Plague in Madagascar - A Tragic Opportunity for Improving Public Health

Genomic diversity of Yersinia pestis from Yunnan Province, China, implies a potential common ancestor as the source of two plague epidemics

Plague, caused by Yersinia pestis, is a zoonotic disease that can reemerge and cause outbreaks following decades of latency in natural plague foci. However, the genetic diversity and spread pattern of Y. pestis during these epidemic-silent cycles remain unclear. In this study, we analyze 356 Y. pestis genomes isolated between 1952 and 2016 in the Yunnan Rattus tanezumi plague focus, China, covering two epidemic-silent cycles. Through high-resolution genomic epidemiological analysis, we find that 96% of Y. pestis genomes belong to phylogroup 1.ORI2 and are subdivided into two sister clades (Sublineage1 and Sublineage2) characterized by different temporal-spatial distributions and genetic diversity. Most of the Sublineage1 strains are isolated from the first epidemic-silent cycle, while Sublineage2 strains are predominantly from the second cycle and revealing a west to east spread. The two sister clades evolved in parallel from a common ancestor and independently lead to two separate epidemics, confirming that the pathogen responsible for the second epidemic following the silent interval is not a descendant of the causative strain of the first epidemic. Our results provide a mechanism for defining epidemic-silent cycles in natural plague foci, which is valuable in the prevention and control of future plague outbreaks.

Protection Induced by Oral Vaccination with a Recombinant Yersinia pseudotuberculosis Delivering Yersinia pestis LcrV and F1 Antigens in Mice and Rats against Pneumonic Plague

A newly attenuated Yersinia pseudotuberculosis strain (designated Yptb1) with triple mutation Δasd ΔyopK ΔyopJ and chromosomal insertion of the Y. pestis caf1R-caf1M-caf1A-caf1 operon was constructed as a live vaccine platform. Yptb1 tailored with an Asd⁺ plasmid (pYA5199) (designated Yptb1[pYA5199]) simultaneously delivers Y. pestis LcrV and F1. The attenuated Yptb1(pYA5199) localized in the Peyer's patches, lung, spleen, and liver for a few weeks after oral immunization without causing any disease symptoms in immunized rodents. An oral prime-boost Yptb1(pYA5199) immunization stimulated potent antibody responses to LcrV, F1, and Y. pestis whole-cell lysate (YPL) in Swiss Webster mice and Brown Norway rats. The prime-boost Yptb1(pYA5199) immunization induced higher antigen-specific humoral and cellular immune responses in mice than a single immunization did, and it provided complete short-term and long-term protection against a high dose of intranasal Y. pestis challenge in mice. Moreover, the prime-boost immunization afforded substantial protection for Brown Norway rats against an aerosolized Y. pestis challenge. Our study highlights that Yptb1(pYA5199) has high potential as an oral vaccine candidate against pneumonic plague.

Evaluation of a multi-species Protein A-ELISA assay for plague serologic diagnosis in humans and other mammal hosts

Background

The Hemagglutination assay (HA) is widely used in plague diagnosis, however, it has a subjective interpretation and demands high amounts of antigen and other immunobiological supplies. On the other hand, the conventional Anti-IgG ELISA is limited by the need of specific conjugates for multiple plague hosts, which leaves a gap for new diagnostic methods able to cover both the diagnosis of human cases and the epidemiological surveillance of multiple sentinel species.

Methods

We developed an ELISA Protein A-peroxidase method to detect anti-F1 antibodies across several species, including humans. To determine the cut-off and performance rates, HA results from 288 samples (81 rabbits, 64 humans, 66 rodents and 77 dogs) were used as reference. Next, we evaluated the agreement between Protein A-ELISA and Anti-IgG ELISA in an expanded sample set (n = 487).

Results

Optimal conditions were found with 250ng/well of F1 and 1:500 serum dilution. Protein A-ELISA showed high repeatability and reproducibility. We observed good correlation rates between the Protein A and IgG ELISAs optical densities and a higher positive/negative OD ratio for the Protein A-ELISA method. The overall sensitivity, specificity and area under the curve for Protein A-ELISA were 94%, 99% and 0.99, respectively. Similar results were observed for each species separately. In the analysis of the expanded sample set, there was a strong agreement between Protein A and IgG assays (kappa = 0.97). Furthermore, there was no cross-reaction with other common infectious diseases, such as dengue, Zika, Chagas disease, tuberculosis (humans) and ehrlichiosis, anaplasmosis and leishmaniasis (dogs).

Conclusions

Altogether, the Protein A-ELISA showed high performance when compared both to HA and Anti-IgG ELISA, with a polyvalent single protocol that requires reduced amounts of antigen and can be employed to any plague hosts.

