Search

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.

Background: Yersinia pestis is a contributing agent to the epidemic disease, plague, which killed an estimated 200 million people during historical times. In this study, a rapid, cheap, sensitive, and specific technique, the lateral flow assay (F1 strips), has been successfully developed to detect this pathogen, by using paired monoclonal antibodies (MAbs) against Y. pestis capsule like fraction 1 (F1) protein. Compared with the polyclonal antibody (PAb) based F1 strips, the Mab-based F1 strips have a remarkable increased detection limitation (10 to 100 folds). Furthermore, besides the limitation and specificity evaluation, the application of this F1 strip on simulated clinical samples indicate the LFA can be a good candidate to detect plague., Methods: Recombinant F1 antigen was expressed and purified from a series of works. The various anti-F1 monoclonal antibodies generated from hybridoma cells were screened with the ELISA technique. To evaluate the feasibility of this Y. pestis F1 test strip, the F1 protein/Y. pestis was spiked into simulated clinical samples such as human serum, mouse bronchoalveolar lavage fluids, and mouse blood to mimic natural infection status. Additionally, this technique was applied to detect the Y. pestis in the environment-captured rats, to evaluate the practical usefulness of the strips., Results: By using this MAb-based-LFA technique, 4 ng/ml of recombinant F1-protein and 10 3  CFU/ml of Y. pestis could be detected in less than 10 mins, which is at least 10-folds than that of the PAb format. On the other hand, although various Yersinia strains were applied to the strips, only Y. pestis strain showed a positive result; all other Yersinia species did not produce a positive signal, indicating the high efficiency and specificity of the MAb-based F1-strips., Conclusion: Based on our findings, we suggest that the MAb-format-LFA will be valuable as a diagnostic tool for the detection of Y. pestis. This report shows that the F1 strip is sufficient to support not only the detection of plague in simulated clinical samples, but also it may be a good candidate to meet the epidemiological surveillance during an outbreak of the biological warfare.

Background: Although the linkage between climate change and plague transmission has been proposed in previous studies, the dominant approach has been to address the linkage with traditional statistical methods, while the possible non-linearity, non-stationarity and low frequency domain of the linkage has not been fully considered. We seek to address the above issue by investigating plague transmission in pre-industrial Europe (AD1347-1760) at both continental and country levels., Methods: We apply Granger Causality Analysis to identify the casual relationship between climatic variables and plague outbreaks. We then apply Wavelet Analysis to explore the non-linear and non-stationary association between climate change and plague outbreaks., Results: Our results show that 5-year lagged temperature and aridity index are the significant determinants of plague outbreaks in pre-industrial Europe. At the multi-decadal time scale, there are more frequent plague outbreaks in a cold and arid climate. The synergy of temperature and aridity index, rather than their individual effect, is more imperative in driving plague outbreaks, which is valid at both the continental and country levels., Conclusions: Plague outbreaks come after cold and dry spells. The multi-decadal climate variability is imperative in driving the cycles of plague outbreaks in pre-industrial Europe. The lagged and multi-decadal effect of climate change on plague outbreaks may be attributable to the complexity of ecological, social, or climate systems, through which climate exerts its influence on plague dynamics. These findings may contribute to improve our understanding of the epidemiology of plague and other rodent-borne or flea-borne infectious diseases in human history.

Background: Plague is caused by Yersinia pestis, a bacterium that disseminates inside of the host at remarkably high rates. Plague bacilli disrupt normal immune responses in the host allowing for systematic spread that is fatal if left untreated. How Y. pestis disseminates from the site of infection to deeper tissues is unknown. Dissemination studies for plague are typically performed in mice by determining the bacterial burden in specific organs at various time points. To follow bacterial dissemination during plague infections in mice we tested the possibility of using bioluminescence imaging (BLI), an alternative non-invasive approach. Fully virulent Y. pestis was transformed with a plasmid containing the luxCDABE genes, making it able to produce light; this lux-expressing strain was used to infect mice by subcutaneous, intradermal or intranasal inoculation., Results: We successfully obtained images from infected animals and were able to follow bacterial dissemination over time for each of the three different routes of inoculation. We also compared the radiance signal from animals infected with a wild type strain and a Δcaf1ΔpsaA mutant that we previously showed to be attenuated in colonization of the lymph node and systemic dissemination. Radiance signals from mice infected with the wild type strain were larger than values obtained from mice infected with the mutant strain (linear regression of normalized values, P<0.05)., Conclusions: We demonstrate that BLI is useful for monitoring dissemination from multiple inoculation sites, and for characterization of mutants with defects in colonization or dissemination.

Background: Yersinia pestis is the causative agent of pneumonic plague; recently, we and others reported that during the first 24-36 hours after pulmonary infection with Y. pestis pro-inflammatory cytokine expression is undetectable in lung tissues., Results: Here, we report that, intranasal infection of mice with CO92 delta yopH mutant results in an early pro-inflammatory response in the lungs characterized by an increase in the pro-inflammatory cytokines Tumor Necrosis Factor-alpha and Interleukin one-beta 24 hours post-infection. CO92 delta yopH colonizes the lung but does not disseminate to the liver or spleen and is cleared from the host within 72 hours post-infection. This is different from what is observed in a wild-type CO92 infection, where pro-inflammatory cytokine expression and immune cell infiltration into the lungs is not detectable until 36-48 h post-infection. CO92 rapidly disseminates to the liver and spleen resulting in high bacterial burdens in these tissues ultimately cumulating in death 72-94 h post-infection. Mice deficient in TNF-alpha are more susceptible to CO92 delta yopH infection with 40% of the mice succumbing to infection., Conclusions: Altogether, our results suggest that YopH can inhibit an early pro-inflammatory response in the lungs of mice and that this is an important step in the pathogenesis of infection.

Background: Secretion of anti-host proteins by Yersinia pestis via a type III mechanism is not constitutive. The process is tightly regulated and secretion occurs only after an appropriate signal is received. The interaction of LcrG and LcrV has been demonstrated to play a pivotal role in secretion control. Previous work has shown that when LcrG is incapable of interacting with LcrV, secretion of anti-host proteins is prevented. Therefore, an understanding of how LcrG interacts with LcrV is required to evaluate how this interaction regulates the type III secretion system of Y. pestis. Additionally, information about structure-function relationships within LcrG is necessary to fully understand the role of this key regulatory protein., Results: In this study we demonstrate that the N-terminus of LcrG is required for interaction with LcrV. The interaction likely occurs within a predicted amphipathic coiled-coil domain within LcrG. Our results demonstrate that the hydrophobic face of the putative helix is required for LcrV interaction. Additionally, we demonstrate that the LcrG homolog, PcrG, is incapable of blocking type III secretion in Y. pestis. A genetic selection was utilized to obtain a PcrG variant capable of blocking secretion. This PcrG variant allowed us to locate a region of LcrG involved in secretion blocking., Conclusion: Our results demonstrate that LcrG interacts with LcrV via hydrophobic interactions located in the N-terminus of LcrG within a predicted coiled-coil motif. We also obtained preliminary evidence that the secretion blocking activity of LcrG is located between amino acids 39 and 53.