Category Archives: Zoonosis

CFP: Contagions sessions at the International Congress for Medieval Studies 2018

by Michelle Ziegler

Contagions: The Society for Historic Infectious Disease Studies has been given the opportunity of organizing three sessions at next year’s International Congress for Medieval Studies. This is the equivalent of a full day at the congress. The Congress will be held from May 10 to May 13, 2018, at Western Michigan University in Kalamazoo Michigan.  Our sessions next year will be:

Interdisciplinary Approaches to Historic Disease I and II

These two sessions are open to any aspect of study on infectious diseases and nutritional disorders in people and animals from the Late Antique to Late Medieval periods (400-1600 CE). These sessions are intended to be interdisciplinary as sessions, not necessarily as individual papers. Presentations on infectious diseases in literature, history, archaeology, and anthropology are all welcome.

Signs of Resilience in Medieval Populations

Major epidemics and natural disasters are ideal situations to study community resilience. No community is resistant to natural disasters; resilience is the best we can expect. Epidemics like the Black Death hit multiple communities in rapid succession but not all communities were equally affected in the short or long term. There are so many questions that can be asked.

  •  What allows some communities to quickly rebound while others dwindle away?
  • How do people mentally cope with a famine and/or massive epidemic?
  • What changes did communities make to better prepare or prevent a similar disaster in the future? Examples would include rebuilding flood walls or rerouting a river, increasing communal food stores, or building a surveillance system to detect the plague.
  • How did past experiences alter the community response to the next epidemic or another disaster?
  • How did responses differ between types of disaster (epidemic, flood, earthquake)? Flooding, at least, would be expected on a regular basis.
  • How did they prioritize their response? For example, did community leaders prioritize the economy (import/export) over public health?
  • What role did religious institutions play in disaster response?


Presentations are limited to 20 minutes. PowerPoint-like presentations are encouraged.  Participant Information Forms and an abstract are due to Michelle Ziegler by September 15th, contact prior to that date would be appreciated. Initial contact can be made through the form below.


Roundtable on Campbell’s Climate, Disease, and Society in the Late Medieval World

by Michelle Ziegler

Bruce Campbell. The Great Transition: Climate, Disease, and Society in the Late Medieval World. Cambridge University Press, 2016.


When I first learned that Bruce Campbell was working on this book, I wondered if it would be the first grand synthesis of the new paradigm. Although there have been some very good regional books in the last couple of years, Campbell has indeed brought forward the first analysis of the Black Death and 14th-century crisis using global evidence. Although not entirely clear from the publisher’s description, this is an economic history that draws on interdisciplinary evidence.

I proposed this session and recruited participants without ever seeing the book (though I had seen his Ellen McArthur Lectures). I got very lucky that the panel matched up so well with the book. The five panelists who were able to attend were (from left to right below) Mongolian historian Christopher Atwood, Historian of Medicine Wendy Turner, Evolutionary Biologist Boris Schmid, Archaeologist Carenza Lewis, and Economic/Environmental Historian Philip Slavin.

roundtable 2017
Great Transition Roundtable: Christopher Atwood, Wendy Turner, Boris Schmid, Carenza Lewis, and Phillip Slavin. (Photo by Nükhet Varlik, used with permission)

Everyone agreed that Campbell’s book will become the foundation upon which the new synthesis of plague history will be built. Campbell synthesized a vast amount of data with a particular appreciation for the integration of climate and disease data. Most agreed that this was a very high-level view of the crisis, an aerial view if you will, that leaves many details to be filled in. Some missed an analysis of the relationship with cascading levels of analysis down to the level of individuals. On the other hand, Atwood remarked that this is far more detailed than would be possible in Asian studies today. Perhaps not surprisingly, this interdisciplinary panel would have liked to see more evidence from other fields such as archaeology and social history used.  As Lewis noted, archaeology, in particular, could have given more support to the economic and environmental arguments without pulling away from the flow of the book.

The global evidence is primarily limited to climate data. Several panelists remarked that it is still very Eurocentric view, and Anglo-centric on top of that. There is more data that could have been gathered particularly from the Mediterranean. War as a syndemic factor and as a result of climate or disease weakened societies was not given much space in Campbell’s analysis. One effect of such a high-level regional treatment is that causes of local mortality from war (including the environmental destruction of war) can be overlooked because it doesn’t effect a large enough piece of territory. Slavin has also pointed out that Campbell’s interpretation tends to come across as somewhat deterministic, here and there. Thus, in discussing the Great European Famine of the early 14th century, Campbell provided an engaging analysis of the environmental context of the famine as its causation, without considering various intermediate links, demographic and institutional. As a result, Slavin noted that Campbell’s interpretation of the Great Famine as an exogenous disaster stands out as unilateral; famines, across space and time, are incredibly complex phenomena.

