A dog-associated primary pneumonic plague in Qinghai Province, China

Phylogenetic Relationships and Evolution of the Genus Eganvirus (186-Type) Yersinia pestis Bacteriophages

Plague is an endemic infectious disease caused by Yersinia pestis. In this study, we isolated fourteen phages with similar sequence arrangements to phage 186; these phages exhibited different lytic abilities in Enterobacteriaceae strains. To illustrate the phylogenetic relationships and evolutionary relationships between previously designated 186-type phages, we analysed the complete sequences and important genes of the phages, including whole-genome average nucleotide identity (ANI) and collinearity comparison, evolutionary analysis of four conserved structural genes (V, T, R, and Q genes), and analysis of the regulatory genes (cI, apl, and cII) and integrase gene (int). Phylogenetic analysis revealed that thirteen of the newly isolated phages belong to the genus Eganvirus and one belongs to the genus Felsduovirus in the family Peduoviridae, and these Eganvirus phages can be roughly clustered into three subgroups. The topological relationships exhibited by the whole-genome and structural genes seemed similar and stable, while the regulatory genes presented different topological relationships with the structural genes, and these results indicated that there was some homologous recombination in the regulatory genes. These newly isolated 186-type phages were mostly isolated from dogs, suggesting that the resistance of Canidae to Y. pestis infection may be related to the wide distribution of phages with lytic capability.

The complex genomic diversity of Yersinia pestis on the long-term plague foci in Qinghai-Tibet plateau

Plague is a typical natural focus disease that circulates in different ecology of vectors and reservoir hosts. We conducted genomic population and phylogenetic analyses of the Yersinia pestis collected from the 12 natural plague foci in China with more than 20 kinds of hosts and vectors. Different ecological landscapes with specific hosts, vectors, and habitat which shape various niches for Y. pestis. The phylogeographic diversity of Y. pestis in different kinds plague foci in China showed host niches adaptation. Most natural plague foci strains are region-and focus-specific, with one predominant subpopulation; but the isolates from the Qinghai-Tibet plateau harbor a higher genetic diversity than other foci. The Y. pestis from Marmota himalayana plague foci are defined as the ancestors of different populations at the root of the evolutionary tree, suggesting several different evolutionary paths to other foci. It has the largest pan-genome and widest SNP distances with most accessory genes enriched in mobilome functions (prophages, transposons). Geological barriers play an important role in the maintenance of local Y. pestis species and block the introduction of non-native strains. This study provides new insights into the control of plague outbreaks and epidemics, deepened the understanding of the evolutionary history of MHPF (M. himalayana plague focus) in China. The population structure and identify clades among different natural foci of China renewed the space cognition of the plague.

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.

Plague Meningitis: A Systematic Review of Clinical Course, Antimicrobial Treatment, and Outcomes

Plague meningitis is a serious and often fatal manifestation of Yersinia pestis infection. In the aftermath of a bioweapon attack with Y pestis, this typically rare manifestation may develop in a substantial number of patients, particularly if treatment delays occur. Risk factors, clinical evolution, and optimal treatment strategies for plague meningitis are not well understood. We searched PubMed Central and other databases for reports of plague meningitis in any language. Articles containing descriptions of patients with plague meningitis and their treatment and outcomes were included. Among 1,496 articles identified in our search, 56 articles describing 84 cases from 1898 to 2015 met inclusion criteria. The median age of patients was 16 years (range 6 weeks to 64 years); 68% were male. Most patients (n = 50, 60%) developed meningitis following primary bubonic plague. Common signs and symptoms included fever (n = 56, 66%), nuchal rigidity (n = 38, 45%), and headache (n = 33, 36%); 29% (n = 24) of patients had focal neurologic deficits such as cranial nerve abnormalities. Almost all (n = 23, 96%) of the 24 patients who did not receive antimicrobials died, and 42% (n = 25) of the 59 patients treated with antimicrobials died. The case fatality rate of patients grouped by antimicrobial received was 50% (1 out of 2) for fluoroquinolones, 19% (4 out of 21) for aminoglycosides, 14% (2 out of 14) for sulfonamides, 11% (2 out of 18) for chloramphenicol, and 0% (0 out of 13) for tetracyclines. Plague meningitis most often occurs as a complication of bubonic plague and can cause focal neurologic deficits. Survival is more likely in patients who receive antimicrobials; tetracyclines, aminoglycosides, and chloramphenicol had the lowest associated case fatality rates.

Environmental suitability of Yersinia pestis and the spatial dynamics of plague in the Qinghai Lake region, China

Plague, a highly infectious disease caused by Yersinia pestis, has killed millions of people in history and is still active in the natural foci of the world nowadays. Understanding the spatiotemporal patterns of plague outbreaks in history is critically important, as it may help facilitate the prevention and control for potential future outbreaks. This study's objective was to estimate the effect of the topography, vegetation, climate, and other environmental factors on the Y. pestis ecological niche. A maximum entropy algorithm spatially modelled plague occurrence data from 2004-2018 and the environmental variables to evaluate the contribution of the variables to the distribution of Y. pestis. Our results found that the average minimum temperature in September (-8 °C to +5 °C) and the sheep population density (250 sheep per km2) were influential in characterising the niche. The rim of Qinghai Lake showed more favourable conditions for Y. pestis presence than other areas within the study area. Identifying various factors will assist any future modelling efforts. Our suitability map identifies hotspots and will help public health officials in resource allocation in their quest to abate future plague outbreaks.

Anaplasma phagocytophilum in Marmota himalayana

Background

Human granulocytic anaplasmosis is a tick-borne zoonotic disease caused by Anaplasma phagocytophilum. Coinfections with A. phagocytophilum and other tick-borne pathogens are reported frequently, whereas the relationship between A. phagocytophilum and flea-borne Yersnia pestis is rarely concerned.

Results

A. phagocytophilum and Yersnia pestis were discovered within a Marmota himalayana found dead in the environment, as determined by 16S ribosomal rRNA sequencing. Comparative genomic analyses of marmot-derived A. phagocytophilum isolate demonstrated its similarities and a geographic isolation from other global strains. The 16S rRNA gene and GroEL amino acid sequence identity rates between marmot-derived A. phagocytophilum (JAHLEX000000000) and reference strain HZ (CP000235.1) are 99.73% (1490/1494) and 99.82% (549/550), respectively. 16S rRNA and groESL gene screenings show that A. phagocytophilum is widely distributed in marmots; the bacterium was more common in marmots found dead (24.59%, 15/61) than in captured marmots (19.21%, 29/151). We found a higher Y. pestis isolation rate in dead marmots harboring A. phagocytophilum than in those without it (² = 4.047, p < 0.05). Marmot-derived A. phagocytophilum was able to live in L929 cells and BALB/c mice but did not propagate well.

