A B C D E F G H I J K L M N O P R S T U V W

MALARIA

What is Malaria ?

Malaria is a major health problem in the tropics and subtropics. It is estimated that about a third of the world population is at risk with over 120 million cases and between 1 and 1.5 million deaths every year. In the UK the number of cases recorded has been increasing over the last 10 years, reaching over 2000 cases a year. Malaria has been known about for thousands of years. It was thought that it was caused by bad air or gases from swabs ("mal air ia"). The disease is acquired mainly by travellers to Africa (mainly West Africa), the Indian sub-continent, Central and South America and South-east Asia. Malaria is caused by a parasite, Plasmodium, of which there are four species (types) that can affect man: Plasmodium falciparum , Plasmodium vivax , Plasmodium ovale and Plasmodium malariae . The disease is mainly transmitted to man by the bite of an infected female mosquito of the Anopheles type. The parasite has a complex life cycle, partly in man and partly in the mosquito. It usually takes 10 to 15 days after being bitten by an infected mosquito for the symptoms to appear. High fever, chills and rigors (shaking) are the main symptoms of malaria. The seriousness of the disease depends on the type of Plasmodium parasite. Malaria caused by Plasmodium Falciparum is the most widespread and considered to be the most dangerous form as it may affect the brain. Malaria is diagnosed in the laboratory by a blood test that allows the parasite to be seen under the microscope.

How does Malaria occur ?

When the parasites penetrate the body of a host, they find their way to the liver where they multiply. After 1 or 2 weeks the parasites are released from the liver, enter the bloodstream and invade the red blood cells. The rupture of the red blood cells releases the parasites and this gives rise to fever. The timing of the fever depends on the type of Plasmodium , e.g. every 48 hours ( P. vivax ), 72 hours ( P. malariae ) or irregularly ( P. falciparum ).

Why does Malaria occur ?

Malaria in British residents visiting malarious areas varies by age, sex and category of travellers. Generally the risk of malaria is highest in immigrants to Britain who return after visiting friends and relations in malarious areas. This may be due to the length of time of their visit or to the false belief that they are immune. The reason for the increase in malaria worldwide is thought to be due to changes in agricultural practices and population migration. Also the mosquitoes (which carry the disease) are becoming resistant to insecticides and the parasites are becoming resistant to some of the drugs used to treat and protect man against the disease.

Treatment Involved for Malaria

Patients with malaria may have a mild illness (e.g. vivax malaria) or severe life-threatening illness (e.g. some cases of falciparum malaria). Quick diagnosis and effective treatment is therefore essential. You may be admitted to hospital. Treatment depends on the type of malaria, the resistance of the parasite to the drugs and the severity of the disease. The antimalarial drugs commonly used include quinine, choloroquine and primaquine. Ideally it is best to prevent malaria. Travellers to malarial areas will need to consult their doctors about antimalarial tablets. Increasingly, many of the parasites in some parts of the world have become immune or resistant to certain antimalarial drugs especially chloroquine. It is important to check for up to date information on the best drugs to use. All travellers will need to take the antimalarial drugs one week before travelling. On return they will need to continue to take the drugs for a full month. There are other preventative measures you can take as well as the drugs. Sleeping under mosquito nets is effective, especially when the net has been impregnated with an antimalarial drug. A number of other measures have also been shown to be effective. These include: using insect repellents (DEET), keeping arms and legs covered (especially between dusk and dawn), electric fans, mosquito coils and vaporising mats.

During Treatment for Malaria

This depends on the type of malaria. Most patients infected with vivax, ovale and malariae recover completely. Side-effects of antimalarial drugs include headache, nausea and diarrhoea, but these are seldom severe.

After Treatment for Malaria

One treated attack of malaria does not protect the patient against being infected again if re-exposed to the parasite.

If Malaria is Left Untreated

Untreated ovale or vivax infections may get better for a while but tend to come back every 2 to 3 months for approximately 10 years. Untreated falciparum infection may be fatal.