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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.
Tuberculosis of the spine causing the collapse
and fusion of several thoracic vertebrae
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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
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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
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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
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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…
[f. 406]
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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. |
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