Conclusions

In this study, A. phagocytophilum was identified for the first time in Marmota himalayana, a predominant Yersinia pestis host. Our results provide initial evidence for M. himalayana being a reservoir for A. phagocytophilum; moreover, we found with the presence of A. phagocytophilum, marmots may be more vulnerable to plague. Humans are at risk for co-infection with both pathogens by exposure to such marmots.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08557-x.

Yersinia pestis antibiotic resistance: a systematic review

Yersinia pestis, the cause of plague and a potential biological weapon, has always been a threatening pathogen. Some strains of Y. pestis have varying degrees of antibiotic resistance. Thus, this systematic review was conducted to alert clinicians to this pathogen’s potential antimicrobial resistance. A review of the literature was conducted for experimental reports and systematic reviews on the topics of plague, Y. pestis, and antibiotic resistance. From 1995 to 2021, 7 Y. pestis isolates with 4 antibiotic resistance mechanisms were reported. In Y. pestis 17/95, 16/95, and 2180H, resistance was mediated by transferable plasmids. Each plasmid contained resistance genes encoded within specific transposons. Strain 17/95 presented multiple drug resistance, since plasmid 1202 contained 10 resistance determinants. Strains 16/95 and 2180H showed single antibiotic resistance because both additional plasmids in these strains carried only 1 antimicrobial determinant. Strains 12/87, S19960127, 56/13, and 59/13 exhibited streptomycin resistance due to an rpsl gene mutation, a novel mechanism that was discovered recently. Y. pestis can acquire antibiotic resistance in nature not only via conjugative transfer of antimicrobial-resistant plasmids from other bacteria, but also by gene point mutations. Global surveillance should be strengthened to identify antibiotic-resistant Y. pestis strains by whole-genome sequencing and drug susceptibility testing.

Distribution and Characteristics of Human Plague Cases and Yersinia pestis Isolates from 4 Marmota Plague Foci, China, 1950-2019

We analyzed epidemiologic characteristics and distribution of 1,067 human plague cases and 5,958 Yersinia pestis isolates collected from humans, host animals, and insect vectors during 1950–2019 in 4 Marmota plague foci in China. The case-fatality rate for plague in humans was 68.88%; the overall trend slowly decreased over time but fluctuated greatly. Most human cases (98.31%) and isolates (82.06%) identified from any source were from the Marmota himalayana plague focus. The tendency among human cases could be divided into 3 stages: 1950–1969, 1970–2003, and 2004–2019. The Marmota sibirica plague focus has not had identified human cases nor isolates since 1926. However, in the other 3 foci, Y. pestis continues to circulate among animal hosts; ecologic factors might affect local Y. pestis activity. Marmota plague foci are active in China, and the epidemic boundary is constantly expanding, posing a potential threat to domestic and global public health.

Plague Exposure in Mammalian Wildlife Across the Western United States

Plague is caused by a bacterial pathogen (Yersinia pestis) that can infect a wide range of mammal species, but its presence in wildlife is often underappreciated. Using a large-scale data set (n = 44,857) that details the extent of Y. pestis exposure in wildlife, we document exposure in 18 wildlife species, including coyotes (Canis latrans), bobcats (Lynx rufus), and black bears (Ursus americanus). Evidence of plague activity is widespread, with seropositive animals detected in every western state in the contiguous United States. Pathogen monitoring systems in wildlife that are both large scale and long-term are rare, yet they open the door for analyses on potential shifts in distribution that have occurred over time because of climate or land use changes. The data generated by these long-term monitoring programs, combined with recent advances in our understanding of pathogen ecology, offer a clearer picture of zoonotic pathogens and the risks they pose.

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.

A Lytic Yersina pestis Bacteriophage Obtained From the Bone Marrow of Marmota himalayana in a Plague-Focus Area in China

A lytic Yersinia pestis phage vB_YpP-YepMm (also named YepMm for briefly) was first isolated from the bone marrow of a Marmota himalayana who died of natural causes on the Qinghai-Tibet plateau in China. Based on its morphologic (isometric hexagonal head and short non-contractile conical tail) and genomic features, we classified it as belonging to the Podoviridae family. At the MOI of 10, YepMm reached maximum titers; and the one-step growth curve showed that the incubation period of the phage was about 10 min, the rise phase was about 80 min, and the lysis amount of the phage during the lysis period of 80 min was about 187 PFU/cell. The genome of the bacteriophage YepMm had nucleotide-sequence similarity of 99.99% to that of the Y. pestis bacteriophage Yep-phi characterized previously. Analyses of the biological characters showed that YepMm has a short latent period, strong lysis, and a broader lysis spectrum. It could infect Y. pestis, highly pathogenic bioserotype 1B/O:8 Y. enterocolitica, as well as serotype O:1b Y. pseudotuberculosis—the ancestor of Y. pestis. It could be further developed as an important biocontrol agent in pathogenic Yersinia spp. infection.

Epidemiological Situation on Plague in 2020. Forecast of Episootic Activity of Natural Plague Foci in the Russian Federation and Other CIS Countries for 2021

