Oldest Malarial Mummies Shed Light on Disease Evolution
Andrew Bossone in Cairo
for National Geographic News
|October 30, 2008|
The oldest known cases of malaria have been discovered in two 3,500-year-old Egyptian mummies, scientists announced.
Researchers in Germany studied bone tissue samples from more than 90 mummies found in the ancient Egyptian city of Thebes, now called Luxor.
Two adult mummies from separate tombs had tissues containing ancient DNA from a parasite known to cause malaria, the researchers announced at a conference last week.
In addition, a separate team at University College London recently found that a pair of 9,000-year-old skeletons—a woman and a baby—discovered off the coast of Israel were infected with the oldest known cases of tuberculosis in modern humans.
Both finds contribute to the burgeoning field of paleopathology, or the study of ancient diseases.
Examining ancient DNA for clues about how and why disease-causing organisms evolve and mutate could have a tremendous impact on modern medicine.
"This will help us understand how these deadly diseases were able to infect humans," said Andreas Nerlich, a pathologist at the Academic Teaching Hospital München-Bogenhausen who found the mummies' malaria.
"Knowing this may help us to find strategies to prevent the introduction of new infectious diseases or the re-emergence of ancient ones."
Combating Drug Resistance
Even with today's medical advances, millions of people die each year from malaria, for which there is no effective vaccine.
Tuberculosis, a potentially fatal bacterial infection, has strains that have grown resistant to antibiotics and other treatments.
(Test your knowledge of illnesses with our infectious diseases quiz.)
"Tuberculosis is becoming a real problem in developed countries such as the U.S. or Switzerland, where [the bacteria] don't react anymore to antibiotics because they have mutated," said Frank Rühli, head of the Swiss Mummy Project at the University of Zurich.
Studying ancient diseases that have changed over time could help scientists better understand how modern diseases mutate in reaction to drugs.
"If you go back in the past and see this genetic fingerprint [of a disease], say a hundred years ago or a thousand years ago or ten thousand years ago, it helps you to assess how it might actually react in the future," said Rühli, who was not involved in either study.
This makes mummies and other ancient human remains even more valuable to paleopathology than written records.
"Humans are the best archives of humans," Rühli said. "If you have papyri on which [ancient doctors] diagnosed diseases, it's less reliable than if you actually have molecular or archaeological proof."
Other diagnostic tools, such as radiology and CT scans, have helped researchers find medical abnormalities in mummies, including arthritis, sclerosis, bone fractures, dental problems, and injuries.
(Related: "King Tut Died From Broken Leg, Not Murder, Scientists Conclude" [December 1, 2006].)
But such scans provide little definitive evidence of an infection, and archaeologists frown on more invasive procedures such as autopsies.
Sampling tissues to look at DNA is both less damaging to the mummy and more precise in terms of studying diseases.
"A CT scan of a mummy may identify changes very suggestive of tuberculosis, while DNA analysis provides a clear proof of the infection by showing the specific pathogen," Nerlich, of the German teaching hospital, said.
Path to a Cure?
Although pathologists have not yet used ancient DNA to develop specific treatments for modern diseases, they believe their work has that potential.
Ancient samples of a microorganism's genetic code can show what its DNA looked like before any of its known mutations developed.
An antibiotic designed to target a disease-causing bacteria in its earliest stages could then potentially cure its modern variations.
But getting to that stage requires studying as many samples as possible.
So far scientists have documented dozens of ancient cases of tuberculosis, contributing to the wealth of knowledge about the disease.
"Mycobacteria [such as tuberculosis] has a very strong cell wall, which we think helps to protect the DNA a bit within the mummies," said Albert Zink, head of the Institute for Mummies and the Iceman in Bolzano, Italy.
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