Developing a historical paradigm based heavily on scientific data is like building a house on shifting sand. Eventually, the sand will swallow the house. The best you can hope for is to be precariously perched on the ridge of a dune.  Most biological data is out of date by the time it is printed in a book. While there were a few misunderstandings, most of the discrepancies between Campbell’s portrait of the plague and other diseases is simply out of date even though he incorporates information up to about 2015. For example, ancient DNA studies have found evidence for at least one, and probably several, (still unlocated) local reservoirs of plague in or near Europe, so the idea that plague was frequently imported from the East no longer holds (but Boris disagrees on this view).

Some other hypotheses on plague transmission, though proposed several years ago, have failed to gain much traction. While evidence continues to mount that the soil plays a role in Yersinia pestis’ survival and that human ectoparasites could be the primary vector at the pandemic level, these hypotheses are not proven yet. This doesn’t mean that they won’t eventually be accepted, just that we are not yet there.

Figure 4.05 REV 6
Stages in the plague cycle (Figure 3.27, Campbell 2016)

I am reproducing figure 3.27 here because I think this will prove to be popular with teachers. With that being said there are a few comments that need to be made about it. The role of the soil in the enzootic environment of the rodent’s burrow is poorly understood at the moment. However, teachers could just explain that level 1 simply represents the environment of the rodent burrow.  Level 5 is where the real debates are going on now among those who study transmission. Campbell does leave open which ectoparasites are involved, human fleas or lice, but there is not yet general acceptance of human ectoparasites as major vectors. It may yet come, but we aren’t there yet. While local cases of pneumonic plague will occur any time there is bubonic plague, it is unlikely to be a major driver in a pandemic. The red box that I have added to the figure is where the really critical events are happening for human epidemics and pandemics. While I do believe that humans should be considered hosts in pandemic level transition, a variety of other hosts, always including rodents, will continue to be instrumental in the amplification and must be involved for the endurance of an outbreak in a locality.

While working with scientific detail is challenging for historians, after Campbell’s book I think it will be necessary to address scientific information at least to the level where there is a consensus. As long as historians stay with information that has been confirmed by a second study or that has obviously gained scientific consensus, the risks of using scientific information really are manageable. Finding a scientist who has your trust to comment on drafts is a good practice (and the reverse for scientists writing history!).

There were some concerns. There was a feeling that correlation does not necessarily equal causation. Schmid and Slavin would have liked to see more evidence of statistical analysis to support the conclusions drawn. They had a sense that the patterns that Campbell noted in a number of his overlapping time series might prove to be coincidental, rather than significant when tested with robust statistics.

Wendy Turner addressed pedological uses of the book. She found that, at least for a history of medicine course, it could not be used alone as a textbook. It does not have enough social history to address the complete impact of the Black Death. I don’t think that was its purpose, as much as some of us hoped it would be.  “The” Black Death book has yet to be written. When it is it will have to address all the social, medical, scientific, economic, and political impacts — a tall order. It is likely that aDNA studies will have more to contribute to shore up the transmission routes of such a project. Campbell’s book could be a major text (if not the only one) for an economic or environmental history course if it is supplemented by other texts. Archaeology as done by Carenza Lewis or Per Lagerås would support Campbell’s overall argument.  Turner and others agreed that it is not written for introductory students and they wondered how even upper-level students would respond to the density of the material. It should be required reading for graduate students who focus on the 14th century or any of the infectious/famine crises.

Atwood observed that historians tend to recognize a “crisis” about every couple of centuries and wondered if these mostly European events/crises over millennia were not tied to changes that had swept across all of Eurasia. In effect, Campbell’s book lays the supportive groundwork for arguing that the Eurasian land mass should be considered as a whole rather than European only or Asian only.  I think we could make an argument that the Afro-Eurasian landmass is one historic unit. The Indian Ocean is still an underappreciated communication avenue.

The most lively discussion with the audience concerned the terminology for the 14th-century events — transformation, crisis, collapse, etc. Positions seemed to be based at least partially on training, with some rejecting the term collapse under any circumstances, while others were more open to its use in areas like “population collapse”.  For me, this is an internal matter for historians to resolve. Terminology can be a fickle thing, but data is always preeminent. And that is a good place to leave this post. Campbell has done us all a service by compiling a huge amount of data that will be the foundation of a new era of analysis of the 14th century and the Black Death. For this above all else, we must be grateful.


Human Parasites of the Roman Empire

Last week photos of Roman toilets were splashed across the web breaking the news that the Romans were not a healthy as most people seem to have assumed. As with many public health interventions, the real value of a sanitation system is out of view (and out of mind) to most people. Its not the toilet that keeps us healthy; its the water treatment plant. Plumbing just moves waste with its microbes and parasites from one place to another.

