Cases of cat-associated human plague in the Western US, 1977-1998

A systematic review of the clinical profile of patients with bubonic plague and the outcome measures used in research settings

BACKGROUND

Plague is a zoonotic disease that, despite affecting humans for more than 5000 years, has historically been the subject of limited drug development activity. Drugs that are currently recommended in treatment guidelines have been approved based on animal studies alone-no pivotal clinical trials in humans have yet been completed. As a result of the sparse clinical research attention received, there are a number of methodological challenges that need to be addressed in order to facilitate the collection of clinical trial data that can meaningfully inform clinicians and policy-makers. One such challenge is the identification of clinically-relevant endpoints, which are informed by understanding the clinical characterisation of the disease-how it presents and evolves over time, and important patient outcomes, and how these can be modified by treatment.

METHODOLOGY/PRINCIPAL FINDINGS

This systematic review aims to summarise the clinical profile of 1343 patients with bubonic plague described in 87 publications, identified by searching bibliographic databases for studies that meet pre-defined eligibility criteria. The majority of studies were individual case reports. A diverse group of signs and symptoms were reported at baseline and post-baseline timepoints-the most common of which was presence of a bubo, for which limited descriptive and longitudinal information was available. Death occurred in 15% of patients; although this varied from an average 10% in high-income countries to an average 17% in low- and middle-income countries. The median time to death was 1 day, ranging from 0 to 16 days.

CONCLUSIONS/SIGNIFICANCE

This systematic review elucidates the restrictions that limited disease characterisation places on clinical trials for infectious diseases such as plague, which not only impacts the definition of trial endpoints but has the knock-on effect of challenging the interpretation of a trial's results. For this reason and despite interventional trials for plague having taken place, questions around optimal treatment for plague persist.

Backyard zoonoses: The roles of companion animals and peri-domestic wildlife

The spillover of human infectious diseases from animal reservoirs is now well appreciated. However, societal and climate-related changes are affecting the dynamics of such interfaces. In addition to the disruption of traditional wildlife habitats, in part because of climate change and human demographics and behavior, there is an increasing zoonotic disease risk from companion animals. This includes such factors as the awareness of animals kept as domestic pets and increasing populations of free-ranging animals in peri-domestic environments. This review presents background and commentary focusing on companion and peri-domestic animals as disease risk for humans, taking into account the human-animal interface and population dynamics between the animals themselves.

Comparative sequence analysis elucidates the evolutionary patterns of Yersinia pestis in New Mexico over thirty-two years

Background

Yersinia pestis, a Gram-negative bacterium, is the causative agent of plague. Y. pestis is a zoonotic pathogen that occasionally infects humans and became endemic in the western United States after spreading from California in 1899.

Methods

To better understand evolutionary patterns in Y. pestis from the southwestern United States, we sequenced and analyzed 22 novel genomes from New Mexico. Analytical methods included, assembly, multiple sequences alignment, phylogenetic tree reconstruction, genotype-phenotype correlation, and selection pressure.

Results

We identified four genes, including Yscp and locus tag YPO3944, which contained codons undergoing negative selection. We also observed 42 nucleotide sites displaying a statistically significant skew in the observed residue distribution based on the year of isolation. Overall, the three genes with the most statistically significant variations that associated with metadata for these isolates were sapA, fliC, and argD. Phylogenetic analyses point to a single introduction of Y. pestis into the United States with two subsequent, independent movements into New Mexico. Taken together, these analyses shed light on the evolutionary history of this pathogen in the southwestern US over a focused time range and confirm a single origin and introduction into North America.

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.

Sialoglycan binding patterns of bacterial AB5 toxin B subunits correlate with host range and toxicity, indicating evolution independent of A subunits