Here, we developed and evaluated an ELISA diagnostic test based on the Protein A-peroxidase conjugate that allows the test to be used for plague laboratorial diagnosis not only in humans, but also in a wide range of mammalian species. This particularity is specifically important for plague epidemiological surveillance, given that Yersinia pestis, the causative agent of plague, have a long list of animal reservoirs across distinct ecosystems. Briefly, we first evaluated the best reaction parameters, such as antigen concentration, serum and protein A-conjugate dilutions. Next, we used serum samples from humans, dogs, rodents and rabbits (n = 288) with known results for plague serology by a conventional method, to evaluate the performance of the new Protein A-ELISA test. We observed a good performance of the novel Protein A-ELISA test, with high sensitivity and specificity rates. Evaluation of the coefficient of variation revealed that the test measurements suffer little variation, and therefore, has high repeatability and reproducibility. Next, by evaluating 487 samples, we observed a high degree of concordance between the Protein A-ELISA with a conventional IgG-based ELISA. Furthermore, this test showed no significant cross-reaction with other common infectious diseases. Altogether, the Protein A-ELISA showed high performance when compared both to HA and Anti-IgG ELISA, with a single protocol that requires reduced amounts of antigen and can be employed to several plague hosts.

Development of a dual antigen lateral flow immunoassay for detecting Yersinia pestis

Background

Yersinia pestis is the causative agent of plague, a zoonosis associated with small mammals. Plague is a severe disease, especially in the pneumonic and septicemic forms, where fatality rates approach 100% if left untreated. The bacterium is primarily transmitted via flea bite or through direct contact with an infected host. The 2017 plague outbreak in Madagascar resulted in more than 2,400 cases and was highlighted by an increased number of pneumonic infections. Standard diagnostics for plague include laboratory-based assays such as bacterial culture and serology, which are inadequate for administering immediate patient care for pneumonic and septicemic plague.

Principal findings

The goal of this study was to develop a sensitive rapid plague prototype that can detect all virulent strains of Y. pestis. Monoclonal antibodies (mAbs) were produced against two Y. pestis antigens, low-calcium response V (LcrV) and capsular fraction-1 (F1), and prototype lateral flow immunoassays (LFI) and enzyme-linked immunosorbent assays (ELISA) were constructed. The LFIs developed for the detection of LcrV and F1 had limits of detection (LOD) of roughly 1–2 ng/mL in surrogate clinical samples (antigens spiked into normal human sera). The optimized antigen-capture ELISAs produced LODs of 74 pg/mL for LcrV and 61 pg/mL for F1 when these antigens were spiked into buffer. A dual antigen LFI prototype comprised of two test lines was evaluated for the detection of both antigens in Y. pestis lysates. The dual format was also evaluated for specificity using a small panel of clinical near-neighbors and other Tier 1 bacterial Select Agents.

Conclusions

LcrV is expressed by all virulent Y. pestis strains, but homologs produced by other Yersinia species can confound assay specificity. F1 is specific to Y. pestis but is not expressed by all virulent strains. Utilizing highly reactive mAbs, a dual-antigen detection (multiplexed) LFI was developed to capitalize on the diagnostic strengths of each target.

The COVID-19 pandemic: Analysing nursing risk, care and careerscapes

This qualitative study explores how junior nurses, and some who were still in training, navigated the complexities and uncertainties engendered by the COVID-19 pandemic. Data are drawn from in-depth interviews with 18 students/nurses in Christchurch, New Zealand. Managing intertwining risk, care and careerscapes takes an intensified form as existing infection control rules, established norms of care, boundaries between home and work and expected career trajectories roil. 'Safe' and 'risky' spaces are porous but maintained using contextual, critical, clinical judgement. Carescapes are stretched, both within and beyond the walls of healthcare settings. Within the COVID-19 riskscape, careerscapes are open to both threat and opportunity. Countries demand much of their healthcare staff in times of heath crises, but have a limited appreciation of what it takes to translate seemingly tightly bounded protocols into effective practice. The labour required in this work of translation is navigated moment by moment. To surface some of this invisible work, those implementing pandemic plans may need to more carefully consider how to incorporate attention to the work/home/public boundary as well as overtly acknowledging the invisible emotional, physical and intellectual labour carried out in crisis risk, care and careerscapes.

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.

