Tropical Disease in the Nineteenth Century

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Tropical Disease in the Nineteenth Century

Overview

The nineteenth century was a period of expansion of western imperialist power into Africa, Asia, the Middle East, Central and South America, and other regions of the world. This involved "population mixing" where one group of people met and lived side by side with another. Inevitably each group met a new "germ pool"—diseases specific to the other group which were now shared. Because the principles of sanitation—provision of clean water and disposal of sewage, etc.—were not fully understood yet by either the newcomers or those who were indigenous to the newly penetrated territories, neither group protected itself properly against infection and cross infection from communicable diseases.

Background

In most cases, the ways in which germs traveled from person to person and caused illnesses were not yet understood in the nineteenth century. The interest of colonists in developing the resources of new territories to meet the needs of the new industries of the West also meant that they introduced different forms of cultivation, such as farming cash crops and the intensified mining of natural resources. In many cases these new activities upset the balance between the people living in a particular environment and the cycle of nature. Sometimes this population mixing, combined with new forms of economic activity, caused epidemics of diseases. Often the new arrivals actually brought diseases with them that the local populations did not have a strong resistance to.

In Somaliland, for instance, smallpox, cholera, influenza, venereal diseases, and tuberculosis epidemics occurred soon after the arrival of colonists from Britain. In Mauritius the arrival of French soldiers who traveled via India with workers brought from India introduced new diseases to the local people for which they had not developed a resistance. The transmission of tropical diseases was a two way process. During the American Civil War (1861-65) one half of the white troops and four out of five of the black troops in the Union Army suffered from malaria. Cholera, typhoid, and other diseases were present in both Europe and North America throughout the nineteenth century and it was not until the science of epidemiology was developed early in the twentieth century that the processes of epidemics were understood and could be combated.

Impact

The building of new roads, railways, public buildings, and plantations required a different type of work force than in traditional societies, and sometimes the colonists resorted to forced labor and cheap labor to undertake these new projects. It took many years to realize that workers camps could themselves become hotbeds of infection, especially if people were poorly fed and housed. The creation of new centers of commerce and agriculture caused "internal migrations," where people from one part of a territory migrated toward the work opportunities. This process also involved population mixing. Sometimes the new cash crops actually caused people to give up their traditional agriculture, leaving the population poorly fed while the new crops were exported to the colonizing countries.

Even the introduction of money as the prevailing form of exchange upset the traditional balance of many societies that had relied on bartering goods to meet people's needs. Sometimes the new money was used for alcohol and sugar-based foods rather than the traditional balanced diets. In countries of the South Pacific, for instance, these changes resulted in widespread diabetes and obesity. In the Songea District of Tanzania so many men left to work in the new plantations and industries elsewhere that the health of the women and children of the families left behind were endangered by malnutrition. In Mauritius, the colonial economy resulted in the country being very dependent on sugar as its one cash crop for export and the population relying on imported food rather than the traditional products of its diet.

By the middle of the nineteenth century there were Western medical doctors and missionaries present in these territories, but their first preoccupation was usually the health of the colonists rather than the colonized people. The armies of the occupying powers had to be kept healthy if they were to be effective. The civil servants and merchants who worked in the territories were likely to fall ill. Usually they had to send their children home after a year or two to be raised by relatives because life was so hazardous in the tropical countries. Often men who were left to work in these conditions without the support of their families took to alcohol which only increased the problems. In 1863 Richard Burton (1821-1890), the explorer, described the Lagos Government house in Nigeria as "a corrugated iron coffin or a plank lined morgue containing a dead Governor once a year."

Many missionaries and other church-based medical personnel did try to improve the welfare of the people in these territories. They offered a different type of medicine than that which the traditional healers practiced and often there were clashes between the two cultures. But there were some areas of agreement. The Yoruba people of Nigeria, for instance, believed that many illnesses were caused by worms or "insects" that were so small that they resemble what came to be known to the tropical medical researchers as bacteria. Many of the people living in the tropical cultures made good use of herbal remedies from the plants available to them, and some of these have since been recognized in Western medicine. Dr. David Livingstone (1813-73), one of the early Western missionaries and explorers in Africa, was always interested to learn about these medicines. These health problems led to the development of "tropical medicine" as a field of research and health as doctors tried to understand the dynamics of the epidemics and communicable diseases.

One of the most important researchers in theses early years of tropical medicine was Patrick Manson (1844-1922), who graduated from Aberdeen University Medical School in Scotland then went to China where he stayed for nearly a quarter of a century, studying the local diseases. In 1878 he observed that filariae, the worms that cause elephantiasis in man, pass part of their life cycle in the Culex mosquito. This made him realize that the parasites that cause many of the tropical diseases are transmitted by other carriers, or vectors. In 1894 he realized that the parasite of malaria also passes part of its life cycle in the mosquito and this was confirmed by another great researcher in the tropical diseases, Ronald Ross (1857-1932), at the end of the nineteenth century. These observations led the governments concerned to undertake mosquito control programs that are still the basis of prevention of tropical diseases. The building of the Panama Canal, for instance, could only be undertaken once it was understood that the laborers had to be protected from mosquitoes that were spreading yellow fever. Yellow fever is caused by a virus transmitted by the bite of the female Aedes aegypti mosquito which breeds in stagnant water near human habitations. Another form of this disease is spread by another species of mosquitoes that live in the trees of tropical jungles.

Ronald Ross, an Englishman born in Almora, India, studied malaria in that country as a member of the Indian Medical Service during the last 20 years of the nineteenth century. In 1897 he observed the malarial parasite in the stomach of the Anopheles mosquito. In West Africa he identified the mosquito that transmits African fever. He eventually received the Nobel Prize in 1902 for his work on malaria, and became a professor at the newly organized Ross Institute and Hospital for Tropical Diseases in London. He was sometimes known as "The Mosquito Man."

Another Scot who was to make a major contribution to the understanding of tropical diseases was William Boog Leishman (1865-1926), who graduated in medicine from Glasgow University then went to India as part of the Army Medical Service. He undertook studies with his microscope of enteric fever and kala azar. When he returned to England he worked on inoculation against typhoid fever, and developed a process of staining blood samples for malaria diagnosis.

In 1873 Dr. Armauer Hansen (1841-1912), a Norwegian, discovered the bacillus that causes leprosy, and nine years later Robert Koch (1843-1910) proved that a related microbe caused tuberculosis. Koch and other German researchers were convinced that infectious diseases were caused by living, parasitic organisms that were passing from animal species to humans. His work on anthrax bacilli was published in 1876 and caused a revolution in the study of tropical diseases. In 1883 he went to Egypt as leader of the German Cholera Commission to study the transmission of that disease, and formulated a series of rules for the control of such epidemics which form the basis of strategies still used today. In 1891 he became director of the new Institute for Infectious Diseases at the Medical Faculty of Berlin. In 1896 he went to South Africa and pioneered the inoculation of healthy animals with material taken from animals already suffering from diseases. He also worked in India and Africa on malaria, blackwater fever, and plague at the end of the nineteenth century. He was awarded the Nobel Prize for Physiology or Medicine in 1905.

However, it was not until well into the twentieth century that effective preventive measures and cures became available, and the field of medical microbiology became a major contributor to the understanding of tropical and other diseases.

SUE RABBITT ROFF