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Malaria - infection and cure

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Introduction

Malaria Malaria is a protozoal disease transmitted by the Anopheles mosquito (see fig.1 below). The illness is caused by one or more of the four plasmodia that infect humans; P. falciparum, P. vivax, P. ovale and P.malariae. The infection is spread when the mosquito seceretes the parasite whilst having its blood meal. Other transmission methods are rare but include: transfusion of blood, in utero as a result of malaria complicating pregnancy, or through the use of shared needles. Fig. 1 Showing the vector, the female anopheles mosquito. Malaria is the most common serious infection of humans. Around 2 billion people live in areas where malaria is endemic. In the western world malaria is episodic occurring mainly in travellers returning from holidays to these areas. (Mandell, 1995). In this look at malaria I will endeavour to look at the following aspects of the illness: The life cycle of the parasite, the pathological changes in the host, conventional and novel therapies, vaccine development and the economic burden it causes. The life cycle of the plasmodium parasite, (see fig.2): Within the Human Host Humans acquire malaria from sporozoites transmitted by the bite of an infected Anopheles mosquito. 1) S porozoites are released from the salivary gland of a female Anopheles mosquito and injected during the blood meal. 2) The sporozoites then travel through the bloodstream and enter individual hepatocytes. 3) Within the hepatocytes, the mature to tissue schizonts. 4) The mature tissue schizonts rupture to release merozoites. ...read more.

Middle

Because of its relationship to quinine the two drugs must not be used together. There have been reports of various undesirable side effects including several cases of acute brain syndrome, which is estimated to occur in 1 in 10,000 to 1 in 20,000 of the people taking this drug. It usually develops about two weeks after starting mefloquine and generally resolves after a few days. The Aminoquinolines work against the parasite by inhibiting proteolysis of haemoglobin in the food vacuole. Fansidar. This is a combination drug, each tablet containing sulphadoxine 500mg. and pyrimethamine 25mg. Both drugs are antifolates and interfere with the synthesis of thymidylate and DNA. It acts by interfering with folate metabolism. Resistance to Fansidar is now widespread and serious side effects have been reported. It is no longer recommended. Artemisinine or Quinhoasu is a sesquiterpene lactone derived from the plant Artemisia annua. This effective anti-malarial is used as extracts in traditional medicine in China for the management of fever resulting from malaria. To improve its bioavailability the derivatives artemether and artesunate have been developed. When used by itself, a high rate of treatment failures has been reported and it is now being combined with mefloquine for the treatment of falciparum malaria. Its main value at present is in the treatment of multi drug resistant falciparum malaria. It is recommended only for treatment not for prophylaxis. Artemisinine and its derivatives are thought to work by binding to the iron in the malarial pigments to yield free radicals that damage parasite proteins close to the parasites food vacuole. ...read more.

Conclusion

The direct and indirect costs of malaria in sub-Saharan Africa exceed $2 billion, according to 1997 estimates. According to UNICEF, the average cost for each nation in Africa to implement malaria control programs is estimated to be at least $300,000 a year. This amounts to about six US cents ($.06) per person for a country of 5 million people. In 1990, 80% of cases were in Africa, with the remainder clustered in nine countries: India, Brazil, Afghanistan, Sri-Lanka, Thailand, Indonesia, Vietnam, Cambodia and China. The disease is endemic in 91 countries currently, with small pockets of transmission in a further eight. P.falciparum is the predominant species, with 120,000,000 new cases and up to 1,000,000 deaths per year globally. It is the P.falciparum species that has given rise to the formidable drug resistant strains emerging in Asia. In 1989, WHO declared malaria control to be a global priority due to the worsening situation, and in 1993, the World Health Assembly urged member states and WHO to increase control efforts. Fig.4 Map showing where malaria is common. In Africa, malaria accounts for up to a third of all hospital admissions, and up to a quarter of all deaths of children under the age of 5. There are up to 800,000 infantile mortalities and a substantial number of miscarriages and very low birth weight babies per year due to the disease. The cost of malaria in economic terms is also high; treatment ranges in cost between $0.80 and $US 5.30 depending on local drug resistance. In Africa it is estimated that an individual receives 40-120 infective mosquito bites per year, compared to only 2 per year in India. ...read more.

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