The aim of the work was to substantiate the forecast of the epidemiological and epizootiological situation in natural foci of plague in the Russian Federation, countries of the near and far abroad for the year of 2021. Characteristics of the distribution of Yersinia pestis strains of the main subspecies (subspecies pestis) of medieval and antique biovars, Caucasian (ssp. caucasica) and central Asian (ssp. central asiatica) subspecies by 45 natural foci of the CIS countries are presented in the paper. The persistence of a multidirectional trend in the dynamics of epizootic activity of natural foci of the CIS countries with the circulation of Y. pestis pestis strains of the medieval biovar of the 2.MED1 phylogenetic branch and the antique biovar of the 0.ANT5, 4.ANT phylogenetic branches in the current decade has been outlined. For the Russian Federation, the development of epizootics is predicted in the Gorno-Altai highland and Tuva mountain natural foci caused by the circulation of Y. pestis pestis strains of the antique biovar 4.ANT and Y. pestis of the Altai biovar of the Central Asian subspecies 0.PE4a in 2021. For the Republic of Kazakhstan, there is a high probability of preserving epizootic activity in the North Aral, Aral-Karakum, Balkhash, Mojynkum, Taukum desert and Ili intermountain natural foci with the circulation of Y. pestis pestis strains of the medieval biovar of the phylogenetic branch 2.MED1. For the Kyrgyz Republic, the forecast for the development of plague epizootics caused by Y. pestis pestis strains of the antique biovar 0.ANT5 phylogenetic branch in the Sarydzhaz and Upper Naryn high-mountain natural foci has been substantiated. A high epidemic risk of epizootic manifestations caused by highly virulent strains of Y. pestis pestis of antique biovars 0.ANT5, 4.ANT and medieval biovar 2.MED1 for the entire territory of the CIS countries is noted. The relevance of implementing forecasts of the epidemiological situation into practice, taking into account the molecular-genetic and epidemiological characteristics of Y. pestis strains circulating in areas of expected epizootic manifestations of plague, is highlighted.

Yersinia pestis: the Natural History of Plague

The Gram-negative bacterium Yersinia pestis is responsible for deadly plague, a zoonotic disease established in stable foci in the Americas, Africa, and Eurasia. Its persistence in the environment relies on the subtle balance between Y. pestis-contaminated soils, burrowing and nonburrowing mammals exhibiting variable degrees of plague susceptibility, and their associated fleas. Transmission from one host to another relies mainly on infected flea bites, inducing typical painful, enlarged lymph nodes referred to as buboes, followed by septicemic dissemination of the pathogen. In contrast, droplet inhalation after close contact with infected mammals induces primary pneumonic plague. Finally, the rarely reported consumption of contaminated raw meat causes pharyngeal and gastrointestinal plague. Point-of-care diagnosis, early antibiotic treatment, and confinement measures contribute to outbreak control despite residual mortality. Mandatory primary prevention relies on the active surveillance of established plague foci and ectoparasite control. Plague is acknowledged to have infected human populations for at least 5,000 years in Eurasia. Y. pestis genomes recovered from affected archaeological sites have suggested clonal evolution from a common ancestor shared with the closely related enteric pathogen Yersinia pseudotuberculosis and have indicated that ymt gene acquisition during the Bronze Age conferred Y. pestis with ectoparasite transmissibility while maintaining its enteric transmissibility. Three historic pandemics, starting in 541 AD and continuing until today, have been described. At present, the third pandemic has become largely quiescent, with hundreds of human cases being reported mainly in a few impoverished African countries, where zoonotic plague is mostly transmitted to people by rodent-associated flea bites.

Two cases of imported pneumonic plague in Beijing, China

INTRODUCTION

Plague is an acute, often fulminating infectious disease caused by Yersinia Pestis transmitted by rodents. It is rarely encountered in clinics, although natural plague foci are widely distributed around the world.

PATIENT CONCERNS

A couple who are cattle and sheep herdsmen from the Inner Mongolia Autonomous Region presented with cough, expectoration and fever. The husband developed sudden onset of fever and bloody sputum after working the soil on his farm. The wife also developed fever after nursing his husband. Both patients were preliminarily diagnosed with severe pneumonia, but antimicrobial treatments in the local hospital were unsuccessful. Their conditions deteriorated and they were transferred to our center.

DIAGNOSIS

Preliminary etiological examinations were unremarkable, while blood and sputum specimens were found to be positive by RT-PCR and colloidal gold-immunochromatography assay targeting the F1 antigen and by reverse indirect hemagglutination assay. Pneumonic plague was confirmed.

INTERVENTIONS

Both patients were transferred to special infectious disease hospital for further treatment.

OUTCOMES

The condition of the female patient deteriorated. The male recovered after treatment, while the female patient finally died.

CONCLUSION

There are 3 main forms of plague: bubonic, pneumonic and septicemic. Humans can be infected by the bites of bacterium-bearing fleas or direct contact of wild animals that died from plague. Human plague can be transmitted by close contact through coughing droplet. Neglected diagnosis of plague could cause severe consequences. Strict surveillance and protection measures should be taken and the public should be alerted about potential risks when epizootic plague is detected.

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.

Delayed diagnosis of fatal pneumonic canine plague: clinical and pathologic features in two naturally infected Colorado dogs

Background

Plague caused by Yersinia pestis is a highly infectious and potentially fatal zoonotic disease that can be spread by wild and domestic animals. In endemic areas of the northern hemisphere plague typically cycles from March to October, when flea vectors are active. Clinical forms of disease include bubonic, septicemic, and pneumonic plague. All clinical forms are uncommon in dogs and the pneumonic form is exceedingly rare.

Case presentation

Two mixed breed young-adult male domestic dogs presented to Colorado veterinarians with fever and vague signs that progressed to hemoptysis within 24 h. Case 1 presented in June 2014, while Case 2 occurred in December 2017. Thoracic radiography of Case 1 and 2 revealed right dorsal and right accessory lobe consolidation, respectively. In Case 1 initial differential diagnoses included pulmonary contusion due to trauma or diphacinone toxicosis. Case 1 was euthanized ~ 24 h post presentation due to progressive dyspnea and hemoptysis. Plague was confirmed 9 days later, after the dog’s owner was hospitalized with pneumonia. Case 2 was treated as foreign body/aspiration pneumonia and underwent lung lobectomy at a veterinary teaching hospital. Case 2 was euthanized after 5 days of hospitalization when bacterial culture of the excised lobe yielded Yersinia pestis. Both dogs had severe diffuse necrohemorrhagic and suppurative pneumonia at post mortem examination.

Conclusions

Both dogs were misdiagnosed due to the atypical lobar presentation of an extremely rare form of plague in a species that infrequently succumbs to clinical disease. Presentation outside of the typical transmission period of plague was also a factor leading to delayed diagnosis in Case 2. Erroneous identification by automated bacterial identification systems was problematic in both cases. In endemic areas, plague should be ruled out early in febrile dogs with acute respiratory signs, hemoptysis, lobar or diffuse pathology, and potential for exposure, regardless of season. Seasonal and geographic distributions of plague may shift with climate change, so vigilance by primary care veterinarians is warranted. Timely submission of samples to a veterinary diagnostic laboratory could expedite accurate diagnosis and reduce potential for human and domestic animal exposure.

