Plague Foci Research Articles

Fleas as Vectors of Especially Dangerous Infections in Jermuk Region, 2010-2016

ObjectiveThe goal was to determine the impact of flea number variation on the epizootic situation in the Jermuk region.IntroductionThe Jermuk region of the Zangezur mezofocus is part of the transcaucasian highland focus of plague. This enzootic area is polyvectorial. The mezofocus has rich fauna with approximately eight species of fleas: Callopsylla caspia, Ctenophthalmus wladimiri, Frontopsylla elata, Amphipsylla rossica, Leptopsylla taschenbergi, Nosopsyllus consimilis, Palaeopsylla vartanovi, and Doratopsylla dampfi. Ct. wladimiri is the most abundant. However, special attention should be paid to C. caspia and N. consimilis as they are the only vectors specific for Yersinia pestis. In these fleas, the bacteria form a plug that blocks digestion and induces starvation. Afflicted fleas bite frenziedly in an effort to feed and the pressure that results releases bacteria from the plug, infecting a new host. Fleas infected with plague during an epizootic are a serious threat to humans, especially when in contact with synanthropic rodents. A survey was conducted to catalog fleas in the foci.MethodsFrom 2010-2016 different species of fleas were collected in Jermuk region of Vayots Dzor by combing the hair of captured rodents and processing their nests with heat and light. Flea species, and their egg-laying status, were identified by microscopic examination.ResultsFrom 2010-2015 the density of C. caspia averaged 23 per hectare. Fleas that were laying eggs were quantified via microscopy. In 2016 a drastic increase in C. caspia density was recorded; flea numbers averaged 225 per hectare. Half of these were actively reproducing (Table 1). These changes in flea numbers occurred with a stable rodent population of 60 per hectare.ConclusionsBecause of the drastic increase in flea density of 2016 compared to the period of 2010-2015, it is likely that diseases that depend on fleas to spread will increase in the near future in Jermuk. So, it is necessary to monitor the epizootic situation of Jermuk, as it is a popular resort in Armenia.

Mongolian Part of the Transboundary Sailugem Natural Plague Focus in 2017. Communication 1. Epizootic condition

Objective – estimation of current epizootic condition of Mongolian part of transboundary Sailugem natural plague focus. Materials and methods . Epizootiological survey was performed for the area of 2335 km 2 , 277 mammals and 516 ectoparasites were investigated for plague. Results and conclusions . Eight Yersinia pestis subsp. pestis strains were isolated, including 7 strains – from grey marmots (6 – from the remains of meals of predatory birds, 1 from a corpse) and 1 – from long-tailed souslik (corpse). Y. pestis DNA was detected in 52 objects. Serological samples showed 40 positive results. Epizootic manifestations, confirmed by isolation of Y. pestis cultures, detection of plague microbe DNA, and positive serological results, were observed across the area of 1611 km 2 covering 69 % of the inspected territory. Epizootic results indicated high infection rate of mass mammal species and first of all grey marmots. The data demonstrated that the extended plague epizooty caused by Y. pestis of the main subspecies occurred in the inspected territory in the carrier settlements. For the first time the circulation of Y. pestis subsp. pestis was registered in the Mongolian part of the transboundary Sailugem focus.

Epizootic Activity of Natural Plague Foci of the Russian Federation in 2008–2017 and Forecast for 2018

Epizootic Activity of Natural Plague Foci of the Russian Federation in 2008–2017 and Forecast for 2018

Ten years of surveillance of the Yulong plague focus in China and the molecular typing and source tracing of the isolates.

