Category Archives: paleomicrobiology

Grandes Chroniques de France The Death of Saint Louis.

The Schistosoma in the Reliquary

The 800th anniversary of the birth of Saint Louis, King of France, in 2014 provided an opportunity to obtain a sample of his relics for “scientific identification”. With all relics the chain of custody and its backstory are critical for evaluation. Most of Louis’ relics held in the Basilica of Saint-Denis  were destroyed during the religious violence of  sixteenth century Paris. Fortunately the process of preserving and transferring Louis home to France from the site of death on crusade in Tunis, North Africa left bits of him in several locations.  Part of the preservation process used at the time removed his intestines and other internal organs to be embalmed separately while the remainder of the body was boiled to clean the bones to return to Paris. The bones were enshrined in Paris, while the heart and some viscera were enshrined at the abbey of Monreale near Palermo by his brother Charles, King of Sicily, who oversaw the preparation of the body and its transport back to France.

San_Domenico47
13th century Reliquary of Saint Louis, Basicilla of St. Dominic, Bologna Italy. (Source: Photo of Georges Jansoone, public domain on Wikipedia)

During a stop over at Bologna en route to Lyon and then Paris, some of his viscera were removed and interned in the Basilica of Saint Dominic. In 1297 Louis, who had died on 25 August 1270, was officially canonized as Saint Louis of France.  A portion of these visceral relics were given for the consecration of the cathedral of Turin in 1895, and these were transferred to the cathedral of Versailles in 1985. It is from this visceral relic that the 2 g specimen was obtained for scientific evaluation.

Microscopic Examination

The plan is to do a full “medical and forensic anthropological analysis” of the remains. The first result released by Phillipe Charlier’s team is the discovery of a semicircular parasite viewed by Scanning Electron Microscope (SEM) analysis, identified as a male Schistosoma based on its size and morphology.  Schistomsoma are a sexually dimorphic flat worm, also known as a blood fluke, that inhabit the capillaries of the abdomen (mesentery or bladder plexus depending on species) and release their eggs into either feces or urine. The eggs hatch in fresh water and must pass through a fresh water snail before emerging as larvae that can inhabit a mammalian host. Only about 50% of the eggs produced actually exit the body.  The adult worms and eggs that do not reach the feces or urine can cause extensive inflammation resulting in granulomas and fibrosis (scar tissue) to the abdominal organs (liver, spleen, intestines, bladder) and the blood vessels of the abdomen causing an accumulation of fluid in the peritoneal cavity.  Eggs that do breach into the lumen of the intestine cause chronic blood loss into the lumen producing chronic bloody stools. In the worst cases the blood loss can cause anemia.

Saint Louis
Source: Charlier, Bouchet, Weil & Bonnet, 2015.

Compare to a SEM preparation of a modern (non-mummified) male Schistosoma:

800px-Schistosoma_20041-300
A C-shaped male schistosoma; the smaller female resides in the canal. (Source: David Williams, Illinois State University made public domain, Wikipedia)

King Louis had not been in Tunis long enough for him to contracted schistosomiasis upon his arrival only a month before his death. When and where he contracted the flat worm infestation is open to more speculation.  have been observed in archaeological remains of one individual from 9th century France, but have not yet been commonly observed. Charlier et al. (2015) suggest that Louis’ previous crusade in North Africa between 1250 and 1254, spending some time imprisoned in Damietta, Egypt, is the most likely period for start of the infection. If this is true, then Louis would have had a chronic infection for about 20 years at the time of his death. Charlier’s team do not believe that Schistosomiasis contributed to his death.

So far they have not observed any other parasites in the sample. This is not necessarily surprising considering that they have not yet identified the anatomic source of the specimen. It is not possible to even guess at the anatomic source from the crumbling, blackened specimen pictured in their study (fig. 1). Their analysis is continuing.

Debating Saint Louis’ Cause of Death

As soon as the schistosoma report was published, the debate on the cause of Louis’ death began in the letters of Forensic Science, Medicine and Pathology (where the report was published). So lets begin with the best account of Louis’ death, and go from there.

