Plague

The Natural and Clinical History of Plague: From the Ancient Pandemics to Modern Insights

The human pathogen Yersinia pestis is responsible for bubonic, septicemic, and pneumonic plague. A deeply comprehensive overview of its historical context, bacteriological characteristics, genomic analysis based on ancient DNA (aDNA) and modern strains, and its impact on historical and actual human populations, is explored. The results from multiple studies have been synthesized to investigate the origins of plague, its transmission, and effects on different populations. Additionally, molecular interactions of Y. pestis, from its evolutionary origins to its adaptation to flea-born transmission, and its impact on human and wild populations are considered. The characteristic combinations of aDNA patterns, which plays a decisive role in the reconstruction and analysis of ancient genomes, are reviewed. Bioinformatics is fundamental in identifying specific Y. pestis lineages, and automated pipelines are among the valuable tools in implementing such studies. Plague, which remains among human history's most lethal infectious diseases, but also other zoonotic diseases, requires the continuous investigation of plague topics. This can be achieved by improving molecular and genetic screening of animal populations, identifying ecological and social determinants of outbreaks, increasing interdisciplinary collaborations among scientists and public healthcare providers, and continued research into the characterization, diagnosis, and treatment of these diseases.

Ancient Yersinia pestis genomes lack the virulence-associated YpfΦ prophage present in modern pandemic strains

Yersinia pestis is the causative agent of at least three major plague pandemics (Justinianic, Medieval and Modern). Previous studies on ancient Y. pestis genomes revealed that several genomic alterations had occurred approximately 5000-3000 years ago and contributed to the remarkable virulence of this pathogen. How a subset of strains evolved to cause the Modern pandemic is less well-understood. Here, we examined the virulence-associated prophage (YpfΦ), which had been postulated to be exclusively present in the genomes of strains associated with the Modern pandemic. The analysis of two new Y. pestis genomes from medieval/early modern Denmark confirmed that the phage is absent from the genome of strains dating to this time period. An extended comparative genome analysis of over 300 strains spanning more than 5000 years showed that the prophage is found in the genomes of modern strains only and suggests an integration into the genome during recent Y. pestis evolution. The phage-encoded Zot protein showed structural homology to a virulence factor of Vibrio cholerae. Similar to modern Y. pestis, we observed phages with a common origin to YpfΦ in individual strains of other bacterial species. Our findings present an updated view on the prevalence of YpfΦ, which might contribute to our understanding of the host spectrum, geographical spread and virulence of Y. pestis responsible for the Modern pandemic.

A Perilous Combination: Streptococcus Coinfection with Human Plague-Report of Two Cases and Review of the Literature, 1937-2022

Background: Plague in humans and animals is caused by Yersinia pestis, a zoonotic gram-negative bacterium endemic in certain regions of Asia, Africa, and the United States. Coinfection with both Y. pestis and Streptococci species has been anecdotally reported in humans and associated with severe and rapidly fatal disease. Methods: This report presents two cases of patients who died following Y. pestis and Streptococcus coinfection. Additional cases of previously published Y. pestis-Streptococcus coinfection were identified and reviewed using a search of electronic databases. Results: The first case patient developed cough and dyspnea following 4 days of fever, malaise, and back pain and died before receiving medical care. Postmortem blood cultures were positive for Y. pestis, Streptococcus pyogenes, and Streptococcus dysgalactiae. The second case patient was hospitalized with fever, vomiting, diarrhea, and dyspnea and died of sepsis and respiratory failure on the day of admission. Y. pestis and Streptococcus pneumoniae were isolated from blood cultures drawn on admission. Seven additional cases of Y. pestis and Streptococcus coinfection were identified, dating between 1948 and 2009. These patients were healthy overall before their illness, with ages ranging from 9 to 60 years. The majority of patients had primary bubonic plague with associated pneumonia or septicemia. None of the patients who died received timely antimicrobial therapy directed against gram-negative pathogens. In every case but one, an occupational or environmental risk factor for plague was later identified. Conclusion: Y. pestis infection begins with a pre-inflammatory phase, during which Y. pestis and other pathogens can rapidly proliferate. Streptococci, which are frequently asymptomatic colonizers, may become invasive in this environment, leading to coinfection. The challenges of diagnosing Y. pestis in the context of coinfection may delay effective treatment. This case series and literature review illustrate the importance of clinicians remaining alert to environmental and occupational exposures in patients presenting with an infectious syndrome, especially in those who have an unexpectedly severe clinical presentation.

[The role of the pulmonologist in an armed conflict]

INTRODUCTION

Recent news points to the eventuality of an armed conflict on the national territory.

STATE OF THE ART

In this situation, pulmonologists will in all likelihood have a major role to assume in caring for the injured, especially insofar as chest damage is a major cause of patient death.

PERSPECTIVES

The main injuries that pulmonologists may be called upon to treat stem not only from explosions, but also from chemical, biological and nuclear hazards. In this article, relevant organizational and pedagogical aspects are addressed. Since exhaustiveness on this subject is unattainable, we are proposing training on specific subjects for interested practitioners.

CONCLUSION

The resilience of the French health system in a situation of armed conflict depends on the active participation of all concerned parties. With this in mind, it is of prime importance that the pneumological community be sensitized to the potential predictable severity of war-related injuries.

Serological evidence of Yersinia pestis infection in rodents and carnivores in Northwestern Iran

BACKGROUND

Plague may recur after several decades in its endemic regions; therefore, the continuous monitoring of wildlife is essential, even when no human cases are reported in the old foci. The present study was conducted to monitor rodents and their ectoparasites as well as carnivores to learn about the epidemiology of plague infection in an old focus of Iran.

METHODOLOGY

The present study was conducted from 2019 to 2020 in Takestan county of Qazvin Province in northwestern Iran. Rodents were caught using live traps, and their fleas were separated. Blood and spleen specimens were taken from the captured rodents. Serum samples were also collected from sheepdogs and wild carnivores. The collected samples were tested by culture, serology (ELISA), and molecular methods to detect Yersinia pestis infection.

FINDINGS

A total of 399 small mammals were caught, of which 68.6% were Meriones persicus. A total of 2438 fleas were collected from the rodents, 95.3% of which were Xenopsylla buxtoni. Overall, 23 out of 377 tested rodents (5.7%, CI 95%, 3.9-9.0) had IgG antibodies against the F1 antigen of Y. pestis, and all the positive samples belonged to M. persicus. Nine (4.8%) out of 186 collected sera from the sheepdogs' serum and one serum from the Canis aureus had specific IgG antibodies against the F1 antigen of Y. pestis. There were no positive cases of Y. pestis in the rodents and fleas based on the culture and real-time PCR.

CONCLUSION

Serological evidence of Y. pestis circulation was observed in rodents and carnivores (sheepdogs and C. aureus). The presence of potential plague vectors and serological evidence of Y. pestis infection in the surveyed animals could probably raise the risk of infection and clinical cases of plague in the studied region. Training health personnel is therefore essential to encourage their detection of possible human cases of the disease.