Plague, caused by Yersinia pestis, was classified as a reemerging infectious disease by the World Health Organization. The five human pneumonic plague cases in Yulong County in 2005 gave rise to the discovery of a Yulong plague focus in Yunnan province, China. Thereafter, continuous wild rodent plague (sylvatic plague) was identified as the main plague reservoir of this focus. In this study, the epizootics in Yulong focus were described, and three molecular typing methods, including the different region (DFR) analysis, clustered regularly interspaced short palindromic repeats (CRISPRs), and the multiple-locus variable number of tandem repeats (VNTR) analysis (MLVA) (14+12), were used for the molecular typing and source tracing of Y. pestis isolates in the Yulong plague focus. Simultaneously, several isolates from the vicinity of Yunnan were used as controls. The results showed that during the 10-year period from 2006 to 2016, an animal plague epidemic occurred in 6 of those years, and 5 villages underwent an animal plague epidemic within a 30-km2 area of the Yulong plague focus. Searching for dead mice was the most effective monitoring method in this plague focus. No positive sample has been found in 6937 captured live rodents thus far, suggesting that the virulence of strains in the Yulong plague focus is stronger and the survival time of mice is shorter after infection. Strains from Lijiang, Sichuan and Tibet were of the same complex based on a typing analysis of DFR and CRISPR. The genetic relationship of Y. pestis illustrated by MLVA “14+12” demonstrates that Tibet and Sichuan strains evolved from the strains 1.IN2 (Qinghai, 1970 and Tibet, 1976), and Lijiang strains are closer to Batang strains (Batang County in Sichuan province, 2011, Himalaya marmot plague foci) in terms of genetic or phylogenic relationships. In conclusion, we have a deeper understanding of this new plague focus throughout this study, which provides a basis for effective prevention and control.

EVALUATION OF HUMORAL AND CELLULAR IMMUNITY LEVEL AMONG PERSONS LIVING IN THE CASPIAN NATURAL SANDY FOCUS TERRITORY AFTER ANTI-PLAGUE REVACCINATION

In view of increasing epidemic danger potential of some natural plague foci and performing measures to provide specific prevention of this infection, it becomes necessary to carefully monitor the state of immunity in vaccinated (revaccinated) individuals. The aim of the study was to assess humoral and cellular immunity levels in the persons after repeated anti-plague revaccination performed for appropriate epidemiological indications. Evaluation of immune responses to anti-plague revaccination was carried out according to studies of blood samples from 20 people aged 24 to 53 years living in the Caspian sandy natural plague focus located at the territory in Kalmykia Republic. Specific antibody titers to the F1 antigen of plague microbe were assessed in blood serum by immunoassay testing using an “ELISA-AT-F1 YERSINIA PESTIS” test system (Russian Research Anti-Plague Institute “Microbe”, Russia), along with spontaneous and concanavalin A-induced production of different cytokines, i.e., IFNγ, TNFα, IL-4, IL-10 (Vector-Best, Russia), IL-17A (Bender Medsystems, Austria). The studies were performed before vaccination, and 1, 6, 12 month after the booster vaccination. The results of the study indicate that immunological reconstitution after revaccination with live plague vaccine occurs occurred mostly according to mixed Th1/Th2 type. Detection of antibodies to the F1 specific plague microbe antigen before and 1 month after revaccination (65 and 85%, respectively) was indicative of development of humoral response. The most informative cytokine markers (IFNγ and TNFα) for evaluation of an anti-plague cellular immune response have been identified. The threefold increase in IFNγ induced production before revaccination indicates to initial immunological competence of all the examined individuals. A high correlation between TNFα and other cytokine levels was determined. The fact of high correlation for the studied cytokines (TNFα, IFNγ, IL-10) indicated to a synchronism in the immunocompetent T helper cell reaction. By measuring the levels of spontaneous and induced cytokine production levels, one may indirectly judge on degree of anti-plague cell immunity in humans.

Ecologic Features of Plague Outbreak Areas, Democratic Republic of the Congo, 2004-2014.

During 2004–2014, the Democratic Republic of the Congo (DRC) declared 54% of plague cases worldwide. Using national data, we characterized the epidemiology of human plague in DRC for this period. All 4,630 suspected human plague cases and 349 deaths recorded in DRC came from Orientale Province. Pneumonic plague cases (8.8% of total) occurred during 2 major outbreaks in mining camps in the equatorial forest, and some limited outbreaks occurred in the Ituri highlands. Epidemics originated in 5 health zones clustered in Ituri, where sporadic bubonic cases were recorded throughout every year. Classification and regression tree characterized this cluster by the dominance of ecosystem 40 (mountain tropical climate). In conclusion, a small, stable, endemic focus of plague in the highlands of the Ituri tropical region persisted, acting as a source of outbreaks in DRC.

