What is the purpose of archaeology? I get this question a lot. The public often wonders about the value of archaeological studies, other than the intrinsic value of filling in the blank pages of the past. However, paleopathology is a sub-field of archaeology which clearly shows the benefits of doing these types of studies. In the last decade, malaria in Europe and the UK has risen (potentially due to global warming). Understanding the impact of malaria in the present requires knowing the history of the disease in the area. Malaria tends to be classified as a recent disease. This is due to the fact that malaria isn’t found on skeletal remains, and written records regarding the disease don’t appear until the last few centuries. In order to discover malaria trends in the past, we need to come up with alternate methods. A new study by Gowland and Western (2012) traces the presence of malaria in England by using spatial epidemiology to analyze the prevalence of skeletal indi- cators of poor health.
Historians argue that malaria has been present in the UK since the Roman occupation began in the 1st century CE. However, it’s also been suggested that it wasn’t endemic to the region until the post-medieval period due to a lack of evidence. In the 15th century CE, there are records of an ‘ague’ of intermittent fevers occurring widespread across the population, but it isn’t completely clear whether this represents malaria. The word ‘malaria’ wasn’t used to describe a disease until the 19th century CE. Simply because there was no word describing it doesn’t mean that it didn’t exist. Malaria doesn’t leave clear marks on the skeleton like the syphilis or tuberculosis, however it does cause anemia which can cause cribra orbitalia (sieve like lesions occurring above the orbits in the skull). While this could also be used as an indicator of many other diseases or poor nutrition, it is a start for examining trends of malaria.
Gowland and Western (2012) examine a sample of Anglo Saxon (410-1050 CE) skeletons from Eastern England that were recovered from a lowland wetland that would have been a likely location for malaria to be occurring. There study consists of a spatial epidemiological study of skeletal remains in order to determine whether there are correlations between nonspecific skeletal indicators of poor health (cribra orbitalia and enamel hypoplasia), geography, topography, and historically recorded evidence of outbreaks of malaria. They looked at 46 sites that overall had 5,802 individuals, and calculated the prevalence of cribra orbitalia among each sites population. This information was put into a Geographic Information System (GIS), along with environmental data and topography. A survey from the British Museum, dating to 1900 CE, charted the presence of malaria in the continent- this was added to the GIS as well.
In order to determine whether there was a relationship between skeletal indicators, the environment, and historic trends of malaria, Gowland and Western (2012) used a function in GIS known as Spatial Autocorrelation (SA). SA measures the “degree of spatial similarity observed among neighboring values”. They found that there is a highly significant correlation between skeletal, indicators of cribra orbitalia, marshy wetlands and historic malaria trends. There was no significant correlation with enamel hypoplasia, meaning general stress or poor health was not the cause of the cribra orbitalia. Another GIS test was done comparing the locations of historically known cases of ‘ague’ and maps of known locations of malaria infected mosquitos done in 1918. Again, there was a positive correlation between the two variables.
Gowland and Western (2012) conclude that there is a spatial relationship between Anglo Saxon cases of high cribra orbitalia and historically recorded malaria cases. It is likely then that malaria did exist, in similar wetland locations, during the 5th century, and potentially earlier. While it may not have been identified as malaria, this doesn’t mean the disease didn’t exist. They conclude that “Spatial epidemiological studies using GIS are not common in palaeopathology, but can be an invaluable tool for integrating historical, geographical, and paleo- pathological variables”. Indeed, this study is able to contradict earlier notions of the recent origins of malaria and is able to trace long term trends of the disease. It also shows a positive relationship between cribra and malaria, and not enamel hypoplasia, meaning that the former is not just caused by general stress. This is a really fascinating study, and hopefully one they will expand to other time periods to continue tracking the trend.
Gowland, R., & Western, A. (2012). Morbidity in the marshes: Using spatial epidemiology to investigate skeletal evidence for malaria in Anglo-Saxon England (AD 410-1050) American Journal of Physical Anthropology, 147 (2), 301-311 DOI: 10.1002/ajpa.21648
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Sounds like a cool article (which I admit I haven’t read, but Gowland’s past work has been excellent)! Something similar has been done in South America by Bethany Turner, who correlated CO/PH frequency with O isotopes to identify immigrants/possible homelands (that may have had water with high parasite loads). I blogged about Bethany’s research (and how it might be applied to Italy) here: http://www.poweredbyosteons.org/2011/10/mapping-parasites-in-ancient-italy.html. But it’s not totally straightforward to compare O isotopes with markers of malaria, since sickle-cell anemia (and other genetic anemias like thalassemia, which was likely endemic in the ancient Mediterranean) can cause changes in O isotopes: http://www.poweredbyosteons.org/2011/06/sickle-cell-disease-oxygen-isotopes-and.html
Anyway, I like that Gowland and Western used GIS… and that they had a massive sample. It must be nice to work in British bioarchaeology. They always seem to have a ton of skeletons to work with!
Malaria is NOT currently a native infection in the UK. Almost all malaria cases in the UK are in people who became infected abroad http://www.nhs.uk/Conditions/Malaria/Pages/Introduction.aspx and there are a few ‘cryptic’ cases, where a malarial insect has entered in luggage or on a plane and survived long enough to bite someone here. http://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1284473843636
However malaria could sometime in the future return to the UK as a result of climate change.
We do know tick-born infections (like Lyme disease) are already on the rise in the UK. http://www.hpa.org.uk/NewsCentre/NationalPressReleases/2012PressReleases/120327tickawaretoreduceLymedisease/
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I always thought of malaria as a tropical disease. My uncle contracted malaria in the late 1940’s while working in Indonesia. I had no idea it had ever been present in the UK. Learning a lot on your blog!