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.

Activation of Heme Oxygenase Expression by Cobalt Protoporphyrin Treatment Prevents Pneumonic Plague Caused by Inhalation of Yersinia pestis

Pneumonic plague, caused by the Gram-negative bacteria Yersinia pestis, is an invasive, rapidly progressing disease with poor survival rates. Following inhalation of Y. pestis, bacterial invasion of the lungs and a tissue-damaging inflammatory response allows vascular spread of the infection. Consequently, primary pneumonic plague is a multiorgan disease involving sepsis and necrosis of immune tissues and the liver, as well as bronchopneumonia and rampant bacterial growth. Given the likely role of the hyperinflammatory response in accelerating the destruction of tissue, in this work we evaluated the therapeutic potential of the inducible cytoprotective enzyme heme oxygenase 1 (HO-1) against primary pneumonic plague. On its own, the HO-1 inducer cobalt protoporphyrin IX (CoPP) provided mice protection from lethal challenge with Y. pestis CO92 with improved pulmonary bacterial clearance and a dampened inflammatory response compared to vehicle-treated mice. Furthermore, CoPP treatment combined with doxycycline strongly enhanced protection in a rat aerosol challenge model. Compared to doxycycline alone, CoPP treatment increased survival, with a 3-log decrease in median bacterial titer recovered from the lungs and the general absence of a systemic hyperinflammatory response. In contrast, treatment with the HO-1 inhibitor SnPP had no detectable impact on doxycycline efficacy. The combined data indicate that countering inflammatory toxicity by therapeutically inducing HO-1 is effective in reducing the rampant growth of Y. pestis and preventing pneumonic plague.

Pneumonic Plague in a Dog and Widespread Potential Human Exposure in a Veterinary Hospital, United States

In December 2017, a dog that had pneumonic plague was brought to a veterinary teaching hospital in northern Colorado, USA. Several factors, including signalment, season, imaging, and laboratory findings, contributed to delayed diagnosis and resulted in potential exposure of >116 persons and 46 concurrently hospitalized animals to Yersinia pestis.

Genetic diversity and spatial-temporal distribution of Yersinia pestis in Qinghai Plateau, China

BACKGROUND

Plague, caused by the bacterium Yersinia pestis, is a highly infectious, zoonotic disease. Hundreds of human plague cases are reported across the world annually. Qinghai Plateau is one of the most severely affected plague regions in China, with more than 240 fatal cases of Y. pestis in the last 60 years. Conventional epidemiologic analysis has effectively guided the prevention and control of local plague transmission; however, molecular genetic analysis is more effective for investigating population diversity and transmission. In this report, we employed different genetic markers to analyze the population structure of Y. pestis in Qinghai Plateau.

METHODOLOGY/PRINCIPAL FINDING

We employed a two-step hierarchical strategy to analyze the phylogeny of 102 Qinghai Plateau isolates of Y. pestis, collected between 1954 and 2011. First, we defined the genealogy of Y. pestis by constructed minimum spanning tree based on 25 key SNPs. Seven groups were identified, with group 1.IN2 being identified as the dominant population. Second, two methods, MLVA and CRISPR, were applied to examine the phylogenetic detail of group 1.IN2, which was further divided into three subgroups. Subgroups of 1.IN2 revealed a clear geographic cluster, possibly associated with interaction between bacteriophage and Y. pestis. More recently, Y. pestis populations appear to have shifted from the east toward the center and west of Qinghai Plateau. This shift could be related to destruction of the local niche of the original plague focus through human activities. Additionally, we found that the abundance and relative proportion of 1.IN2 subgroups varied by decade and might be responsible for the fluctuations of plague epidemics in Qinghai Plateau.

CONCLUSION/SIGNIFICANCE

Molecular genotyping methods provided us with detailed information on population diversity and the spatial-temporal distribution of dominant populations of Y. pestis, which will facilitate future surveillance, prevention, and control of plague in Qinghai Plateau.

Seroprevalence and spatial distribution dynamics of Yersinia pestis antibodies in dogs and cats from plague foci in the State of Ceará, Northeastern Brazil

INTRODUCTION

In Brazil, the plague is established in several foci located mainly in the northeastern part of the country, where it alternates between active and quiescent periods. These foci in the State of Ceará have high epidemiological importance. In addition to other plague detection activities, plague areas can be monitored through serological surveys of dogs and cats (domestic carnivores), which, following feeding on plague-infected rodents, can develop mild to severe forms of the disease and produce long-lasting antibodies. This study aimed to characterize the circulation dynamics and spatial distribution of Yersinia pestis antibodies in dogs and cats in plague foci areas of Ceará.

METHODS

An ecological study was conducted to analyze the temporal series and spatial distribution of secondary data obtained from domestic carnivore serum surveillance in Ceará's plague areas from 1990 to 2014.

RESULTS

Joinpoint analysis revealed that the overall trend was a reduction in antibody-positive animals. The mean proportion of antibody-positivity during the whole study period was 1.5% (3,023/203,311) for dogs, and 0.7% (426/61,135) for cats, with more than 4% antibody-positivity in dogs in 1997 and 2002. Antibody titers ranging from 1/16 to 1/64 were frequent. Despite fluctuations and a significant reduction, in recent years, there were antibody-positive animals annually throughout the study period, and the localities containing antibody-positive animals increased in number.

CONCLUSION

Yersinia pestis is actively circulating in the study areas, posing a danger to the human population.

Molecular epidemiological investigations of plague in Eastern Province of Zambia

Background

Plague is a flea-borne zoonotic and invasive disease caused by a gram negative coccobacillus bacterium called Yersinia pestis. Plague has caused three devastating pandemics globally namely: the Justinian, Black Death and Oriental plague. The disease in the Eastern Province of Zambia has been reported in Nyimba and Sinda Districts in the past 15 years. The aim of this study was to investigate the molecular epidemiology of plague in the two affected districts. Polymerase Chain Reaction (PCR), targeting Plasminogen activator gene (pla gene) of Y. pestis, was performed on suspected human bubo aspirates (n = 7), rodents (n = 216), shrews (n = 27) and fleas (n = 1494). Of these, one positive sample from each source or host was subjected to sequencing followed by phylogenetic analysis.

