Malaria is a disease caused by the parasite Plasmodium, which is transmitted by the bite of an infected mosquito. Only the Anopheles genus of the mosquito can transmit Malaria. The symptoms of the disease include fever, vomiting, and/or headache.
A characteristic malarial fever has ‘hot’, ‘wet’, and ‘cold’ phases and appears 10 to 15 days after the mosquito bites. To diagnose malaria, blood slides are examined under a microscope, where the parasite is seen inside red blood cells. Rapid diagnostic test kits (RDTs) are used for diagnosing malaria in remote areas where microscopes cannot be used.
Plasmodium vivax or P. falciparum are the most common malarial parasites, while P. malariae and P. ovale are other rarer forms. Of these, infection with P. falciparum is the most fatal if left untreated, possibly leading to kidney and brain complications, and even death. Chloroquine was the treatment of choice for malaria and is still followed in most countries for treatment of P. Vivax, but P. falciparum has developed resistance to it. As a result, Artemisinin-based combination therapy is now presently advised as the primary treatment for malaria. Among preventive measures, the use of insecticide treated nets at home and indoor residual spraying of insecticides are recommended for malaria. These precautions act by decreasing exposure to bites of infected mosquitoes.
- Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected mosquitoes.
- A child dies of malaria every 30 seconds.
- Malaria is preventable and curable.
- Approximately half of the world’s population is at risk of malaria, particularly those living in lower-income countries.
- Travellers from malaria-free areas to disease “hot spots” are especially vulnerable to the disease.
- Malaria takes an economic toll – cutting economic growth rates by as much as 1.3% in countries with high disease rates.
Malaria is caused by parasites of the species Plasmodium. The parasites are spread to people through the bites of infected mosquitoes.
There are four types of human malaria:
- Plasmodium falciparum
- Plasmodium vivax
- Plasmodium malariae
- Plasmodium ovale.
Plasmodium falciparum and Plasmodium vivax are the most common. Plasmodium falciparum is the most deadly. In Americas 77% of the infections are due to Plasmodium vivax.
Malaria transmission rates can differ depending on local factors such as rainfall patterns (mosquitoes breed in wet conditions), the proximity of mosquito breeding sites to people, and types of mosquito species in the area. Some regions have a fairly constant number of cases throughout the year – these countries are termed “malaria endemic”. In other areas there are “malaria seasons” usually coinciding with the rainy season.
Large and devastating epidemics can occur when the mosquito-borne parasite is introduced into areas where people have had little prior contact with the infecting parasite and have little or no immunity to malaria, or when people with low immunity move into areas where malaria cases are constant. These epidemics can be triggered by wet weather conditions and further aggravated by floods or mass population movements driven by conflict.
The common first symptoms — fever, headache, chills and vomiting — usually appear 10 to 15 days after a person is infected. If not treated promptly with effective medicines, malaria can cause severe illness and is often fatal.
Who is at risk?
Most cases and deaths are in sub-Saharan Africa. However, Asia, Latin America, the Middle East and parts of Europe are also affected. In 2006, malaria was present in 109 countries and territories.
Specific risks follow.
- Travellers from malaria-free regions, with little or no immunity, who go to areas with high disease rates are very vulnerable.
- Non-immune pregnant women are at high risk of malaria. The illness can result in high rates of miscarriage and cause over 10% of maternal deaths (soaring to a 50% death rate in cases of severe disease) annually.
- Semi-immune pregnant women risk severe anaemia and impaired fetal growth even if they show no signs of acute disease. An estimated 200 000 of their infants die annually as a result of malaria infection during pregnancy.
HIV-infected pregnant women are also at increased risk.
Early treatment of malaria will shorten its duration, prevent complications and avoid a majority of deaths. Because of its considerable drag on health in low-income countries, malaria disease management is an essential part of global health development. Treatment aims to cure patients of the disease rather than to diminish the number of parasites carried by an infected person.
The best available treatment, particularly for P. falciparum malaria, is a combination of drugs known as artemisinin-based combination therapies (ACTs). However, the growing potential for parasite resistance to these medicines is undermining malaria control efforts (see below). There are no effective alternatives to artemisinins for the treatment of malaria either on the market or nearing the end of the drug development process.
AHO Programme of action
- prompt treatment for all episodes of disease (within 24 hours of the onset of symptoms if possible);
- use of insecticide-treated nets for night-time prevention of mosquito bites;
- for pregnant women in highly endemic areas, preventive doses of sulfadoxine—pyrimethamine (IPT/SP) to periodically clear the placenta of parasites;
- indoor residual spraying to kill mosquitoes that rest on the walls and roofs of houses.
Prevention focuses on reducing the transmission of the disease by controlling the malaria-bearing mosquito. Two main interventions for vector control are:
- use of mosquito nets treated with long-lasting insecticide, a very cost-effective method;
- indoor residual spraying of insecticides.
These core interventions can be locally complemented by other mosquito vector control methods (for example, reducing standing water habitats where insects breed, among other approaches).
Mosquito control efforts are being strengthened in many areas, but there are significant challenges, including:
- increasing mosquito resistance to key insecticides DDT and pyrethroids, particularly in Africa;
- a lack of alternative, effective insecticides;
- changing behaviours of local malaria-bearing mosquitoes, which can result from vector control efforts (as insects move to more hospitable areas).
There are no equally effective and efficient insecticide alternatives to DDT and pyrethroids, and the development of new pesticides is an expensive, long-term endeavour. Vector management practices that enforce the sound management of insecticides are essential.
Insecticide resistance detection should be a routine feature of national control efforts to ensure that the most effective vector control methods are being used.
Beyond the human toll, malaria wreaks significant economic havoc in high-rate areas, decreasing Gross Domestic Product (GDP) by as much as 1.3% in countries with high levels of transmission. Over the long-term, these aggregated annual losses have resulted in substantial differences in GDP between countries with and without malaria (particularly in Africa).
Malaria’s health costs include both personal and public expenditures on prevention and treatment. In some heavy-burden countries, the disease accounts for:
- up to 40% of public health expenditures
- 30% to 50% of inpatient hospital admissions
- up to 60% of outpatient health clinic visits.
Malaria disproportionately affects poor people who cannot afford treatment or have limited access to health care, and traps families and communities in a downward spiral of poverty.
AHO believes that malaria can be eliminated from intense national commitments and coordinated efforts with partners.