This is a post that I am very excited to write, since the findings were made by Michigan State University bioarchaeologists!
When studying diseases in the past, one of the primary goals is to understand its antiquity. This is done by finding the earliest evidence of the disease in skeletal remains. Diseases in the past can be identified macroscopically, by noting pathological changes to the skeleton, microscopically, by finding changes in the cells of the bone. However, identification by these methods can be difficult. Bone can only grow or be destroyed, and while the patterns vary for different diseases there is a high amount of overlap making diagnosis complicated. DNA is the only technique that is completely reliable in the identification. Mutolo et al. (2011), bioarchaeologists from MSU, have used DNA in order to identify brucellosis in ancient Albanian human remains.
Brucellosis is a highly infectious disease that is acquired from contact with infected animals. Often the transmission is conducted through unsterilized milk or meat. The primary infection by the disease causes sweating, muscular pain, and respiratory illness. In the secondary stage, it tends to focus itself around the joints and vertebrae, where it is identified as lytic lesions (areas of bony destruction). The bone loss begins as mild osteoporosis, but can become extreme enough to cause spondylitis in the vertebrae or osteomyelitis in the long bones. Due to its propensity to focus on these regions, its differential diagnosis is tuberculosis, which also causes bone loss in the joints and spine. Mays et al. (2001) found it difficult to determine in their analysis of skeletons from Wharram Percy, whether they were suffering from TB or brucellosis. The only clear indicator of which disease is present, is DNA evidence of the pathogen itself.
The materials for the study came from Butrint and Diaporit, both cities in Albania. Both sites were used repeatedly from the 2nd century BCE to the early middle ages. The sites were valuable both as ports of trade, and also as strategic sites for controlling the Straits of Corfu. From excavations, Mutolo et al. (2011) recovered 48 individuals from Butrint and 26 individuals from Diaporit. From these remains, two 17-21 year old male individuals from the Butrint collection were found to have lytic lesions along their vertebrae. Both date from approximately 1020–1260 CE. The lesions were consistent with a number of vertebral pathologies, including tuberculosis and brucellosis.
In order to determine the exact cause of the pathology, DNA testing was employed. In addition to the two males, they also collected samples from three 5-7th century individuals: an adult male from Diaporit who displayed widespread enthesopathic activity, an adult female from Diaporit who had osteophytic changes in the vertebrae, and an adult female from Butrint exhibiting lesions on the skull and extensive periosteal reaction in the long bones. Finally, they collected samples from two individuals from the Diaporit assemblage with no visible skeletal pathologies to serve as the control. From each individual they took a vertebra, portions of the rib ends, and a section of long bones.
The result of the DNA testing showed that the two young males from the 10-12th centuries were both infected with brucellosis, and no other individual tested did. Testing was also done on all skeletal material to determine if tuberculosis was present, but none was found in any of the specimens. Mutolo et al. (2011) point out how the signs of brucellosis found in their remains is not completely consistent with modern diagnosis or the diagnosis of other archaeologists. Many have argued that the necessary signs of brucellosis include the presence of Parrot beak osteophytes, which are created in the healing process, and the inflammation of the vertebral bodies creating decreased space between them. However, none of these signs were apparent in the two individuals from Butrint. Mutolo et al. (2011) note that “Such discrepancies in skeletal brucellosis identiﬁcation have led many researchers to emphasize the importance of using molecular methods in ancient DNA studies”. While DNA identification is pivotal towards identification of disease, there are limits. DNA extraction is not a simple process, which means error can enter at many stages. In addition to this, microorganisms can cause breakdown of the DNA while bone is still interred in the earth, which can destroy or alter the DNA. DNA is not the anathema to the problems of pathology identification, rather it is another line of evidence to be considered. Mutolo et al. (2011) are able to use DNA in conjunction with the other skeletal evidence to successfully identify the pathology. My only wish is that we learned more about the background and context of the site and the disease. While they briefly mention the finding of infected cheeses from the region, and the history of brucellosis, this taste of the context provides more questions rather than satisfying answers. I look forward to seeing the future interpretations from my department on this specific case!
Michael J. Mutolo, Lindsey L. Jenny, Amanda R. Buszek, Todd W. Fenton, & David R. Foran (2011). Osteological and Molecular Identiﬁcation of Brucellosis in Ancient Butrint, Albania American journal of physical anthropology : 10.1002/ajpa.21643
Mays, S., Taylor, G., Legge, A., Young, D., & Turner-Walker, G. (2001). Paleopathological and biomolecular study of tuberculosis in a medieval skeletal collection from England American Journal of Physical Anthropology, 114 (4), 298-311 DOI: 10.1002/ajpa.1042