THE USE OF UNMANNED AERIAL VEHICLE TO IMPROVE THE EFFICIENCY OF NATURE PLAGUE FOCUS MONITORING

New technologies based on remote sensing, has been actively developing now for the increasing the effectiveness of nature plague foci monitoring. The unmanned aerial vehicle (UAV) «GeoScan–101» was used for monitoring and for orthophoto creating. The monitoring was carried out at Caspian nature plague focus on a stationary square 4 ha. The accounting of rodents’ holes had been implemented previously. Gerbils Meriones tamariscinus is the host of plague microbe in the Caspian natural plague focus. The monitoring using UAV allows identifying 78,26 % of Meriones tamariscinus holes as well as Microtus socialis and Ellobius talpinus. The comprehensive using remote sensing from space and data from drone (a high-resolution picture in real time) for elaboration data of remote sensing allows increasing the effectiveness of nature plague foci survey, where the hosts have the holes small diameter: the gerbils' genus Meriones and the voles’ genus Microtus.

Nine Whole-Genome Assemblies of Yersinia pestis subsp. microtus bv. Altaica Strains Isolated from the Altai Mountain Natural Plague Focus (No. 36) in Russia.

ABSTRACTWe report here the draft genome sequences of nine Yersinia pestis subsp. microtus bv. Altaica strains isolated from the Altai Mountain plague focus (no. 36), which represent the 0.PE4 phylogroup circulating in populations of Mongolian pika (Ochotona pallasi).

Phenotypic and Molecular Genetic Characteristics of Yersinia pestis at an Emerging Natural Plague Focus, Junggar Basin, China.

The 15th natural plague focus in China, the Junggar Basin plague focus, is located near an important communication route connecting China and Central Asia and was discovered after 2005. To characterize the phenotypic and genetic diversity of the Yersinia pestis population in this newly established focus, we collected 25 Y. pestis strains from six counties across Junggar Basin in 2005-2006, and determined their biochemical features and genotypes based on multiple-locus variable number of tandem repeats analysis and clustered regularly interspaced short palindromic repeats analysis. We inferred the phylogenetic positions and possible sources of the Junggar strains by comparing their genotypes with the genetic diversity for known representative Y. pestis strains. Our results indicate that the major genotype of Junggar strains belongs to 2.MED1, a lineage of biovar Medievalis with identical biochemical characters and high virulence in mice. Although share a similar ecology, the 2.MED1 in Junggar Basin are not descended from known strains in the neighboring Central Asian Desert plague foci. Therefore, the emergence of the Junggar Basin plague focus is not attributable to the recent clonal spread of Y. pestis from Central Asia. We also identified two distinct minor genotypes in Junggar Basin, one of which clusters genetically with the 0.ANT1 strains of the Tianshan Mountain natural plague focus and another belongs to a 1.IN lineage not previously reported. Our study clarifies the phenotypic and genetic characters of Junggar Y. pestis strains. These findings extend our knowledge of the population diversity of Y. pestis and will facilitate future plague surveillance and prevention in Junggar Basin and adjacent regions.

СОСТОЯНИЕ ЧИСЛЕННОСТИ ВТОРОСТЕПЕННЫХ НОСИТЕЛЕЙ В ПРИРОДНЫХ ОЧАГАХ ЧУМЫ СЕВЕРНОГО КАВКАЗА ЗА ПЕРИОД 2012 – 2017 гг.

СОСТОЯНИЕ ЧИСЛЕННОСТИ ВТОРОСТЕПЕННЫХ НОСИТЕЛЕЙ В ПРИРОДНЫХ ОЧАГАХ ЧУМЫ СЕВЕРНОГО КАВКАЗА ЗА ПЕРИОД 2012 – 2017 гг.

АНАЛИЗ СИСТЕМАТИЧЕСКОЙ ПРИНАДЛЕЖНОСТИ ПРОСТЕЙШИХ ИЗ ПОЧВ ГОРНО-АЛТАЙСКОГО ВЫСОКОГОРНОГО ОЧАГА ЧУМЫ

АНАЛИЗ СИСТЕМАТИЧЕСКОЙ ПРИНАДЛЕЖНОСТИ ПРОСТЕЙШИХ ИЗ ПОЧВ ГОРНО-АЛТАЙСКОГО ВЫСОКОГОРНОГО ОЧАГА ЧУМЫ

Эпидемическая активность современных антропоургических очагов чумы и факторы ее определяющие (на примере Вьетнама)

Эпидемическая активность современных антропоургических очагов чумы и факторы ее определяющие (на примере Вьетнама)

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.