Yersinia pestis and Plague: some knowns and unknowns

Since its first identification in 1894 during the third pandemic in Hong Kong, there has been significant progress of understanding the lifestyle of Yersinia pestis, the pathogen that is responsible for plague. Although we now have some understanding of the pathogen's physiology, genetics, genomics, evolution, gene regulation, pathogenesis and immunity, there are many unknown aspects of the pathogen and its disease development. Here, we focus on some of the knowns and unknowns relating to Y. pestis and plague. We notably focus on some key Y. pestis physiological and virulence traits that are important for its mammal-flea-mammal life cycle but also its emergence from the enteropathogen Yersinia pseudotuberculosis. Some aspects of the genetic diversity of Y. pestis, the distribution and ecology of plague as well as the medical countermeasures to protect our population are also provided. Lastly, we present some biosafety and biosecurity information related to Y. pestis and plague.

Subversion of GBP-mediated host defense by E3 ligases acquired during Yersinia pestis evolution

Plague has caused three worldwide pandemics in history, including the Black Death in medieval ages. Yersinia pestis, the etiological agent of plague, has evolved a powerful arsenal to disrupt host immune defenses during evolution from enteropathogenic Y. pseudotuberculosis. Here, we find that two functionally redundant E3 ligase of Y. pestis, YspE1 and YspE2, can be delivered via type III secretion injectisome into host cytosol where they ubiquitinate multiple guanylate-binding proteins (GBPs) for proteasomal degradation. However, Y. pseudotuberculosis has no such capability due to lacking functional YspE1/2 homologs. YspE1/2-mediated GBP degradations significantly promote the survival of Y. pestis in macrophages and strongly inhibit inflammasome activation. By contrast, Gbp^{chr3−/−, chr5−/−} macrophages exhibit much lowered inflammasome activation independent of YspE1/2, accompanied with an enhanced replication of Y. pestis. Accordingly, Gbp^{chr3−/−, chr5−/−} mice are more susceptible to Y. pestis. We demonstrate that Y. pestis utilizes E3 ligases to subvert GBP-mediated host defense, which appears to be newly acquired by Y. pestis during evolution.

Guanylate-binding proteins (GBPs) recognize pathogen containing vacuoles, leading to lysis of this intracellular niche and induction of inflammasomes. Here, Cao et al. show that Y. pestis, the causative agent of plague, secret two functionally redundant E3 ligase, YspE1 and YspE2, into the host’s cytosol to ubiquitinate multiple GBPs for proteasomal degradation to subvert host immune defense. This capability appears to be newly acquired by Y. pestis during evolution, since its closely related progenitor Y. pseudotuberculosis is unable to do so.

Are Lockdowns Effective in Managing Pandemics?

The present coronavirus crisis caused a major worldwide disruption which has not been experienced for decades. The lockdown-based crisis management was implemented by nearly all the countries, and studies confirming lockdown effectiveness can be found alongside the studies questioning it. In this work, we performed a narrative review of the works studying the above effectiveness, as well as the historic experience of previous pandemics and risk-benefit analysis based on the connection of health and wealth. Our aim was to learn lessons and analyze ways to improve the management of similar events in the future. The comparative analysis of different countries showed that the assumption of lockdowns’ effectiveness cannot be supported by evidence—neither regarding the present COVID-19 pandemic, nor regarding the 1918–1920 Spanish Flu and other less-severe pandemics in the past. The price tag of lockdowns in terms of public health is high: by using the known connection between health and wealth, we estimate that lockdowns may claim 20 times more life years than they save. It is suggested therefore that a thorough cost-benefit analysis should be performed before imposing any lockdown for either COVID-19 or any future pandemic.

Mathematical modeling and optimal control of SARS-CoV-2 and tuberculosis co-infection: a case study of Indonesia

A new mathematical model incorporating epidemiological features of the co-dynamics of tuberculosis (TB) and SARS-CoV-2 is analyzed. Local asymptotic stability of the disease-free and endemic equilibria are shown for the sub-models when the respective reproduction numbers are below unity. Bifurcation analysis is carried out for the TB only sub-model, where it was shown that the sub-model undergoes forward bifurcation. The model is fitted to the cumulative confirmed daily SARS-CoV-2 cases for Indonesia from February 11, 2021 to August 26, 2021. The fitting was carried out using the fmincon optimization toolbox in MATLAB. Relevant parameters in the model are estimated from the fitting. The necessary conditions for the existence of optimal control and the optimality system for the co-infection model is established through the application of Pontryagin’s Principle. Different control strategies: face-mask usage and SARS-CoV-2 vaccination, TB prevention as well as treatment controls for both diseases are considered. Simulations results show that: (1) the strategy against incident SARS-CoV-2 infection averts about 27,878,840 new TB cases; (2) also, TB prevention and treatment controls could avert 5,397,795 new SARS-CoV-2 cases. (3) In addition, either SARS-CoV-2 or TB only control strategy greatly mitigates a significant number of new co-infection cases.

Can Bacteriophages Replace Antibiotics?

Increasing antibiotic resistance numbers force both scientists and politicians to tackle the problem, and preferably without any delay. The application of bacteriophages as precision therapy to treat bacterial infections, phage therapy, has received increasing attention during the last two decades. While it looks like phage therapy is here to stay, there is still a lot to do. Medicine regulatory authorities are working to deliver clear instructions to carry out phage therapy. Physicians need to get more practical experience on treatments with phages. In this opinion article I try to place phage therapy in the context of the health care system and state that the use phages for precision treatments will require a seamless chain of events from the patient to the phage therapy laboratory to allow for the immediate application of phages therapeutically. It is not likely that phages will replace antibiotics, however, they will be valuable in the treatment of infections caused by multidrug resistant bacteria. Antibiotics will nevertheless remain the main treatment for a majority of infections.

Complete Protection Against Yersinia pestis in BALB/c Mouse Model Elicited by Immunization With Inhalable Formulations of rF1-V10 Fusion Protein via Aerosolized Intratracheal Inoculation

Pneumonic plague, caused by Yersinia pestis, is an infectious disease with high mortality rates unless treated early with antibiotics. Currently, no FDA-approved vaccine against plague is available for human use. The capsular antigen F1, the low-calcium-response V antigen (LcrV), and the recombinant fusion protein (rF1-LcrV) of Y. pestis are leading subunit vaccine candidates under intense investigation; however, the inability of recombinant antigens to provide complete protection against pneumonic plague in animal models remains a significant concern. In this study, we compared immunoprotection against pneumonic plague provided by rF1, rV10 (a truncation of LcrV), and rF1-V10, and vaccinations delivered via aerosolized intratracheal (i.t.) inoculation or subcutaneous (s.c.) injection. We further considered three vaccine formulations: conventional liquid, dry powder produced by spray freeze drying, or dry powder reconstituted in PBS. The main findings are: (i) rF1-V10 immunization with any formulation via i.t. or s.c. routes conferred 100% protection against Y. pestis i.t. infection; (ii) rF1 or rV10 immunization using i.t. delivery provided significantly stronger protection than rF1 or rV10 immunization via s.c. delivery; and (iii) powder formulations of subunit vaccines induced immune responses and provided protection equivalent to those elicited by unprocessed liquid formulations of vaccines. Our data indicate that immunization with a powder formulation of rF1-V10 vaccines via an i.t. route may be a promising vaccination strategy for providing protective immunity against pneumonic plague.

