Scientists have traced multiple tuberculosis strains back to a single late Roman ancestor. The findings support current scientific estimates that indicate tuberculosis (TB) emerged only 6,000 years ago. Previous theories suggested that the ancestral microbe was much more ancient, perhaps 70,000 years old. The paper has been published in the journal Nature Communications.
Samples were taken from 26 of the 265 naturally mummified bodies found in an 18th century Hungarian crypt located in a Dominican church in Vác, Hungary. The burial chamber was bricked up more than 150 years ago and forgotten about until it was rediscovered in 1994.
At the time of discovery, the crypt harbored hundreds of hand-painted coffins that contained finely dressed denizens of Vác. The dry air and coffin wood chips (to absorb bodily fluids) may have aided the mummification process and prevented the clothes from fully rotting. The mummies now reside at the Hungarian Natural History Museum.
To determine the source of the infectious disease, a team of researchers isolated the bacterial DNA of several TB strains that infected eight of the 26 mummified bodies they studied. They found 14 different tuberculosis genomes. Surprisingly, the researchers discovered that many of the bodies harbored more than one TB strain, suggesting mixed strains were common during the peak of the epidemic in Europe.
"Microbiological analysis of samples from contemporary TB patients usually report a single strain of tuberculosis per patient," said geneticist Mark Pallen of the University of Warwick. "By contrast, five of the eight bodies in our study yielded more than one type of tuberculosis—remarkably, from one individual, we obtained evidence of three distinct strains.”
All of those samples belonged to M. tuberculosis Lineage 4, a notorious TB strain that accounts for over a million cases a year. Historically, tuberculosis has ravaged Europe since prehistoric times, killing nearly one in seven people during the early 19th century.
Image Credit: Left: Mycobacterium tuberculosis bacteria, which cause TB / NIAID. Right: Dominican church that housed the Vác mummies / András Tumbász
Presently, there are still millions of cases of TB, with more than 1 million deaths in 2013, according to the World Health Organization (WHO). The scientists say their research is significant for tracing the evolutionary history of TB as well as combating the disease in modern times.
“By showing that historical strains can be accurately mapped to contemporary lineages," said Pallen, "we have ruled out, for early modern Europe, the kind of scenario recently proposed for the Americas, that is, wholesale replacement of one major lineage by another."