Bacteriophages fEV-1 and fD1 Infect Yersinia pestis

Bacteriophages vB_YpeM_fEV-1 (fEV-1) and vB_YpeM_fD1 (fD1) were isolated from incoming sewage water samples in Turku, Finland, using Yersinia pestis strains EV76 and KIM D27 as enrichment hosts, respectively. Genomic analysis and transmission electron microscopy established that fEV-1 is a novel type of dwarf myovirus, while fD1 is a T4-like myovirus. The genome sizes are 38 and 167 kb, respectively. To date, the morphology and genome sequences of some dwarf myoviruses have been described; however, a proteome characterization such as the one presented here, has currently been lacking for this group of viruses. Notably, fEV-1 is the first dwarf myovirus described for Y. pestis. The host range of fEV-1 was restricted strictly to Y. pestis strains, while that of fD1 also included other members of Enterobacterales such as Escherichia coli and Yersinia pseudotuberculosis. In this study, we present the life cycles, genomes, and proteomes of two Yersinia myoviruses, fEV-1 and fD1.

Modeling the Cost-Effectiveness of Interventions to Prevent Plague in Madagascar

Plague (Yersinia pestis) remains endemic in certain parts of the world. We assessed the cost-effectiveness of plague control interventions recommended by the World Health Organization with particular consideration to intervention coverage and timing. We developed a dynamic model of the spread of plague between interacting populations of humans, rats, and fleas and performed a cost-effectiveness analysis calibrated to a 2017 Madagascar outbreak. We assessed three interventions alone and in combination: expanded access to antibiotic treatment with doxycycline, mass distribution of doxycycline prophylaxis, and mass distribution of malathion. We varied intervention timing and coverage levels. We calculated costs, quality-adjusted life years (QALYs), and incremental cost-effectiveness ratios from a healthcare perspective. The preferred intervention, using a cost-effectiveness threshold of $1350/QALY (GDP per capita in Madagascar), was expanded access to antibiotic treatment with doxycycline with 100% coverage starting immediately after the first reported case, gaining 543 QALYs at an incremental cost of $1023/QALY gained. Sensitivity analyses support expanded access to antibiotic treatment and leave open the possibility that mass distribution of doxycycline prophylaxis or mass distribution of malathion could be cost-effective. Our analysis highlights the potential for rapid expansion of access to doxycycline upon recognition of plague outbreaks to cost-effectively prevent future large-scale plague outbreaks and highlights the importance of intervention timing.

A decade of plague in Madagascar: a description of two hotspot districts

BACKGROUND

Human plague cases, mainly in the bubonic form, occur annually in endemic regions of the central highlands of Madagascar. The aim of this study was to compare the dynamics of the epidemiological features of the human plague in two districts of the central highlands region.

METHODS

In Madagascar, all clinically suspected plague cases that meet clinical and epidemiological criteria specified in the World Health Organization (WHO) standard case definition are reported to the national surveillance system. Data on plague cases reported between 2006 and 2015 in the districts of Ambositra and Tsiroanomandidy were analysed. Statistical comparisons between the epidemiological characteristics of the two districts were conducted.

RESULTS

A total of 840 cases of plague were reported over the studied period, including 563 (67%) probable and confirmed cases (P + C). Out of these P + C cases, nearly 86% (488/563) were cases of bubonic plague. Reported clinical forms of plague were significantly different between the districts from 2006 to 2015 (p = 0.001). Plague cases occurred annually in a period of 10 years in the Tsiroanomandidy district. During the same period, the Ambositra district was characterized by a one-year absence of cases.

CONCLUSION

The differences in the epidemiological situation with respect to the plague from 2006 to 2015 in the two central highlands districts may suggest that several factors other than biogeographical factors determine the representation of the plague and its dynamics in this region. Considering the epidemiological situations according to the specific contexts of the districts could improve the results in the fight against the plague in Madagascar.

Epidemiology, Ecology and Prevention of Plague in the West Nile Region of Uganda: The Value of Long-Term Field Studies

Plague, a fleaborne rodent-associated zoonosis, is a neglected disease with most recent cases reported from east and central Africa and Madagascar. Because of its low incidence and sporadic occurrence, most of our knowledge of plague ecology, prevention, and control derives from investigations conducted in response to human cases. Long-term studies (which are uncommon) are required to generate data to support plague surveillance, prevention, and control recommendations. Here we describe a 15-year, multidisciplinary commitment to plague in the West Nile region of Uganda that led to significant advances in our understanding of where and when persons are at risk for plague infection and how to reduce morbidity and mortality. These findings provide data-driven support for several existing recommendations on plague surveillance and prevention and may be generalizable to other plague foci.