Many pathogenic bacteria secrete AB₅ toxins that can be virulence factors. Cytotoxic A subunits are delivered to the cytosol following B subunit binding to specific host cell surface glycans. Some B subunits are not associated with A subunits, for example, YpeB of Yersinia pestis, the etiologic agent of plague. Plague cannot be eradicated because of Y. pestis' adaptability to numerous hosts. We previously showed selective binding of other B₅ pentamers to a sialoglycan microarray, with sialic acid (Sia) preferences corresponding to those prominently expressed by various hosts, for example, N-acetylneuraminic acid (Neu5Ac; prominent in humans) or N-glycolylneuraminic acid (Neu5Gc; prominent in ruminant mammals and rodents). Here, we report that A subunit phylogeny evolved independently of B subunits and suggest a future B subunit nomenclature based on bacterial species names. We also found via phylogenetic analysis of B subunits, which bind Sias, that homologous molecules show poor correlation with species phylogeny. These data indicate ongoing lateral gene transfers between species, including mixing of A and B subunits. Consistent with much broader host range of Y. pestis, we show that YpeB recognizes all mammalian Sia types, except for 4-O-acetylated ones. Notably, YpeB alone causes dose-dependent cytotoxicity, which is abolished by a mutation (Y77F) eliminating Sia recognition, suggesting that cell proliferation and death are promoted via lectin-like crosslinking of cell surface sialoglycoconjugates. These findings help explain the host range of Y. pestis and could be important for pathogenesis. Overall, our data indicate ongoing rapid evolution of both host Sias and pathogen toxin-binding properties.

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.

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.

Plague Transmission from Corpses and Carcasses

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

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

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

An overview of global epidemics and the challenges faced

In this chapter, the global epidemiological events causing infections that ravaged humanity throughout its existence by bringing hardship to rich and poor nations alike are aggregated and presented. Among these, the largest known epidemics including the recent COVID-19 pandemic will be highlighted along with the analysis of the actual and common reason behind the occurring of all the epidemic scenarios. The epidemiological and nonepidemiological impacts of the most fatal pandemics recorded in history are also discussed. The vulnerable countries’ readiness for coping with epidemics is assessed in terms of different indices. Furthermore, the current and future challenges in fighting epidemiological events are on the frontline and a number of preparative measures and strategies have been suggested.

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.

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.

Animal Exposure and Human Plague, United States, 1970-2017

Since 1970, >50% of patients with plague in the United States had interactions with animals that might have led to infection. Among patients with pneumonic plague, nearly all had animal exposure. Improved understanding of the varied ways in which animal contact might increase risk for infection could enhance prevention messages.

2019 AAFP Feline Zoonoses Guidelines

Aim:

The overarching purpose of the 2019 AAFP Feline Zoonoses Guidelines (hereafter referred to as the ‘Guidelines’) is to provide accurate information about feline zoonotic diseases to owners, physicians and veterinarians to allow logical decisions to be made concerning cat ownership.

Scope and accessibility:

The Panelists are physicians and veterinarians who worked closely together in an attempt to make these Guidelines a document that can be used to support the International One Health movement. This version of the Guidelines builds upon the first feline zoonosis panel report, published in 2003 ( catvets.com/guidelines ), and provides an updated reference list and recommendations. Each of the recommendations received full support from every Panelist. Primary recommendations are highlighted in a series of ‘Panelists’ advice’ boxes.

A Case of Letting the Cat out of The Bag-Why Trap-Neuter-Return Is Not an Ethical Solution for Stray Cat (Felis catus) Management

Trap-Neuter-Return (TNR) programs, in which stray cats are captured, neutered and returned to the environment are advocated as a humane, ethical alternative to euthanasia. We review the TNR literature in light of current debate over whether or not there should be further TNR trials in Australia. We revisit the problems arising from stray cats living in association with human habitation and estimate how many stray cats would have to be processed through a scientifically-guided TNR program to avoid high euthanasia rates. We also identify 10 ethical and welfare challenges that have to be addressed: we consider the quality of life for stray cats, where they would live, whether the TNR process itself is stressful, whether TNR cats are vulnerable to injury, parasites and disease, can be medically treated, stray cats' body condition and diet, and their impacts on people, pet cats, and urban wildlife, especially endemic fauna. We conclude that TNR is unsuitable for Australia in almost all situations because it is unlikely to resolve problems caused by stray cats or meet ethical and welfare challenges. Targeted adoption, early-age desexing, community education initiatives and responsible pet ownership have greater promise to minimize euthanasia, reduce numbers rapidly, and address the identified issues.

