Results of using the serological method of epidemiological investigation of plague foci in the Muyunkum and Eastern Kyzylkum deserts in 1978-1982

Results of serological examination of 81,853 mammals from the Muyunkum and 26,303 from the Eastern Kyzylkum deserts were compared with results of a corresponding bacteriological examination for plague. In both foci and in all phases throughout the epizootic of plague, the serological method made it possible to detect infected animals 6-10 times more frequently in comparison with the bacteriological method. The big meriones mice, i.e., the basic carriers of plague in natural foci, were found to be infected considerably more (in percentage) frequently than the meridian meriones. Differences in the reactivity of meriones to the invasion of plague microbe were observed in both foci (the indices of titres in the antigen neutralization reaction were considerably higher in the Eastern Kyzylkums). The serological method of investigation is highly informative in evaluating both the present state of epizootic activity of a plague focus and its activity in the past.     

Results of a trial of a plague monoclonal antibody erythrocyte diagnostic agent

Plague antibody monoclonal erythrocyte diagnosticum was studied in serological tests simultaneously with commercial plague antibody erythrocyte diagnosticum prepared on the basis of hyperimmune horse serum and with commercial plague antigenic erythrocyte diagnosticum. In this investigation the suspensions of numerous strains of Yersinia pestis, other closely related and heterologous organisms, experimentally infected wild and laboratory animals, as well as samples of materials obtained from small rodents caught in several natural foci of plague, were studied. The monoclonal diagnosticum was, practically, not inferior to the similar commercial preparation with respect to the frequency of positive results and the activity of the materials under study in serological tests, but showed greater specificity, as it reacted strictly with Y. pestis capsular antigen.     

Complex method for epizootiological and epidemiological surveillance

A complex method for the epizootological and epidemiological surveillance of a number of bacterial and viral infections on the territories inside and outside their natural foci has been developed. The investigation techniques are described and the data on the isolation rate of each causative agent in different geographical zones are presented. In the natural foci of plague and tularemia, as well as on the territories outside such foci, the causative agents of intestinal yersiniosis, pseudotuberculosis, salmonellosis, erysipeloid, staphylococci and streptococci, arena- and arboviruses have been isolated from the rodents and ectoparasites under study. The results of this investigation suggest that the method may be recommended for use in medical institutions dealing with the problems of infections originating from natural foci.     

Exploration of natural foci of tularemia and plague in Armenia using the serological examination of bird droppings and excrements of predatory mammals]

Forty strains of tularemia and 619 of plague microbes were isolated in 1974 in bacteriological examination of natural plague and tularemia foci from a great number of small mammals and their ectoparasites. At the same time in serological examination (in the antibody neutralization test) of bird pellets, 52 mummified cadavers, and 34 excretion samples of mammalian beasts of prey collected in Armenia (its central and North-Western part) in 1973 the antigen of tularemia microbe was revealed in 73, 8, and 3, and of plagye--in 42, 5, and 1 cases, respectively. In one of the sites examined the number of positive findings failed to exceed 10--17%, this indicating a low intensity of the epizootic in the majority of the places. Judging by the mean titres of the serological test, which varied from 1:12 to 1:1428 in examination for tularemia and from 1:12 to 1428 in examination for plague, it was possible to detect both epizootics coursing during the examination, and those which occurred several monts ago. Tularemia and plague foci were not infrequently present at the same territories, and these diseases could involve the same individual animals of Microtus arvalis (Pall.). The data obtained pointed to the greater effectiveness of examination of bird's pellets and excretions of mammalian beasts of prey for the reconnaisance investigation of the natural foci of plague and tularemia in comparison with the bacteriological methods applied usually.     

Isepamycin in prophylaxis and treatment of experimental plague due to FI+ and FI- variants of plague microbe]

The efficacy of isepamycin vs. other aminoglycosides was studied in vitro and on albino mice with experimental plague due to natural antigen valuable strains of the plague microbe and the pathogen variants deprived of the ability to produce the capsular antigen fraction I (FI- phenotype). The MICs of isepamycin for the strains of the plague microbe (20 FI+ and 20FI-) were 1.0-4.0 mg\l, that did not differ from those of streptomycin, kanamycin, amikacin and tobramycin. The ED50 of isepamycin in the prophylaxis and treatment of the experimental plague of the mice had no statistically significant differences from the ED50 of the other aminoglycosides. The efficacy index of isepamycin was > 10(4), that did not differ from that of streptomycin, amikacin and gentamicin, irrespective of the strain phenotype (Y. pestis 231 FI+ or Y. pestis 231 FI-). The same as the other aminoglycosides, isepamycin in doses equivalent to the human average daily doses, protected 80-100% of the albino mice from death when used in the prophylaxis and therapy of plague irrespective of the strain phenotype. The results of the study made it possible to consider isepamycin as an agent promising for the prophylaxis and treatment of plague.     

