Background To Malaria - Edited

Background to Malaria The word mosquito is a Spanish word that literally means little fly, besides both being insects and having wings the physical similarity ends there. Like flies mosquitoes are vectors of many diseases. Mosquitoes are carriers of Dengue fever, Filaris, West Nile Encephalitis and Malaria. Malaria is a serious and sometimes fatal disease which is spread by mosquitoes. According to the World Health Organization 40% of the world's population, mostly those living in the world's poorest countries are at risk from malaria. Malaria is especially devastating in sub Saharan Africa where a child dies every 30 seconds from the disease. Many children who survive an episode of severe malaria may suffer from learning impairments or brain damage. Malaria is caused when parasites are injected into the host by the female Anopheles mosquito when she bites her victim. (Male mosquitoes do not bite as they feed on flower nectar.) Anopheles mosquitoes can only transmit malaria after they have been infected through a previous blood meal taken from an infected person. Anopheles Mosquitoes Anopheles mosquitoes tend to breed in bodies of permanent fresh water. They have abdomens with pointed tips. They include several species, such as the common malaria mosquito (Anopheles Quadrimaculatus) that can spread malaria to humans. Female Anopheles mosquitoes bite because they are searching for isoleucine. Isoleucine is an amino acid found in the blood. Female mosquitoes need the isoleucine to make eggs. If they find isoleucine then they may lay hundreds of eggs; but if they do not find it then they may only lay about ten. Whilst humans are a good source of isoleucine, buffalo and rats have higher quantities in their blood, however, as there are more humans than buffalo on the planet humans get more bites! The mouthparts of the female Anopheles mosquito are constructed so that they pierce the skin, literally sucking the blood out. Her saliva lubricates the opening and has an anti coagulant in it which causes a small quantity of blood to flow freely without clotting. (The mosquito saliva plus the injury to the skin creates the stinging and irritation we associate with mosquito bites.)

How Infection Takes Place When a mosquito bites a malaria infected person, a small amount of blood is taken in which contains the microscopic malaria parasites. The parasites grow and mature in the mosquito’s gut for a week or more then travels to the mosquito’s salivary glands. When the mosquito next takes a blood meal, these parasites mix with the saliva and are injected into the bite. Once in the blood, the parasites travel to the liver and enter liver cells to grow and multiply. During this "incubation period", the infected person has no symptoms. After as few as 8 days or as long as several months, the parasites leave the liver cells and enter red blood cells. Once in the cells, they continue to grow and multiply. After they mature, the infected red blood cells rupture, freeing the parasites to attack and enter other red blood cells. This can cause anaemia. Severe anaemia is often the cause of death in areas with intense malaria transmission. If left untreated, the disease progresses to severe malaria and results in convulsions and coma. Severe malaria often causes death if there is no treatment. Toxins released when the red cells burst are what cause the typical fever, chills, and flu-like malaria symptoms. Symptoms of Malaria Malaria symptoms include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting, and diarrhoea may also occur. Malaria may cause anaemia and jaundice (yellow colouring of the skin and eyes) because of the loss of red blood cells. Plasmodium Falciparum (PF) Malaria if not promptly treated may cause kidney failure, seizures, mental confusion, coma, and death. The Mosquito Life Cycle Female mosquitoes can develop hundreds of eggs at each blood meal. They lay them in or around water. The eggs are attached to one another to form a raft or the individual eggs float on the water. The eggs hatch within 24-48 hours releasing larvae that are commonly known as "wrigglers" because you can see them wriggling up and down from the surface of the water. Wrigglers occur in all kinds of standing water, such as; ditches, puddles, guttering and unkempt bird baths to name just a few. In 7-10 days after the eggs hatch, larvae change to pupa before becoming adult mosquitoes. The newly emerging mosquito has to stand on still water for a few minutes to dry its wings before it can fly away. That is one reason that mosquitoes don't breed in rapidly moving water such as running brooks and streams or even a pond that has a fountain.

The female mosquito begins to seek out an animal to feed on several days after emerging from the water. Adult mosquitoes can live for a period of four to eight weeks. Types of Malaria There are four types of malaria, Plasmodium Vivax, Plasmodium Malariae, Plasmodium Ovale and Plasmodium Falciparum. The most serious type is Plasmodium Falciparum malaria, (also known as PF Malaria) which can be the more lifethreatening. PF Malaria accounts for up to 80% of malaria related deaths world wide and 90% of malaria related deaths in sub Saharan Africa. Malaria In Pregnant Women Each year, approximately 50 million women living in malariaendemic countries throughout the world become pregnant, of whom over half live in tropical areas of Africa with intense transmission of Plasmodium Falciparum. An estimated 10,000 of these women and 200,000 of their infants die as a result of malaria infection during pregnancy, and severe malarial anaemia contributes to more than half of these deaths.

The following websites were used in the preparation of this article: http://www.pa.msu.edu/sciencet/ask_st/061197.html http://www.cdc.gov/malaria/faq.htm http://science.howstuffworks.com/mosquito.htm http://www.jhu.edu/~shcenter/malaria.html http://www.drgreene.org/body.cfm?id=21&action=detail&ref=60 http://www.wisegeek.com/why-do-mosquitoes-bite.htm http://www.loc.gov/rr/scitech/mysteries/mosquitoes.html http://www.worldswimformalaria.com/en/AboutMalaria.aspx http://www.amref.org/index.asp?PageID=50&PiaID=1 http://www.medindia.net/patients/patientinfo/mosquito.htm http://www.westchestergov.com/health/WNVmosquito_life_cycle.htm http://www.sbri.org/diseases/malaria.asp http://www.rbm.who.int/cmc_upload/0/000/015/372/RBMInfosheet_1.pdf http://www.malaria.org/malariaglossary.html http://www.who.int/malaria/pregnantwomenandinfants.html