Malaria

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Malaria is a disease prevalent in Sub Saharan Africa, Asia and North and South America. It is caused by the parasite, Plasmodium[1]. There are five species of Plasmodium that infect humans; Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae and Plasmodium knowlesi.[2] The parasite is spread by the bite of an infected mosquito. The mosquito acts as a vector. The effect on the human body is that the parasites multiply in the liver which then goes on to infect the red blood cells[3].
A person infected by the parasite usually has the following symptoms: a fever, vomiting and/or a headache[4]. Symptoms appear between 10 and 15 days after the mosquito bite.
If left untreated, the effects can be lethal[5]. The blood supply to all major organs can be disturbed[6].

Life cycle

Malaria sporozoites are injected into the host by female Anopheles mosquito. Once in the blood stream they travel  to the liver where they invade the hepatocytes. While in the hepatocytes the sporozoites grow and divide to form thousands of haploid merozoites in each hepatocyte. The merozoites then exit the liver re-entering the blood stream and infecting erythrocytes and reproducing asexually. This continues until the erythrocytes eventually lyse. This process in the cause of malaria related anaemia. This cycle of replication can continue for up to 3 days. Some merozoites, however, do not divide asexually and instead develop into the sexual forms of the parasite; male and female gametocytes. These cells circulate in the blood stream until the host is bitten by another Anopheles mosquito. Gametocyte infected erythrocytes are taken into the mosquito stomach where they lyse, releasing the gametocytes. The gametocyte then develop into gametes and fuse to form diploid ookinetes. Ookinetes develop into oocysts. While in the cysts ookinetes differentiate into sporozoites. Eventually the cysts burst releasing the sporozoites into the body of mosquito. The cell then migrate to salivary glands of the mosquito, ready to repeat the cycle [7][8].

Treatment 

Currently, the best recommended treatment for this disease is artemisinin-based combination therapy[9]. This therapy make use of a combination of drugs using artemisinin derivatives taken from a highly potent Chinese plant called Artemesia annua combined with other drug from a different class. Some artemisinin derivatives include dihydroartemisinin, artesunate and artemether[10] while examples of companion drugs are lumefantrine, mefloquine, amodiaquine, sulfadoxine/pyrimethamine, piperaquine and chlorproguanil/dapsone[11].

References

  1. World Health Organisation, Health topics: Malaria article. Available at http://www.who.int/topics/malaria/en/ (last accessed 30.11.2012)
  2. Malaria Parasites." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 27 Oct. 2015. Web.
  3. World Health Organisation, Health topics: Malaria article. Available at http://www.who.int/topics/malaria/en/ (last accessed 30.11.2012)
  4. World Health Organisation, Health topics: Malaria article. Available at http://www.who.int/topics/malaria/en/ (last accessed 30.11.2012)
  5. World Health Organisation, Health topics: Malaria article. Available at http://www.who.int/topics/malaria/en/ (last accessed 30.11.2012)
  6. World Health Organisation, Health topics: Malaria article. Available at http://www.who.int/topics/malaria/en/ (last accessed 30.11.2012)
  7. cycleNational institute of allergy and infectious diseases,2012, http://www.niaid.nih.gov/topics/Malaria/Pages/lifecycle.aspx, date acessed; 30/11/2012
  8. World Health Organisation, Health topics: Malaria article. Available at http://www.who.int/topics/malaria/en/ (last accessed 30.11.2012)
  9. Malaria Consortium, Artemisinin-based Combination Therapy. Available at http://www.malariaconsortium.org/pages/112.htm (last accessed 27th November 2014)
  10. Malaria Consortium, Artemisinin-based Combination Therapy. Available at http://www.malariaconsortium.org/pages/112.htm (last accessed 27th November 2014)
  11. Malaria Consortium, Artemisinin-based Combination Therapy. Available at http://www.malariaconsortium.org/pages/112.htm (last accessed 27th November 2014)
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