Nano-Antibacterials Using Medicinal Plant Components: An Overview

Gradual emergence of new bacterial strains, resistant to one or more antibiotics, necessitates development of new antibacterials to prevent us from newly evolved disease-causing, drug-resistant, pathogenic bacteria. Different inorganic and organic compounds have been synthesized as antibacterials, but with the problem of toxicity. Other alternatives of using green products, i.e., the medicinal plant extracts with biocompatible and potent antibacterial characteristics, also had limitation because of their low aqueous solubility and therefore less bioavailability. Use of nanotechnological strategy appears to be a savior, where phytochemicals are nanonized through encapsulation or entrapment within inorganic or organic hydrophilic capping agents. Nanonization of such products not only makes them water soluble but also helps to attain high surface to volume ratio and therefore high reaction area of the nanonized products with better therapeutic potential, over that of the equivalent amount of raw bulk products. Medicinal plant extracts, whose prime components are flavonoids, alkaloids, terpenoids, polyphenolic compounds, and essential oils, are in one hand nanonized (capped and stabilized) by polymers, lipids, or clay materials for developing nanodrugs; on the other hand, high antioxidant activity of those plant extracts is also used to reduce various metal salts to produce metallic nanoparticles. In this review, five medicinal plants, viz., tulsi (Ocimum sanctum), turmeric (Curcuma longa), aloe vera (Aloe vera), oregano (Oregano vulgare), and eucalyptus (Eucalyptus globulus), with promising antibacterial potential and the nanoformulations associated with the plants' crude extracts and their respective major components (eugenol, curcumin, anthraquinone, carvacrol, eucalyptus oil) have been discussed with respect to their antibacterial potency.

Novel RNA Extraction Method for Dual RNA-seq Analysis of Pathogen and Host in the Early Stages of Yersinia pestis Pulmonary Infection

Pneumonic plague, caused by Yersinia pestis, is a rapidly progressing lethal infection. The various phases of pneumonic plague are yet to be fully understood. A well-established way to address the pathology of infectious diseases in general, and pneumonic plague in particular, is to conduct concomitant transcriptomic analysis of the bacteria and the host. The analysis of dual RNA by RNA sequencing technology is challenging, due the difficulties of extracting bacterial RNA, which is overwhelmingly outnumbered by the host RNA, especially at the critical early time points post-infection (prior to 48 h). Here, we describe a novel technique that employed the infusion of an RNA preserving reagent (RNAlater) into the lungs of the animals, through the trachea, under deep anesthesia. This method enabled the isolation of stable dual mRNA from the lungs of mice infected with Y. pestis, as early as 24 h post-infection. The RNA was used for transcriptomic analysis, which provided a comprehensive gene expression profile of both the host and the pathogen.

Not Just a 'Breath of Death': Indirect Consequences of Working in a COVID-19 Unit

We carried out a survey in the Czech Republic between January and February 2021 to evaluate the impact of COVID-19 on doctors working in the COVID-19 unit. A rise in 250,000 cases were seen in the Czech Republic during the time of the survey. The indirect impact of the disease on doctors working in COVID-19 units and strategies to control the situation in the Czech Republic were evaluated here. About 35% doctors were concerned with health issues, 40% had tested positive for SARS-CoV-2 antigen, 51% reported lack of support for those who had contracted COVID-19 and 163 agreed that medical, psychological counselling and financial services should be provided. Most doctors experienced moderate and severe degrees of psychological impact. Doctors with the least working experience and those with at least 21 to 35 years were most affected. Mental fatigue was the most common reported psychosomatic effect. The effects were higher in doctors who were more concerned about working in COVID-19 units. Around 87% agreed that the best strategy in controlling the situation in the Czech Republic would be ‘preventive measures in combination with vaccination’. History shows us that pandemics can occur in multiple waves. Subsequent waves, inadequate support as well as unparalleled workload can lead to a serious rise in psychological disorders amongst HCWs worldwide.

The neurological sequelae of pandemics and epidemics

Neurological manifestations in pandemics frequently cause short and long-term consequences which are frequently overlooked. Despite advances in the treatment of infectious diseases, nervous system involvement remains a challenge, with limited treatments often available. The under-recognition of neurological manifestations may lead to an increase in the burden of acute disease as well as secondary complications with long-term consequences. Nervous system infection or dysfunction during pandemics is common and its enduring consequences, especially among vulnerable populations, are frequently forgotten. An improved understanding the possible mechanisms of neurological damage during epidemics, and increased recognition of the possible manifestations is fundamental to bring insights when dealing with future outbreaks. To reverse this gap in knowledge, we reviewed all the pandemics, large and important epidemics of human history in which neurological manifestations are evident, and described the possible physiological processes that leads to the adverse sequelae caused or triggered by those pathogens.

Development of a PCR-lateral flow assay for rapid detection of Yersinia pestis, the causative agent of plague

Plague is a zoonotic disease caused by Yersinia pestis, a Gram-negative, rod shaped coccobacillus, which is primarily found in rodents and can be transmitted to humans through flea bite. The disease has three major clinical forms bubonic (by flea bite), pneumonic (by respiratory droplets) and septicemic plague. Y. pestis is classified as a category 'A' agent by NIAID, USA due to its high mortality and easy person to person dissemination. The conventional diagnostic methods available for Y. pestis show cross-reactivity with other enteropathogenic bacteria making its detection difficult. There is a need to develop sensitive and specific molecular assay for accurate detection of Y. pestis. PCR is well suited molecular biology tool for rapid diagnosis of plague but after completion of thermal cycling steps, it requires additional time to analyze amplified product using agarose gel electrophoresis. In the present study, PCR assay coupled with lateral flow strips has been developed for rapid detection of Y. pestis. Lateral flow strips give an alternative to gel electrophoresis and permit easy and rapid detection of PCR products. The PCR was performed with 5' 6-FAM and biotin tagged primers specific for Y. pestis, targeting yihN gene located on chromosome. The PCR product was analyzed using lateral flow strips which yielded result within 2-3 minutes. The analytical sensitivity of PCR-lateral flow (PCR-LF) assay was 1 pg genomic DNA of Y. pestis and 500 copies of target DNA sequence harboured in a recombinant plasmid. The assay could detect Y. pestis DNA extracted from spiked human blood samples containing ≥10⁴ CFU per mL of bacteria. The assay was found to be specific and did not cross react with other closely related bacterial species. The developed assay was highly specific, sensitive and also did not require agarose gel electrophoresis for post amplification analysis.

Plague Transmission from Corpses and Carcasses

Knowing whether human corpses can transmit plague will inform policies for handling the bodies of those who have died of the disease. We analyzed the literature to evaluate risk for transmission of Yersinia pestis, the causative agent of plague, from human corpses and animal carcasses. Because we could not find direct evidence of transmission, we described a transmission pathway and assessed the potential for transmission at each step. We examined 3 potential sources of infection: body fluids of living plague patients, infected corpses and carcasses, and body fluids of infected corpses. We concluded that pneumonic plague can be transmitted by intensive handling of the corpse or carcass, presumably through the inhalation of respiratory droplets, and that bubonic plague can be transmitted by blood-to-blood contact with the body fluids of a corpse or carcass. These findings should inform precautions taken by those handling the bodies of persons or animals that died of plague.

