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Ancient Enemies
Many bacteria and viruses have been affecting people since antquity, but there are many more that are of recent origin. We learn about the afflictions of our ancestors by studying human remains, art, and literature. The nature of the infection and its mode of transmission also help us determine how long a microbial organism has existed. Our knowledge of the plague, for example, is obtained through the writings and drawings of physicians, poets and writers who lived during a time when this "Pestilence" swept through the Old World, leaving death and despair. In retrospect, scientists were able to trace its deadly path through Europe and determine that the disease was caused by bacteria and transmitted by fleas - both facts that were unknown to the medieval physician.
Based on the evidence available, it is clear that many infections are as old as humankind itself. Others have appeared only when changes in lifestyle and environment have allowed them to survive, or when they were able to infect animal hosts. While some organisms have been infecting humans in Europe, North Africa or Asia for a very long time, people living in the Americas, Australia, New Zealand, or the Pacific Islands were apparently free of those infections until European contact.
The field of science that deals with the study of disease in ancient human remains is called paleopathology.
Paleopathology: Organisms with Hosts other than Humans
Microbes with animal hosts (as opposed to those that live freely in soil or water) fall into two main groups those whose normal habitat is a host other than humans, and those whose normal habitat is in humans. The former includes pathogens from wild animals, such as Pasteurella pestis, caused by rat fleas and responsible for bubonic plague. Breakouts such as the Black Death occur when the disease becomes epidemic among the host animals, and are usually sporadic. While plague might have affected prehistoric people, the first written evidence comes in an account by Rufus of Ephesus describing an epidemic in Syria and North Africa during the first century A.D. The next major outbreak was the Plague of Justinian in the 6th century, followed by the Black Death in the 14th century. A small series of subsequent outbreaks followed over the next 400 years. Plague seemingly disappeared for awhile, but reemerged in Canton, China in 1894.
Epidemiorum, Hippocrates |
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Tuberculosis of the spine causing the collapse and fusion of several thoracic vertebrae |
Microbes native to domesticated animals, such as bovine tuberculosis, began to be transmitted to humans in Neolithic times (about 10,000 B.C.), when people began keeping dairy herds. Tuberculosis passed in milk tends to produce glandular, abdominal and skeletal tuberculosis. The most characteristic skeletal lesion is the deformity caused by collapsed spinal vertebrae, called Pott's disease. Domestication was probably also responsible for Brucella abortis, Bacillus anthracis, and salmonella poisoning in cattle, pigs, and poultry spreading to human populations. Organisms harbored in insects include the yellow fever virus, spread most often by the Aedes aegypti mosquito. It probably evolved in Central Africa during prehistoric times, but was first recorded in 1750. A third category of human-based pathogens are those in which the organism persists for years, communicable in sputum, pus, or other discharges. These organisms were ideally suited to survive in the widely dispersed populations of the earliest humans. These diseases include syphilis and its related treponemal infections - yaws, bejel, and pinta, as well as tuberculosis, leprosy, gonorrhea, and trachoma. |
Tibia with syphilis |
Syphilis is caused by Treponema pallidum, which probably evolved in the Old World around 7000 B.C., causing a non-venereal form of the disease and spreading in areas with warm climates. It then began to cause venereal syphilis in a mild form around 3000 B.C., assisted by changes in lifestyle arising from urbanization. In the 16th century, this form was supplanted by the more virulent mutation that produced the syphilis epidemic associated with the return of Columbus from the Americas in the 1500s. This later mutant is now found throughout the world |
Tibia showing severe osteomyelitis |
The last group of human-based organisms is the commensal type, permanent inhabitants of our skin and mucous membranes. Usually harmless, they wait for an opportunity to break out when the body's natural defenses are lowered. They were almost certainly associated with our primate ancestors. Non-human primates today harbor similar organisms, and present-day humans living in isolated areas, such as remote tribes of Papua New Guinea, have the same commensal microbes as those in the urban areas of the Western world. Staphylococcus aureus, a bacteria normally living in the nose, can cause osteomyclitis and abscesses, which have been detected in Old and New World remains of considerable antiquity. Escherichia coli (E.coli), normally present in our intestinal tract, can cause peritonitis when the bowel is pierced as well as spontaneous infections such as appendicitis. Both have been detected in Egyptian mummies. |
Plague
Plagues, infectious diseases causing a high rate of mortality, date back several thousand years. A smallpox plague in Rome nearly two thousand years ago killed an estimated million of Roman citizens during a fifteen-year reign of terror. The conquest of the New World was also largely due to disease - smallpox, measles and influenza - as well as swords and gunpowder. But the term plague is most often associated with the disease that decimated the medieval European population during the Middle Ages.
