Malaria is a serious infectious disease caused by parasites that are transmitted to humans through infected mosquitoes. The parasites travel through the bloodstream to the liver, where they reproduce and infect red blood cells. There are four parasitic species that cause the disease in humans:
Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale. The two most common species are P. falciparum and P. vivax, with P. falciparum being the most deadly. A fifth species of parasite, Plasmodium knowlesi, causes malaria in monkeys and recently, some humans (World Health Organizaton, 2014).
Malaria is a preventable and curable disease, yet every year it is estimated that it affects 300 to 500 million people and causes 2 to 4 million deaths. Most deaths, up to 90%, occur in Africa, where it kills a child every 30 seconds (Tortora, Funke, & Case, 2013, p. 670).
Where does Malaria Occur?
Malaria is a worldwide disease, but its severity is most pronounced in tropical Asia, Africa, and Central and South America, where it is called an endemic disease, meaning it is a disease constantly present in the population. Recently, it has began to show up in areas where it was once nearly eradicated, such as the United States, eastern Europe, and central Asia due to increased travel to malarial areas and an increase in immigration from malarial areas (Tortora, Funke, & Case, 2013, p. 670).
(http://eschooltoday.com/malaria/causes-of-malaria-infection.html, September 13, 2014)
Malaria in the United States
Malaria was once an endemic disease in the US, affecting 49 out of 50 states. By the 1960s, however, the disease was nearly eradicated thanks to effective mosquito control and elimination methods. In 2011, the number of malaria cases in the US hit a 40-year high with an estimated 2,000 cases diagnosed. Almost all of these cases were the result of travel to malaria infested regions of the world (Fox, 2013).
How is Malaria Transmitted?
Malaria is usually transmitted through the bite of an infected mosquito, although in rare cases it can be transmitted via blood transfusions. The female Anopheles mosquito is considered the vector of malaria, an animal that carries pathogens from one host to another, while the protozoan Plasmodium, is the parasite (Tortora, Funke, & Case, 2013, p. 670). The Life Cycle of Plasmodium (Tortora, Funke, & Case, 2013, p. 352)
- An infected Anopheles mosquito bites a human; sporozoites (the infective stage of Plasmodium) travel through the bloodstream to the liver.
- The sporozoites produce thousands of merozoites (the vegetative form of Plasmodium) in the liver cells.
- The merozoites are released into the bloodstream and may infect new red blood cells.
- The merozoite develops into the ring stage in a red blood cell.
- The ring stage grows and divides, producing merozoites.
- Merozoites are released when the red blood cell ruptures, which infect new blood cells and develop into male and female gametocytes.
- Another mosquito bites the infected human and ingests the gametocytes.
- In the mosquito's digestive tract, the gametocytes combine to form a zygote.
- The resulting sporozoites migrate to the salivary glands of the mosquito.
- The infected mosquito bites a human.
(http://classconnection.s3.amazonaws.com/935/flashcards/1270935/jpg/vivax1331056813960.jpg, September 13, 2014)
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