Beyond skirmishing and entrenching the camp nothing was done, as King Louis was awaiting the arrival of his brother Charles of Anjou (now King of Sicily). Whilst they were waiting encamped, John Tristan fell sick, and died on board one of the ships on August 3rd. A few days later the Legate also died and many other persons, some of fever, some of dysentery. Philip, the King’s eldest son, fell sick with fever; and the King was taken with dysentery (the complaint to which he nearly succumbed in his first Crusade) and died on August 25th. (Guillaume de Nangis account in the Memoirs of Lord Joinville, Book 4, Ch. 4)

Strangely, the plague has traditionally been claimed as Louis’ cause of death. This is completely unfounded since the Black Death will not bring epidemic Yersinia pestis back to the Mediterranean for another 77 years! There is nothing in the account above to suggest plague. This has rightly been dismissed as Louis’ cause of death.

Eric Faure wrote a letter arguing that malaria was a possible cause based on reports of Louis’ history of tertian fevers dating back to the 1242. Faure suggests that Louis went on his first crusade in thanksgiving for surviving “cerebral malaria with a coma” after a relapse in 1244. Cerebral malaria is usually caused by Plasmodium falciparum, which is not a chronic (relapse causing) infection. If Louis suffered relapses of malaria contracted in France then it was most likely Plasmodium vivax, which rarely causes cerebral malaria. Whether or not Louis had cerebral malaria in the 1240s, this doesn’t really inform of his his health in 1270.  Faure also notes that some of the men on Louis’ last crusade had intermittent fevers suggestive of malaria. Faure reaches too far suggesting that the dysentery was a symptom of malaria. Gastrointestinal symptoms are possible but rare in malaria and usually then in children. Philippe Charlier responded with a letter dismissing Faure’s suggestion to look for Plasmodium in the remains, because they would not have caused Louis’ death. Following the report in Lord Joinville’s memoir (quoted above), Charlier reports in his letter that his team is now looking for evidence of bacteria, viruses or amoeba in the embalmed “intestines” that are more likely to be the cause of the “dysenteric syndrome” reported in “Louis and his court”.

I will be watching for the final report, but the idea of a single enteric pathogen being the cause of death may not really represent reality. Based on Joinville’s memoir is appears that the “court” was suffering from a variety of camp diseases found in most medieval armies on prolonged campaigns. In such a situation, co-infection is highly likely particularly with chronic parasites. Indeed, Louis was probably not the only one in camp with schistosomiasis lingering from previous travels.  Although I doubt malaria caused Louis’ dysentery, it is quite possible he was suffering from chronic malaria and that it contributed to weakening his health, making him more susceptible to other pathogens. Indeed co-infection with Schistosoma and Plasmosdium could have made him quite anemic.  It would still be worth knowing if Louis had an active malaria infection, even if Shigella or another enteric pathogen was the primary cause of death.

References:

Charlier, P., Bouchet, F., Weil, R., & Bonnet, B. (Oct. 2015). Schistosomiasis in the mummified viscera of Saint-Louis (1270 AD). Forensic Science, Medicine, and Pathology, 1–2. http://doi.org/10.1007/s12024-015-9722-4

Faure, E. (Dec. 2015). The infections of Saint-Louis: possible involvement of malaria.[Letter]  Forensic Science, Medicine, and Pathology, 1–1. http://doi.org/10.1007/s12024-015-9732-2

Charlier, P. (2016). Neither plague nor malaria, but dysentery as a cause of death for St. Louis. [Letter]  Forensic Science, Medicine, and Pathology, 1–1. http://doi.org/10.1007/s12024-015-9738-9

The Memoirs of Lord Joinvilletranslated by Ethel Wedgwood, E-text. University of Virginia library

Louis IV of France, Wikipedia.

WHO fact sheet: Schistosomiasis

Schistosoma, Wikipedia

Michael Walsh, Schistosomiasis on the Infection Landscapes blog. See this page for the best description of the medical effects of schistosomiasis.

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.

still_life_tor_marancia_vatican
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.

References:

Mitchell, P. D. (2016). Human parasites in the Roman World: health consequences of conquering an empire. Parasitology, 1–11. http://doi.org/10.1017/S0031182015001651

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).

Keeping Bronze Age Yersinia pestis in Perspective

Graphic abstract from ____
Graphic abstract from Rasmussen et al, 2015.

The latest plague news to splash across headlines is the discovery of Yersinia pestis aDNA in seven Bronze Age remains from Eurasia.  The most important findings in this new study are not anthropological; they are evolutionary. This paper allows us to drop a couple more evolutionary mile markers. Finding  7% of the tested remains  (7 out of 101) positive for plague is surprising, but I’m not yet ready to believe that it was endemic over such a huge area scattered over 2000 years. Not yet anyway.