Assessment of Musculoskeletal Injuries Associated with Palpation, Infection Control Practices, and Zoonotic Disease Risks among Utah Clinical Veterinarians

OBJECTIVES

Practicing veterinarians are exposed to unique occupational hazards and zoonotic diseases. National studies have highlighted an increase risk to injuries and a lack of veterinary awareness for these hazards. In Utah (and likely other states), reports of acquired zoonoses are sporadic, and underlying risk factors poorly understood. To better clarify occupational risk factors, the knowledge, attitudes, and behaviors of Utah veterinarians were examined.

METHODS

A total sample of 809 Utah veterinarians were identified from the 2017 licensure listing provided by the Utah Division of Professional Licensing. These individuals were invited to participate in an internet-based survey to self-report musculoskeletal injuries associated with large animal palpation practices. The relationships between some variables and Precaution awareness (PA) score rankings were examined using logistic regression and odds ratios.

RESULTS

Of 809 veterinarians, 223 (28%) responded, with 209 self-identifying as clinical veterinarians. Frequent palpation of large animals (equine or bovine) was performed by 43 (22%) of 197 responding veterinarians. Joint pain or injury was experienced by 29 (67%) of 43 responding veterinarians who frequently palpated large animals (equine or bovine). Animal bites, needle-sticks, and cuts were the most frequently reported injuries within the past year. There were 44 (22%) of 197 respondents who reported having contracted a zoonotic disease. Most of the respondents failed to use appropriate PPE when examining an ill animal or when handling potentially infectious specimens. Clinical veterinarians who have less than 10 years of experience and work in a practice providing clinic-based services were 2.3 and 3.8 times more likely to have low PA rankings, respectively.

CONCLUSION

Our work underscores the importance for continued clinical veterinarian education on occupational risks associated with musculoskeletal injuries, animal bites, needle-sticks, and cuts. The fact that survey veterinarians reported a high level of zoonotic disease infection illustrates the need for education and training on proper PPE use. Further work is needed to understand why precaution awareness scores were low among this sample of participants in this study. Additional follow-up with veterinarians is recommended to assess availability of large animal handling facilities and safety practices to prevent musculoskeletal injuries.

Identifying the social and environmental determinants of plague endemicity in Peru: insights from a case study in Ascope, La Libertad

BACKGROUND

Plague remains a public health problem in specific areas located in Bolivia, Brazil, Ecuador and Peru. Its prevention and control encompasses adequate clinical management and timely laboratory diagnosis. However, understanding communities' interaction with its surrounding ecosystem as well as the differences between community members and institutional stakeholders regarding the root causes of plague might contribute to understand its endemicity. We aim at bridging the traditionally separate biological and social sciences by elucidating communities' risk perception and identifying knowledge gaps between communities and stakeholders. This approach has been used in other areas but never in understanding plague endemicity, nor applied in the Latin American plague context. The objectives were to identify (i) plague risk perception at community level, (ii) perceived social and environmental determinants of plague endemicity, and (iii) institutions that need to be involved and actions needed to be taken as proposed by stakeholders and community members. The study was performed in 2015 and took place in Ascope rural province, La Libertad Region, in Peru, where the study areas are surrounded by intensive private sugarcane production.

METHODS

We propose using a multi-level discourse analysis. Community households were randomly selected (n = 68). Structured and semi-structured questionnaires were applied. A stakeholder analysis was used to identify policy makers (n = 34). In-depth interviews were performed, recorded and transcribed. Descriptive variables were analyzed with SPSS®. Answers were coded following variables adapted from the Commission on Social Determinants of Health and analyzed with the assistance of ATLAS.ti®.

RESULTS

Results showed that risk perception was low within the community. Policy-makers identified agriculture and sugarcane production as the root cause while community answers ranked the hygiene situation as the main cause. Stakeholders first ranked governmental sectors (education, housing, agriculture and transport) and the community prioritized the health sector. Social surveillance and improving prevention and control were first cited by policy-makers and community members, respectively.

CONCLUSIONS

The determinants of plague endemicity identified by the two groups differed. Similarly, actions and sectors needed to be involved in solving the problem varied. The gaps in understanding plague root causes between these two groups might hinder the efficiency of current plague prevention and control strategies.

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.

