LETTERS Address for correspondence: Alex R. Cook, present in some skeletons from port To the Editor: The letter of Ayy- Department of Statistics and Applied Probability, cities in France, or that body lice adurai et al. (1) reminded us of a little- National University of Singapore, 6 Science might, under certain circumstances, known paper (2) on rats and Black Dr 2, Singapore 117546; email: alex.richard. transmit the Orientalis biotype of Y. Death by our colleague and mentor [email protected] pestis; their work appears careful and David E. Davis. He researched and considered. However, given the differ- wrote in his retirement after years of ences mentioned above and improved research and refl ection on rat ecology knowledge on the rapidity of virus mu- and rodent-borne diseases (3,4). Rat- tation and worldwide transmission po- tus rattus is commonly recognized tential, we merely argue that the sim- as the vertebrate host of fl ea-borne plest explanation for medieval plagues plague that swept through Europe in has yet to be ruled out: that they may the 1300s, killing >50% of the popu- have resulted from a human-to-human lation. Davis believed this explanation Body Lice, Yersinia transmitted virus. Adding complexity did not fi t what he knew of the eco- pestis Orientalis, to an already complicated etiologic logic requirements of fl eas and black theory, and stating such as historical rats. He studied reports of archeologic and Black Death fact based on limited geography and excavations and reviewed poems, me- To the Editor: A scientifi c de- sample size, does not seem congruent dieval bestiaries, and paintings and bate with public health implications with Occam’s razor. concluded that these rats were scarce wages: What caused the medieval during the Black Death era. European plague epidemics known Mark Welford and Brian Bossak His theory, based on historical as Black Death? Recent articles note Author affi liation: Georgia Southern Univer- information and investigative trips to inconsistencies between a rat fl ea– sity, Statesboro, Georgia, USA Europe, was that invasive rats, if pres- borne pandemic of Yersinia pestis (the DOI: 10.3201/eid1610.100683 ent, mostly occurred in low densities bacterium that causes bubonic plague) in port areas, not in rural inland ar- and the documented characteristics of References eas. He noted that the expected rodent Black Death (1, among others). Ayya- die-offs with bubonic plague were durai et al. (2) acknowledge that a rat 1. Welford MR, Bossak BH. Validation of in- not associated with human epidemics verse seasonal peak mortality in medieval and that rodent fl eas would not have fl ea–only hypothesis does not fi t Black plagues, including the Black Death, in com- Death observations, but they resolve parison to modern Yersinia pestis–variant been active during winter to transmit theoretical transmission inconsisten- diseases. PLoS ONE. 2009;4:e8401. DOI: plague. Flea-borne transmission from cies through a louse-borne hypothesis. 10.1371/journal.pone.0008401 rodents usually causes a few deaths 2. Ayyadurai S, Sebbane F, Raoult D, Dran- per household, but deaths of entire Ayyadurai et al. base their surety of court M. Body lice, Yersinia pestis Orien- fact—that medieval “plagues” were talis, and Black Death. Emerg Infect Dis. households commonly occurred in caused by Y. pestis infection—on a 2010;16:892–3. the medieval epidemics. Human-to- 2007 study (3) in which 5 of 36 teeth 3. Drancourt M, Signoli M, Vu Dang L, Bizot human transmission of pneumonic B, Roux V, Tzortzis S, et al. Yersinia pestis plague must have occurred, but as de- of “plague” victims, none of which Orientalis in remains of ancient plague pa- were dated to the Black Death era tients. Emerg Infect Dis. 2007;13:332–3. scribed by Ayyadurai et al., there was (1347–1351), contained biological ev- DOI: 10.3201/eid1302.060197 evidence of human bubonic plague, idence of Y. pestis. The 3 locations in 4. Duncan CJ, Scott S. What caused the Black suggesting vector involvement. Davis Death? Postgrad Med J. 2005;81:315–20. did not present a viable reservoir/vec- that study were all port cities: 2 on the 5. Gilbert MT, Cuccui J, White W, Lynnerup Mediterranean Sea and 1 on the Rhone N, Titball RW, Cooper A, et al. Absence tor hypothesis for plague transmission; River. As Duncan and Scott (4) note, of Yersinia pestis–specifi c DNA in human this and the later, well-known associa- bubonic plague most likely existed teeth from fi ve European excavations of tion of R. rattus and other rodents with putative plague victims. Microbiology. plague throughout the world, may par- endemically near ship-borne trade, un- 2004;150:341–54. like the fast-moving epidemic fronts tially explain why his ideas received exhibited by medieval “plagues.” Address for correspondence: Mark Welford, little attention. The fi nding that human Moreover, Gilbert et al. (5) found no Georgia Southern University, Geology and body lice can be bubonic plague vec- Y. pestis DNA in 61 skeletons from Geography, 68 Georgia Ave, Bldg 201, tors suggests a mechanism for human- primarily nonport locations in Eng- Statesboro, GA 30460-8149, USA; email: to-human transmission continuing land, France, and Denmark. [email protected] during winter in inland areas and, as We do not dispute the authors’ suggested by the authors, could also claim that Y. pestis might have been explain total deaths in households. Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 16, No. 10, October 2010 1649 LETTERS Robert G. McLean presence of Y. pestis–specifi c biomol- Death because of its high prevalence and Michael W. Fall ecules in 14th–18th-century human in medieval Europe (11). Far from Author affi liation: National Wildlife Research remains in 11 sites in Europe. These “adding complexity to an already Center, Fort Collins, Colorado, USA locations include 7 nonport, inland complicated etiology theory,” as Wel- sites <650 km from the coasts (4–6) in ford and Bossak stated, it seems to us DOI: 10.3201/eid1610.100822 addition to 3 Justinian (nonport) loca- that the cumulative evidence provid- tions (4,7). Therefore, the fact that Y. ed by paleomicrobiologic demonstra- References pestis was the etiologic agent of Black tion and by our recent work (1) clari- 1. Ayyadurai S, Sebbane F, Raoult D, Death can no longer be disputed; the fi es the epidemiology of the Black Drancourt M. Body lice, Yersinia pes- inconsistencies correctly noted by Death and the subsequent epidemics. tis, and Black Death. Emerg Infect Dis. Welford and Bossak actually ques- Louse transmission of Y. pestis also 2010;16:892–3. 2. Davis DE. The scarcity of rats and the tion the reservoir and the vector of explains inconsistencies rightly noted Black Death: an ecological history. J In- Y. pestis during the Black Death and by Welford and Bossak and provides terdiscip Hist. 1986;16:455–70. DOI: the following epidemics rather than a reason for the current plague cases 10.2307/204499 its cause. McLean and Fall remind in poor areas of the world where poor 3. Anonymous. Profi les of previous Wild- life Disease Association leaders: David E. us that the cumulative work of their hygiene is common. A search for al- Davis 1913–1994. J Wildl Dis 1995; 31(1 mentor, David E. Davis, suggested ternative hypotheses, including the suppl):15. that black rat ectoparasites could not previous viral hypothesis for Black 4. Davis DE. The characteristics of rat popu- have been likely vectors of medieval Death, may not be necessary (2). lations. Q Rev Biol. 1953;28:373–401. DOI: 10.1086/399860 plague in Europe, based on the facts The analogic reasoning based on that expected die-offs of rats were not observations of current infectious dis- Address for correspondence: Robert G. reported and that the rodents’ fl eas eases cannot be applied to the medi- McLean, National Wildlife Research Center, would not have been active during eval Black Death. Paleomicrobiologic US Department of Agriculture/Animal and Plant winter in medieval Europe (8). evidence and historical data force us Health Inspection Service/Wildlife Services, McLean and Fall acknowledge to change the paradigm and to ques- 4101 LaPorte Ave, Fort Collins, CO 80521, that our experimental data pave the tion the established dogma about the USA; email: [email protected] way toward an alternative scenario epidemiology of plague. McLean and of body louse–borne transmission of Fall remind us that, even in science, the Black Death. Such transmission of alternative hypotheses have trouble Y. pestis was observed by Blanc and challenging dogma (8). Black Death is Baltazard during a cluster of bubonic one of many areas at the intersection plague cases in households in Mo- of microbiology and history for which rocco during World War II (9). These many hypotheses have been proposed In Response: Commenting on authors demonstrated that the body and none has received confi rmation; our recent demonstration that the hu- louse could be infected when living these hypotheses have been repeated man body louse was a likely vector of on a septicemic patient, could stay for so long that they became accepted Black Death (the medieval European alive for 7 days with infectious feces, as demonstrated truths. plague epidemics) (1), Welford and and could transmit plague (9). Dem- Bossak (2) point out that quantitative onstration of Y. pestis in human lice Michel Drancourt and qualitative inconsistencies in data collected from Black Death burials and Didier Raoult for Black Death and modern plague would be a step toward understand- Author affi liations: Université de la Médi- argue against concluding that Yersinia ing the epidemiology of Black Death; terranée, Marseille, France; and Editorial pestis is the etiologic agent of Black this technically demanding approach Board, Emerging Infectious Diseases, Cen- Death (3).