Results

The plasminogen activator gene (pla gene) of Y. pestis was detected in 42.8% bubo aspirates, 6.9% rodents, 3.7% shrew and 0.8% fleas. The fleas were from pigs (n = 4), goats (n = 5) and rodents (n = 3). The sequencing and phylogenetic analysis suggested that the pla gene of Y. pestis in Nyimba and Sinda was similar and the isolates demonstrated a high degree of evolutionary relationship with Antiqua strains from the Republic of Congo and Kenya.

Conclusion

It can be concluded that pla gene of Y. pestis was present in various hosts in the two districts and the strains circulating in each district were similar and resembles those in the Republic of Congo and Kenya.

Electronic supplementary material

The online version of this article (10.1186/s12866-017-1146-8) contains supplementary material, which is available to authorized users.

Pneumonic Plague in Johannesburg, South Africa, 1904

Plague is a potentially dangerous reemerging disease. Because modern outbreaks are relatively infrequent, data for epidemiologic study are best found in historical accounts. In 1905, the Rand Plague Committee published a report describing an explosive outbreak of 113 cases of pneumonic plague that occurred in Johannesburg, South Africa, in 1904. Using these data, we investigated social, spatial, and temporal dynamics and quantified transmissibility as measured by the time-varying reproduction number. Risk for transmission was highest when friends, family members, and caregivers approached the sick. Reproduction numbers were 2–4. Transmission rates rapidly diminished after implementation of control measures, including isolation and safer burial practices. A contemporaneous smaller bubonic plague outbreak associated with a low-key epizootic of rats also occurred. Clusters of cases of pneumonic plague were mostly limited to the Indian community; cases of bubonic plague were mostly associated with white communities and their black African servants.

Plague: Recognition, Treatment, and Prevention

Plague is caused by Yersinia pestis and is not commonly encountered in clinics, although natural plague foci are widely distributed around the world. Y. pestis has been listed as a category A bioterrorism agent. A neglected diagnosis will cause severe consequences. Therefore, this minireview briefly introduces the current understanding on Y. pestis and then focuses on practical aspects of plague, including clinical manifestations, diagnosis, treatment, and prevention, to alert clinicians about this notorious disease.

Identification of Risk Factors Associated with Transmission of Plague Disease in Eastern Zambia

Plague is a fatal, primarily rodent-flea-borne zoonotic disease caused by Yersinia pestis. The identification of risk factors of plague was investigated through questionnaire interview and conducting focus group discussion (FGD) in Sinda and Nyimba districts of eastern Zambia. A total of 104 questionnaires were administered to individual respondents and 20 groups consisting of 181 discussants, which comprised FGD team in this study. The study revealed that trapping, transportation, and preparation of rodents for food exposed the community to rodent and their fleas suggesting that plague may have occurred primarily by either flea bites or contact with infected wild rodents. The study also revealed that most people in communities consumed rodents as part of their regular diet; therefore, contact with small wild mammals was a common practice. The mode of transportation of freshly trapped rodents, in particular, carcasses risked human to flea bites. Questionnaire respondents (75%) and FGD discussants (55%) indicated that trappers preferred to carry rodent carcasses in small bags, whereas 55.8% and 20% respectively, reported hunters carrying carcasses in their pockets. Carrying of carcass skewers on trappers' shoulders was reported by 38.4% and 20% of individual respondents and FGD, respectively. All these activities were exposing humans to rodents and their fleas, the natural reservoirs and vectors of plague, respectively. This study also showed that there is a statistically significant (χ² = 4.6878, P < 0.05), between digging of rodents from their burrows and the presence of fleas on the hunter's bodies or clothes, which exposes humans to potentially flea bites in an enzootic cycle.

Potential Roles of Pigs, Small Ruminants, Rodents, and Their Flea Vectors in Plague Epidemiology in Sinda District, Eastern Zambia

A cross-sectional study was conducted in the Eastern part of Zambia that previously reported a plague outbreak. The aim of the study was to evaluate the potential role of pigs, goats, and sheep as sero-surveillance hosts for monitoring plague, and to investigate the flea vectors and potential reservoir hosts to establish the current status of plague endemicity in the district. Serum samples were collected from 96 rodents, 10 shrews, 245 domestic pigs, 232 goats, and 31 sheep, whereas 106 organs were eviscerated from rodents and shrews. As for fleas, 1,064 Echidnophaga larina Jordan & Rothschild, 7 Xenopsylla cheopis (Rothschild), and 382 Echidnophaga gallinacea (Westwood) were collected from these animals in 34 villages. Enzyme-Linked Immunosorbent Assay (ELISA) and Polymerase Chain Reaction (PCR) tests were performed on serum, and organs and fleas to determine IgG antibodies against Fraction 1 antigen and pla gene of Yersinia pestis, respectively. ELISA results showed that 2.83% (95% CI = 0.59-8.05) rodents, 9.0% (95% CI = 5.71-13.28) domestic pigs, 4.7% (95% CI = 2.39-8.33) goats, and 3.2% (95% CI = 0.08-16.70) sheep were positive for IgG antibodies against Fra1 antigen of Y. pestis. On PCR, 8.4% (95% CI = 3.96-15.51) of the rodents were detected with Y. pestis pla gene, whereas all fleas were found negative. The common fleas identified were E. larina from pigs, whereas X. cheopis were the only fleas collected from rodents. The presence of sero-positive animals as well as the occurrence of X. cheopis on local rodents suggests that Y. pestis remains a risk in the district.

Mechanism study on a plague outbreak driven by the construction of a large reservoir in southwest china (surveillance from 2000-2015)

BACKGROUND

Plague, a Yersinia pestis infection, is a fatal disease with tremendous transmission capacity. However, the mechanism of how the pathogen stays in a reservoir, circulates and then re-emerges is an enigma.

METHODOLOGY/PRINCIPAL FINDINGS

We studied a plague outbreak caused by the construction of a large reservoir in southwest China followed 16-years' surveillance.