Antimicrobial Treatment and Prophylaxis of Plague: Recommendations for Naturally Acquired Infections and Bioterrorism Response

This report provides CDC recommendations to U.S. health care providers regarding treatment, pre-exposure prophylaxis, and postexposure prophylaxis of plague. Yersinia pestis, the bacterium that causes plague, leads to naturally occurring disease in the United States and other regions worldwide and is recognized as a potential bioterrorism weapon. A bioweapon attack with Y. pestis could potentially infect thousands, requiring rapid and informed decision making by clinicians and public health agencies. The U.S. government stockpiles a variety of medical countermeasures to mitigate the effects of a bioterrorism attack (e.g., antimicrobials, antitoxins, and vaccines) for which the 21st Century Cures Act mandates the development of evidence-based guidelines on appropriate use. Guidelines for treatment and postexposure prophylaxis of plague were published in 2000 by a nongovernmental work group; since then, new human clinical data, animal study data, and U.S. Food and Drug Administration approvals of additional countermeasures have become available. To develop a comprehensive set of updated guidelines, CDC conducted a series of systematic literature reviews on human treatment of plague and other relevant topics to collect a broad evidence base for the recommendations in this report. Evidence from CDC reviews and additional sources were presented to subject matter experts during a series of forums. CDC considered individual expert input while developing these guidelines, which provide recommended best practices for treatment and prophylaxis of human plague for both naturally occurring disease and following a bioterrorism attack. The guidelines do not include information on diagnostic testing, triage decisions, or logistics involved in dispensing medical countermeasures. Clinicians and public health officials can use these guidelines to prepare their organizations, hospitals, and communities to respond to a plague mass-casualty event and as a guide for treating patients affected by plague.

Antibiotic Therapy of Plague: A Review

Plague-a deadly disease caused by the bacterium Yersinia pestis-is still an international public health concern. There are three main clinical forms: bubonic plague, septicemic plague, and pulmonary plague. In all three forms, the symptoms appear suddenly and progress very rapidly. Early antibiotic therapy is essential for countering the disease. Several classes of antibiotics (e.g., tetracyclines, fluoroquinolones, aminoglycosides, sulfonamides, chloramphenicol, rifamycin, and β-lactams) are active in vitro against the majority of Y. pestis strains and have demonstrated efficacy in various animal models. However, some discrepancies have been reported. Hence, health authorities have approved and recommended several drugs for prophylactic or curative use. Only monotherapy is currently recommended; combination therapy has not shown any benefits in preclinical studies or case reports. Concerns about the emergence of multidrug-resistant strains of Y. pestis have led to the development of new classes of antibiotics and other therapeutics (e.g., LpxC inhibitors, cationic peptides, antivirulence drugs, predatory bacteria, phages, immunotherapy, host-directed therapy, and nutritional immunity). It is difficult to know which of the currently available treatments or therapeutics in development will be most effective for a given form of plague. This is due to the lack of standardization in preclinical studies, conflicting data from case reports, and the small number of clinical trials performed to date.

Neurologic Manifestations of the World Health Organization's List of Pandemic and Epidemic Diseases

The World Health Organization (WHO) monitors the spread of diseases globally and maintains a list of diseases with epidemic or pandemic potential. Currently listed diseases include Chikungunya, cholera, Crimean-Congo hemorrhagic fever, Ebola virus disease, Hendra virus infection, influenza, Lassa fever, Marburg virus disease, Neisseria meningitis, MERS-CoV, monkeypox, Nipah virus infection, novel coronavirus (COVID-19), plague, Rift Valley fever, SARS, smallpox, tularemia, yellow fever, and Zika virus disease. The associated pathogens are increasingly important on the global stage. The majority of these diseases have neurological manifestations. Those with less frequent neurological manifestations may also have important consequences. This is highlighted now in particular through the ongoing COVID-19 pandemic and reinforces that pathogens with the potential to spread rapidly and widely, in spite of concerted global efforts, may affect the nervous system. We searched the scientific literature, dating from 1934 to August 2020, to compile data on the cause, epidemiology, clinical presentation, neuroimaging features, and treatment of each of the diseases of epidemic or pandemic potential as viewed through a neurologist's lens. We included articles with an abstract or full text in English in this topical and scoping review. Diseases with epidemic and pandemic potential can be spread directly from human to human, animal to human, via mosquitoes or other insects, or via environmental contamination. Manifestations include central neurologic conditions (meningitis, encephalitis, intraparenchymal hemorrhage, seizures), peripheral and cranial nerve syndromes (sensory neuropathy, sensorineural hearing loss, ophthalmoplegia), post-infectious syndromes (acute inflammatory polyneuropathy), and congenital syndromes (fetal microcephaly), among others. Some diseases have not been well-characterized from a neurological standpoint, but all have at least scattered case reports of neurological features. Some of the diseases have curative treatments available while in other cases, supportive care remains the only management option. Regardless of the pathogen, prompt, and aggressive measures to control the spread of these agents are the most important factors in lowering the overall morbidity and mortality they can cause.

History of the Plague: An Ancient Pandemic for the Age of COVID-19

During the fourteenth century, the bubonic plague or Black Death killed more than one third of Europe or 25 million people. Those afflicted died quickly and horribly from an unseen menace, spiking high fevers with suppurative buboes (swellings). Its causative agent is Yersinia pestis, creating recurrent plague cycles from the Bronze Age into modern-day California and Mongolia. Plague remains endemic in Madagascar, Congo, and Peru. This history of medicine review highlights plague events across the centuries. Transmission is by fleas carried on rats, although new theories include via human body lice and infected grain. We discuss symptomatology and treatment options. Pneumonic plague can be weaponized for bioterrorism, highlighting the importance of understanding its clinical syndromes. Carriers of recessive familial Mediterranean fever (FMF) mutations have natural immunity against Y. pestis. During the Black Death, Jews were blamed for the bubonic plague, perhaps because Jews carried FMF mutations and died at lower plague rates than Christians. Blaming minorities for epidemics echoes across history into our current coronavirus pandemic and provides insightful lessons for managing and improving its outcomes.

Pandemics Throughout History

The emergence and spread of infectious diseases with pandemic potential occurred regularly throughout history. Major pandemics and epidemics such as plague, cholera, flu, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) have already afflicted humanity. The world is now facing the new coronavirus disease 2019 (COVID-19) pandemic. Many infectious diseases leading to pandemics are caused by zoonotic pathogens that were transmitted to humans due to increased contacts with animals through breeding, hunting and global trade activities. The understanding of the mechanisms of transmission of pathogens to humans allowed the establishment of methods to prevent and control infections. During centuries, implementation of public health measures such as isolation, quarantine and border control helped to contain the spread of infectious diseases and maintain the structure of the society. In the absence of pharmaceutical interventions, these containment methods have still been used nowadays to control COVID-19 pandemic. Global surveillance programs of water-borne pathogens, vector-borne diseases and zoonotic spillovers at the animal-human interface are of prime importance to rapidly detect the emergence of infectious threats. Novel technologies for rapid diagnostic testing, contact tracing, drug repurposing, biomarkers of disease severity as well as new platforms for the development and production of vaccines are needed for an effective response in case of pandemics.