Results of Epizootiological Survey of the Mongolian Part of Trans-Baikal Steppe Natural Plague Focus in 2017

Objective of the study is to obtain the data on the state of Severokerulensky plague focus in Mongolia, adjacent to the Trans-Baikal steppe focus in the south. A reconnaissance investigation on plague in the territory of Dornod aimak was carried out by efforts of the joint Russian-Mongolian group of specialists. Material samples were tested under extended scheme using bacteriological, biological, serological, and molecular-genetic methods. Negative test results on plague allow for reporting the absence of risks of intensive and extensive epizooty development and agent importation into the territory of Russia. Though it is necessary to continue the survey in the territory of Khentii aimak, where the presence of active plague foci is registered.

Study of Interactions of Microscopic Fungi Isolated from Burrow Microbiotopes of Great Gerbil and Little Souslik with Plague Agent and its Vectors

At present there is strong evidence of the long-term persistence of Yersinia pestis in soil during interepizootic period in nonculturable and L-forms of bacteria. This information helps to reveal the mechanisms of emergence, establishment and extinction of plague foci. Deciphering causes of transformation of plague microbe in rodent burrows is possible only under condition of detailed study of biocenotic relations of plague causative agent with each of the multiple biocenosis components, including microorganisms -permanent inhabitants of the burrow microbiotopes in natural plague foci. Purpose of the study: Study of interactions of microscopic fungi-micromycetes iso-lated from burrow microbiotopes of great gerbil and little souslik in the Ural-Emba interfluve and in Nogai steppe with plague agent and its vectors. Materials and methods: The effect of 74 micromycete species, isolated in natural plague foci, on Yersinia pestis virulent strains was studied in vitro and in vivo (in organisms of X. skrjabini fleas). In the experiments in vitro fungi metabolites were applied on the lawns of Y. pestis test-cultures with subsequent recording of the size of lysed zones. Fleas were challenged in tubes with filtering-paper strips impregnated by fungal cultural liquid and then LT100 value was calculated. In the experiments in vivo fungus conidia were applied on the surface of insect cuticle; flea challenging with plague was carried out on agonizing white mice infected by plague microbe. Insect challenge with plague and fungal conidia was alternated in different succession. Results and discussion: Of 74 micromycete strains 78.4% produced antagonistic effect in relation to 1-5 Y. pestis strains. Ashergillus versicolor, A. clavatus, A. sulfereus, Mucor racematus, Penicillium baarnensens, P. sp. relative to P. charlesii, P. sp. relative to P. martensii, P. insectus, P. chrysogenum fungi induced growth suppression of all five test strains of Y. pestis. High antibiotic activity of fungi metabolites was accompanied by insecticidal activity against Xenopsylla skrjabini fleas. Microscopic fungi P. funiculosum, P. cyclopium, P. chrisogenum, P. charlesii. P. canescens, A. versicolor induced 100% flea death on 4-6 day. As a result of insect pretreatment by conidia of P. funiculosum with subsequent challenging with plague microbe block formation in fleas decreased 14 times, and the number of Y. pestis cells after 12 days was 25-33 times less independent of succession, in which insects were challenged with microorganisms. Conclusion. It is supposed that micromycetes could play an important role in natural plague foci, adjusting epizootic activity of plague vectors and causative agent.

Specific Appurtenance, Numbers, and Dynamics of Interaction of Acanthamoeba from Soils of Gorno-Altai High-Mountain Plague Focus with Yersinia pestis Strains

Objective of the study is to analyze the appurtenance, numbers, and dynamics of interaction of acanthamoeba from soils of GornoAltai plague focus with Yersinia pestis 367 strain, isolated in 2016 in enzootic territory of this focus. Materials and methods. Utilized were soil amoeba from Gorno-Altai high-mountain focus and the strain Y. pestis 367 of the main subspecies of antique biovar, isolated there in 2016. Determination of systematic relation of the isolated amoeba was carried out using PCR with genus specific primers and sequencing of the obtained PCR fragments followed by identification of nucleotide sequences against GenBank database. Localization of Y. pestis cells in acanthamoeba was performed using fluorescent antibody technique by means of Axio Imager Z2 (Carl Zeiss, Germany). Results and conclusions. For the first time ever established has been the presence of Acanthamoeba castellanii in soils of burrows of Marmota altaica in the numbers of up to 300000 cells/gr in Gorno-Altai high-mountain focus. Investigated has been the dynamics of interaction of these microorganisms. Preservation of the agent in vacuoles of endoplasmatic reticulum within 14 days has been revealed. It is an indicative of the possibility of Y. pestis persistence in amoeba of Acanthamoeba subspecies in soil biocoenosis of Gorno-Altai high-mountain plague focus.

