MALARLIFE • NEWS
How malaria is transmitted
15 October 2001


A Short History of Malaria: Malaria fights back - again and again!
Summary of a BBC Horizon television programme shown on 15^th October 1998 "Mosquito!"

The mosquito anopheles has been described as the most dangerous insect in the world. It is no wonder, estimates vary, some suggesting that 2 million people die from malaria each year, others that each day 10,000 children still die of malaria - which means over 3½ million per year.

The female mosquito lands on the skin and inserts its mouth parts until it finds a blood vessel. The wall of the blood vessel is damaged, blood pours out, and the mosquito prevents this blood from clotting by injecting, from its saliva, an anti-coagulant. The blood provides an excellent meal, it is concentrated protein which supports their production of eggs. Sometimes a female mosquito will drink so much blood that it can hardly fly and, afterwards, must rest, exhausted, for a whole day. If an anopheles mosquito feeds on someone infected with malaria parasites, it takes them into its own body, and then when it feeds again it inject the parasites into another human being. Once inside the human body they spend a week in the liver, and then enter red blood cells and join the bloodstream. The parasites are protozoa; inside the human body they mutate and destroy red blood cells, thus causing horrendous problems in internal organs, or heart failure, suffocation of the brain or coma.

How the cause of malaria was discovered

The word malaria comes from the Italian mal-aria, or bad airs, because, in the nineteenth century people associated malaria with the bad air of stagnant marshes. Then scientists discovered that the blood of people with malaria was full of parasites - and these parasites were nowhere to be found anywhere near the marshes. The important breakthrough in understanding was made in the 1890s by Ronald Ross, a British doctor who was treating soldiers with malaria in India and who subsequently was awarded the Nobel Prize. He came across a paper that suggested that suggested that mosquitoes might spread the parasite. He collected mosquitoes and fed them with the blood of people infected with malaria parasites. He wanted to see what happened to the parasite once it was inside the mosquito's body, for it seemed impossible that a creature that lived in warm human blood could live in a cold-blooded insect. He found that the parasites died within the mosquitoes, until he dissected the common anopheles mosquito. In the gut of this mosquito, he found cyst-like shapes, the eggs of malaria parasites. The eggs hatched, releasing thousands of rod-like parasites into the mosquito. The parasites migrated through the wall of the mosquito's gut into its body, and wriggled their way through the body and up into the head, and, one by one, into the salivary glands. They were ready for injection when the mosquito next fed.

Fighting malaria

With this knowledge, people were, for the first time, in a position to intervene in the 'malaria cycle' in order to prevent the spread of the disease.

First idea: destroy the breeding grounds of the mosqitoes. Mosquito larvae live underwater, so marshes were drained, slow-moving rivers were cleared and oil was spread on the surface of the water. Even bombs were used to destroy the larvae and their habitat. As a result of these methods, Mussolini was able to announce, in the 1930s that, for the first time, the area around Rome was free of malaria for the first time in history. Keeping marshes drained, however, was a mammoth task.

Second idea: kill the mosquitoes with insecticide. Whenever American troops had been involved in a military campaign in an area where malaria was present, they lost more troops to malaria than they did in battle. Consequently, during the Second World War the American military devoted huge financial resources to research into possible insecticides, and discovered a cheap compound that was so deadly that even the tiniest quantities completely destroyed the nervous system of mosquitoes. It was the famous DDT. Using DDT, the World Health Organisations aimed to destroy all mosquitoes and therefore eradicate malaria throughout the entire world by the 1990s. The programme met with considerable success; malaria was eradicated from Europe, North America and Russia, and dramatically reduced in South America, India and Sri Lanka. Mosquitoes are, however, remarkably resilient insects, and they began to develop a resistance to DDT. One female can produce up to 1,000 offspring in a lifetime. If only one of these offspring happens to be resistant against an insecticide, it does not take long for insect populations of a significant size to be totally resistant. New insecticides were developed, but these were much more expensive. The aim of eradicating malaria world-wide was abandoned. In Florida, USA, mosquitoes are successfully kept under control, but with an annual budget of $300 million. Virtually no other country could afford that sort of money.

Third idea: kill the parasite. The malaria parasite evades the normal immune systems in our bodies because it lives inside the red blood cells. Scientists were, therefore, unable to develop a vaccine, so they began to research drugs. It had been long known that quinine, which came from the cinchona plant in South America, taken in large quantities over a long period of time, was very effective in killing malaria parasites, but had many side-effects. Gradually, cheaper and safer drugs were developed, the best known of which was chloraquine. This saved millions of lives. In the cool comfort of the insect's body, however, the protozoa reproduce, and, as they multiply, they constantly create new mutations, each genetically different from the other. Consequently, as soon as a new drug was developed, the parasite learned how to become resistant to that drug.

In 1967 Chairman Mao launched a new initiative to solve the problem of malaria. Because everything in the West was considered decadent, including medicine, scientists looked at the herbs which had played a key role in ancient Chinese medicine. Eventually they found a 2,000 year old recipe for a tea to be made from Artemisia that claimed to cure malaria. They distilled the tea, and by chemical means isolated the active compound. The subsequent drug they produced was remarkable, it cleared the blood of malaria parasites quicker than any drug in history! The Chinese claimed that the molecule of the drug was completely different from any other anti-malarial; it contained an endo-peroxide which, usually in the history of medical research, was stable. Many western scientists were sceptical, and did not understand how it succeeded in killing the parasites.