The new phylogenetic tree places Y. pestis in humans since the Bronze Age and the origin of the species as far back 50,000 years ago.  It also opens up questions on the original reservoir species and the location of the birth of the species, although central Asia is still the most likely location.

Figure6
Stretching out the Yersinia pestis tree. Blue arrows are gains and red arrows are losses. (Rasmussen et al, 2015)

 

So let’s look at the genetic results in three areas highlighted by Rasmussen et al: flea transmission, Pla activity, and suppression of the immune response stimulating flagellin production. These traits are critical to producing bubonic plague as we know today.

Late phase flea transmission of modern Yersinia pestis is dependent on the ability to survive in and colonize the flea. The Bronze Age strains have all of the plasmids and virulence genes of modern strains except one, the ymt gene that encodes the murine toxin. The basic tool set of modern strains also have deactivated or knocked-out the protein products of three ancestral genes that hinder Yersinia pestis biofilm formation. Remnants of these genes persist as pseudogenes in modern strains. (A pseudogene is the corpse of a former gene.) This genetic combination allows Y. pestis to survive in the mid-gut of the flea, persist longer and form a biofilm; a necessity for late phase flea transmission. However, as Monica Green reminded me,  ymt is not required for early phase flea transmission, dirty-needle style (Johnson et al, 2014). In fact, since Y. pestis does not need to persist long or multiply at all, there are no known genes needed to be present or absent for early phase transmission.  As I recently reviewed, early phase transmission is very common and effective (see Eisen, Dennis & Gage, 2015). Based on the dates of their samples, they estimate that ymt was gained in about 1000 BC. In the RISE509 strain from Afanasievo Gora in southern Siberia, the pde3 is inactive but the other two, pde2 and rcsA, are still functional. Taken together this genetic combination should allow early phase flea transmission but not late phase flea transmission that requires biofilm formation. They are still mid-way in developing late phase flea transmission. This makes sense for a microbe being transmitted dirty-needle style, providing the opportunity for natural selection to develop late phase transmission bit by bit. While early phase transmission can support regional epizootics and epidemics,  late phase flea transmission is probably important for long distance transmission by fleas in grain or textiles, or by sea.

The recent discovery of the Pla gene in Citrobacter koseri and Escherichia coli, other enteric opportunistic flora, but not found in Yersinia pseudotuberculosis, suggests that lateral gene transfer  brought the plasmid to the young Y. pestis while still in the enteric environment (Hänsch et al, 2015) . This is consistent with Y. pestis Pla and Salmonella enterica PgeE both evolving from the same ancestral omptin ancestor in an enteric environment (Haiko et al, 2009).  This suggests that Y. pestis may have remained an enteric organism for some time after it split from Y. pseudotuberculosis.

Six of seven Bronze Age Y. pestis strains contain the Pla gene required for deep tissue invasion and bubo formation. Rasmussen et al (2015) suggest that the strain lacking the Pla gene has lost it and that this gene has been lost more than once in the phylogenetic tree. In other words, Pla was present in the common ancestral strain. However, to support development of bubonic plague Pla needed to gain a mutation at position 259 that these strains lack (Haiko et al, 2009). So the Pla gene without the mutation at position 259 can support pneumonic plague but not bubonic in the Pestoides F strain (0.PE2) of Y. pestis (Zimbler et al, 2015).  On the other hand, Sebbane et al (2006) showed that strains completely lacking Pla can still develop primary septicemic plague following flea transmission. They can envision an “evolutionary scenario in which plague emerged as a flea-borne septicemic disease of limited transmissibility”(Sebbane et al, 2006).  Without the polymorphism at position 259, bubo formation should be retarded, if not suppressed.

A third genetic difference of possible significance is the apparent ability to produce flagellin, a major activator of the human innate immune system. Modern Y. pestis strains have deactivated the production of flagellin by a frameshift mutation in the regulatory gene flhD. The Bronze Age strains lack this frameshift and so presumably had normal flagellin production. However, Y. pseudotuberculosis and  Y. enterocolitica down regulate production at mammalian body temperatures. If the ancestral Y. pestis did also then its possible that it wasn’t a factor in human infections.  Experimentally recreating the regulatory environment from  Y. pseudotuberculosis would be much more difficult than simply inserting an intact copy of the gene in a modern strain of Y. pestis.

Predicting the impact of these ancestral genes is highly conjectural. This combination of genes has never been studied together. Since these strains were isolated from human remains we can assume that there is a path for transmission and pathogenesis. The reliance on early phase flea transmission, the less virulent pla allele and the possible production of flagellin suggest that Bronze Age local (dermal) infections from flea bites would be less virulent (more survivable). Interestingly, these milder local infections may have been immunogenic.