Human case of bubonic plague resulting from the bite of a wild Gunnison's prairie dog during translocation from a plague-endemic area

Plague is a zoonotic disease (transmitted mainly by fleas and maintained in nature by rodents) that causes severe acute illness in humans. We present a human plague case who became infected by the bite of a wild Gunnison's prairie dog, and a good practical example of the One Health approach that resulted in a rapid public health response. The exposure occurred while the animal was being transported for relocation to a wildlife refuge after being trapped in a plague enzootic area. This is the first report of a human plague case resulting from the bite of a Gunnison's prairie dog. Additionally, we present an observation of a longer incubation period for plague in captive prairie dogs, leading to a recommendation for a longer quarantine period for prairie dogs during translocation efforts.

Serological and PCR investigation of Yersinia pestis in potential reservoir hosts from a plague outbreak focus in Zambia

Background

Plague is a bacterial zoonotic disease, caused by Yersinia pestis. Rodents are the natural hosts with fleas as the vehicle of disease transmission. Domestic and wild dogs and cats have also been identified as possible disease hosts. In Zambia, plague outbreaks have been reported in the Southern and Eastern regions in the last 20 years. Based on these observations, Y. pestis could possibly be endemically present in the area.

Methods

To substantiate such possibility, sera samples were collected from rodents, shrews, dogs and cats for detection of antibodies against Fraction 1 gene (Fra1) of Y. pestis while organs from rodents and shrews, and fleas from both dogs and rodents were collected to investigate plasminogen activator gene (pla gene) of Y. pestis using ELISA and PCR respectively.

Results

A total of 369 blood samples were collected from domestic carnivores, shrews and domestic and peri-domestic rodents while 199 organs were collected from the rodents and shrews. Blood samples were tested for antibodies against Fra1 antigen using ELISA and 3% (5/165) (95% CI 0.99–6.93%) dogs were positive while all cats were negative. Of 199 sera from rodents and shrews, 12.6% (95% CI 8.30–17.98%) were positive for antibodies against Fra1 using anti-rat IgG secondary antibody while using anti-mouse IgG secondary antibody, 17.6% (95% CI 12.57–23.60%) were positive. PCR was run on the organs and 2.5% (95% CI 0.82–5.77%) were positive for plasminogen activator gene of Y. pestis and the amplicons were sequenced and showed 99% identity with Y. pestis reference sequences. All 82 fleas collected from animals subjected to PCR, were negative for pla gene. The specific rat-flea and dog-flea indices were 0.19 and 0.27 respectively, which were lower than the level required to enhance chances of the disease outbreak.

Conclusions

We concluded that plague was still endemic in the area and the disease may infect human beings if contact is enhanced between reservoir hosts and flea vectors. The lower specific rodent-flea Indices and absence of Y. pestis in the potential vectors were considered to be partly responsible for the current absence of plague outbreaks despite its presence in the sylvatic cycle.

Diseases Transmitted by Cats

Humans and cats have shared a close relationship since ancient times. Millions of cats are kept as household pets, and 34% of households have cats. There are numerous diseases that may be transmitted from cats to humans. General modes of transmission, with some overlapping features, can occur through inhalation (e.g., bordetellosis); vector-borne spread (e.g., ehrlichiosis); fecal-oral route (e.g., campylobacteriosis); bite, scratch, or puncture (e.g., rabies); soil-borne spread (e.g., histoplasmosis); and direct contact (e.g., scabies). It is also likely that the domestic cat can potentially act as a reservoir for many other zoonoses that are not yet recognized. The microbiology of cat bite wound infections in humans is often polymicrobial with a broad mixture of aerobic (e.g., Pasteurella, Streptococcus, Staphylococcus) and anaerobic (e.g., Fusobacterium, Porphyromonas, Bacteroides) microorganisms. Bacteria recovered from infected cat bite wounds are most often reflective of the oral flora of the cat, which can also be influenced by the microbiome of their ingested prey and other foods. Bacteria may also originate from the victim's own skin or the physical environment at the time of injury.