Outbreak of Pneumonic Plague in 2017 on Madagascar

The causes of emergence and development of pneumonic plague outbreak in 2017 on Madagascar were analyzed. Summarized were the literature data, characterizing the spatial and biocoenotic structure of natural plague focus on Madagascar, assessed were the risk factors of plague infection among rural and urban population of the island, as well as the properties of Yersinia pestis strains isolated there in the XX century. It is substantiated that the distinctive type of plague outbreaks on Madagascar is a rural one. It is demonstrated that one of the main causes of wide spread of plague in 2017 is importation of the infection from central regions of the Republic of Madagascar into big cities with further formation of multiple epidemic foci. Confirmed was the circulation of Y. pestis strains that belong to the third branch of irradiation of oriental biovar (1.ORI3). Discussed are the issues of diagnostics and treatment of plague in epidemic foci in the territory of the Republic of Madagascar. The evidence is provided to the fact that the plague outbreak in 2017 on Madagascar is the consequence of a lower surveillance level, first and foremost undervaluation of specific and non-specific prophylaxis capacities regarding this infection.

Application of GIS Technologies for Determination of Boundaries and Area of Epizootic Regions within Natural Plague Foci

Spatial indicators of epizooties in natural plague foci are used for justified planning and carrying out measures on epidemiological welfare provision for the population residing in enzootic territories. Plague affected regions are identified by real geographical coordinates of epizootic sites. Objective of the study is to develop numerical methods for determination of boundaries and area of epizootic regions according to the results of epizootiological monitoring. Materials and methods. Utilized are the digital maps of the natural plague foci, the data on epizootic points, and computer software. Results and conclusions. Buffer zones in the form of circumference of 5 km radius were established around each epizootic point with the help of computer application “ArcGIS 10.x” as a counterpart of circular extrapolation method. Resultant epizootic region over a certain season was generated by several overlapping circumferences. Evaluated were the area and extension of the region, as well as the presence of epidemiologically significant objects within its bonds. Actual positioning of the region, visualized on the focus map, is used for specified task assignment as regards carrying out of various preventive measures in this or that part of the area.

Evaluation of Effectiveness of Yersinia pestis Molecular Diagnostics in the Field Material from Sarydzhas Focus in Kyrgyzstan

Objective of the study is to assess the effectiveness of the methods for molecular diagnostics and identification of Yersinia pestis strains in the field material obtained from Sarydzhas high-mountain focus in Kyrgyz Republic. Materials and methods. Investigated were the samples of the field material, isolated in 2016 in Sarydzhas high-mountain plague focus, using conventional methods of laboratory diagnostics and PCR with hybridization-fluorescent and electrophoretic registration of results. Results and conclusions. It is demonstrated that in a number of cases molecular-genetic method has a higher resolution as compared to conventional methods of laboratory diagnostics of plague. It proves the necessity of wider usage of molecular-diagnostic methods in epizootiological monitoring of plague in natural foci in Kyrgyz Republic.

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

In Brazil, the plague is established in several foci located mainly in the northeastern part of the country, where it alternates between active and quiescent periods. These foci in the State of Ceará have high epidemiological importance. In addition to other plague detection activities, plague areas can be monitored through serological surveys of dogs and cats (domestic carnivores), which, following feeding on plague-infected rodents, can develop mild to severe forms of the disease and produce long-lasting antibodies. This study aimed to characterize the circulation dynamics and spatial distribution of Yersinia pestis antibodies in dogs and cats in plague foci areas of Ceará. An ecological study was conducted to analyze the temporal series and spatial distribution of secondary data obtained from domestic carnivore serum surveillance in Ceará's plague areas from 1990 to 2014. Joinpoint analysis revealed that the overall trend was a reduction in antibody-positive animals. The mean proportion of antibody-positivity during the whole study period was 1.5% (3,023/203,311) for dogs, and 0.7% (426/61,135) for cats, with more than 4% antibody-positivity in dogs in 1997 and 2002. Antibody titers ranging from 1/16 to 1/64 were frequent. Despite fluctuations and a significant reduction, in recent years, there were antibody-positive animals annually throughout the study period, and the localities containing antibody-positive animals increased in number. Yersinia pestis is actively circulating in the study areas, posing a danger to the human population.