The Diverse Roles of the Global Transcriptional Regulator PhoP in the Lifecycle of Yersinia pestis

Yersinia pestis, the causative agent of plague, has a complex infectious cycle that alternates between mammalian hosts (rodents and humans) and insect vectors (fleas). Consequently, it must adapt to a wide range of host environments to achieve successful propagation. Y. pestis PhoP is a response regulator of the PhoP/PhoQ two-component signal transduction system that plays a critical role in the pathogen’s adaptation to hostile conditions. PhoP is activated in response to various host-associated stress signals detected by the sensor kinase PhoQ and mediates changes in global gene expression profiles that lead to cellular responses. Y. pestis PhoP is required for resistance to antimicrobial peptides, as well as growth under low Mg²⁺ and other stress conditions, and controls a number of metabolic pathways, including an alternate carbon catabolism. Loss of phoP function in Y. pestis causes severe defects in survival inside mammalian macrophages and neutrophils in vitro, and a mild attenuation in murine plague models in vivo, suggesting its role in pathogenesis. A Y. pestisphoP mutant also exhibits reduced ability to form biofilm and to block fleas in vivo, indicating that the gene is also important for establishing a transmissible infection in this vector. Additionally, phoP promotes the survival of Y. pestis inside the soil-dwelling amoeba Acanthamoeba castellanii, a potential reservoir while the pathogen is quiescent. In this review, we summarize our current knowledge on the mechanisms of PhoP-mediated gene regulation in Y. pestis and examine the significance of the roles played by the PhoP regulon at each stage of the Y. pestis life cycle.

Neuroimaging in Zoonotic Outbreaks Affecting the Central Nervous System: Are We Fighting the Last War?

When preparing for the coronavirus disease 2019 pandemic and its effects on the CNS, radiologists should be familiar with neuroimaging appearances in past zoonotic infectious disease outbreaks. Organisms that have crossed the species barrier from animals to humans include viruses such as Hendra, Nipah, Severe Acute Respiratory Syndrome, and influenza, as well as bacteria and others. Brain CT and MR imaging findings have included cortical abnormalities, microinfarction in the white matter, large-vessel occlusion, and features of meningitis. In particular, the high sensitivity of diffusion-weighted MR imaging in detecting intracranial abnormalities has been helpful in outbreaks. Although the coronaviruses causing the previous Severe Acute Respiratory Syndrome outbreak and the current coronavirus disease 19 pandemic are related, it is important to be aware of their similarities as well as potential differences. This review describes the neuroimaging appearances of selected zoonotic outbreaks so that neuroradiologists can better understand the current pandemic and potential future outbreaks.

An open-label, randomized, non-inferiority trial of the efficacy and safety of ciprofloxacin versus streptomycin + ciprofloxacin in the treatment of bubonic plague (IMASOY): study protocol for a randomized control trial

Background

Bubonic plague is the primary manifestation of infection with Yersinia pestis, accounting for 90% of all plague cases and with 75% of global cases reported in Madagascar. All drugs in use for treating plague are registered based on experimental data and anecdotal evidence, and no regimen currently recommended is supported by a randomized clinical trial. The IMASOY trial intends to fill this knowledge gap by comparing two 10-day regimens included in the national guidelines in Madagascar. The primary objective of the trial is to test the hypothesis that ciprofloxacin monotherapy is non-inferior to streptomycin followed by ciprofloxacin for the treatment of bubonic plague, thus avoiding the need for injectable, potentially toxic, aminoglycosides.

Methods

A two-arm parallel-group randomized control trial will be conducted across peripheral health centres in Madagascar in five districts. Males and non-pregnant females of all ages with suspected bubonic or pneumonic plague will be recruited over the course of three plague ‘seasons’. The primary endpoint of the trial is to assess the proportion of patients with bubonic plague who have a therapeutic response to treatment (defined as alive, resolution of fever, 25% reduction in the size of measurable buboes, has not received an alternative treatment and no clinical decision to continue antibiotics) as assessed on day 11.

Discussion

If successful, the trial has the potential to inform the standard of care guidelines not just in Madagascar but in other countries afflicted by plague. The trial is currently ongoing and expected to complete recruitment in 2022.

Trial registration

ClinicalTrials.gov NCT04110340. Registered on 1 October 2019

Factors Influencing Atypical Clinical Presentations during the 2017 Madagascar Pneumonic Plague Outbreak: A Prospective Cohort Study

In late 2017, Madagascar experienced a large urban outbreak of pneumonic plague, the largest outbreak to date this century. During the outbreak, there were widespread reports of plague patients presenting with atypical symptoms, such as prolonged duration of illness and upper respiratory tract symptoms. Reported mortality among plague cases was also substantially lower than that reported in the literature (25% versus 50% in treated patients). A prospective multicenter observational study was carried out to investigate potential reasons for these atypical presentations. Few subjects among our cohort had confirmed or probable plague, suggesting that, in part, there was overdiagnosis of plague cases by clinicians. However, 35% subjects reported using an antibiotic with anti-plague activity before hospital admission, whereas 55% had antibiotics with anti-plague activity detected in their serum at admission. Although there may have been overdiagnosis of plague by clinicians during the outbreak, the high frequency of community antibiotic may partly explain the relatively few culture-positive sputum samples during the outbreak. Community antibiotic use may have also altered the clinical presentation of plague patients. These issues make accurate detection of patients and the development of clinical case definitions and triage algorithms in urban pneumonic plague outbreaks difficult.

A forensic evaluation of plague - a re-emerging infectious disease with biowarfare potential

Plague is an acute infectious disease caused by the gram-negative cocco-bacillus Yersinia pestis. It has been responsible for 200 million deaths throughout history with three major pandemics. There are three forms: bubonic, septicaemic and pneumonic, each carrying a significant mortality rate. The usual transmission is from fleas carried by rodents. Recently, it has been listed as one of the reemerging infectious diseases globally, with a potential use in bioterrorism. At autopsy there may be lymphadenopathy, fulminant pneumonia or diffuse interstitial pneumonitis. However any organ may be affected with myocarditis, meningitis, pharyngitis and hepatic and splenic necrosis. The lethality of plague with the resurgence in numbers of cases, development of antibiotic resistance, recent occurrence in urban areas and the lack of a vaccine make it a disease not to be missed in the mortuary.