As Y. pestis moved away from an enteric lifestyle, producing a septicemia was necessary for either flea transmission or development of a secondary pneumonia with aerosol transmission. I find it hard to believe that Bronze Age Siberia or Estonia had a large enough population for sustained pneumonic transmission. Since Pulex irritans can transmit Y pestis without development of a biofilm, there is no reason to see humans as a dead-end to flea transmission even as early as the Bronze Age.

Humans could have also contracted septicemic plague by ingesting infected meat. Although natural ingestion infections are very rare today, this mode remains effective. A village size outbreak could easily occur from sharing a large infected animal as happened in Afghanistan in 2007. In that outbreak a single infected camel shared among two villages produced 83 probable cases of plague with 17 deaths, a case fatality rate of 20.5%. (Leslie et al, 2011).  Last but certainly not least, the further back we go in Yersinia pestis‘ evolution the more likely ingestion is to be a mode of transmission like its ancestor Yersinia pseudotuberculosis.

Its takes more than good transmission to cause a demographic changing epidemic over large areas like the Eurasian continent. It also requires a fairly high human density and good trade or communication routes. Humans play the the most important role in transmitting plague of pandemic size. I can’t say if the cultural factors that make such large epidemics possible were in place in Bronze Age Eurasia.

Let’s keep things in perspective before we conjure up the specter of virgin soil epidemics of plague in the Bronze Age. Yersinia pestis is the kind of over achiever that may have been a player in Bronze Age demographics but it would be nice to have a lot more evidence before jumping to that conclusion.

References:

Rasmussen, S., Allentoft, M. E., Nielsen, K., Orlando, L., Sikora, M., Sjögren, K.-G., et al. (2015). Early Divergent Strains of Yersinia pestis in Eurasia 5,000 Years Ago. Cell, 163(3), 571–582. http://doi.org/10.1016/j.cell.2015.10.009

Eisen, R. J., Dennis, D. T., & Gage, K. L. (2015). The Role of Early-Phase Transmission in the Spread of Yersinia pestis. Journal of Medical Entomology, tjv128–10. http://doi.org/10.1093/jme/tjv128

Johnson, T. L., Hinnebusch, B. J., Boegler, K. A., Graham, C. B., MacMillan, K., Montenieri, J. A., et al. (2014). Yersinia murine toxin is not required for early-phase transmission of Yersinia pestis by Oropsylla montana (Siphonaptera: Ceratophyllidae) or Xenopsylla cheopis (Siphonaptera: Pulicidae). Microbiology, 160(Pt_11), 2517–2525. http://doi.org/10.1099/mic.0.082123-0

LESLIE, T., WHITEHOUSE, C. A., YINGST, S., BALDWIN, C., KAKAR, F., MOFLEH, J., et al. (2011). Outbreak of gastroenteritis caused by Yersinia pestis in Afghanistan. Epidemiology and Infection, 139(5), 728–735. http://doi.org/10.1017/S0950268810001792

Sebbane, F., Jarrett, C. O., Gardner, D., Long, D., & Hinnebusch, B. J. (2006). Role of the Yersinia pestis plasminogen activator in the incidence of distinct septicemic and bubonic forms of flea-borne plague. Proceedings of the National Academy of Sciences of the United States of America, 103(14), 5526–5530. http://doi.org/10.1073/pnas.0509544103

Zimbler, D. L., Schroeder, J. A., Eddy, J. L., & Lathem, W. W. (2015). Early emergence of Yersinia pestis as a severe respiratory pathogen. Nature Communications, 6, 1–10. http://doi.org/10.1038/ncomms8487

Hänsch, S., Cilli, E., Catalano, G., Gruppioni, G., Bianucci, R., Stenseth, N. C., et al. (2015). The pla gene, encoding plasminogen activator, is not specific to Yersinia pestis. BMC Research Notes, 1–3. http://doi.org/10.1186/s13104-015-1525-x

Haiko, J., Kukkonen, M., Ravantti, J. J., Westerlund-Wikstrom, B., & Korhonen, T. K. (2009). The Single Substitution I259T, Conserved in the Plasminogen Activator Pla of Pandemic Yersinia pestis Branches, Enhances Fibrinolytic Activity. Journal of Bacteriology, 191(15), 4758–4766. http://doi.org/10.1128/JB.00489-09