CONCLUSIONS/SIGNIFICANCE

The results show the prevalence of plague within the natural plague focus is closely related to the stability of local ecology. Before and during the decade of construction the reservoir on the Nanpan River, no confirmed plague has ever emerged. With the impoundment of reservoir and destruction of drowned farmland and vegetation, the infected rodent population previously dispersed was concentrated together in a flood-free area and turned a rest focus alive. Human plague broke out after the enzootic plague via the flea bite. With the construction completed and ecology gradually of human residential environment, animal population and type of vegetation settling down to a new balance, the natural plague foci returned to a rest period. With the rodent density decreased as some of them died, the flea density increased as the rodents lived near or in local farm houses where had more domestic animals, and human has a more concentrated population. In contrast, in the Himalayan marmot foci of the Qinghai-Tibet Plateau in the Qilian Mountains. There are few human inhabitants and the local ecology is relatively stable; plague is prevalence, showing no rest period. Thus the plague can be significantly affected by ecological shifts.

Plague in China 2014-All sporadic case report of pneumonic plague

Background

Yersinia pestis is the pathogen of the plague and caused three pandemics worldwide. Pneumonic plague is rarer than bubonic and septicemic plague. We report detailed clinical and pathogenic data for all the three sporadic cases of pneumonic plagues in China in 2014.

Case presentation

All the three patients are herders in Gansu province of China. They were all infected by Yersinia pestis and displayed in the form of pneumonic plague respectively without related. We tested patient specimens from the upper (nasopharyngeal swabs) or the lower (sputum) respiratory tract and whole blood, plasma, and serum specimens for Yersinia pestis. All patients had fever, cough and dyspnea, and for patient 2 and 3, unconscious. Respiratory symptoms were predominant with acute respiratory failure. The chest X-ray showed signs consistent with necrotizing inflammation with multiple lobar involvements. Despite emergency treatment, all patients died of refractory multiple organ failure within 24 h after admission to hospital. All the contacts were quarantined immediately and there were no secondary cases.

Conclusions

Nowadays, the plague is epidemic in animals and can infect people who contact with the infected animals which may cause an epidemic in human. We think dogs maybe an intermediate vector for plague and as a source of risk for humans who are exposed to pet animals or who work professionally with canines. If a patient has been exposed to a risk factor and has fever and dyspnea, plague should be considered. People who had contact with a confirmed case should be isolated and investigated for F1 antigen analysis and receive post-exposure preventive treatment. A vaccination strategy might be useful for individuals who are occupationally exposed in areas where endemically infected reservoirs of plague-infected small mammals co-exist.

Whole genome multilocus sequence typing as an epidemiologic tool for Yersinia pestis

Human plague is a severe and often fatal zoonotic disease caused by Yersinia pestis. For public health investigations of human cases, nonintensive whole genome molecular typing tools, capable of defining epidemiologic relationships, are advantageous. Whole genome multilocus sequence typing (wgMLST) is a recently developed methodology that simplifies genomic analyses by transforming millions of base pairs of sequence into character data for each gene. We sequenced 13 US Y. pestis isolates with known epidemiologic relationships. Sequences were assembled de novo, and multilocus sequence typing alleles were assigned by comparison against 3979 open reading frames from the reference strain CO92. Allele-based cluster analysis accurately grouped the 13 isolates, as well as 9 publicly available Y. pestis isolates, by their epidemiologic relationships. Our findings indicate wgMLST is a simplified, sensitive, and scalable tool for epidemiologic analysis of Y. pestis strains.

A review of methods for subtyping Yersinia pestis: From phenotypes to whole genome sequencing

Numerous subtyping methods have been applied to Yersinia pestis with varying success. Here, we review the various subtyping methods that have been applied to Y. pestis and their capacity for answering questions regarding the population genetics, phylogeography, and molecular epidemiology of this important human pathogen. Methods are evaluated in terms of expense, difficulty, transferability among laboratories, discriminatory power, usefulness for different study questions, and current applicability in light of the advent of whole genome sequencing.

Primary case of human pneumonic plague occurring in a Himalayan marmot natural focus area Gansu Province, China

A case of primary pneumonic plague (PPP) caused by Yersinia pestis is reported. This case occurred in the largest plague area in China. The patient died after contact with a dog that had captured an infected marmot. Three of 151 contacts were shown to be positive for antibody against F1 antigen by indirect hemagglutination assay, but none had clinical symptoms. There was no secondary case.

Immunological and clinical response of coyotes (Canis latrans) to experimental inoculation with Yersinia pestis

Multiple publications have reported the use of coyotes (Canis latrans) in animal-based surveillance efforts for the detection of Yersinia pestis. Coyotes are likely exposed via flea bite or oral routes and are presumed to be resistant to the development of clinical disease. These historic data have only been useful for the evaluation of the geographic distribution of Y. pestis in the landscape. Because the canid immunologic response to Y. pestis has not been thoroughly characterized, we conducted experimental inoculation of captive-reared, juvenile coyotes (n = 8) with Y. pestis CO92 via oral or intradermal routes. We measured the humoral response to Y. pestis fraction 1 capsular protein (anti-F1) and found a significant difference between inoculation groups in magnitude and duration of antibody production. The anti-F1 titers in animals exposed intradermally peaked at day 10 postinoculation (PI; range = 1∶32 to 1∶128) with titers remaining stable at 1∶32 through week 12. In contrast, orally inoculated animals developed higher titers (range = 1∶256 to 1∶1,024) that remained stable at 1∶256 to 1∶512 through week 6. No clinical signs of disease were observed, and minimal changes were noted in body temperature, white blood cell counts, and acute phase proteins during the 7 days PI. Gross pathology was unremarkable, and minimal changes were noted in histopathology at days 3 and 7 PI. Rechallenge at 14 wk PI via similar dosage and routes resulted in marked differences in antibody response between groups. Animals in the orally inoculated group produced a striking increase in anti-F1 titers (up to 1∶4,096) within 3 days, whereas there was minimal to no increase in antibody response in the intradermal group. Information gathered from this experimental trial may provide additional insight into the spatial and temporal evaluation of coyote plague serology.

