Ronald Ross
Ronald Ross
Malaria is an unpleasant, sometimes deadly, disease which is contracted mainly in tropical countries. For centuries there seemed no hope of controlling it, for scientists had little idea as to how it was passed on from person to another. Towards the end of 19th century, however, suggestions were made by experts in tropical medicine that the mosquito, an insect pest abounding in the tropics, was in some way responsible.
Although these theories were based on considerable evidence, there was no actual proof. The credit for finding this must go chiefly to Ronald Ross (1847 – 1932), a British doctor working in India. Encouraged by Sir Patrick Manson, an eminent authority on tropical medicine, Ronald Ross spent a great deal of time and energy trying to track down a definite link between malaria and the mosquito. After years of intensive work examining all kinds of mosquitoes under a microscope, he discovered in one of them, a female Anopheles, an unusual kind of cell. On further investigation the cell was found to contain few granules of black pigment, exactly like that of malaria parasite in man. This was proof of the link which Ronald Ross had been seeking so long. The mosquito had been identified and so had the means by which it transmitted the disease to man.
The detailed life story of the parasite has proved to be rather complicated. Briefly the mosquito takes it in when biting a malaria infected sufferer. The parasite reproduced in the mosquito’s stomach and eventually makes their way to its salivary glands. When the mosquito bites another man the parasite is transferred into the bloodstream of the victim, infecting him.
The life cycle of malaria parasites in the human body.
The best way to prevent malaria from spreading, then, is to exterminate the mosquito. Mosquitoes lay their eggs on ponds and swamps. After a time small larvae emerge from the eggs. The larvae breathe through their “tails”, thrusting them up through the water surface to do so. By covering the pond with a thin layer of oil it is possible to prevent the larvae from breathing and so kill them off. Other methods are used to. The swamps can sometimes be drained, though this is expensive. Natural enemies of the mosquito, such as the top-minnow or the salt-water killifish, may also be introduced into lakes to make it impossible for them to breed in large numbers. Such methods have proved to be extremely effective and today malaria is not nearly so widespread as formerly.
In recognition of Ronald Ross’s work he received a Nobel Prize (in 1902) and a knighthood (1911). Towards the end of his life the Ross Institute and Hospital for Tropical Diseases was founded, Ronald Ross himself as its first director.