Spatiotemporal analysis of bubonic plague in Pernambuco, northeast of Brazil: Case study in the municipality of Exu

Along with other countries in America, plague reached Brazil through the sea routes during the third pandemic. A brief ports phase was followed by an urban phase that took place in smaller inland cities and finally, it attained the rural area and established several foci where the ecological conditions were suitable for its continued existence. However, the geographic dispersion of plague in Brazil is still poorly studied. To better understand the disease dynamics, we accessed satellite-based data to trace the spatial occurrence and distribution of human plague cases in Pernambuco, Northeastern Brazil and using the municipality of Exu as study case area. Along with the satellite data, a historical survey using the Plague Control Program files was applied to characterize the spatial and temporal dispersion of cases in the period of 1945-1976. Kernel density estimation, spatial and temporal clusters with statistical significance and maximum entropy modeling were used for spatial data analysis, by means of the spatial analysis software packages. The use of geostatistical tools allowed evidencing the shift of the infection from the urban to the wild-sylvatic areas and the reemergence of cases after a period of quiescence, independent of the reintroduction from other plague areas.

DNA Nanostructures in the Fight Against Infectious Diseases

Throughout history, humanity has been threatened by countless epidemic and pandemic outbreaks of infectious diseases, from the Justinianic Plague to the Spanish flu to COVID-19. While numerous antimicrobial and antiviral drugs have been developed over the last 200 years to face these threats, the globalized and highly connected world of the 21st century demands for an ever-increasing efficiency in the detection and treatment of infectious diseases. Consequently, the rapidly evolving field of nanomedicine has taken up the challenge and developed a plethora of strategies to fight infectious diseases with the help of various nanomaterials such as noble metal nanoparticles, liposomes, nanogels, and virus capsids. DNA nanotechnology represents a comparatively recent addition to the nanomedicine arsenal, which, over the past decade, has made great progress in the area of cancer diagnostics and therapy. However, the past few years have seen also an increasing number of DNA nanotechnology-related studies that particularly focus on the detection and inhibition of microbial and viral pathogens. Herein, a brief overview of this rather young research field is provided, successful concepts as well as potential challenges are identified, and promising directions for future research are highlighted.

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.

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.

Comparative assessment on rodent impacts and cultural perceptions of ecologically based rodent management in 3 Afro-Malagasy farming regions

Rodents generate negative consequences for smallholder farmers in Africa that directly impact household and livestock damage, food security, and public health. Ecologically Based Rodent Management (EBRM) seeks sustainable solutions for the mitigation of rodent damage through assessments of rodent population dynamics, agro-ecosystems, and socio-cultural contexts. We adopt a comparative approach across 3 rural Afro-Malagasy smallholder farming regions in South Africa, Tanzania, and Madagascar to assess the household impacts of rodent pests and current perceptions and preferences associated with several rodent control measures. We conducted focus group questionnaires and interviews in different study site locations. Rodents assert multiple impacts on Afro-Malagasy farmers demonstrating recurrent and emerging agricultural and household costs, and public health impacts. We identify a significant knowledge gap in educating communities about the application of different EBRM approaches in favor of acute poisons that are perceived to be more effective. Cultural issues and taboos also have a significant impact on the social acceptance of rodent hunting as well as biological control using indigenous predators. We advocate for an enhanced investigation of the socio-cultural beliefs associated with different rodent practices to understand the factors underlying social acceptance. A collaborative approach that integrates the perspectives of target communities to inform the design of EBRM initiatives according to the specific agro-ecosystem and socio-cultural context is necessary to ensure programmatic success.

Performance of plague rapid diagnostic test compared to bacteriology: a retrospective analysis of the data collected in Madagascar

Background

Plague is a highly fatal disease caused by Yersinia pestis. Late diagnosis hampers disease outcome and effectiveness of control measures, induces death and disease spread. Advance on its diagnosis was the use of lateral flow rapid diagnostic test (RDT).

Methods

We assessed the performance of the plague RDT based on Y. pestis F1 antigen detection more than 15 years after its deployment in Madagascar. We compared the RDT with bacteriological culture results, using data from plague notified cases collected during the periods for which both tests were performed independently and systematically.

Results

Used with bubonic plague (BP) patient samples, RDTs had a sensitivity of 100% (95% CI: 99.7–100%), a specificity of 67% (95% CI: 64–70%) with a good agreement between bacteriology and RDT results (86%; κ = 0.70, 95% CI 0.67–0.73). For pneumonic plague (PP), RDT had a sensitivity of 100% (95% CI: 91–100%) and a specificity of 59% (95% CI: 49–68%) and concordance between the bacteriological and plague RDT results was moderate (70%; κ = 0.43, 95% CI 0.32–0.55). Analysis focusing on the 2017–2018 plague season including the unprecedented epidemic of PP showed that RDT used on BP samples still had a sensitivity of 100% (95% CI: 85–100%) and a specificity of 82% (95% CI: 48–98%) with a very good agreement with bacteriology 94% (κ = 0.86, 95% CI 0.67–1); for PP samples, concordance between the bacteriological and plague RDT results was poor (61%; κ = − 0.03, 95% CI -0.17 – 0.10).