Remote monitoring of the progression of primary pneumonic plague in Brown Norway rats in high-capacity, high-containment housing

Development of new vaccines, diagnostics, and therapeutics for biodefense or other relatively rare infectious diseases is hindered by the lack of naturally occurring human disease on which to conduct clinical trials of efficacy. To overcome this experimental gap, the U.S. Food and Drug Administration established the Animal Rule, in which efficacy testing in two well-characterized animal models that closely resemble human disease may be accepted in lieu of large-scale clinical trials for diseases with limited natural human incidence. In this report, we evaluated the Brown Norway rat as a model for pneumonic plague and describe the natural history of clinical disease following inhalation exposure to Yersinia pestis. In high-capacity, high-containment housing, we monitored temperature, activity, heart rate, and rhythm by capturing electronic impulses transmitted from abdominal telemeter implants. Using this system, we show that reduced activity and development of fever are sensitive indications of disease progression. Furthermore, we identified heart arrhythmias as contributing factors to the rapid progression to lethality following the fever response. Together, these data validate the Brown Norway rat as an experimental model for human pneumonic plague and provide new insight that may ultimately lead to novel approaches in postexposure treatment of this devastating infection.

Two-step source tracing strategy of Yersinia pestis and its historical epidemiology in a specific region

Source tracing of pathogens is critical for the control and prevention of infectious diseases. Genome sequencing by high throughput technologies is currently feasible and popular, leading to the burst of deciphered bacterial genome sequences. Utilizing the flooding genomic data for source tracing of pathogens in outbreaks is promising, and challenging as well. Here, we employed Yersinia pestis genomes from a plague outbreak at Xinghai county of China in 2009 as an example, to develop a simple two-step strategy for rapid source tracing of the outbreak. The first step was to define the phylogenetic position of the outbreak strains in a whole species tree, and the next step was to provide a detailed relationship across the outbreak strains and their suspected relatives. Through this strategy, we observed that the Xinghai plague outbreak was caused by Y. pestis that circulated in the local plague focus, where the majority of historical plague epidemics in the Qinghai-Tibet Plateau may originate from. The analytical strategy developed here will be of great help in fighting against the outbreaks of emerging infectious diseases, by pinpointing the source of pathogens rapidly with genomic epidemiological data and microbial forensics information.

Yersinia pestis biovar Microtus strain 201, an avirulent strain to humans, provides protection against bubonic plague in rhesus macaques

Yersinia pestis biovar Microtus is considered to be a virulent to larger mammals, including guinea pigs, rabbits and humans. It may be used as live attenuated plague vaccine candidates in terms of its low virulence. However, the Microtus strain's protection against plague has yet to be demonstrated in larger mammals. In this study, we evaluated the protective efficacy of the Microtus strain 201 as a live attenuated plague vaccine candidate. Our results show that this strain is highly attenuated by subcutaneous route, elicits an F1-specific antibody titer similar to the EV and provides a protective efficacy similar to the EV against bubonic plague in Chinese-origin rhesus macaques. The Microtus strain 201 could induce elevated secretion of both Th1-associated cytokines (IFN-γ, IL-2 and TNF-α) and Th2-associated cytokines (IL-4, IL-5, and IL-6), as well as chemokines MCP-1 and IL-8. However, the protected animals developed skin ulcer at challenge site with different severity in most of the immunized and some of the EV-immunized monkeys. Generally, the Microtus strain 201 represented a good plague vaccine candidate based on its ability to generate strong humoral and cell-mediated immune responses as well as its good protection against high dose of subcutaneous virulent Y. pestis challenge.

Homology analysis of pathogenic Yersinia species Yersinia enterocolitica, Yersinia pseudotuberculosis, and Yersinia pestis based on multilocus sequence typing

We developed a multilocus sequence typing (MLST) scheme and used it to study the population structure and evolutionary relationships of three pathogenic Yersinia species. MLST of these three Yersinia species showed a complex of two clusters, one composed of Yersinia pseudotuberculosis and Yersinia pestis and the other composed of Yersinia enterocolitica. Within the first cluster, the predominant Y. pestis sequence type 90 (ST90) was linked to Y. pseudotuberculosis ST43 by one locus difference, and 81.25% of the ST43 strains were from serotype O:1b, supporting the hypothesis that Y. pestis descended from the O:1b serotype of Y. pseudotuberculosis. We also found that the worldwide-prevalent serotypes O:1a, O:1b, and O:3 were predominated by specific STs. The second cluster consisted of pathogenic and nonpathogenic Y. enterocolitica strains, two of which may not have identical STs. The pathogenic Y. enterocolitica strains formed a relatively conserved group; most strains clustered within ST186 and ST187. Serotypes O:3, O:8, and O:9 were separated into three distinct blocks. Nonpathogenic Y. enterocolitica STs were more heterogeneous, reflecting genetic diversity through evolution. By providing a better and effective MLST procedure for use with the Yersinia community, valuable information and insights into the genetic evolutionary differences of these pathogens were obtained.

Plague gives surprises in the first decade of the 21st century in the United States and worldwide

Plague is an ancient disease caused by the bacterium Yersinia pestis and transmitted by rodent flea bites that continues to surprise us with first-ever events. This review documents plague in human cases in the 1st decade of the 21st century and updates our knowledge of clinical manifestations, transmission during outbreaks, diagnostic testing, antimicrobial treatment, and vaccine development. In the United States, 57 persons were reported to have the disease, of which seven died. Worldwide, 21,725 persons were affected with 1,612 deaths, for a case-fatality rate of 7.4%. The Congo reported more cases than any other country, including two large outbreaks of pneumonic plague, surpassing Madagascar, which had the most cases in the previous decade. Two United States scientists suffered fatal accidental exposures: a wildlife biologist, who carried out an autopsy on a mountain lion in Arizona in 2007, and a geneticist with subclinical hemochromatosis in Chicago, who was handling an avirulent strain of Y. pestis in 2009. Antimicrobial drugs given early after the onset of symptoms prevented many deaths; those recommended for treatment and prophylaxis included gentamicin, doxycycline, and fluoroquinolones, although fluoroquinolones have not been adequately tested in humans. Fleas that do not have their guts blocked by clotted blood meals were shown to be better transmitters of plague than blocked fleas. Under development for protection against bioterrorist use, a subunit vaccine containing F1 and V antigens of Y. pestis was administered to human volunteers eliciting antibodies without any serious side effects. These events, although showing progress, suggest that plague will persist in rodent reservoirs mostly in African countries burdened by poverty and civil unrest, causing death when patients fail to receive prompt antimicrobial treatment.