Bacteriologic and serologic studies of an outbreak of plague in the State of Paraíba, Brazil

During a plaque outbreak in the Borborema Plateau focus (Paraiba), bacteriological and serological studies were carried out in material from 452 patients (48 positives), 1,938 rodents and other small mammals (75 positives), 4,756 dogs (141 positives) and 2,047 cats (57 positives) obtained from 41 counties (out of which, 21 produced positive samples). Twenty Yersinia pestis strains isolated from material from 3 patients and 17 rodents, displayed biochemical reactions, virulence factors, antibiotic susceptibility and animal experimental pathogenicity similar to those observed in strains previously isolated. According to our findings this recent plague outbreak did not exhibit different factors from those observed during prior outbreaks in other plague foci in the northeast of Brazil.     

The epidemiological patterns of pseudotuberculosis in Khabarovsk Territory]

Materials on the epidemiological characterization of pseudotuberculosis at the Khabarovsk Territory taken as a whole and in individual settlements, as well as on the evaluation of epizootic situation in natural foci of infection and foci created by human activities, are presented. The results of laboratory studies of vegetables, washings from environmental objects, soil specimens, material taken from rodents are demonstrated and the characterization of the virulent properties of isolated Yersinia pseudotuberculosis strains is given. Two periods (1976-1982 and 1983-1989) were distinguished by their main epidemiological features. The most important feature of the second period is the shift of the seasonal morbidity rise to the middle of summer, which is explained by activation of the mechanism of transmission of this infection due to the supply of early vegetables infected in local vegetable stores. An essential role of wild and synanthropic Muridae as the reservoir of infection is shown; these rodents and the soil maintain the circulation of the infective agent accumulating in the most favorable habitat, vegetable stores. The regularities established in this work contribute to the improvement of epidemiological surveillance.     

Biocenosis of the natural foci of sapronotic infections (the results of 15-year observations)

The summarized results of original studies, carried out in 1988-2003 by scientists of the Gamaleya Research Institute of Epidemiology and Microbiology, are discussed. The part dealing with the regularity and mechanisms of the circulation of pathogenic bacteria in the biocenosis of soil and water reservoirs includes the following subjects: population and intracellular interactions with protozoa; the evaluation of different representatives of hydrobios as hosts and the transmission along trophic biocenotic chains; the effect of algae and their metabolic products on bacterial populations; the possibility of the colonization of higher plants from the soil and the subsequent infection of rodents; the variability and clonal structure of bacterial population in its interaction with protozoa and plants; the chain of Yersinia circulation in agrocenosis. The part dealing with the mechanisms of the prolonged reservation of causative agents includes such subjects as the reversible transition of bacteria into the latent (uncultivable) state in soils and water reservoirs, as well as the biological inductors of this process; the prolonged preservation of latent bacteria in the cysts of protozoa and blue-green algae; the indication of causative agents in the natural foci of plague and pseudotuberculosis. On the basis of the original investigations and the data of literature new theoretical review in the field of the natural foci and the epidemiology of sapronotic infections have been formulated.     

Evaluation of the results of animal studies with a scheme of serologic reactions according to a table of standards]

The authors suggest a method of processing of the data of examination of the animals in the system of serological reactions for the purpose of diagnosis of epizootic situations in the natural plague foci. Positive results are recorded in a table in the form of a grid whose cells correspond to all possible variants of the two reaction titres. The table is divided into 6 sections into which the results differing by the correlation and the absolute reaction titres (the standard grid) are placed. The frequency of reactions is determined by the grid sections in the regions in which the character of the epizootic development in nature was studied by bacteriological examination of the animals. The diagnostic scale is drawn by the results of such standard observations. The trial of the suggested method was carried out in the regions of plague epizootics among the Rhombomys optimus Licht. in the Lowland Kara-Kum; it was possible to differentiate the signs of epizootic situations there in greater detail than by the methods suggested earlier.     

