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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Mosquito-malaria theory | 1/3 | https://en.wikipedia.org/wiki/Mosquito-malaria_theory | reference | science, encyclopedia | 2026-05-05T10:06:59.882762+00:00 | kb-cron |
Mosquito-malaria theory (or sometimes mosquito theory) was a scientific theory developed in the latter half of the 19th century that solved the question of how malaria was transmitted. The theory proposed that malaria was transmitted by mosquitoes, in opposition to the centuries-old medical dogma that malaria was due to bad air, or miasma. The first scientific idea was postulated in 1851 by Charles E. Johnson, who argued that miasma had no direct relationship with malaria. Although Johnson's hypothesis was forgotten, the arrival and validation of the germ theory of diseases in the late 19th century began to shed new lights. When Charles Louis Alphonse Laveran discovered that malaria was caused by a protozoan parasite in 1880, the miasma theory began to subside. An important discovery was made by Patrick Manson in 1877 that mosquitos could transmit human filarial parasite. Inferring from such novel discovery, Albert Freeman Africanus King proposed the hypothesis that mosquitoes were the source of malaria. In the early 1890s Manson himself began to formulate the complete hypothesis, which he eventually called the mosquito-malaria theory. According to Manson, malaria was transmitted from human to human by a mosquito. The theory was scientifically proved by Manson's confidant Ronald Ross of the Indian Medical Service in the late 1890s. Ross discovered that malaria was transmitted by the biting of specific species of mosquito. For this Ross won the Nobel Prize for Physiology or Medicine in 1902. Further experimental proof was provided by Manson who induced malaria in healthy human subjects from malaria-carrying mosquitoes. Thus the theory became the foundation of malariology and the strategy of control of malaria.
== Early concepts == Malaria was prevalent in the Roman Empire, and the Roman scholars associated the disease with the marshy or swampy lands where the disease was particularly rampant. It was from those Romans the name "malaria" originated. They called it malaria (literally meaning "bad air") as they believed that the disease was a kind of miasma that was spread in the air, as originally conceived by ancient Greeks. Since then, it was a medical consensus for centuries that malaria was spread due to miasma, the bad air. However, in medieval West Africa, specifically at Djenné, the people were able to relate mosquitos with malaria. The first record of argument against the miasmatic nature of malaria was from Irish-American surgeon John Crawford, who wrote an article "Mosquital Origin of Malarial Disease" in Baltimore Observer in 1807, but it provoked no consequences. It was instead ridiculed as impossible, and his work has since been lost. An American physician, Charles Earl Johnson, provided a systematic and elaborate arguments against miasmatic origin of malaria in 1851 before the Medical Society of North Carolina. Some of his important points were:
The delta of the Mississippi was a recorded healthy place although it has a nearby river, ponds, marshes and much stagnant water. Labourers of North Carolina were the healthiest people of working classes in spite of their constant exposure to swamps, and drinking swamp water. South American countries such as British Guiana and Brazil which were literally flooded with tropical swamps were free from malaria epidemics. Java Island in Southeast Asia, a region known for epidemics, had luxuriant vegetation and agricultural fields, supplemented with hot and wet tropical climate, ideal for miasmatic disease, was but the healthiest part of Asia. A highly polluted River Thames, which should cause miasmatic diseases, was but a good source of drinking water. On the other hand, the driest regions such as Guinea in Africa, Spain, Malta, Gibraltar, and several states of America, were frequented with malarial fevers.
== Scientific grounds ==
=== Disproof of miasma theory of malaria === The notion that malaria was due to miasma was negated by the discovery of malarial parasite. A German physician Johann Heinrich Meckel was the first to observe in 1847 the protozoan parasites which he recognised only as black pigment granules from the blood and spleen of a patient who died of malaria. But he did not understand the parasitic nature and significance of those granules in connection with malaria. In 1849 a German pathologist Rudolf Virchow realised that it could be those granules that were responsible for the disease. In 1879 an Italian biologist Ettore Afanasiev further argued that the granules were definitely the causative agents.
A major discovery was made by a French Army physician Charles Louis Alphonse Laveran working in Algeria, North Africa. At the hospital in Bône (now Annaba), he noticed spherical bodies from a patient's blood film, free or adherent to red blood cells. On 6 November 1880 he observed from one patient's blood the actual living parasite, describing it as "a pigmented spherical body, filiform elements which move with great vivacity, displacing the neighboring red blood cells." He also observed the process of maturation of the parasite (which is now called exflagellation of microgametocytes). He meticulously examined 200 patients, and noted the cellular bodies in all 148 cases of malaria but never in those without malaria. He also found that after treatment with quinine, the parasites disappeared from blood. These findings clearly indicated that the parasite was the cause of malaria, and establishing the germ theory (nature) of malaria. He named the parasite Oscillaria malariae (later renamed Plasmodium malariae) and reported his discovery to the French Academy of Medicine in Paris on 23 November and 28 December. For his discovery he was awarded the Nobel Prize for Physiology or Medicine in 1907.