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==Causes== | ==Causes== | ||
Malaria is a [[Vector (biology)|vector]]-borne [[infectious disease]] caused by [[protozoan]] [[parasite]]s. | Malaria is a [[Vector (biology)|vector]]-borne [[infectious disease]] caused by [[protozoan]] [[parasite]]s.'' P. vivax'' is the most common cause of infection, responsible for about 80 % of all malaria cases. However, ''P. falciparum'' is the most important cause of disease, and responsible for about 15% of infections and 90% of deaths.<ref>{{cite journal | author = Mendis K, Sina B, Marchesini P, Carter R | title = The neglected burden of Plasmodium vivax malaria. | url=http://www.ajtmh.org/cgi/reprint/64/1_suppl/97.pdf | journal = Am J Trop Med Hyg | volume = 64 | issue = 1-2 Suppl | pages = 97-106 | year = 2001 | pmid = 11425182}}</ref> | ||
==Epidemiology and Demographics== | ==Epidemiology and Demographics== | ||
Revision as of 22:41, 24 July 2014
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Malaria overview On the Web |
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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. 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.
Historical Perspective
Malaria is considered one of the oldest infections known to mankind. The symptoms of malaria were first believed to be caused by noxious elements.[1] It was not until 1880 when Charles Louis Alphone Laveran discovered the Plasmodium parasite in blood smears of patients with malaria.[2] The role of mosquitos in the transmission of malaria to humans was discovered a few years later. Consequently, the entire life cycle of the Plasmodium parasite remained enigmatic until 1982.[3] Although malaria has always been treated using quinine, an alkaloid derived from barks of cinchona, the first synthetic quinine was produced in 1948.[4][5] In 2014, the first candidate for anti-malarial vaccine was developed.
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.
Classification
The classification of malaria can be made according to the strains of Plasmodium species. There are 5 common Plasmodium species that infect humans: P. falciparum, P. ovale, P. vivax, P. malariae, and P. knowlesi. Malaria can also be classified according to severity of infection: uncomplicated vs. severe.
Causes
Malaria is a vector-borne infectious disease caused by protozoan parasites. P. vivax is the most common cause of infection, responsible for about 80 % of all malaria cases. However, P. falciparum is the most important cause of disease, and responsible for about 15% of infections and 90% of deaths.[6]
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.
Risk Factors
Common risk factors for malaria include thalassemias and Duffy antigen. Sickle cell disease and G6PD deficiency are known to confer protection against malaria.
Diagnosis
Symptoms
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.
Treatment
Medical Therapy
Active malaria infection with P. falciparum is a medical emergency requiring hospitalization. Infection with P. vivax, P. ovale or P. malariae can often be treated on an outpatient basis. Treatment of malaria involves supportive measures as well as specific antimalarial drugs. When properly treated, someone with malaria can expect a complete cure.[7]
Primary Prevention
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.
Secondary Prevention
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.
Cost-Effectiveness of Therapy
Although effective anti-malarial drugs are on the market, the disease remains a threat to people living in endemic areas who have no proper and prompt access to effective drugs. Access to pharmacies and health facilities, as well as drug costs, are major obstacles. Médecins Sans Frontières estimates that the cost of treating a malaria-infected person in an endemic country was between US $0.25 and $2.40 per dose in 2002.[8]
References
- ↑ Cox FE (2010). "History of the discovery of the malaria parasites and their vectors". Parasit Vectors. 3 (1): 5. doi:10.1186/1756-3305-3-5. PMC 2825508. PMID 20205846.
- ↑ Laveran CL (1982). "Classics in infectious diseases: A newly discovered parasite in the blood of patients suffering from malaria. Parasitic etiology of attacks of malaria: Charles Louis Alphonse Laveran (1845-1922)". Rev Infect Dis. 4 (4): 908–11. PMID 6750753.
- ↑ Krotoski WA, Collins WE, Bray RS, Garnham PC, Cogswell FB, Gwadz RW; et al. (1982). "Demonstration of hypnozoites in sporozoite-transmitted Plasmodium vivax infection". Am J Trop Med Hyg. 31 (6): 1291–3. PMID 6816080.
- ↑ Seeman JI (2007). "The Woodward-Doering/Rabe-Kindler total synthesis of quinine: setting the record straight". Angew Chem Int Ed Engl. 46 (9): 1378–413. doi:10.1002/anie.200601551. PMID 17294412.
- ↑ Kaufman TS, Rúveda EA (2005). "The quest for quinine: those who won the battles and those who won the war". Angew Chem Int Ed Engl. 44 (6): 854–85. doi:10.1002/anie.200400663. PMID 15669029.
- ↑ Mendis K, Sina B, Marchesini P, Carter R (2001). "The neglected burden of Plasmodium vivax malaria" (PDF). Am J Trop Med Hyg. 64 (1-2 Suppl): 97–106. PMID 11425182.
- ↑ If I get malaria, will I have it for the rest of my life? CDC publication, Accessed 14 Nov 2006
- ↑ Medecins Sans Frontieres, "What is the Cost and Who Will Pay?"