Conclusions

RDT performance appeared to be similar for the diagnosis of BP and PP except during the 2017 PP epidemic where RDT performance was low. This RDT, with its good sensitivity on both plague clinical forms during a normal plague season, remained a potential test for alert. Particularly for BP, it may be of great value in the decision process for the initiation of therapy. However, for PP, RDT may deliver false negative results due to inconsistent sample quality. Plague diagnosis could be improved through the development of next generation of RDTs.

Zoonotic Infections and Biowarfare Agents in Critical Care: Anthrax, Plague, and Tularemia

Bacterial zoonotic infections are rare in developed countries in the twenty-first century but may cause major morbidity and mortality in developing regions of the world. In addition, their potential use as biological weapons makes early recognition and effective empiric therapy important for the critical care practitioner. Anthrax, plague, and tularemia share overlapping presenting syndromes, including fulminant respiratory infections and less severe but still highly morbid lymphocutaneous infections. Although all three may be transmitted as infectious aerosols, only plague has a risk of direct human-to-human transmission. Diagnostic testing will require special precautions for laboratory staff and most often involvement of regional and national reference laboratories. Empiric therapy with aminoglycosides may be life-saving for plague and tularemia, while the treatment of anthrax is complex and varies depending on the site of infection. In outbreaks or for post-exposure prophylaxis, treatment with doxycycline or a fluoroquinolone is recommended for all three diseases.

A Recombinant Attenuated Yersinia pseudotuberculosis Vaccine Delivering a Y. pestis YopENt138-LcrV Fusion Elicits Broad Protection against Plague and Yersiniosis in Mice

In this study, a novel recombinant attenuated Yersinia pseudotuberculosis PB1+ strain (χ10069) engineered with ΔyopK ΔyopJ Δasd triple mutations was used to deliver a Y. pestis fusion protein, YopE amino acid 1 to 138-LcrV (YopENt138-LcrV), to Swiss Webster mice as a protective antigen against infections by yersiniae. χ10069 bacteria harboring the pYA5199 plasmid constitutively synthesized the YopENt138-LcrV fusion protein and secreted it via the type 3 secretion system (T3SS) at 37°C under calcium-deprived conditions. The attenuated strain χ10069(pYA5199) was manifested by the establishment of controlled infection in different tissues without developing conspicuous signs of disease in histopathological analysis of microtome sections. A single-dose oral immunization of χ10069(pYA5199) induced strong serum antibody titers (log10 mean value, 4.2), secretory IgA in bronchoalveolar lavage (BAL) fluid from immunized mice, and Yersinia-specific CD4+ and CD8+ T cells producing high levels of tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and interleukin 2 (IL-2), as well as IL-17, in both lungs and spleens of immunized mice, conferring comprehensive Th1- and Th2-mediated immune responses and protection against bubonic and pneumonic plague challenges, with 80% and 90% survival, respectively. Mice immunized with χ10069(pYA5199) also exhibited complete protection against lethal oral infections by Yersinia enterocolitica WA and Y. pseudotuberculosis PB1+. These findings indicated that χ10069(pYA5199) as an oral vaccine induces protective immunity to prevent bubonic and pneumonic plague, as well as yersiniosis, in mice and would be a promising oral vaccine candidate for protection against plague and yersiniosis for human and veterinary applications.

Rapid Detection of Genetic Engineering, Structural Variation, and Antimicrobial Resistance Markers in Bacterial Biothreat Pathogens by Nanopore Sequencing

Widespread release of Bacillus anthracis (anthrax) or Yersinia pestis (plague) would prompt a public health emergency. During an exposure event, high-quality whole genome sequencing (WGS) can identify genetic engineering, including the introduction of antimicrobial resistance (AMR) genes. Here, we developed rapid WGS laboratory and bioinformatics workflows using a long-read nanopore sequencer (MinION) for Y. pestis (6.5 h) and B. anthracis (8.5 h) and sequenced strains with different AMR profiles. Both salt-precipitation and silica-membrane extracted DNA were suitable for MinION WGS using both rapid and field library preparation methods. In replicate experiments, nanopore quality metrics were defined for genome assembly and mutation analysis. AMR markers were correctly detected and >99% coverage of chromosomes and plasmids was achieved using 100,000 raw sequencing reads. While chromosomes and large and small plasmids were accurately assembled, including novel multimeric forms of the Y. pestis virulence plasmid, pPCP1, MinION reads were error-prone, particularly in homopolymer regions. MinION sequencing holds promise as a practical, front-line strategy for on-site pathogen characterization to speed the public health response during a biothreat emergency.