Rapid detection of Yersinia pestis recombinant fraction 1 capsular antigen

Yersinia pestis, an infectious bacterium that is a causative agent of plague, a disease which has been shown to be one of the most feared in history and which has caused millions of deaths. The capsule-like fraction 1 (F1) antigen expressed by Y. pestis is a known specific marker for the identification of the bacteria; therefore, the detection of F1 is important for Y. pestis recognition. In this study, a rapid, sensitive, and specific technique, the lateral flow assay (LFA), was successfully developed to detect Y. pestis by the recombinant F1 antigen. The assay that utilized an anti-F1 polyclonal antibody (Pab) to identify the bacteria was based on a double-antibody sandwich format on a nitrocellulose membrane. With the LFA method, 50 ng/ml of recombinant F1 protein and 10(5) CFU/mL of Y. pestis could be detected in less than 10 min. This assay also showed no cross-reaction with other Yersinia spp. or with some selected capsule-producing Enterobacteriaceae strains. Furthermore, detection of Y. pestis in simulated samples has been evaluated. The detection sensitivity of Y. pestis in various matrices was 10(5) CFU/mL, which was identical to that in PBS buffer. The results obtained suggest that LFA is an excellent tool for detection of Y. pestis contamination in an environment and hence can be used to monitor plague diseases when they emerge.

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.

YfbA, a Yersinia pestis regulator required for colonization and biofilm formation in the gut of cat fleas

For transmission to new hosts, Yersinia pestis, the causative agent of plague, replicates as biofilm in the foregut of fleas that feed on plague-infected animals or humans. Y. pestis biofilm formation has been studied in the rat flea; however, little is known about the cat flea, a species that may bridge zoonotic and anthroponotic plague cycles. Here, we show that Y. pestis infects and replicates as a biofilm in the foregut of cat fleas in a manner requiring hmsFR, two determinants for extracellular biofilm matrix. Examining a library of transposon insertion mutants, we identified the LysR-type transcriptional regulator YfbA, which is essential for Y. pestis colonization and biofilm formation in cat fleas.

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.

Yersinia Pestis Infection in Cats

Overview:

Plague, the medieval ‘Black Death’, is caused by a Gram-negative coccobacillus, Yersinia pestis, which also infects cats. As in people, it is transmitted from rodents through flea bites; it occurs in Asia, Africa and the Americas in flea-infested regions, all year round, and where rodent reservoirs are abundant. A poor prognosis is associated with high fever, and the pulmonary and septicaemic forms. Antibiotic therapy, flea control and avoidance of rodent contacts have made this infection manageable.

Fleas infesting pets in the era of emerging extra-intestinal nematodes

Modifications in climatic conditions, movements of hosts and goods, changes in animal phenology and human behaviour and increase of wildlife, are presently concurring in the geographic spread of vectors and cardio-respiratory nematodes, e.g. Dirofilaria immitis, Angiostrongylus vasorum, Aelurostrongylus abstrusus and Capillaria aerophila. All these factors may also influence dispersion and clinical significance of fleas, thus posing relevant challenges in those regions where other parasites are emerging at the same time. Ctenocephalides felis, Ctenocephalides canis and Pulex irritans cause discomfort, nuisance, allergic reactions, anaemia, and may transmit several pathogens, some of them are of importance for public health. The present article reviews the importance of fleas in small animal practice and their sanitary relevance for dogs, cats and humans, and discusses current control methods in the present era of emerging extra-intestinal nematodes, towards a possible changing perspective for controlling key parasites affecting companion animals.

Zoonotic vector-borne bacterial pathogens in California mountain lions (Puma concolor), 1987-2010

Sera collected from 442 mountain lions in 48 California counties between the years of 1987 and 2010 were tested using immunofluorescence assays and agglutination tests for the presence of antibodies reactive to Yersinia pestis, Francisella tularensis, Bartonella henselae, Borrelia burgdorferi, and Anaplasma phagocytophilum antigens. Data were analyzed for spatial and temporal trends in seropositivity. Seroprevalences for B. burgdorferi (19.9%) and B. henselae (37.1%) were relatively high, with the highest exposure in the Central Coast region for B. henselae. B. henselae DNA amplified in mountain lion samples was genetically similar to human-derived Houston-1 and domestic cat-derived U4 B. henselae strains at the gltA and ftsZ loci. The statewide seroprevalences of Y. pestis (1.4%), F. tularensis (1.4%), and A. phagocytophilum (5.9%), were comparatively low. Sera from Y. pestis- and F. tularensis-seropositive mountain lions were primarily collected in the Eastern and Western Sierra Nevada, and samples reactive to Y. pestis antigen were collected exclusively from adult females. Adult age (≥ 2 years) was a risk factor for B. burgdorferi exposure. Over 70% of tested animals were killed on depredation permits, and therefore were active near areas with livestock and human residential communities. Surveillance of mountain lions for these bacterial vector-borne and zoonotic agents may be informative to public health authorities, and the data are useful for detecting enzootic and peridomestic pathogen transmission patterns, particularly in combination with molecular characterization of the infecting organisms.

