Malaria Disease and Control

Plasmodium falciparum infection is estimated to cause more than 1 million deaths and around half a billion clinical malaria episodes per year among African children. Anaemia is probably the most frequent severe complication of malaria, although its insidious nature and vague symptomatology have led to its under-recognition as a major public health problem until recently.

Survivors from attacks of the more clinically apparent cerebral malaria may be left with developmental problems and epilepsy. In older children, malaria is an important cause of absenteeism from school and there is good evidence that malaria is a cause of poverty and poor economic growth.

Geographical variations in the pattern of malaria

Although malaria is a problem throughout most of tropical Africa, there is substantial variation in malaria epidemiology across the continent. The complexities of the epidemiological picture are compounded in some settings by marked seasonality in transmission.

The clinical pattern of malaria seen in a particular area is strongly influenced by the number of infectious bites an individual receives each year, the entomological inoculation rate (EIR). EIRs ranging from less than one to more than 1,000 infectious bites per person per year have been documented. Data are scanty on the sub-Saharan African population distribution according to the level of transmission. It is likely that a significant minority lives in areas of intense malaria transmission, where the dominant burden of clinical malaria is seen in children under the age of one year and the main form of severe malaria is severe anaemia.

In less intense transmission settings, which constitute the majority of sub-Saharan Africa, and where transmission is strongly seasonal, the main burden of malaria is seen in slightly older children (aged 1- 4 years) and cerebral malaria is encountered more frequently. However, even in such settings, the absolute number of malaria deaths in infants is disproportionately high. There is a need for malaria control activities to take into account these geographical variations in the pattern of malaria.

Increased commitment for malaria research and control

An increasing awareness of the burden of malaria in Africa and, in particular its economic costs, has led to an increased commitment from the international community to support research on malaria and attempts to control the disease. This is well illustrated by the Abuja declaration, which arose out of the African Summit to Roll Back Malaria in 2000 and was attended by 44 senior African statesmen who committed themselves "to an intensive effort to halve the malaria mortality for Africa's people by 2010”. Moreover, the Global Fund to Fight AIDS, TB and Malaria, formed in 2002, has increased available support for malaria control. However, this renewed interest in improving malaria control is greatly compromised by the very limited number of tools available. At present, those recommended by the World Health Organization (WHO) and Roll Back Malaria (RBM) are:

• Indoor Residual Spraying (IRS) with insecticides, primarily with DDT
• Prompt treatment of clinical attacks of malaria with an effective drug
• Insecticide-treated nets and other materials (ITN)
• Intermittent preventive treatment with sulphadoxine-pyrimethamine (SP) for pregnant women (IPTp)

Urgent need to refine the use of available control tools

Fortunately, after several decades of relative neglect, malaria research has also started to attract more attention and support. Major advances have been made recently in elucidating the molecular biology of P. falciparum and the mosquito that transmits malaria, and in malaria vaccinology.

However, although reasonable progress is being made, it is likely to be many years before a highly effective malaria vaccine is available for deployment on a wide scale. In the meantime, there is an imperative to refine the use of available tools if malaria control is to be optimised, and there is an urgent need for novel approaches to malaria control, especially in infants, who are the group at highest risk of death from malaria and associated severe anaemia.

For comprehensive information about malaria and its control refer to the WHO website on malaria at http://apps.who.int/malaria/