Health in the XXI Century: a vision of the European Youth

MALARIA: from the beginning to our days

All ancient literatures, from Sumeria, Egypt, India or China speak about high and oscillating fevers, associated to humid places, mostly, in summer and autumn , that devastated whole villages. This makes us believe that malaria (also know as paludism) is very old.

Malaria requires a mosquito for the transmission of the disease/infection and these exist over all tropical regions. Malaria has already existed in temperate regions like Europe but, in these regions it has been eradicated.

The propagation of the disease to other areas can be related to Man's evolution, namely with commercial trades among countries and with the creation of lakes and swamps to agricultural irrigation. In the first case, the mosquito was transported; in the second, the host and the infectious agent spread, and new areas were created to the reproduction of the vector.

In our days, with the discovery of the parasite and the vector, a lot of studies have been done, not only having in mind the cure and prevention of malaria by medication, or candidates for vaccines, but it is also important that under-structures exist to aid the health and control programmes of malaria.

The circle of life of the parasite

A malária humana é uma doença causada por 4 espécies de parasitas, Plasmodium falciparum, Plasmodium vivax,, Plasmodium malariae e Plasmodium ovale, irregularmente distribuídos pelas regiões tropicais. Estes têm dois hospedeiros: o mosquito Anopheles (fêmea), que se alimenta de sangue e o Homem.

Human malaria is a disease that is caused by four species of parasites: the Plasmodium Falciparum, Plasmodium, Vivax, Plasmodium Malariae, Plasmodium Ovale, irregularly distributed through the Tropical Regions. These have two hosts: the mosquito anopheles (female) that is fed on blood, and man.

During the human blood meal, the Anopheles may feed on plasmodium gametocytes from the infected man's blood circulation. In the mosquito's stomach gametes are formed and these, by fertilization produce eggs or zygotes which in this case are called oocysts. Inside these the parasites called sporozoites are developed, eventually they are in movement and invasive, and they travel to the mosquito's salivary glands. By feeding itself again, the mosquito will inoculate its glands in the second hosts (man) blood flow. These sporozoites search for hepatic cells to star their development.

Here they will multiply themselves and once they are in blood flow, they will invade the red blood cells. The parasite begins another phase of development and maturation, leading to the destruction of the red blood cells. This is the phase of the clinical signals which makes the infected person look for a doctor and treatment. It is also in this phase that gametocytes are formed and if a person is bitten during this phase by a female (Anopheles) mosquito, he will be infected, closing with this, the circle of the life of the plasmodium.

Only the female Anopheles mosquito is vector of the disease because only the female needs a human blood meal to mature her eggs.

The symptoms

The symptoms appear about one or two weeks after a person has been infected and they are characterised by:

Headaches;

Vague pains in trunk and limbs;

These symptoms may be vaguely different depending on the infectious agent. If the disease is not treated, the cold fits and fevers may continue until the high phases have passed. If the infection occurs in people who have no immunity defence, the malaria may lead to death.

People chronically ill with paludism suffer from anaemia, headaches, muscular pains and a general bad state.

How to treat?

The oldest remedy is the bark of the quina tree (quinquina) and its main essence - quinine, its salts and derivatives. This is very efficient on treating tertian and quartan malaria (the fever appears on alternate days, and every four days respectively), but when the disease is tropical, there is the risk of breaking out a hemoglobinuria fever.

Today synthetic antimalarial are produce (for example: cloroquinine, primaquina, among others), that don't cause hypersensitizing.

Today, there lacks new medication and the plasmodia is, frequently, resistant to the medication they used. As the production of new medication is quite expensive, the industry has not produced them whit quality.

Prevention and precautions for travellers

Because malaria exists in quite a large scale of the tropical countries, travellers should be advised about the risk of being infected with it, in the country of their destination and before leaving. If they live in Portugal, they should go to a doctor specialised in tropical disease in the Institute of Hygiene and Tropical Medicine(a consult to the traveller). Where they will be given info on chemoprofilexia. People should also reduce their contact with the mosquitoes, especially when the sun rises or sets, because this is the mosquitoes' feeding time and there are more risks of being contaminated with plasmodium.

For protection against mosquitoes people should:

Use clothes that make it difficult for the mosquitoes to bite them;

Only use repellent on the parts of skin exposed or on clothes;

Sleep with mosquito- curtains;

Avoid going near rivers and lakes at sunrise or sunset.

An anti-malaria vaccine? When?

The development of a vaccine against malaria has been a great problem to the scientists who investigate this disease.

This problem became even bigger after the discovery of the Plasmodium Falciparum's great resistance to cloroquinine. There are also indices that a parasite of the same family- the Plasmodium Vivax- offers the same resistance. The Plasmodium Malarie and the Plasmodium Ovale are parasites that cause less symptomology.

Despite that, a lot of work has been done and might lead to the creation of a vaccine. Studies of the Walter Reed Institute, of the North American Army, are an example of this.

They have achieved good results with the experimental vaccine against malaria. Three doses of the vaccine were injected in seven voluntaries before being exposed to the Anopheles mosquito, where the Plasmodium Falciparum, which causes diseases, lodges. Only one of those seven voluntaries was infected with malaria after being exposed.

The synthetical vaccine was composed by a protein expressed by the sporozoites or by the parasite's cells (whose structure was identified for the first time, by the couple Victor and Ruth Nussenzweig, over more then ten years ago), and, by a linking structure that stimulated the body's immunity (antigen of the surface of the hepatitis B)

A spokesman from the English laboratory Smith Kline Beecham says that "scientifically it was the first time that an experimental vaccine, still with great capacity of being improved, achieved so good protection against the parasite before it entered the red blood cells" .

Still concerning the vaccine, the scientist Ruth Nussenweig from the medical school of the New York University claimed: "it would be important to determinate the efficiency of the product on people who live in areas where the disease is endemic, where the levels of transmission are high and where many parasites exist. Another reason why it will still take a while before a vaccine, which prevents malaria, can be talked about.