With 40 percent of the world's population living in malaria-endemic regions, malaria is by far the most important tropical parasitic disease affecting humankind and killing more people than any other communicable disease, with the exception of tuberculosis. An estimated 3.2 billion people living in 107 countries are at risk of malaria transmission. The disease is endemic now in Southeast Asia, the Western Pacific region, and Africa where it is the most important cause of death in the under-five age group, causing approximately 800,000 deaths per year. In fact, more than 90 percent of the annual cases of Malaria occur in sub-Saharan Africa. (Division of Parasitic Diseases; Keiser et al.)
Globally, the estimated number of malaria cases is between 350 and 500 million per year, with the estimated number of deaths being between 1.5 to 2.7 million annually. Children under five and pregnant women are the most vulnerable, with fatalities far exceeding those caused by HIV/AIDS. This is because these two groups have little or no protective immunity against the disease. (Boutayeb)
The most affected countries are Uganda, Tanzania, Malawi, Mozambique, and Namibia, where malaria is the principal cause of death and work absenteeism. In Europe (50,000 cases in 1990) and the US (1,500 cases in 2004), most cases of malaria are imported by travelers and military personnel, and these represent a very small percentage of the total cases worldwide. (Girard et al)
As transmission depends on its mosquito vector, climate and geography play an important role. Any condition favorable to mosquito breeding, such as global warming, the rainy season, and events like El Nino, can therefore increase the transmission of the disease. Agricultural and irrigation projects, such as the creation of dams, commercial tree cropping, and deforestation, also influence the transmission as these create new habitats for malaria-transmitting mosquitoes. (Girard et al)
Social and Economic Toll
Malaria inflicts considerable costs both at the individual and governmental levels. The estimated annual cost of malaria, by its direct effect on the African continent, is US$12 billion. It has also slowed the annual economic growth in the region by 1.3 percent. (Boutayeb)
The toll on individuals includes lost lives, medical costs for prevention and treatment, chronic debilitation, and lost wages because of absenteeism, as one attack of the disease leads to an estimated loss of 10 days of labor. Children surviving malaria may have impaired physical and cognitive development, as well as poor school attendance, which may interfere with their opportunities of education and future employment. (Division of Parasitic Diseases)
In endemic countries, at the governmental level, malaria poses a heavy public health and, therefore, economic burden that hinders economic growth. For example, in Mozambique, 60 percent of hospital-admitted children suffered from malaria as did 40 percent of the outpatients in 2002. In these countries, costs include control measures, such as spraying insecticides, distributing insecticide-treated bed nets, purchasing drugs, and maintaining health facilities. All of these factors have a negative impact on the social and economic development of these countries. (Girard et al)
Foreseeable Way Out?
In the early 1900s, malaria was endemic across every continent, with the exception of Antarctica. With the use of insecticides in control programs in the 1950s, malaria was wiped out of North America, Europe, and Australia. (Girard et al) So, given that control programs have definitely been shown to work, why has its control in Africa and other endemic countries been so challenging?
The main challenges facing malaria control programs, such as the emergence of drug resistance and mosquito insecticide resistance, make key control strategies less effective. At present, malaria-endemic countries also face additional challenges, including political turmoil, civil conflicts, displaced persons, and mass movements of refugees. (Gelb; Keiser et al.)
This was evident in Central Asia during the early 1990s when several countries experienced malaria epidemics and sometimes endemics of mainly P. vivax. This reemergence was mostly due to the discontinuation of control interventions as a result of the political instability and armed conflicts. When national control policies were reestablished in 1997, the incidence of the disease decreased steadily. Such problems are also evident in Africa along with the problem of population growth (which puts an increased number of children at risk). This makes the control of the disease extremely difficult. (Walther, B. and Walther, M.)
Control programs include a combination of mosquito control factors, such as indoor sprays, insecticide-treated bed nets, and environmental manipulation. This manipulation encompasses changes made to the environment to make it unsuitable for the breeding of mosquitoes. Some of the techniques are the drainage of small collections of water as well as the removal of containers and old tires around homes, which may collect water and make for suitable breeding places for mosquitoes. (Girard et al.; Keiser et al.)
These control measures have been shown to be very effective in eliminating or significantly reducing malaria in areas with mild to moderate transmission. However, in areas with high transmission, such as Africa, these control programs would cost too much (around US$2 billion annually for an indefinite period) and would then only reduce the burden, rather than eliminate the disease, as long as they can be sustained. This means that the only realistic tool for the eradication of malaria would be a vaccine, especially with the emergence of drug-resistant strains of malarial parasites. (Walther, B. and Walther, M.)
Unfortunately, currently there is no anti-malaria vaccine available. Despite the advances in studies and clinical trials, there are many obstacles hindering the vaccine production. These include a lack of understanding of the types of immune responses needed for protection, as well as a difficulty in identifying and producing the right antigen (the part of the parasite that induces protective immunity in humans) to be used in the vaccine. In addition, there are technical, logistical, and financial obstacles, such as the fact that the market for a malaria vaccine is viewed as being commercially unattractive. There are also scientific, medical, and ethical considerations that need to be taken into account in planning and conducting the clinical trials. (Girard et al)
Clearly, there are ethical implications regarding the testing of novel vaccines and anti-malarial drugs on humans. Because malaria is mainly a disease of children and pregnant women who in addition to being poor and uneducated are especially vulnerable to exploitation, it is imperative that these populations be protected during research and that their rights and welfare be safeguarded. (Kilama)
When asked about the ethical implications regarding the testing of novel anti-malarial drugs, Jaya Banerji, communications manager of Medicines for Malaria Venture, replied. Once tests have proved nontoxic and well-tolerated in animals, the drug is ready for testing in humans. People recruited for the clinical trials must sign a consent form stating that they have been well-informed about the new drug and are aware of the possible side effects. No drug is tested on humans without their explicit, signed consent. Early phases of clinical development are performed on healthy volunteers, while the later phases are conducted in areas where malaria is present.
Global Malaria Program
As the annual number of malaria cases is expected to double by 2020 because of the expected growth of the world's population, it is not surprising that the World Health Organization (WHO) now considers malaria as one of its top priorities. The WHO launched the Roll Back Malaria initiative in 1998. The initiative, a partnership that brought together the main groups concerned with malaria control, had three main targets, known as the Abuja targets. These targets were set to ensure that by the year 2005,
- At least 60 percent of malaria cases would have access to effective treatment.
- At least 60 percent of those at risk would have access to protective measures.
- At least 60 percent of pregnant women at risk would have access to intermittent preventive treatment.
However, although some success has been achieved, these goals have not yet been realized on a large scale. For the first time in almost 20 years, the WHO has also launched new malaria treatment guidelines as part of the Global Malaria Program. The guidelines attempt to change policies placed by different countries regarding the treatment of malaria so as to delay the development of drug resistance. To this end, the WHO recommends the use of Artemisinin-Based Combination Therapies (ACTs).(World Health Organization; Gelb)
"Effective drugs are encountering widespread resistance in the malaria parasite. These drugs are far too often failing to treat and cure malaria patients," Banerji explained. Today, the most effective available anti-malarial drug is artemisinin. "In order to delay the effects of possible resistance to artemisinin, the WHO urges all countries to use this drug in combination with other anti-malarials," Banerji added. It is to be seen if such efforts will be able to finally reduce the burden of malaria and put an end to the unacceptable human and economic losses it has already cause.
