Centuries of silence cannot keep ancient Egyptian mummies from sharing their secrets with scientists. From archaeologists determining cultural practices to chemists studying embalming, mummies have revealed libraries of information. Now such mummies are also yielding evidence about the diseases of the past by giving up the facts encoded in their preserved DNA, and new research may have pinned down the ancient homeland of a modern scourge.
Leishmaniasis--a disease caused by microscopic parasites, like malaria, and transmitted by sand flies--results in painful skin sores and in its most vicious form causes at least 500,000 deaths worldwide every year. Endemic to northeastern Africa, it also afflicts South and Central America as well as the Middle East; as many as 650 U.S. soldiers experienced it during the first year of the invasion of Iraq. The lethal form--visceral leishmaniasis, also known as kala azar, or black fever in the Hindi language of India, where the disease was first discovered by British doctors--is particularly prevalent in Sudan, and some authorities have claimed it originated there.
Albert Zink of Ludwig-Maximilians University in Munich and his colleagues tested the DNA of bone samples from 91 ancient Egyptian mummies and 70 from old Nubia--modern Sudan--to determine if they had suffered from leishmaniasis. In nine of the 70 Nubian mummies--taken from graves stretching as far back as A.D. 550--mitochondrial DNA of the parasite was discovered, proving the disease was endemic at least that far back. It likely has even more ancient roots; four of the Egyptian mummies carried the parasite's DNA, each dating from the Middle Kingdom period of 2050 to 1650 B.C. when trade ties with Nubia were strongest. Egyptian mummies from prior and later periods showed no sign of the disease, according to the research in the October issue of Emerging Infectious Diseases. "In this study, we haven't found evidence for Leishmania DNA in the samples from the New Kingdom to the Late Period, which are 500 to 1,000 years younger than those from the Middle Kingdom," Zink notes. "Therefore, we think that the presence of leishmaniasis is more due to the close cultural contacts of the Egyptians and the Nubians."
In addition to highlighting the old cultural ties between Egypt and Nubia, it also adds further weight to the theory that visceral leishmaniasis first developed in the region now known as Sudan. And the technique has been applied to other diseases, such as tuberculosis and malaria, to trace their development. "We can contribute to a better understanding of pathogen evolution and, thereby, to a more efficient treatment and control of infectious diseases," Zink says. The pathogens that proved a curse to ancient mummies may yet provide a cure for ancient scourges that still plague humanity.