WHAT IS MALARIA?
Malaria is a disease that affects animals, in particular birds, monkeys and humans. It is caused by infection of the red blood cells by the protozoans of the parasite plasmodium.
In humans, malaria occurs in four forms, each caused by a different species of parasite. In each form the symptoms are similar i.e; fever, chills and sweating, but they vary in severity. Malaria is also known as ague, jungle fever, marsh fever, periodic fever and paludism.
Malaria is common in the tropics and sub-tropics and in some temperate areas. It has been eliminated from almost all of Europe and large areas in Central and South America, but is a major problem in parts of Africa and southeastern Asia. There is concern that the effects of global warming may see malaria carrying mosquitoes again in parts of Europe.
WHAT ARE THE DIFFERENT FORMS OF MALARIA?
Benign tertiary malaria is the mildest form and is caused by Plasmodium vivax. Symptoms may begin to appear two weeks after infection and the fever may occur every second day after the initial attack.
Plasmodium ovale causes a rare form of the disease which is similar to benign tertian malaria.
Jungle fever, malignant tertian malaria is caused by Plasmodium falciparum. This is responsible for most of the deaths from malaria, mainly due to the fact that the organisms from this form, block the blood vessels to the brain.
Quartan malaria is caused by Plasmodium malariae. This has a longer incubation period than the others. The first attack does not appear until 18 to 40 days after infection. The attacks then recur about every third day.
HOW DOES MALARIA SPREAD?
The female mosquito Anopheles is responsible for the spread of the parasite plasmodium which causes malaria. This tiny single-celled parasite enters the bloodstream in the saliva of the mosquito when it bites through the skin. Once in the bloodstream, the plasmodia rupture the red blood cells before travelling to the liver, where they multiply before re-entering the blood to attack the red blood cells again. This causes regular bouts of fever in the victim, usually every three days.
When another female mosquito bites the malaria victim, she swallows the plasmodia circulating in the bloodstream The plasmodia can only reproduce in the stomach of the female mosquito. Here thousands of male and female plasmodia are produced. These travel from the stomach of the female to her salivary glands to be transmitted again when the mosquito bites.
WHAT ARE THE SYMPTOMS OF MALARIA?
Depending on the type of protozoan involved the first symptoms will appear about 10 days to 6 weeks after the mosquito bite. These symptoms include tiredness, headache, muscular pains and a slight temperature. As the parasites multiply the symptoms become more severe. There is a feeling of intense cold which gives way to hot flushes and a high fever and delirium, with nausea, dizziness and delirium. In some cases the victim recovers for a temporary period until the next attack. In the more severe forms the attacks continue without any remission taking an extreme toll on the victim.
HOW IS MALARIA TREATED?
Malaria has been treated with quinine since 1638. This is an extract from the cinchona tree . Quinine suppresses the growth of the protozoans in the bloodstream. In 1930 a drug named atrobine came into use . This drug was more effective than quinine and did not have the same toxic side effects. In 1945 another new drug named chloroquine came on the market and was found to be extremely effective in preventing and virtually curing jungle fever. It also had less toxic effects than either of the other drugs. However, it has recently been found that the plasmodia which cause jungle fever, have been shown to be developing resistance to chloroquine and other synthetic malaria drugs. In strains resistant to chloroquine and synthetic drugs, quinine is still used.
Work is been carried out to develop a malaria vaccine and several are undergoing clinical trials in human volunteers to test safety and effectiveness.