准噶尔盆地荒漠景观不同地貌类型鼠、蚤多样性及分布特征

为揭示鼠、蚤空间分布特征与变化规律,本研究以准噶尔盆地鼠疫自然疫源地为靶区,基于鼠类和蚤类的样点采集数据,计算不同地貌的鼠、蚤生态学指标并分析其相关性。基于不同行政区生态学指标计算结果,借助Moran′s I指数、重心模型、标准差椭圆等分析方法探究不同行政区鼠、蚤生态学指标的聚类特征,开展鼠、蚤的空间分布特征及变化规律的相关研究。结果表明：(1)通过对不同地貌鼠、蚤生态指标的研究,可得出鼠、蚤的物种多样性和生态优势度呈负相关,表明在物种多样性较高的群落中,鼠、蚤生态优势度表现不明显。鼠类物种多样性较高的地貌类型与蚤类物种多样性呈正相关,证实鼠类(宿主)物种数量增加,蚤类(寄生)物种的数量也在增加。低海拔地区鼠、蚤群落的相似性总体上大于中海拔地区群落相似性,且相似性系数q值与Cody指数呈相反变化趋势;(2)不同鼠、蚤指标单变量Moran′s I指数表明,鼠类数量、子午沙鼠数量、蚤类均匀度的全局Moran′s I指数大于0,且P值小于0.05,表现出空间集聚现象。单变量局部空间自相关分析结果表明,部分鼠、蚤指标存在多种聚类模式,其中最为典型的聚类模式是高—高聚类模式。不同鼠、蚤指标双变量...     

Inhibitor production, a stable feature of plague pathogen

Application of the methods developed by the author to the plague causative agent isolated in six natural plague foci provided detection of its ability to synthesize a factor inhibiting the growth of the producing strain and cultures isolated from the same focus. In the strains isolated from these foci the inhibitor presence was stable on the agar consisting of fermentative casein hydrolysate and 0.6 per cent of lithium chloride when the indicator strains were incubated under definite temperature conditions. The results of the present study and previous studies of the author, as well as the literature data suggested that the ability to synthesize the inhibitor is a stable feature of the plague causative agent.     

Cyclic kinetics and mathematical expression of the primary immune response to soluble antigen

The kinetics and the distribution of antigen and antibody were shown to be similar in four species of experimental animals and in two species of wild rodents immunized with the protein-polysaccharide capsular plague antigen. Serologically active antigen and antibody were detected in homologous conjugating serological tests. Soluble antigen persists at the injection site for as long as a week and adsorbed antigen for two weeks or more. Antigen persists in the blood of animals for 2–4 days. In regional popliteal lymph nodes, antigen was detected for the first days, followed by antibody in both lymph node and blood. Plasma cell response was more intensive in animals inoculated with adsorbed antigen. The gradual decrease of antigen at the injection site shows superimposed up-and-down changes, mostly parallel with the antibody in the popliteal lymph node and blood, as well as with plasma cell response in the regional lymph node. Serological cycles were related to the resistance of immunized white mice to plague infection. Cyclic kinetics of specific polysaccharide in the faeces of dysentery patients was found.     

云南省剑川县鼠疫自然疫源地宿主媒介情况分析

了解鼠疫自然疫源地的宿主、媒介群落结构及其种群动态,为提出针对性的鼠疫防控策略与机制提供依据.云南省剑川县属于齐氏姬鼠和大绒鼠鼠疫自然疫源地的核心区,该区域小型兽类种类丰富,存在2种类型鼠疫菌,为进一步研究疫源地的演变提供了重要的现场模型.本文对剑川县1976-2019年鼠疫监测资料进行整理和分析,发现该疫源地室内共捕...     

Yersinia pestis strains isolated in natural plague foci of Caucasus and Transcaucasia in the context of the global evolution of species

BackgroundPlague is a highly dangerous vector-borne infectious disease that has left a significant mark on history of humankind. There are 13 natural plague foci in the Caucasus, located on the territory of the Russian Federation, Azerbaijan, Armenia and Georgia. We performed whole-genome sequencing of Y. pestis strains, isolated in the natural foci of the Caucasus and Transcaucasia. Using the data of whole-genome SNP analysis and Bayesian phylogeny methods, we carried out an evolutionary-phylogeographic analysis of modern population of the plague pathogen in order to determine the phylogenetic relationships of Y. pestis strains from the Caucasus with the strains from other countries.ResultsWe used 345 Y. pestis genomes to construct a global evolutionary phylogenetic reconstruction of species based on whole-genome SNP analysis. The genomes of 16 isolates were sequenced in this study, the remaining 329 genomes were obtained from the GenBank database. Analysis of the core genome revealed 3315 SNPs that allow differentiation of strains. The evolutionary phylogeographic analysis showed that the studied Y. pestis strains belong to the genetic lineages 0.PE2, 2.MED0, and 2.MED1. It was shown that the Y. pestis strains isolated on the territory of the East Caucasian high-mountain, the Transcaucasian high-mountain and the Priaraksinsky low-mountain plague foci belong to the most ancient of all existing genetic lineages - 0.PE2.ConclusionsOn the basis of the whole-genome SNP analysis of 345 Y. pestis strains, we describe the modern population structure of the plague pathogen and specify the place of the strains isolated in the natural foci of the Caucasus and Transcaucasia in the structure of the global population of Y. pestis. As a result of the retrospective evolutionary-phylogeographic analysis of the current population of the pathogen, we determined the probable time frame of the divergence of the genetic lineages of Y. pestis, as well as suggested the possible paths of the historical spread of the plague pathogen.     