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.

Zoonotic diseases associated with free-roaming cats

Free-roaming cat populations have been identified as a significant public health threat and are a source for several zoonotic diseases including rabies, toxoplasmosis, cutaneous larval migrans because of various nematode parasites, plague, tularemia and murine typhus. Several of these diseases are reported to cause mortality in humans and can cause other important health issues including abortion, blindness, pruritic skin rashes and other various symptoms. A recent case of rabies in a young girl from California that likely was transmitted by a free-roaming cat underscores that free-roaming cats can be a source of zoonotic diseases. Increased attention has been placed on trap-neuter-release (TNR) programmes as a viable tool to manage cat populations. However, some studies have shown that TNR leads to increased immigration of unneutered cats into neutered populations as well as increased kitten survival in neutered groups. These compensatory mechanisms in neutered groups leading to increased kitten survival and immigration would confound rabies vaccination campaigns and produce naïve populations of cats that can serve as source of zoonotic disease agents owing to lack of immunity. This manuscript is a review of the various diseases of free-roaming cats and the public health implications associated with the cat populations.

Evidence of Yersinia pestis DNA from fleas in an endemic plague area of Zambia

Background

Yersinia pestis is a bacterium that causes plague which infects a variety of mammals throughout the world. The disease is usually transmitted among wild rodents through a flea vector. The sources and routes of transmission of plague are poorly researched in Africa, yet remains a concern in several sub-Saharan countries. In Zambia, the disease has been reported on annual basis with up to 20 cases per year, without investigating animal reservoirs or vectors that may be responsible in the maintenance and propagation of the bacterium. In this study, we undertook plague surveillance by using PCR amplification of the plasminogen activator gene in fleas.

Findings

Xenopsylla species of fleas were collected from 83 rodents trapped in a plague endemic area of Zambia. Of these rodents 5 had fleas positive (6.02%) for Y. pestis plasminogen activator gene. All the Y. pestis positive rodents were gerbils.

Conclusions

We conclude that fleas may be responsible in the transmission of Y. pestis and that PCR may provide means of plague surveillance in the endemic areas of Zambia.

Treatment of neuroterrorism

Bioterrorism is defined as the intentional use of biological, chemical, nuclear, or radiological agents to cause disease, death, or environmental damage. Early recognition of a bioterrorist attack is of utmost importance to minimize casualties and initiate appropriate therapy. The range of agents that could potentially be used as weapons is wide, however, only a few of these agents have all the characteristics making them ideal for that purpose. Many of the chemical and biological weapons can cause neurological symptoms and damage the nervous system in varying degrees. Therefore, preparedness among neurologists is important. The main challenge is to be cognizant of the clinical syndromes and to be able to differentiate diseases caused by bioterrorism from naturally occurring disorders. This review provides an overview of the biological and chemical warfare agents, with a focus on neurological manifestation and an approach to treatment from a perspective of neurological critical care.

Microbiology of animal bite wound infections

The microbiology of animal bite wound infections in humans is often polymicrobial, with a broad mixture of aerobic and anaerobic microorganisms. Bacteria recovered from infected bite wounds are most often reflective of the oral flora of the biting animal, which can also be influenced by the microbiome of their ingested prey and other foods. Bacteria may also originate from the victim's own skin or the physical environment at the time of injury. Our review has focused on bite wound infections in humans from dogs, cats, and a variety of other animals such as monkeys, bears, pigs, ferrets, horses, sheep, Tasmanian devils, snakes, Komodo dragons, monitor lizards, iguanas, alligators/crocodiles, rats, guinea pigs, hamsters, prairie dogs, swans, and sharks. The medical literature in this area has been made up mostly of small case series or case reports. Very few studies have been systematic and are often limited to dog or cat bite injuries. Limitations of studies include a lack of established or inconsistent criteria for an infected wound and a failure to utilize optimal techniques in pathogen isolation, especially for anaerobic organisms. There is also a lack of an understanding of the pathogenic significance of all cultured organisms. Gathering information and conducting research in a more systematic and methodical fashion through an organized research network, including zoos, veterinary practices, and rural clinics and hospitals, are needed to better define the microbiology of animal bite wound infections in humans.