Vaccine Potential of a Recombinant Bivalent Fusion Protein LcrV-HSP70 Against Plague and Yersiniosis

To counteract the deadly pathogens, i.e., Y. pestis, Y. enetrocolitica, and Y. pseudotuberculosis, we prepared a recombinant DNA construct lcrV-hsp70 encoding the bivalent fusion protein LcrV-HSP70. The lcrV gene of Y. pestis and hsp70 domain II DNA fragment of M. tuberculosis were amplified by PCR. The lcrV amplicon was first ligated in the pET vector using NcoI and BamHI restriction sites. Just downstream to the lcrV gene, the hsp70 domain II was ligated using BamHI and Hind III restriction sites. The in-frame and the orientation of cloned lcrV-hsp70 were checked by restriction analysis and nucleotide sequencing. The recombinant bivalent fusion protein LcrV-HSP70 was expressed in E. coli and purified by affinity chromatography. The vaccine potential of LcrV-HSP70 fusion protein was evaluated in formulation with alum. BALB/c mice were vaccinated, and the humoral and cellular immune responses were studied. The fusion protein LcrV-HSP70 induced a strong and significant humoral immune response in comparison to control animals. We also observed a significant difference in the expression levels of IFN-γ and TNF-α in LcrV–HSP70-immunized mice in comparison to control, HSP70, and LcrV groups. To test the protective efficacy of the LcrV–HSP70 fusion protein against plague and Yersiniosis, the vaccinated mice were challenged with Y. pestis, Y. enterocolitica, and Y. pseudotuberculosis separately. The bivalent fusion protein LcrV–HSP70 imparted 100% protection against the plague. In the case of Yersiniosis, on day 2 post challenge, there was a significant reduction in the number of CFU of Y. enterocolitica and Y. pseudotuberculosis in the blood (CFU/ml) and the spleen (CFU/g) of vaccinated animals in comparison to the LcrV, HSP70, and control group animals.

Rapid diagnostic tests for plague

BACKGROUND

Plague is a severe disease associated with high mortality. Late diagnosis leads to advance stage of the disease with worse outcomes and higher risk of spread of the disease. A rapid diagnostic test (RDT) could help in establishing a prompt diagnosis of plague. This would improve patient care and help appropriate public health response.

OBJECTIVES

To determine the diagnostic accuracy of the RDT based on the antigen F1 (F1RDT) for detecting plague in people with suspected disease.

SEARCH METHODS

We searched the CENTRAL, Embase, Science Citation Index, Google Scholar, the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov up to 15 May 2019, and PubMed (MEDLINE) up to 27 August 2019, regardless of language, publication status, or publication date. We handsearched the reference lists of relevant papers and contacted researchers working in the field.

SELECTION CRITERIA

We included cross-sectional studies that assessed the accuracy of the F1RDT for diagnosing plague, where participants were tested with both the F1RDT and at least one reference standard. The reference standards were bacterial isolation by culture, polymerase chain reaction (PCR), and paired serology (this is a four-fold difference in F1 antibody titres between two samples from acute and convalescent phases).

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and extracted data. We appraised the methodological quality of each selected studies and applicability by using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. When meta-analysis was appropriate, we used the bivariate model to obtain pooled estimates of sensitivity and specificity. We stratified all analyses by the reference standard used and presented disaggregated data for forms of plague. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included eight manuscripts reporting seven studies. Studies were conducted in three countries in Africa among adults and children with any form of plague. All studies except one assessed the F1RDT produced at the Institut Pasteur of Madagascar (F1RDT-IPM) and one study assessed a F1RDT produced by New Horizons (F1RDT-NH), utilized by the US Centers for Disease Control and Prevention. We could not pool the findings from the F1RDT-NH in meta-analyses due to a lack of raw data and a threshold of the test for positivity different from the F1RDT-IPM. Risk of bias was high for participant selection (retrospective studies, recruitment of participants not consecutive or random, unclear exclusion criteria), low or unclear for index test (blinding of F1RDT interpretation unknown), low for reference standards, and high or unclear for flow and timing (time of sample transportation was longer than seven days, which can lead to decreased viability of the pathogen and overgrowth of contaminating bacteria, with subsequent false-negative results and misclassification of the target condition). F1RDT for diagnosing all forms of plague F1RDT-IPM pooled sensitivity against culture was 100% (95% confidence interval (CI) 82 to 100; 4 studies, 1692 participants; very low certainty evidence) and pooled specificity was 70.3% (95% CI 65 to 75; 4 studies, 2004 participants; very low-certainty evidence). The performance of F1RDT-IPM against PCR was calculated from a single study in participants with bubonic plague (see below). There were limited data on the performance of F1RDT against paired serology. F1RDT for diagnosing pneumonic plague Performed in sputum, F1RDT-IPM pooled sensitivity against culture was 100% (95% CI 0 to 100; 2 studies, 56 participants; very low-certainty evidence) and pooled specificity was 71% (95% CI 59 to 80; 2 studies, 297 participants; very low-certainty evidence). There were limited data on the performance of F1RDT against PCR or against paired serology for diagnosing pneumonic plague. F1RDT for diagnosing bubonic plague Performed in bubo aspirate, F1RDT-IPM pooled sensitivity against culture was 100% (95% CI not calculable; 2 studies, 1454 participants; low-certainty evidence) and pooled specificity was 67% (95% CI 65 to 70; 2 studies, 1198 participants; very low-certainty evidence). Performed in bubo aspirate, F1RDT-IPM pooled sensitivity against PCR for the caf1 gene was 95% (95% CI 89 to 99; 1 study, 88 participants; very low-certainty evidence) and pooled specificity was 93% (95% CI 84 to 98; 1 study, 61 participants; very low-certainty evidence). There were no data providing data on both F1RDT and paired serology for diagnosing bubonic plague.

AUTHORS' CONCLUSIONS

Against culture, the F1RDT appeared highly sensitive for diagnosing either pneumonic or bubonic plague, and can help detect plague in remote areas to assure management and enable a public health response. False positive results mean culture or PCR confirmation may be needed. F1RDT does not replace culture, which provides additional information on resistance to antibiotics and bacterial strains.

Climate drivers of plague epidemiology in British India, 1898-1949

Plague, caused by Yersinia pestis infection, continues to threaten low- and middle-income countries throughout the world. The complex interactions between rodents and fleas with their respective environments challenge our understanding of human plague epidemiology. Historical long-term datasets of reported plague cases offer a unique opportunity to elucidate the effects of climate on plague outbreaks in detail. Here, we analyse monthly plague deaths and climate data from 25 provinces in British India from 1898 to 1949 to generate insights into the influence of temperature, rainfall and humidity on the occurrence, severity and timing of plague outbreaks. We find that moderate relative humidity levels of between 60% and 80% were strongly associated with outbreaks. Using wavelet analysis, we determine that the nationwide spread of plague was driven by changes in humidity, where, on average, a one-month delay in the onset of rising humidity translated into a one-month delay in the timing of plague outbreaks. This work can inform modern spatio-temporal predictive models for the disease and aid in the development of early-warning strategies for the deployment of prophylactic treatments and other control measures.

A new recombinant F1 antigen as a cost and time-effective tool for plague diagnosis

The Yersinia pestis capsular antigen F1 is widely used in plague laboratory diagnosis. Here, we describe the production of an F1 recombinant protein within reduced time and biosafety requirements. Its evaluation in hemagglutination tests indicated that the recombinant F1 can replace the conventional F1 protein for plague diagnosis.

