Malaria

Malaria is a mosquito-borne infectious disease of humans and other animals caused by parasitic protozoans (a group of single-celled microorganisms) belonging to the genus Plasmodium. 

A general diagram of a plasmodium protozoan. image: Jfbranch14 /wikipedia


Origin of the word and term malaria

The term malaria originates from Medieval Italian: mala aria—"bad air"; the disease was formerly called ague or marsh fever due to its association with swamps and marshland. 

The term first appeared in the English literature about 1829.

Malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches. In severe cases it can cause yellow skin, seizures, coma, or death. 

The disease is transmitted by the biting of mosquitos, and the symptoms usually begin ten to fifteen days after being bitten. If not properly treated, people may have recurrences of the disease months later. 

In those who have recently survived an infection, reinfection usually causes milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria.

Life_Cycle_of_the_Malaria_Parasite

The life cycle of the malaria parasite.
 image: National Institutes of Health (NIH) /wikipedia


The disease is most commonly transmitted by an infected female Anopheles mosquito. The mosquito bite introduces the parasites from the mosquito's saliva into a person's blood. 

Anopheles_stephensi.jpeg

Anopheles stephensi mosquito. Only female mosquitoes feed on blood; male mosquitoes feed on plant nectar, and do not transmit the disease. The females of the Anopheles genus of mosquito prefer to feed at night.
image: Jim Gathany CDC/ wikipedia

The parasites travel to the liver where they mature and reproduce. 

Five species of Plasmodium can infect and be spread by humans. 

 Most deaths are caused by P. falciparum because P. vivax, P. ovale, and P. malariae generally cause a milder form of malaria.

The species P. knowlesi rarely causes disease in humans. 

Diagnosis

 Malaria is typically diagnosed by the microscopic examination of blood using blood films, or with antigen-based rapid diagnostic tests.  Methods that use the polymerase chain reaction to detect the parasite's DNA have been developed, but are not widely used in areas where malaria is common due to their cost and complexity.

Prevention

The risk of disease can be reduced by preventing mosquito bites by using mosquito nets and insect repellents, or with mosquito-control measures such as spraying insecticides and draining standing water. 

Medications

Several medications are available to prevent malaria in travellers to areas where the disease is common. Occasional doses of the medication sulfadoxine/pyrimethamine are recommended in infants and after the first trimester of pregnancy in areas with high rates of malaria. 

Despite a need, no effective vaccine exists, although efforts to develop one are ongoing. 

Treatments

 The recommended treatment for malaria is a combination of antimalarial medications that includes an artemisinin. 

The second medication may be either mefloquine, lumefantrine, or sulfadoxine/pyrimethamine.

Resistance to treatments 

Quinine along with doxycycline may be used if an artemisinin is not available. It is recommended that in areas where the disease is common, malaria is confirmed if possible before treatment is started due to concerns of increasing drug resistance. 

Resistance among the parasites has developed to several antimalarial medications; for example, chloroquine-resistant P. falciparum has spread to most malarial areas, and resistance to artemisinin has become a problem in some parts of Southeast Asia.

Distribution and economic implications

The disease is widespread in the tropical and subtropical regions that exist in a broad band around the equator. 

This includes much of Sub-Saharan Africa, Asia, and Latin America. Malaria is commonly associated with poverty and has a major negative effect on economic development.

 Elevated occurrence of chloroquine- or multi-resistant malaria  Occurrence of chloroquine-resistant malaria  No Plasmodium falciparum or chloroquine-resistance  No malaria. image: Percherie / wikipedia

 In Africa, it is estimated to result in losses of US$12 billion a year due to increased healthcare costs, lost ability to work, and negative effects on tourism.

The World Health Organization reports there were 198 million cases of malaria worldwide in 2013. This resulted in an estimated 584,000 to 855,000 deaths, the majority (90%) of which occurred in Africa.





source adapted from :  Malaria. (2016, January 25). In Wikipedia, The Free Encyclopedia. Retrieved 23:27, January 30, 2016, from https://en.wikipedia.org/w/index.php?title=Malaria&oldid=701675443