A cluster of primary pneumonic plague transmitted in a truck cab in a new enzootic focus in China

We investigated a cluster of five cases of severe pneumonia from one village in Yunnan Province, China. We searched for severe pneumonia in the village and hospitals. We interviewed patients and family members about exposures. We tested acute and convalescent sera for antigen and antibody of severe acute respiratory syndrome, avian influenza, and plague. The only common exposure of the five patients was riding together in the enclosed cab of a truck for 1.5 hours while taking the first patient to the hospital. Seroconversion to plague F1 antigen confirmed plague in three survivors. Unfamiliarity of clinicians with plague and lack of sputum examination, blood culture, or postmortem examination delayed the diagnosis. No plague cases occurred among family and village contacts and health care workers. High infectivity in this cluster was limited to a crowded, poorly ventilated truck.

Efficacy of ciprofloxacin-gentamicin combination therapy in murine bubonic plague

Potential benefits of combination antibiotic therapy for the treatment of plague have never been evaluated. We compared the efficacy of a ciprofloxacin (CIN) and gentamicin (GEN) combination therapy with that of each antibiotic administered alone (i) against Yersinia pestis in vitro and (ii) in a mouse model of bubonic plague in which animals were intravenously injected with antibiotics for five days, starting at two different times after infection (44 h and 56 h). In vitro, the CIN+GEN combination was synergistic at 0.5x the individual drugs’ MICs and indifferent at 1x- or 2x MIC. In vivo, the survival rate for mice treated with CIN+GEN was similar to that observed with CIN alone and slightly higher than that observed for GEN alone 100, 100 and 85%, respectively when treatment was started 44 h post challenge. 100% of survivors were recorded in the CIN+GEN group vs 86 and 83% in the CIN and GEN groups, respectively when treatment was delayed to 56 h post-challenge. However, these differences were not statistically significant. Five days after the end of treatment, Y. pestis were observed in lymph nodes draining the inoculation site (but not in the spleen) in surviving mice in each of the three groups. The median lymph node log₁₀ CFU recovered from persistently infected lymph nodes was significantly higher with GEN than with CIN (5.8 vs. 3.2, p = 0.04) or CIN+GEN (5.8 vs. 2.8, p = 0.01). Taken as the whole, our data show that CIN+GEN combination is as effective as CIN alone but, regimens containing CIN are more effective to eradicate Y. pestis from the draining lymph node than the recommended GEN monotherapy. Moreover, draining lymph nodes may serve as a reservoir for the continued release of Y. pestis into the blood – even after five days of intravenous antibiotic treatment.

Plague: history and contemporary analysis

Plague has caused ravaging outbreaks, including the Justinian plague and the "black death" in the Middle Ages. The causative agents of these outbreaks have been confirmed using modern molecular tests. The vector of plague during pandemics remains the subject of controversy. Nowadays, plague must be suspected in all areas where plague is endemic in rodents when patients present with adenitis or with pneumonia with a bloody expectorate. Diagnosis is more difficult in the situation of the reemergence of plague, as in Algeria for example, told by the first physician involved in that outbreak (NM). When in doubt, it is preferable to prescribe treatment with doxycycline while waiting for the test results because of the risk of fatality in individuals with plague. The typical bubo is a type of adenitis that is painful, red and nonfluctuating. The diagnosis is simple when microbiological analysis is conducted. Plague is a likely diagnosis when one sees gram-negative bacilli in lymph node aspirate or biopsy samples. Yersinia pestis grows very easily in blood cultures and is easy to identify by biochemical tests and MALDI-TOF mass spectrometry. Pneumonic plague and septicemic plague without adenitis are difficult to diagnose, and these diagnoses are often made by chance or retrospectively when cases are not part of an epidemic or related to another specific epidemiologic context. The treatment of plague must be based on gentamicin or doxycycline. Treatment with one of these antibiotics must be started as soon as plague is suspected. Analysis of past plague epidemics by using modern laboratory tools illustrated the value of epidemic buboes for the clinical diagnosis of plague; and brought new concepts regarding its transmission by human ectoparasites.

Yersinia pestis: examining wildlife plague surveillance in China and the USA

Plague is a zoonotic disease caused by the bacterium Yersinia pestis Lehmann and Neumann, 1896. Although it is essentially a disease of rodents, plague can also be transmitted to people. Historically, plague has caused massive morbidity and mortality events in human populations, and has recently been classified as a reemerging disease in many parts of the world. This public health threat has led many countries to set up wild and domestic animal surveillance programs in an attempt to monitor plague activity that could potentially spill over into human populations. Both China and the USA have plague surveillance programs in place, but the disease dynamics differ in each country. We present data on plague seroprevalence in wildlife and review different approaches for plague surveillance in the 2 countries. The need to better comprehend plague dynamics, combined with the fact that there are still several thousand human plague cases per year, make well-designed wildlife surveillance programs a critical part of both understanding plague risks to humans and preventing disease outbreaks in the future.

Ultrasound and infections on the Tibetan Plateau()

INTRODUCTION

The authors report on an ultrasound (US) outreach program for the nomadic people living in Yushu, a remote area of Qinghai, Tibet, People's Republic of China (PRC) about 4800 m above sea level. The program was carried out in cooperation with ROKPA INTERNATIONAL, a non-profit organization (NGO) that aims at helping the poorest peoples living in remote regions of the world.

MATERIALS AND METHODS

A hand-held US scanner (Sonosite 180 Plus, Sonosite Inc., Bothell, WA, USA) equipped with a 3.5-5 MHz convex probe was used at a local clinic for 21 days in 2007 and for 32 days in 2009.

RESULTS

A total of 1128 US examinations were performed (578 in 2007 and 550 in 2009). The main diagnoses were: Echinococcal cysts (66 cases; 6.23%) - Biliary tract and intrahepatic gallstones (10% of patients examined) - Ascariasis - Acute and chronic hepatitis, liver cirrhosis, abdominal masses - Abdominal tuberculosis - Miscellaneous (trophoblastic tumor, megacalicosis, splenomegaly in acute leukemia). After the first experience in 2007, collaboration with the local hospital was established for the treatment of patients affected by active echinococcal cysts using albendazole and puncture, aspiration and injection of scolicidal agent and re-aspiration (PAIR) and subsequent follow-up.

DISCUSSION AND CONCLUSIONS

US scanning was well accepted by the local population and allowed diagnosis, classification and choice of treatment of the echinococcal cysts according to recent criteria based on a stage-specific approach. Percutaneous treatment was also introduced, but more training of local healthcare providers is needed to secure continuation of this practice. Further experience may help improve the standard of health care services offered to the nomadic populations in this remote area.