Deliberate release: Plague - A review

Yersinia pestis is the causative agent of plague and is considered one of the most likely pathogens to be used as a bioweapon. In humans, plague is a severe clinical infection that can rapidly progress with a high mortality despite antibiotic therapy. Therefore, early treatment of Y. pestis infection is crucial. This review provides an overview of its clinical manifestations, diagnosis, treatment, prophylaxis, and protection requirements for the use of clinicians.

We discuss the likelihood of a deliberate release of plague and the feasibility of obtaining, isolating, culturing, transporting and dispersing plague in the context of an attack aimed at a westernized country. The current threat status and the medical and public health responses are reviewed. We also provide a brief review of the potential prehospital treatment strategy and vaccination against Y. pestis. Further, we discuss the plausibility of antibiotic resistant plague bacterium, F1-negative Y. pestis, and also the possibility of a plague mimic along with potential strategies of defense against these. An extensive literature search on the MEDLINE, EMBASE, and Web of Science databases was conducted to collate papers relevant to plague and its deliberate release. Our review concluded that the deliberate release of plague is feasible but unlikely to occur, and that a robust public health response and early treatment would rapidly halt the transmission of plague in the population. Front-line clinicians should be aware of the potential of a deliberate release of plague and prepared to instigate early isolation of patients. Moreover, front-line clinicians should be weary of the possibility of suicide attackers and mindful of the early escalation to public health organizations.

Drought-induced spatio-temporal synchrony of plague outbreak in Europe

Plague synchronously swept across separated regions in Europe throughout history. However, the spatio-temporal synchrony of plague and its driving mechanism have not been thoroughly investigated. In this study, we transformed the historical European plague database spanned 1347-1800 CE into country-level time-series that differentiated large-scale plague outbreak from counted data. We found that there are 74 years in which two or more countries in our study region (UK, France, Germany, Spain, and Italy) experienced large-scale plague outbreak in the same year. Our Multivariate Ripley's K-function results showed that the onset year and the cessation year of large-scale plague outbreak are synchronized at the 0-23-year and 0-20-year windows, respectively. The temporal association between such synchrony and climatic forcing was further investigated using the Superposed Epoch Analysis, and drought was found to be responsible for the synchrony. Integrating our results with a literature survey, we suggested that prior to the peak of plague, the occurrence of drought and the subsequent reintroduced rainfall dampened both the rodent community and human society and boosted the number of fleas that carried plague. Such a synthesis facilitated the outbreak of plague. At the same time, high temperature associated with such drought also confined the geographic diffusion of the plague. Hence, although continental mega-drought could initiate the synchrony of plague outbreak, the synchrony actually consisted of a number of localized plague outbreak events scattering across different regions in Europe. According to the projected rising trend of drought in terms of its magnitude, duration, and geographic extent, the risk of synchrony of rodent-borne diseases in Europe will be significantly elevated, especially in France, Italy, and Spain.

Phylogeography of the second plague pandemic revealed through analysis of historical Yersinia pestis genomes

The second plague pandemic, caused by Yersinia pestis, devastated Europe and the nearby regions between the 14th and 18th centuries AD. Here we analyse human remains from ten European archaeological sites spanning this period and reconstruct 34 ancient Y. pestis genomes. Our data support an initial entry of the bacterium through eastern Europe, the absence of genetic diversity during the Black Death, and low within-outbreak diversity thereafter. Analysis of post-Black Death genomes shows the diversification of a Y. pestis lineage into multiple genetically distinct clades that may have given rise to more than one disease reservoir in, or close to, Europe. In addition, we show the loss of a genomic region that includes virulence-related genes in strains associated with late stages of the pandemic. The deletion was also identified in genomes connected with the first plague pandemic (541-750 AD), suggesting a comparable evolutionary trajectory of Y. pestis during both events.

Robust Th1 cellular and humoral responses generated by the Yersinia pestis rF1-V subunit vaccine formulated to contain an agonist of the CD137 pathway do not translate into increased protection against pneumonic plague

Yersinia pestis is the causative agent of plague and is a re-emerging pathogen that also has the potential as a biological weapon, necessitating the development of a preventive vaccine. Despite intense efforts for the last several decades, there is currently not a vaccine approved by the FDA. The rF1-V vaccine adjuvanted with Alhydrogel is a lead candidate subunit vaccine for plague and generates a strong Th2-mediate humoral response with a modest Th1 cellular response. As immune protection against Y. pestis requires both humoral and Th1 cellular responses, modifying the rF1-V subunit vaccine formulation to include a robust inducer of Th1 responses may improve efficacy. Thus, we reformulated the subunit vaccine to include SA-4-1BBL, an agonist of the CD137 costimulatory pathway and a potent inducer of Th1 response, and assessed its protective efficacy against pneumonic plague. We herein show for the first time a sex bias in the prophylactic efficacy of the Alhydrogel adjuvanted rF1-V vaccine, with female mice showing better protection against pneumonic plague than male. The sex bias for protection was irrespective of the generation of comparable levels of rF1-V-specific antibody titers and Th1 cellular responses in both sexes. The subunit vaccine reformulated with SA-4-1BBL generated robust Th1 cellular and humoral responses. A prime-boost vaccination scheme involving prime with rF1-V + Alhydrogel and boost with the rF1-V + SA-4-1BBL provided protection in male mice against pneumonic plague. In marked contrast, prime and boost with rF1-V reformulated with both adjuvants resulted in the loss of protection against pneumonic plague, despite generating high levels of humoral and Th1 cellular responses. While unexpected, these findings demonstrate the complexity of immune mechanisms required for protection. Elucidating mechanisms responsible for these differences in protection will help to guide the development of better prophylactic subunit vaccines effective against pneumonic plague.

Historical and genomic data reveal the influencing factors on global transmission velocity of plague during the Third Pandemic

Quantitative knowledge about which natural and anthropogenic factors influence the global spread of plague remains sparse. We estimated the worldwide spreading velocity of plague during the Third Pandemic, using more than 200 years of extensive human plague case records and genomic data, and analyzed the association of spatiotemporal environmental factors with spreading velocity. Here, we show that two lineages, 2.MED and 1.ORI3, spread significantly faster than others, possibly reflecting differences among strains in transmission mechanisms and virulence. Plague spread fastest in regions with low population density and high proportion of pasture- or forestland, findings that should be taken into account for effective plague monitoring and control. Temperature exhibited a nonlinear, U-shaped association with spread speed, with a minimum around 20 °C, while precipitation showed a positive association. Our results suggest that global warming may accelerate plague spread in warm, tropical regions and that the projected increased precipitation in the Northern Hemisphere may increase plague spread in relevant regions.

