Author Archives: obenedictow

Invalidation of early-phase transmission as an epizootic and epidemiological theory

Dear colleagues,

New plague research has just been published with particular importance for the discussion of the early-phase transmission and transmission by proventricular blockage. B.J. Hinnebusch, Senior Investigator at the Laboratory of Zoonotic Pathogens, NIH, NIAID, Rocky Mountain Laboratories, has long been one of the sharpest critics of the early-phase theory of transmission, see, for instance, his article “Biofilm-Dependent and Bio-Film-Independent Mechanisms of using Transmission of Yersinia pestis by Fleas”, Advances in Experimental Medicine and Biology, 954; 2012:  237‒243. In these days, he publishes with co-authors an evidently crucial article on this topic: Hinnebusch, B.J. Bland, D.M., Bosio, C.F., Jarrett, C.O., “Comparative Ability of Oropsylla montana and Xenopylla cheopis Fleas to transmitt Yersinia pestis by two Different Mechanisms” PLOS Neglected Tropical Diseases | DOI: 10…1371/journal.pntd.0005276 January 12, 2017: 1-15.

They used fleas of Oropsylla montana provided by two of the central advocates of the early-phase theory, which excludes that different strains of this flea could affect the outcome. The conventional vector of plague ‘par excellence’, Xenopsylla cheopis, was used for comparison. Contrary to earlier assertions by the advocates of the early-phase theory that Oropsylla montana rarely develop proventricular blockage, it was shown to block earlier and surviving longer after becoming blocked than X. Cheopis, and that transmission by blockage was as good as or better than observed for X. cheopis. This (re)confirmed earlier research on the vector capacity of this species of flea (see, e.g., the fully referenced comments in my monograph The Black Death and Later Plague Epidemic in the Scandinavian Countries, 2016: 377, 403, 630, 658).

In this article, the early-phase theory is dismantled as an important or significant means or mechanism of transmission of plague. In a personal communication by email of 01.03.17, Hinnebusch states that “In fact, I think early-phase transmission only has a role in very special circumstances, such as during an epizootic of plague in a dense [rodent] population that is both highly susceptible (LD50< 10) and that routinely develops very high bacteremia levels (>108 to 109 Y. pestis/ml) before death.  High flea density is also a likely precondition, as intermittent challenges from just a few fleas at a time would frequently lead to resistance rather than productive, transmissible disease (bacteremia).”

This also means that early-phase transmission is of no significance in plague epidemics, except perhaps, at the individual level, the occasional transmission of immunity-inducing tiny doses of plague bacteria (that will be easily dealt with by the human immune apparatus). It will also become clear that Hinnebusch et al. corroborate and deepen earlier plague research: it is pointed out that this type of early-phase transmission was identified by the Indian Plague Research Commission (IPRC) in 1907 and that the pioneering studies of Bacot of the IPRC on blockage in fleas IPRC 1914 and 1915, are still tenable and relevant. The bibliography contains studies from the entire 1900s, not least 1940s, which have kept their value as fine research.

Finally, I will point out that my recently published monograph contains a long study of early-phase transmission in Chapter 12: 625-655 (with bibliographic references included in the General Bibliography). Its conclusions and basic analysis agree with this recent study by Hinnebusch et al.

Kind regards,

Ole J. Benedictow,

Emeritus Professor

Ole Benedictow – Introduction & new publication

Dear all,

My monograph The Black Death and Later Plague Epidemics in the Scandinavian Countries: Perspectives and Controversies, Berlin: De Greuter, pp. 736, has just appeared: it is published in hardcover edition and also on the Internet in the form of Open access, De Greuter Open, https://www.degruyter.com/viewbooktoc/product/212904 . The book provides much new work on the Black Death, but also translations of works that so far has not been available in English. It also contains several long chapters that relate thoroughly to questions and controversies with respect to the presence of black rats in the Nordic countries (pp. 395-451 with three maps), transmission and dissemination by human ectoparasites, and the early-phase transmission theory or hypothesis rather (as long its advocates cannot explain how pathogenic doses of plague bacteria in the foregut of fleas are moved into a new bite site against the strong stream of a new blood meal).

This involves also the gathering together and presentation of all data on plague bacteraemia in rats and human beings to clarify their potential roles as sources of infection of feeding fleas and lice, the prevalence of bacteremia in rats and human beings measured as number of plague bacteria per mL (mm3) of blood, the volume of blood fleas or lice ingest (µL), and, thus, the potential role of human ectoparasites and rat fleas in the transmission and dissemination of plague bacteria. Finally, there is discussion of border values of Lethal Doses of transmission in the case of human beings and the presence and conditions for transmission of LDs of plague bacteria. There are also studies of the pattern, rhythm and seasonality of the spread of plague epidemics as reflections of and, thus, sources of information on the processes of transmission and dissemination.

The introductory general chapter on plague contains also two specific subchapters that really are lengthy articles. In Chapter 1.5, all paleobiological data on finds of aDNA or F1 antigen of Y. pestis in putative plague graves are gathered together with a comprehensive presentation of the research history and achievements of the new discipline of paleobiology in plague-related research, pp. 73-99. Chapter 1.4, reverts to the topic of alternative theories of plague, in this case an epidemiological alternative, which so far has not been addressed seriously and critically: ‘Serious Plague History under Pressure: The Twelfth Theory of Historical Plague. Comments on the Recent paper “Climate-driven Introductions of the Black Death and Successive Plague Reintroductions into Europe”, pp. 35-72. The relevant points on the role of human ectoparasites in the epidemiology of plague are discussed in the chapters mentioned above.

I will be grateful for all critical and supplementary reactions, which can come to good use now that my English publisher has asked me to write a 2nd edn. of my monograph on the Black Death and I am working on it to the hilt. This is also the case with respect to my previous monograph What Disease was Plague? On the Controversy over the Microbiological Identity of Plague Epidemics of the Past, Leiden: Brill , pp. 746.

Happy New Year to all,

Ole J. Benedictow
Emeritus Professor,
Department of History,
University of Oslo