Disease and its control

Disease--its control
In the past, before scientists discovered that viruses and bacteria are the causes of most diseases, people made all sorts of futile and unscientific attemps to ward off disease. They burnt strongly smelling woods in their houses; they tied charms over the doorway of their houses to keep out, as they thought, diseases-carrying spirits; they carried other charms about on their persons or made incisions in thier skin into which they rubbed certain powders; and, at times, to ward off epidemics, a whole town might offer sacrifices to certain spirits believed to be responsible for bringing or controlling the certain diseases, such as smallpox.
However, after the bacteria causing many disease were discovered, one after the other, during the nineteenth century, it became possible to begin an organised and scientific attack on these old enemies of mankind. Careful study revealed the life histories of bacteria--where they lived, what bubonic plague, for instance, a disease which had killed millions in Europe in the past, were found not only infected people but also in the blood of infected rats. A British bacteriologist, P. L. Simond, showed that these bacteria are passed from rats to Man by an infected rat-flea, a little insect which lives on the rat as a parasite.
Once the whole intricate set-up was known, the first really positive steps could be taking towards eliminating the disease. Rats were destroyed where possible by trapping and poisoning, and by reducing number of places where they could breed and find food. A second line of attack was to stop infection from taking place, by discouraging and eliminating fleas. This was achieved simply by getting people to raise thier personal standards of cleanliness (rats and fleas are usually found in dirty houses) and by using strong insecticides.
It has been possible in the same way and by similar methods to starts a successful battle against our own familiar but deadly pests--the carriers of disease like smallpox, sleeping sickness, and malaria. For instance, there is a campaign to wipe out sleeping sickness by continued attacks on tsetse fly which carries it. In the same way Malaria Control Units are mounting vigorous campaigns against the mosquitoes which brings us malaria. First the Units carry out extensive surveys to give them full information about the habits of the mosquitoes, then they decide how best to destroy the breeding places. In some cases they organise the drainage of land or arrange for the land to be reclaimed altogether, so that there will no longer be any pools of stagnant water for mosquitoes to breed in. In places where drainage is impossible, such as in creek or delta areas where there are large expanses of almost completely stagnant water, spraying with insecticides may be the only way of making the places unsafe for mosquitoes.
For diseases like smallpox and tuberculosis, which have no insect carrier but spread by Man himself, either when he coughs deadly germs into the air, as with T.B., or when dried-up spores from an infected person float into the air and infect other people, as with smallpox, the most effective way of preventing the diseases from spreading, and the only hope of wiping them out completely in the future, is by immunisation.
Immunisation is done by injecting into a person's blood-stream dead or severely weakened forms of the virus or bacteria known to cause diseas. The body then becomes mildly infected, i.e. the person has a very mild attack of the disease. As a result of this the body builds up a supply of natural chemical (anti-bodies) which help to overcome the disease. In certain disease, such anti-bodies remain in the bloodstream, and make it possible for the body to resist future attacks by the same kind of bacteria.
In the case of smallpox, although the effects of immunisation (called vaccination) may not last for ever, and vaccination has to be renewed every two or three years, it is nevertheless so effective that it is considered possible to wipe smallpox out completely. By intensive vaccination and revaccination of all the people in a given area over a period of years, until there are no longer any active cases of the disease to start a new epidemic.