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Class Notes: Bioarchaeology

Sunday: September 25, 2011

Week 3: Infectious Pathogens

Tuesday:

Dental caries is the process of  tooth decay. Once a cavity opens up into the pulp chamber of a tooth, bacteria has access to the arteries and nerves inside. It can then move into the alveolar bone, to which the body will react with resorption, forming a puss-filled abscess. This can go on until so much bone has been resorbed that the problem tooth falls out, known in bioarchaeological terms as ante-mortem tooth loss (AMTL). [Side note: researchers today believe there is a causal link between the S. mutans bacteria and heart disease.] Bioarchaeologists will look at dental caries for trends between sexes, social classes, and populations to determine cultural causes of the disease.

Periosteal reactions (PR) are another indicator of interest. These are “non-specific” in that they can be observed, but the cause cannot be determined usually because too many different circumstances lead to the same reaction. They are generally found on shallow bones (shin bones for instance) and are thought to be related to an infection resulting from trauma. A specific form of PR is osteomyelitis, which is diagnostic of the staph infection caused by S. aureus. These systemic infections cause the body to carve out the infection, literally creating a bone island and causing a gaping sore in the skin to drain the fluids.

Treponemal disease is caused by both venerable and non-venerable syphilis, from the T. pallidum bacteria. It is diagnosable from stellate lesions and “saber shins”. Contrary to popular belief, it was not introduced to the New World from Europeans, although contact did put much stress on populations and caused them to grow much denser which rapidly increased the prevalence of treponema.

Tuberculosis (TB) affects the ribs followed by vertebrae, which collapses creating a hunchback appearance known as Pott’s Disease. TB creates a good discussion for the Osteological Paradox. Some individuals may die of TB before their skeleton has had time to react, thereby looking completely healthy compared to an individual who was able to live with the disease long enough for boney reactions to occur, leaving a visibly unhealthy skeleton. The Osteological Paradox is something that must always be considered when working with skeletal populations.

Leprosy is another common disease found in bioarchaeological studies. Caused by M. leprae, it may not always be fatal. Diagnostic characteristics include atrophy of the face, peripherals, and appendages. It is currently thought this this disease was brought to the Americas by the Europeans.

Thursday:

Common non-specific diseases include Cribra Orbitalia (CO) and Porotic Hyperostosis (PH) which are often associated with each other and with iron deficiency, or anemia. These show in the roof of the orbits (CO) or along the flat bones of the skull (PH). It could be an issue of the Osteological Paradox again – are these individuals lacking in iron, or are their bodies fighting off an infection of some kind by limiting the iron available for the infection to feed on? For instance, a person affected with Sickle Cell Anemia has a higher survival rate against malaria because sickle shaped cells prevent the parasite from rapidly reproducing, thus allowing the body time to resist the infection. The idea of health has many facets which must be considered in bioarchaeology.

 

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  1. There is a lot to learn before you go trying to figure out how old or sex the person was.

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