Paleoparasitology specialist Piers Mitchell put the Roman public health system to the test by evaluating the evidence for human parasites in archaeological remains from before, during and after the Roman Empire. Comparisons before and after the empire are more difficult in North Africa and the Middle East because these areas had long standing sophisticated civilizations before the Roman empire. There is more clarity between civilizations in Europe since Celtic and Germanic societies did not have anything like Roman infrastructure. Contrary to his expectations, there were just as many parasites and ectoparasites in the Roman era as before or after.  In some cases the empire helped spread parasites across Europe. Relative amounts of parasites across times is difficult to ascertain for a huge variety of reasons. So while the same parasites were present, the degree of infestation would have varied by place and time period, and archaeology can’t reliably predict this.

The Roman achilles’ heel was their use of human waste for fertilizer and fecal contamination of rivers.  Human waste was added to the other manure and redistributed to farm fields and the watershed. What they could not have understood is that human waste is a greater risk for the transmission of human parasites and bacterial diseases. Mitchell also suggests that Roman bath water, that was rarely changed, could have transmitted worm eggs and other parasites. Aquaducts did bring in cleaner water to some of the larger cities but the system could be contaminated and not all Roman sites had access to water from aquaducts. Walter Scheidel (2015:8) has claimed that the city of Rome itself was an example of the”urban graveyard” effect with a very unhealthy population despite having a “heavily subsidized food and water supply”. Scheidel emphasizes the impact of malaria and gastrointestinal disease. We should also keep in mind that a large proportion of gastrointestinal disease would have been bacterial or viral.

Second century Roman mosaic of foodstuffs

As the mosaic to the left shows, the Romans did change agriculture throughout the empire. They spread Mediterranean preferences for cereals and more fish and other aquatic food sources. Mitchell suggests that the Roman love for fish products, especially the fermented fish sauce garum, probably help spread fish tapeworms found throughout the empire. Many parasites and bacterial spores have evolved to withstand preserving methods like smoking, pickling, and osmotic preservation (like salting or sugaring).  Whipworm was the most common parasite found, but round worms and tape worms were also common. Lancet liver flukes were widespread and indicate the (presumably accidental) consumption of ants.  Antibody based detection (ELISA) has been able to identify Entamoeba histolytica that causes the usually endemic amoebic dysentery (as opposed to the epidemic bacterial dysentery caused by Shigella species). Although not strictly speaking parasites, Mitchell notes an abundance of evidence for flies around cesspits suggesting that they contributed to the spread of diseases associated with fecal contamination. He also notes that schistosomiasis has not been identified in Roman Europe, even though it has been found in medieval European remains.

Turning to ectoparasites, Mitchell found ample evidence of head lice, body lice, public lice, human fleas and bed bugs across the Romanized world. Human fleas (pulex irritans) have been particularly well preserved in Roman, Anglo-Scandinavian and medieval York in Britain. Mitchell notes that human fleas and body lice were present in over 50 archaeological layers at York. He concludes that “the Roman habit of washing in public baths does not seem to have decreased their risk of contracting ectoparasites, compared with Viking and Medieval people who did not use public baths in the same way” (Mitchell 2016: 6). Mitchell suggests that there were enough ectoparasites to support particularly lice transmitted diseases. He notes that Plague of Justinian was transmitted by fleas but is non-committal on the likely specific vector.

In examining the impact of the Roman empire, Mitchell notes that the transition from a wide variety of zoonotic parasites to those primarily associated with human fecal contamination had already occurred before the Roman expansion out of Italy. This shift is paralleled elsewhere and is tied to shift from hunter-gathers to settled agriculture. Whipworm, roundworm and amoebic dysentery were the primary parasites of Roman Europe, while the Romans seem to have made a lesser impact on North Africa and the Middle East where endemic zones of parasites were well established.

Malaria is the one parasitic disease I would have liked to see Mitchell discuss more. Mitchell notes that malarial aDNA has been found in Egypt and anemia possibly caused by malaria in Italy. He overlooks all the malaria work by Robert Sallares including malarial aDNA from Late Roman Italy and better anemia studies correlating with malaria have been done in Italy and Britain by Rebecca Gowland’s group. Yet, malaria is such a big topic that it would be hard to cover along with all the other parasites.


Mitchell, P. D. (2016). Human parasites in the Roman World: health consequences of conquering an empire. Parasitology, 1–11.

Scheidel, W. (2015). Death and the City: Ancient Rome and Beyond. Available at SSRN 2609651.

See also:

Hall, A., & Kenward, H. (2015). Sewers, Cesspits, and middens: a survey of the evidence of 2000 years of waste disposal in York, UK. In P. D. Mitchell (Ed.), Sanitation, latrines and intestinal parasites in past populations (pp. 99–120).