Malaria is one of the leading causes of death and illness in the world. The World Health Organization (WHO) estimated that there are at least

• 276 million infected

• 110 million new cases a year

• 1-2 million deaths a year

Reporting is poor, particularly in Africa, where only 1 of an estimated 16 cases is reported, compared to 1 in 6 in Asia and 1 in 2.5 in the Americas.

About 1,000 imported cases occur in the United States every year.

Parasites
 
Malaria is a group of four related diseases caused by protozoan parasites of the genus Plasmodium: P. falciparum, P. vivax, P. malariae and P. ovale. P. falciparum occurs throughout the tropics and causes the most deadly form of malaria.

Symptoms

Intermittent high fevers, shivering chills, body pains, headaches, fatigue, nausea, vomiting, diarrhea and anemia are common symptoms. More severe outcomes include spleen enlargement, liver and kidney failure, brain damage and death.

Immunity

The severity of symptoms depends upon the parasite species as well as the age, previous health status and immunity of the infected person. Immunity is acquired through repeated exposure to the infection. Infants are born with maternal antibodies to malaria, but lose them soon after birth. Various human genetic traits (sickle-cell anemia and thalassemia) confer partial resistance to infection.

Child Survival

Approximately 1 million children die with or of malaria every year in Africa, where the disease is a leading cause of infant mortality.

Newborns with malaria have anemia, lowered birth weight or reduced immune response to vaccines or infections. These conditions are compounded by malnutrition and other infections contributing to severe morbidity and death.

Maternal Health

Infection during pregnancy may result in maternal anemia, miscarriage or neonatal death, suppression of the maternal immune system and renal insufficiency. Malaria is most severe during first pregnancies.

Malaria Control

Disease control strategies must be developed locally because malaria transmission is highly variable. Both vector control and chemotherapy are needed. Integration into primary health care systems should be promoted.

Progress has been made in vaccine development, but an effective vaccine for use in the field is still years away.

Chemotherapy

Chloroquine is the drug most commonly used to treat malaria. Alternative compounds include mefloquine (Lariam®), quinine, Fansidar®, and artemisinin.

Resistance of P. falciparum malaria to chloroquine treatment was first recorded in Thailand in 1957 and has spread to 20 countries of Asia and the Near East. It also affects 12 Latin American and Caribbean countries and nearly all sub-saharan countries. Resistance to alternative drugs has also been detected in some areas, limiting the possibility of controlling malaria through exclusively medical interventions.

Vector Control

Sixty of the 400 species of Anopheles mosquitoes are vectors of malaria. Control measures effective against one mosquito species may be useless against related species because of differences in resting and feeding preferences and breeding habitats.

Vector control methods include indoor house spraying, environmental management to reduce mosquito breeding sites, insecticide-impregnated bednets and biological control with fish or microbial insecticides.

Fifty-six anopheline species have developed resistance to the insecticides most commonly used for house spraying. Resistance usually occurs where the same or related insecticides are used in agriculture.

Environmental Health

Deforestation, migration and development projects (dams, roads and irrigation) that cause rapid environmental change often lead to increased malaria transmission. To control the negative effects of development on health, disease prevention and control measures must be built into development plans.