Rat and Pneumonic models for Third Pandemic

Lice models for Second Pandemic

Sample sites

References1. WHO (1999). Plague manual: Epidemiology, Distribution, Survaillance and Control. Tech. rep. 99.2.2. Houhamdi, L, et. al. (2006). Experimental Model to Evaluate the Human Body Louse as a Vector of Plague, J Inf Dis 191.11 p. 1589-1596.3. Piarroux, AD, et. al. (2013). Plague Epidemics and Lice, Democratic Republic of Congo. Emg Inf Dis 19.3, p. 505-6.4. Hufthammer, AK, and Walløe, L (2013). Rats could not have been intermediate hosts for Yersinia pestis during medi-eval plague epidemics in Northern Europe. J Ach Sci 40, p. 1752-1759.5. Tran, TNN, et. al. (2011). Brief communication: Co-detection of Bartonella quintana and Yersinia pestis in a 11th-15th century burial site in Bondy, France. Am J Phys Anth 145.3, p. 489-494.

Pneumonic model Lice model Rat model

DIC R0 Beta DIC R0 Beta DIC R0 Beta

Givry 1348 638 1.1 0.44 578 1.9 0.066 621 1.3 0.069

Florence 1400 3773 1.0 0.42 1775 1.8 0.063 7944 1.4 0.080London 1563 4527 1.0 0.42 1483 1.6 0.061 3515 1.2 0.059Eyam 1666 433 1.0 0.41 436 1.4 0.057 466 1.1 0.048Stockholm 1710 2038 1.0 0.42 599 1.7 0.062 874 1.1 0.050Moscow 1771 5967 1.0 0.43 3153 1.8 0.063 >10000 1.3 0.068

Sydney 1900 143 1.2 0.49 90 1.6 0.061 96 1.1 0.053Hong Kong 1903 698 1.0 0.42 354 1.7 0.062 313 1.1 0.055Harbin 1910 527 1.2 0.48 552 2.8 0.079 1263 1.8 0.136

Human ectoparasites spread plague during the Black Death and Second Pandemic

Katharine R. Dean1, Nils Chr. Stenseth1, Lars Walløe2, Ole Christian Lingærde3, Barbara Bramanti1, and Boris V. Schmid1

IntroductionPlague, caused by Yersinia pestis, can spread through human populations by multiple transmission pathways. Modern plague transmission is well-doc-umented for the Third Pandemic (beginning in the mid-19th CE), and the most commonly reported routes of infection in humans are by fleas during a rodent epizootic, or directly between humans by infectious droplets from a pneumonic infection.1 However, there is controversy over how plague spread during the Black Death (1346-1353), and throughout the Second Pandemic (13th-19th CE), due to the relatively high mortality and rapid ge-ographic spread in Europe as compared to India.

MethodsWe made three susceptible-infected-recovered (SIR) models to test each of the proposed transmission mechanisms for plague in Europe: primary pneumonic plague, bubonic plague with a human ectoparasite vector, and bubonic plague with rats and fleas.

We used mortality data from historical records to compare three epidem-ics of known pneumonic or rat transmission from the Third Pandemic to six European epidemics (shown in the map) from the Second Pandemic with unknown transmission. We fitted the deterministic models in a Bayesian framework to the observed data by estimating the transmission parame-ters, and the initial number of susceptible and infected hosts, using MCMC in PyMC2. We assigned a best fitting model for each epidemic using the de-viance information criterion (DIC) and we estimated R0 using the next-gen-eration matrix method.

ResultsThe results show that a model of human ectoparasite transmission with body lice (Pediculus humanus humanus) fits epidemics during the Black Death and Second Pandemic over rat-borne and pneumonic transmission routes.

ConclusionsIndirect evidence for the role of body lice in the transmission of plague has come from a variety of sources: experimental studies, co-detection of plague and a louse-borne disease in a skeleton from medieval France, the collection of plague infected lice during epidemics, and a lack of archeolog-ical evidence for rats in Northern Europe during the Second Pandemic. 2,3,4,5 Our results support the hypothesis of an alternate mode of plague trans-mission by a human ectoparasite vector in Europe during the Second Pan-demic. Our comparative modeling approach, using Bayesian inference, al-lowed us to utilize limited mortality data to compare modern and historical epidemics. This work supports the growing body of evidence that plague was not spread primarily by rats in Europe, and therefore has epidemiolog-ical characteristics different from modern plague epidemics.

Author Affiliations1. Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Norway2. Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Norway3. Department of Computer Science, University of Oslo, Norway*We would like to thank Jukka Corander for his contribution to the methods

Date Pop SizeDatapoints

Data type Notes

Givry, France Jul 1348 – Nov 1348 1 500 138 Daily Black Death/Second Pandemic

Florence, Italy May 1400 – Nov 1400 60 000 180 Daily Second Pandemic

London, England Jun 1563 – Jan 1564 80 000 33 Weekly Second Pandemic

Eyam, England Jun 1666 – Nov 1666 350 143 Daily Second Pandemic

Stockholm, Sweden Aug 1710 – Feb 1711 55 000 24 Weekly Second Pandemic

Moscow, Russia Jul 1771 – Dec 1771 300 000 160 Daily Second Pandemic

Sydney, Australia Feb 1900 – Aug 1900 400 000 26 Weekly Third Pandemic; Rat transmission

Hong Kong, China Jan 1903 – Dec 1903 250 000 50 Weekly Third Pandemic; Rat transmission

Harbin, China Dec 1910 – Feb 1911 25 000 68 Daily Third Pandemic; Pneumonic transmission

ERCEA Funded MEDPLAG: 324249

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