Fleas as parasites of the family Canidae

Historically, flea-borne diseases are among the most important medical diseases of humans. Plague and murine typhus are known for centuries while the last years brought some new flea-transmitted pathogens, like R. felis and Bartonella henselae. Dogs may play an essential or an accidental role in the natural transmission cycle of flea-borne pathogens. They support the growth of some of the pathogens or they serve as transport vehicles for infected fleas between their natural reservoirs and humans. More than 15 different flea species have been described in domestic dogs thus far. Several other species have been found to be associated with wild canids. Fleas found on dogs originate from rodents, birds, insectivores and from other Carnivora. Dogs therefore may serve as ideal bridging hosts for the introduction of flea-borne diseases from nature to home. In addition to their role as ectoparasites they cause nuisance for humans and animals and may be the cause for severe allergic reactions.

Plague: Infections of Companion Animals and Opportunities for Intervention

Plague is a zoonotic disease, normally circulating in rodent populations, transmitted to humans most commonly through the bite of an infected flea vector. Secondary infection of the lungs results in generation of infectious aerosols, which pose a significant hazard to close contacts. In enzootic areas, plague infections have been reported in owners and veterinarians who come into contact with infected pets. Dogs are relatively resistant, but can import infected fleas into the home. Cats are acutely susceptible, and can present a direct hazard to health. Reducing roaming and hunting behaviours, combined with flea control measures go some way to reducing the risk to humans. Various vaccine formulations have been developed which may be suitable to protect companion animals from contracting plague, and thus preventing onward transmission to man. Since transmission has resulted in a number of fatal cases of plague, the vaccination of domestic animals such as cats would seem a low cost strategy for reducing the risk of infection by this serious disease in enzootic regions.

Landscape and residential variables associated with plague-endemic villages in the West Nile region of Uganda

Plague, caused by the bacteria Yersinia pestis, is a severe, often fatal disease. This study focuses on the plague-endemic West Nile region of Uganda, where limited information is available regarding environmental and behavioral risk factors associated with plague infection. We conducted observational surveys of 10 randomly selected huts within historically classified case and control villages (four each) two times during the dry season of 2006 (N = 78 case huts and N = 80 control huts), which immediately preceded a large plague outbreak. By coupling a previously published landscape-level statistical model of plague risk with this observational survey, we were able to identify potential residence-based risk factors for plague associated with huts within historic case or control villages (e.g., distance to neighboring homestead and presence of pigs near the home) and huts within areas previously predicted as elevated risk or low risk (e.g., corn and other annual crops grown near the home, water storage in the home, and processed commercial foods stored in the home). The identified variables are consistent with current ecologic theories on plague transmission dynamics. This preliminary study serves as a foundation for future case control studies in the area.

Ecology and transmission of Buruli ulcer disease: a systematic review

Buruli ulcer is a neglected emerging disease that has recently been reported in some countries as the second most frequent mycobacterial disease in humans after tuberculosis. Cases have been reported from at least 32 countries in Africa (mainly west), Australia, Southeast Asia, China, Central and South America, and the Western Pacific. Large lesions often result in scarring, contractual deformities, amputations, and disabilities, and in Africa, most cases of the disease occur in children between the ages of 4-15 years. This environmental mycobacterium, Mycobacterium ulcerans, is found in communities associated with rivers, swamps, wetlands, and human-linked changes in the aquatic environment, particularly those created as a result of environmental disturbance such as deforestation, dam construction, and agriculture. Buruli ulcer disease is often referred to as the "mysterious disease" because the mode of transmission remains unclear, although several hypotheses have been proposed. The above review reveals that various routes of transmission may occur, varying amongst epidemiological setting and geographic region, and that there may be some role for living agents as reservoirs and as vectors of M. ulcerans, in particular aquatic insects, adult mosquitoes or other biting arthropods. We discuss traditional and non-traditional methods for indicting the roles of living agents as biologically significant reservoirs and/or vectors of pathogens, and suggest an intellectual framework for establishing criteria for transmission. The application of these criteria to the transmission of M. ulcerans presents a significant challenge.