Das Buch der Cirugia |
The oldest printed textbook on surgery in the German language. The patient shows the three attending physicians a plague lesion or bubo under his arm. |
The [Fasciculus Medicinae]; Fasciculus medicine in quo continentur: videlicet… |
This book was the first illustrated medical textbook compiled for private use and for purposes of academic teaching. The illustration depicts a patient in the beginning stages of death. A robed physician stands by his side smelling a pomander which he is holding in one hand while with the other he feels the patient's pulse. A male attendant on the right carries a metal basket for embers that was used to burn aromatic substances as preventatives against infection. In only four years, from 1347-1341, plague, or "the pestilence" as it was called in the 14th century, killed as many as one of every three people in Europe. For centuries plague was spread along trade routes by traders who dispersed their goods as well as a number of rodents with their fleas to new geographic areas. |
Unaware of the microbial cause of the disease, some blamed earthquakes or claimed that unseasonable winds had poisoned the air. People wore masks to avoid evil vapors, and carried herbs and perfumes to negate them. The Pope at his palace in Avignon sat between two huge fires meant to purify the air.
In the Middle Ages, people never suspected that bacteria transmitted by fleas carried by rats were spreading the disease. Medieval doctors had no effective drugs, and their treatments, including bloodletting, enemas and a bland diet, proved powerless against these microbes.
Even after the initial wave subsided in 1352, plague reappeared in lesser epidemics every ten years or so for the rest of the 1300's. After 1400, recurrences were less severe and more localized. Experts suggest that the rat, flea and bacteria populations had achieved some balance. These epidemics took their toll on the population and the social balance of Europe, resulting in creation of a new order that helped to break down class distinctions between peasants and landowners, thus paving the way for the Renaissance and the Protestant Reformation.
Plague still exists today. In 1993, ten countries reported 2065 cases to the World Health Organization. Plague is curable if treated early with antibiotics.
Paleopathology: Organisms with Humans as their only Host
There are infections in which the organisms can persist in convalescent or contact carriers. The infections last for just a week to a month, but a certain number of those who recover carry the organisms in their nose, throat, or intestinal tract. People without any symptoms can also act as carriers. These infections include scarlet fever, tonsillitis, diphtheria, pneumonia, cerebrospinal meningitis, typhoid, paratyphoid, dysentery, poliomyelitis, and infectious hepatitis.
Many disease-causing microbes have chosen humans as their only host. This represents both opportunity and liability. Their goal is to survive, but the strategies vary, which is a measure of how long peoples' relationship with them has existed.
In some infections, including measles, smallpox and mumps, the microbes disappear when recovery or death occurs. In this case, they usually have only a short period during the active phase of the disease to infect another host. This can vary from 7 to 14 days, to several months in the case of smallpox. When they infect an unexposed population, they tend to cause short-lived epidemics because of their easy transmissibility. With the possible exception of influenza, survivors are immune for life and cannot even act as symptomless carriers.
The survival of these organisms depends on the existence of a large enough human population to ensure a constant supply of susceptible children and close person-to-person contact. Therefore, it is unlikely that they would have existed in the scattered communities of the early Paleolithic (Stone Age) hunter-gatherers.
