drug research and vaccine research for many years.

Challenges looking forward

• Sustainability: Steady progress will require (1) progressive growth in donor resources as additional countries become ready to support enhanced malaria control efforts, (2) better evaluation measures that demonstrate genuine and lasting health gains by individuals and communities, and (3) a strategy for bringing about a more unified effort, both within the USG (integrating malaria with other health and development investments) and between the USG and the multiple other host country, bilateral, multilateral, corporate, and non-governmental entities that now actively operate in this field. Host governments will be under constant pressure to sustain their high-level financial and infrastructure commitments and to improve their surveillance, program planning and evaluation capacities.
• Eradication as a global goal: In 2007, the Bill and Melinda Gates Foundation proposed another global malaria eradication effort, which has stirred debate over whether true malaria eradication or improved malaria control should be the stated goal. Concern remains that many of the tools essential for true eradication of malaria do not yet exist in usable forms: e.g., an effective vaccine and drugs and insecticides not susceptible to development of resistance.
• Possible impacts of climate change: an ongoing research program will be needed to examine the possible impacts of temperature changes and shifting rainfall patterns on the epidemiology and spread of falciparum malaria.