Human plague system associated with rodent diversity and other environmental factors

Plague remains a threat to public health and is considered as a re-emerging infectious disease today. Rodents play an important role as major hosts in plague persistence and driving plague outbreaks in natural foci; however, few studies have tested the association between host diversity in ecosystems and human plague risk. Here we use zero-inflated generalized additive models to examine the association of species richness with human plague presence (where plague outbreaks could occur) and intensity (the average number of annual human cases when they occurred) in China during the Third Pandemic. We also account for transportation network density, annual precipitation levels and human population size. We found rodent species richness, particularly of rodent plague hosts, is positively associated with the presence of human plague. Further investigation shows that species richness of both wild and commensal rodent plague hosts are positively correlated with the presence, but only the latter correlated with the intensity. Our results indicated a positive relationship between rodent diversity and human plague, which may provide suggestions for the plague surveillance system.

The Plague Doctor of Venice

There is a distinctive Venetian carnival mask with sinister overtones and historical significance to physicians because it belongs to the 'Doctor of the Plague'. The costume features a beaked white mask, black hat and waxed gown. This was worn by mediaeval Plague Doctors as protection according to the Miasma Theory of disease propagation. The plague (or Black Death), ravaged Europe over several centuries with each pandemic leaving millions of people dead. The cause of the contagion was not known, nor was there a cure, which added to the widespread desperation and fear. Venice was a major seaport, and each visitation of the plague (beginning in 1348) devastated the local population. In response, Venetians were among the first to establish the principles of quarantine and 'Lazarets' which we still use today. Plague outbreaks have occurred in Australia, notably in Sydney (1900-1925), and continue to flare up in poorer communities, most recently in Madagascar (2017). Antibiotics are the mainstay of treatment, but there are concerns regarding the emergence of resistant pathogenic strains of Yersinia pestis, and their potential use in bio-terrorism.

Predatory bacteria can protect SKH-1 mice from a lethal plague challenge

With the rise of antimicrobial resistance, novel ways to treat bacterial infections are required and the use of predatory bacteria may be one such approach. Bdellovibrio species have been shown in vitro to predate on a wide range of other Gram-negative bacteria, including CDC category A/B pathogens such as Yersinia pestis. The data reported here show that treatment of SKH-1 mice with Bdellovibrio bacteriovorus HD100 provided significant protection from a lethal challenge of Yersinia pestis CO92. This is the first report of protection conferred by predation in vivo against a systemic pathogen challenge. However, this protective effect was not observed in a preliminary study with Balb/c mice. Therefore the effects of the predatory bacteria are complex and may be dependent on immune status/genetics of the host. Overall, predatory bacteria may have utility as a therapeutic modality but further work is required to understand the predator-host interaction.

Human Macrophages Clear the Biovar Microtus Strain of Yersinia pestis More Efficiently Than Murine Macrophages

Yersinia pestis is the etiological agent of the notorious plague that has claimed millions of deaths in history. Of the four known Y. pestis biovars (Antiqua, Medievalis, Orientalis, and Microtus), Microtus strains are unique for being highly virulent in mice but avirulent in humans. Here, human peripheral lymphocytes were infected with the fully virulent 141 strain or the Microtus strain 201, and their transcriptomes were determined and compared. The most notable finding was that robust responses in the pathways for cytokine-cytokine receptor interaction, chemokine signaling pathway, Toll-like receptor signaling and Jak-STAT signaling were induced at 2 h post infection (hpi) in the 201- but not the 141-infected lymphocytes, suggesting that human lymphocytes might be able to constrain infections caused by strain 201 but not 141. Consistent with the transcriptome results, much higher IFN-γ and IL-1β were present in the supernatants from the 201-infected lymphocytes, while inflammatory inhibitory IL-10 levels were higher in the 141-infected lymphocytes. The expressions of CSTD and SLC11A1, both of which are functional components of the lysosome, increased in the 201-infected human macrophage-like U937 cells. Further assessment of the survival rate of the 201 bacilli in the U937 cells and murine macrophage RAW 264.7 cells revealed no viable bacteria in the U937 cells at 32 hpi.; however, about 5–10% of the bacteria were still alive in the RAW264.7 cells. Our results indicate that human macrophages can clear the intracellular Y. pestis 201 bacilli more efficiently than murine macrophages, probably by interfering with critical host immune responses, and this could partially account for the host-specific pathogenicity of Y. pestis Microtus strains.

Insects and the Transmission of Bacterial Agents

Arthropods are small invertebrate animals, among which some species are hematophagous. It is during their blood meal that they can transmit pathogenic microorganisms that they may be harboring to the vertebrate host that they parasitize, which in turn will potentially develop a vector-borne disease. The transmission may occur directly through their bite, but also through contaminated feces. Zoonotic diseases, diseases that can naturally be transmitted between humans and animals, are a considerable part of emerging diseases worldwide, and a major part of them are vector-borne. Research and public attention has long been focused on malaria and mosquito-borne arboviruses, and bacterial vector-borne diseases remains today a neglected field of medical entomology. Despite the emphasis on Lyme disease in recent decades, and despite the major outbreaks caused by bacteria in the last few centuries, this field has in fact been poorly explored and is therefore relatively poorly known, other than the most famous examples such as the plague and epidemic typhus outbreaks. Here we propose to review the state of knowledge of bacterial agents transmitted by arthropod vectors.

Transcriptomic studies and assessment of Yersinia pestis reference genes in various conditions

Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) is a very sensitive widespread technique considered as the gold standard to explore transcriptional variations. While a particular methodology has to be followed to provide accurate results many published studies are likely to misinterpret results due to lack of minimal quality requirements. Yersinia pestis is a highly pathogenic bacterium responsible for plague. It has been used to propose a ready-to-use and complete approach to mitigate the risk of technical biases in transcriptomic studies. The selection of suitable reference genes (RGs) among 29 candidates was performed using four different methods (GeNorm, NormFinder, BestKeeper and the Delta-Ct method). An overall comprehensive ranking revealed that 12 following candidate RGs are suitable for accurate normalization: gmk, proC, fabD, rpoD, nadB, rho, thrA, ribD, mutL, rpoB, adk and tmk. Some frequently used genes like 16S RNA had even been found as unsuitable to study Y. pestis. This methodology allowed us to demonstrate, under different temperatures and states of growth, significant transcriptional changes of six efflux pumps genes involved in physiological aspects as antimicrobial resistance or virulence. Previous transcriptomic studies done under comparable conditions had not been able to highlight these transcriptional modifications. These results highlight the importance of validating RGs prior to the normalization of transcriptional expression levels of targeted genes. This accurate methodology can be extended to any gene of interest in Y. pestis. More generally, the same workflow can be applied to identify and validate appropriate RGs in other bacteria to study transcriptional variations.

Application of UPT-POCT in Anti-bioterrorism and Biosecurity

With the exception of toxins, bioterrorism agents are mainly microorganisms, many of which cause serious infectious diseases. Up-converting phosphor technology-based point-of-care testing (UPT-POCT) can detect bioterrorism agents from various samples with high sensitivity and specificity, in particular it shows robust performance for complicated samples, such as food, powder, viscera and grains. The tolerance of UPT-POCT to sample is based on the physical and luminescence stability of UCNPs, the stable covalent interaction between UCNPs and antibody, as well as the strong buffering capacity of the detection system. Reliable results can be obtained in a short time period using a portable biosensor by nonprofessionals owing to the simple nature of UPT-POCT operation and sample pre-treatment.