Malaria overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Malaria is a vector-borne infectious disease caused by protozoan parasites. It is widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Each year, it causes disease in approximately 650 million people and kills between one and three million, most of them young children in Sub-Saharan Africa. Malaria is commonly associated with poverty, but is also a cause of poverty and a major hindrance to economic development.
Malaria is one of the most common infectious diseases and an enormous public-health problem. The disease is caused by protozoan parasites of the genus Plasmodium. The most serious forms of the disease are caused by Plasmodium falciparum and Plasmodium vivax, but other related species (Plasmodium ovale, Plasmodium malariae, and sometimes Plasmodium knowlesi) can also infect humans. This group of human-pathogenic Plasmodium species is usually referred to as malaria parasites.
Malaria parasites are transmitted by female Anopheles mosquitoes. The parasites multiply within red blood cells, causing symptoms that include symptoms of anemia (light headedness, shortness of breath, tachycardia etc.), as well as other general symptoms such as fever, chills, nausea, flu-like illness, and in severe cases, coma and death. Malaria transmission can be reduced by preventing mosquito bites with mosquito nets and insect repellents, or by mosquito control measures such as spraying insecticides inside houses and draining standing water where mosquitoes lay their eggs.
Although some are under development, no vaccine is currently available for malaria; preventative drugs must be taken continuously to reduce the risk of infection. These prophylactic drug treatments are often too expensive for most people living in endemic areas. Most adults from endemic areas have a degree of long-term recurrent infection and also of partial resistance; the resistance reduces with time and such adults may become susceptible to severe malaria if they have spent a significant amount of time in non-endemic areas. They are strongly recommended to take full precautions if they return to an endemic area. Malaria infections are treated through the use of antimalarial drugs, such as quinine or artemisinin derivatives, although drug resistance is increasingly common.
Historical Perspective
Malaria has infected humans for over 50,000 years, and may have been a human pathogen for the entire history of our species.[1] Indeed, close relatives of the human malaria parasites remain common in chimpanzees, our closest relatives.[2] References to the unique periodic fevers of malaria are found throughout recorded history, beginning in 2700 BC in China.[3] The term malaria originates from Medieval Italian: mala aria — "bad air"; and the disease was formerly called ague or marsh fever due to its association with swamps.
Pathophysiology
Malaria in humans develops via two phases: an exoerythrocytic (hepatic) and an erythrocytic phase. When an infected mosquito pierces a person's skin to take a blood meal, sporozoites in the mosquito's saliva enter the bloodstream and migrate to the liver.
Causes
Malaria is a vector-borne infectious disease caused by protozoan parasites. Malaria is commonly associated with poverty, but is also a cause of poverty and a major hindrance to economic development.
Epidemiology and Demographics
It is widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Each year, it causes disease in approximately 650 million people and kills between one and three million, most of them young children in Sub-Saharan Africa.
References
- ↑ Joy D, Feng X, Mu J; et al. (2003). "Early origin and recent expansion of Plasmodium falciparum". Science. 300 (5617): 318–21. PMID 12690197.
- ↑ Escalante A, Freeland D, Collins W, Lal A (1998). "The evolution of primate malaria parasites based on the gene encoding cytochrome b from the linear mitochondrial genome". Proc Natl Acad Sci U S A. 95 (14): 8124–9. PMID 9653151.
- ↑ Cox F (2002). "History of human parasitology". Clin Microbiol Rev. 15 (4): 595–612. PMID 12364371.