Modeling Pneumonic Plague in Human Precision-Cut Lung Slices Highlights a Role for the Plasminogen Activator Protease in Facilitating Type 3 Secretion

Pneumonic plague is the deadliest form of disease caused by Yersinia pestis Key to the progression of infection is the activity of the plasminogen activator protease Pla. Deletion of Pla results in a decreased Y. pestis bacterial burden in the lung and failure to progress into the lethal proinflammatory phase of disease. While a number of putative functions have been attributed to Pla, its precise role in the pathogenesis of pneumonic plague is yet to be defined. Here, we show that Pla facilitates type 3 secretion into primary alveolar macrophages but not into the commonly used THP-1 cell line. We also establish human precision-cut lung slices as a platform for modeling early host/pathogen interactions during pneumonic plague and solidify the role of Pla in promoting optimal type 3 secretion using primary human tissue with relevant host cell heterogeneity. These results position Pla as a key player in the early host/pathogen interactions that define pneumonic plague and showcase the utility of human precision-cut lung slices as a platform to evaluate pulmonary infection by bacterial pathogens.

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.

Current State of the Problem of Vaccine Development for Specific Prophylaxis of Plague

Emergence of large-scale plague outbreaks in Africa and South America countries in the modern period, characterized by high frequency of pneumonic plague development (including with lethal outcome) keeps up the interest of scientists to the matters of development and testing of means for specific prophylaxis of this particularly dangerous infectious disease. WHO workshop that was held in 2018 identified the general principles of optimization of design and testing of new-generation vaccines effectively protecting the population from plague infection. Application of the achievements of biological and medical sciences for outlining rational strategy for construction of immunobiological preparations led to a certain progress in the creation of not only sub-unit vaccines based on recombinant antigens, but also live and vector preparations on the platform of safe bacterial strains and replicating and non-replicating viruses in recent years. The review comprehensively considers the relevant trends in vaccine construction for plague  prevention, describes advantages of the state-of-the art methodologies for their safety and efficiency enhancement.

Epidemiological characteristics of an urban plague epidemic in Madagascar, August-November, 2017: an outbreak report

BACKGROUND

Madagascar accounts for 75% of global plague cases reported to WHO, with an annual incidence of 200-700 suspected cases (mainly bubonic plague). In 2017, a pneumonic plague epidemic of unusual size occurred. The extent of this epidemic provides a unique opportunity to better understand the epidemiology of pneumonic plagues, particularly in urban settings.

METHODS

Clinically suspected plague cases were notified to the Central Laboratory for Plague at Institut Pasteur de Madagascar (Antananarivo, Madagascar), where biological samples were tested. Based on cases recorded between Aug 1, and Nov 26, 2017, we assessed the epidemiological characteristics of this epidemic. Cases were classified as suspected, probable, or confirmed based on the results of three types of diagnostic tests (rapid diagnostic test, molecular methods, and culture) according to 2006 WHO recommendations.

FINDINGS

2414 clinically suspected plague cases were reported, including 1878 (78%) pneumonic plague cases, 395 (16%) bubonic plague cases, one (<1%) septicaemic case, and 140 (6%) cases with unspecified clinical form. 386 (21%) of 1878 notified pneumonic plague cases were probable and 32 (2%) were confirmed. 73 (18%) of 395 notified bubonic plague cases were probable and 66 (17%) were confirmed. The case fatality ratio was higher among confirmed cases (eight [25%] of 32 cases) than probable (27 [8%] of 360 cases) or suspected pneumonic plague cases (74 [5%] of 1358 cases) and a similar trend was seen for bubonic plague cases (16 [24%] of 66 confirmed cases, four [6%] of 68 probable cases, and six [2%] of 243 suspected cases). 351 (84%) of 418 confirmed or probable pneumonic plague cases were concentrated in Antananarivo, the capital city, and Toamasina, the main seaport. All 50 isolated Yersinia pestis strains were susceptible to the tested antibiotics.

INTERPRETATION

This predominantly urban plague epidemic was characterised by a large number of notifications in two major urban areas and an unusually high proportion of pneumonic forms, with only 23% having one or more positive laboratory tests. Lessons about clinical and biological diagnosis, case definition, surveillance, and the logistical management of the response identified in this epidemic are crucial to improve the response to future plague outbreaks.

FUNDING

US Agency for International Development, WHO, Institut Pasteur, US Department of Health and Human Services, Laboratoire d'Excellence Integrative Biology of Emerging Infectious Diseases, Models of Infectious Disease Agent Study of the National Institute of General Medical Sciences, AXA Research Fund, and the INCEPTION programme.