Anthropurgic foci of pseudotuberculosis and the mechanisms of their formation in groups of servicemen

At the period of 1982 - 2003, morbidity rate in pseudotuberculosis and the Yersinia pseudotuberculosis culture rates in groups of servicemen (from different abiotic objects, from humans and small rodents) in different geographic zones were studied. The cases of the isolation of Y. pseudotuberculosis were most frequently registered in groups of servicemen in the Far East and the Kola Peninsula. In these regions the highest morbidity rate in pseudotuberculosis was registered among servicemen. The contamination rate of vegetables during the year was always greater than in other objects under study, including small rodents. The study demonstrated that in the Armed Forces could appear, temporary and relatively constant anthropurgic foci of pseudotuberculosis even in non endemic regions. They were formed in the objects of the food supply service due to the supply of contaminated vegetables. Synanthropic rodents played a secondary role, though they too facilitated the formation of new anthropurgic foci. Under definite conditions anthropurgic foci could exist autonomously, independently of natural foci.     

The epidemiologic classification of plague morbidity

On the basis of the analysis of plague morbidity in the world in the XX century all epidemic foci are subdivided into 3 groups: primary, indirect primary and secondary. Each group is characterized by its specific type of morbidity in accordance with infective factors: factors connected with the natural foci of infection in group 1, economic and synanthropic factors, as well as laboratory infections, in group 2 and anthroponotic factors in group 3. In its turn, each type of morbidity differs in routes, sources, mechanisms and clinical forms of infection. In accordance with the conditions of infection, the natural foci of plague can be subdivided into mono-, oligo- and multifactor foci. The typing of plague morbidity facilitates more target-oriented organization of antiplague measures.     

Lysogeny by phages specific to Yersinia pestis in bacteria of the microbiocenoses of wild plague-carrying rodents

For the first time lysogenic bacteria of the genus Escherichia, spontaneously producing bacteriophages specific to the infective agent of plague, have been detected in the microbiocenoses of midday gerbils, plague carrier in the Volga-Urals natural focus. The morphological, cultural and biochemical properties of 22 lysogenic Escherichia strains isolated from wild rodents, as well as the spectra of the lytic activity of temperate bacteriophages produced by the above-mentioned microorganisms have been studied. Proceeding from the findings obtained in this research, all the strains have been divided into 3 lysotypes.     

Identification of Yersinia pestis as the causative organism of plague in India as determined by 16S rDNA sequencing and RAPD-based genomic fingerprinting

Eighteen isolates of bacteria obtained from the sputum of pneumonic plague patients and from the liver and spleen of rodents from the plague-affected areas of India during 1994-1995 when analyzed by 16S rDNA analysis clearly demonstrated that all 18 isolates exhibit an average similarity of 98.5% with the genus Yersinia and 99.1% with Yersinia pestis, thus identifying the isolates as Y. pestis. The isolates from the human plague patients were found to be genetically more homogeneous compared to the isolates from the rodents which were more heterogeneous. An epidemiological linkage among the rodents and human patients is also indicated by 16S rDNA analysis, which suggests that only a sub-population of the rodents was probably the source of the infectious pathogen to the humans initiating the outbreak of the epidemic. The results of the randomly amplified DNA polymorphisms (RAPD)-based DNA fingerprinting are in agreement with the above conclusions.     

Ecological Aspects of Evolution of the Plague Microbe Yersinia pestis and the Genesis of Natural Foci

A new hypothesis of the origin of the plague microbe in the Mongolian bobak (Marmota sibirica Radde, 1862) populations in Central Asia during the Pleistocene is based on the ideas of its relative phylogenetic recency. The Late Pleistocene cooling, which induced a deep freezing of the grounds in southern Siberia, Mongolia, and Manchuria, is considered as an inducer of speciation. The main ecological factors of the plague microbe evolution include the species specific behavior of the Mongolian bobak as it prepared to hibernate related to its occurrence in arid petrophytic landscapes and the larval parasitism of the flea Oropsylla silantiewi Wagn., 1898 in winter. Genesis of the plague foci is divided into two periods: natural-historical and biosocial. During the first period, the primary natural foci in Eurasia were formed and, during the second period, synanthropic (rat) and secondary natural foci appeared with the participation of humans in Africa, The New World, and on some tropical islands.