Google Trends Predicts Present and Future Plague Cases During the Plague Outbreak in Madagascar: Infodemiological Study

Background

Plague is a highly infectious zoonotic disease caused by the bacillus Yersinia pestis. Three major forms of the disease are known: bubonic, septicemic, and pneumonic plague. Though highly related to the past, plague still represents a global public health concern. Cases of plague continue to be reported worldwide. In recent months, pneumonic plague cases have been reported in Madagascar. However, despite such a long-standing and rich history, it is rather difficult to get a comprehensive overview of the general situation. Within the framework of electronic health (eHealth), in which people increasingly search the internet looking for health-related material, new information and communication technologies could enable researchers to get a wealth of data, which could complement traditional surveillance of infectious diseases.

Objective

In this study, we aimed to assess public reaction regarding the recent plague outbreak in Madagascar by quantitatively characterizing the public’s interest.

Methods

We captured public interest using Google Trends (GT) and correlated it to epidemiological real-world data in terms of incidence rate and spread pattern.

Results

Statistically significant positive correlations were found between GT search data and confirmed (R²=0.549), suspected (R²=0.265), and probable (R²=0.518) cases. From a geospatial standpoint, plague-related GT queries were concentrated in Toamasina (100%), Toliara (68%), and Antananarivo (65%). Concerning the forecasting models, the 1-day lag model was selected as the best regression model.

Conclusions

An earlier digital Web search reaction could potentially contribute to better management of outbreaks, for example, by designing ad hoc interventions that could contain the infection both locally and at the international level, reducing its spread.

Outbreak science: recent progress in the detection and response to outbreaks of infectious diseases

The frequency of reported outbreaks of infectious diseases has increased over the past 3 decades, with predictions that this rise will continue. Outbreak response continues to follow nine basic principles: establish the presence of an outbreak, verify the diagnosis, make a case definition, find cases and contacts, conduct basic epidemiology, test hypotheses, institute control measures, communicate the situation and establish ongoing surveillance. Within each of these areas, significant advances have been made over the past 5 years using progress in digital, laboratory, epidemiology and anthropological equipment or techniques. Irrespective of these, future outbreaks of high-consequence are inevitable, and vigilance and preparation must continue in order to prevent significant mortality, morbidity and socio-economic crisis.

Plague vaccine: recent progress and prospects

Three great plague pandemics, resulting in nearly 200 million deaths in human history and usage as a biowarfare agent, have made Yersinia pestis as one of the most virulent human pathogens. In late 2017, a large plague outbreak raged in Madagascar attracted extensive attention and caused regional panics. The evolution of local outbreaks into a pandemic is a concern of the Centers for Disease Control and Prevention (CDC) in plague endemic regions. Until now, no licensed plague vaccine is available. Prophylactic vaccination counteracting this disease is certainly a primary choice for its long-term prevention. In this review, we summarize the latest advances in research and development of plague vaccines.

Rapid antimicrobial susceptibility testing and β-lactam-induced cell morphology changes of Gram-negative biological threat pathogens by optical screening

BACKGROUND

For Yersinia pestis, Burkholderia pseudomallei, and Burkholderia mallei, conventional broth microdilution (BMD) is considered the gold standard for antimicrobial susceptibility testing (AST) and, depending on the species, requires an incubation period of 16-20 h, or 24-48 h according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. After a diagnosis of plague, melioidosis or glanders during an outbreak or after an exposure event, the timely distribution of appropriate antibiotics for treatment or post-exposure prophylaxis of affected populations could reduce mortality rates.

RESULTS

Herein, we developed and evaluated a rapid, automated susceptibility test for these Gram-negative bacterial pathogens based on time-lapse imaging of cells incubating in BMD microtitre drug panels using an optical screening instrument (oCelloScope). In real-time, the instrument screened each inoculated well containing broth with various concentrations of antibiotics published by CLSI for primary testing: ciprofloxacin (CIP), doxycycline (DOX) and gentamicin (GEN) for Y. pestis; imipenem (IPM), ceftazidime (CAZ) and DOX for B. mallei; and IPM, DOX, CAZ, amoxicillin-clavulanic acid (AMC) and trimethoprim-sulfamethoxazole (SXT) for B. pseudomallei. Based on automated growth kinetic data, the time required to accurately determine susceptibility decreased by ≥70% for Y. pestis and ≥ 50% for B. mallei and B. pseudomallei compared to the times required for conventional BMD testing. Susceptibility to GEN, IPM and DOX could be determined in as early as three to six hours. In the presence of CAZ, susceptibility based on instrument-derived growth values could not be determined for the majority of B. pseudomallei and B. mallei strains tested. Time-lapse video imaging of these cultures revealed that the formation of filaments in the presence of this cephalosporin at inhibitory concentrations was detected as growth. Other β-lactam-induced cell morphology changes, such as the formation of spheroplasts and rapid cell lysis, were also observed and appear to be strain- and antibiotic concentration-dependent.

CONCLUSIONS

A rapid, functional AST was developed and real-time video footage captured β-lactam-induced morphologies of wild-type B. mallei and B. pseudomallei strains in broth. Optical screening reduced the time to results required for AST of three Gram-negative biothreat pathogens using clinically relevant, first-line antibiotics compared to conventional BMD.

Enhancing preparation for large Nipah outbreaks beyond Bangladesh: Preventing a tragedy like Ebola in West Africa

The Nipah virus has been transmitted from person-to-person via close contact in non-urban parts of India (including Kerala May 2018), Bangladesh, and the Philippines. It can cause encephalitis and pneumonia, and has a high case fatality rate. Nipah is a One Health zoonotic infectious disease linked to fruit bats, and sometimes pigs or horses. We advocate anticipating and preparing for urban and larger rural outbreaks of Nipah. Immediate enhanced preparations would include standardized guidance on infection prevention and control, and personal protective equipment, from the World Health Organization (WHO) on their OpenWHO website and 2018 "Managing Epidemics" handbook, along with adding best clinical practices by experts in countries with multiple outbreaks such as Bangladesh and India. Longer-term enhanced preparations include accelerating development of field diagnostics, antiviral drugs, immune-based therapies, and vaccines. WHO-coordinated multi-partner protocols to test investigational treatments, diagnostics, and vaccines are needed, by analogy to such protocols for Ebola during the unanticipated pan-epidemic in Guinea, Liberia, and Sierra Leone. Anticipating and preparing now for urban and rural Nipah outbreaks in nations with no experience with Nipah will help avoid the potential for what the United Nations 2016 report on Ebola in West Africa called a "preventable tragedy".

Vital Signs: Trends in Reported Vectorborne Disease Cases - United States and Territories, 2004-2016

Introduction

Vectorborne diseases are major causes of death and illness worldwide. In the United States, the most common vectorborne pathogens are transmitted by ticks or mosquitoes, including those causing Lyme disease; Rocky Mountain spotted fever; and West Nile, dengue, and Zika virus diseases. This report examines trends in occurrence of nationally reportable vectorborne diseases during 2004–2016.

Methods

Data reported to the National Notifiable Diseases Surveillance System for 16 notifiable vectorborne diseases during 2004–2016 were analyzed; findings were tabulated by disease, vector type, location, and year.

Results

A total 642,602 cases were reported. The number of annual reports of tickborne bacterial and protozoan diseases more than doubled during this period, from >22,000 in 2004 to >48,000 in 2016. Lyme disease accounted for 82% of all tickborne disease reports during 2004–2016. The occurrence of mosquitoborne diseases was marked by virus epidemics. Transmission in Puerto Rico, the U.S. Virgin Islands, and American Samoa accounted for most reports of dengue, chikungunya, and Zika virus diseases; West Nile virus was endemic, and periodically epidemic, in the continental United States.

Conclusions and Implications for Public Health Practice

Vectorborne diseases are a large and growing public health problem in the United States, characterized by geographic specificity and frequent pathogen emergence and introduction. Differences in distribution and transmission dynamics of tickborne and mosquitoborne diseases are often rooted in biologic differences of the vectors. To effectively reduce transmission and respond to outbreaks will require major national improvement of surveillance, diagnostics, reporting, and vector control, as well as new tools, including vaccines.

[The plague: An overview and hot topics]

Plague is a bacterial zoonosis caused by Yersinia pestis, usually found in fleas and small rodents that constitute the reservoir of the disease. It is transmitted to humans by flea bite, contact with rodents or inhalation of infected droplets. There are three clinical forms: bubonic plague, pulmonary plague and septicemic plague. The usual presentation is a flu-like syndrome possibly accompanied by an inflammatory lymphadenopathy which appears after 1 to 7days of incubation. Bubonic plague has a case fatality rate of about 50% while other forms of plague are almost always fatal without treatment. Diagnosis can be confirmed by usual bacteriological techniques (Gram examination, culture) but also by serological examination, use of rapid diagnostic tests or PCR. Although aminoglycosides are traditionally regarded as the most effective treatment, fluoroquinolones or cyclins are currently recommended in France. Plague is one of the re-emerging diseases according to the WHO and Madagascar suffered in 2017 the most important plague epidemic of the 21st century with more than 2000 cases and 200 deaths. Peru and the Democratic Republic of Congo are also considered endemic areas. Public health measures and a relentless fight against poverty are the cornerstone of the control of the disease. Vaccine improvement in endemic areas may also play an important role.