[The specific features of relations of the fleas Xenopsylla cheopis L. to the plague microbe of the Altai subspecies, its L-forms and revertant].

The rate and changes in the formation of bacterial lumps and blocks of the proventriculus in Xenopsylla cheopis fleas in their contamination with the plague microbe of the Altai subspecies, its L-form and revertant were studied to clarify the specific features of relations with the vector, including its transmission ability. The plague microbe of the Altai subspecies, which was exposed to L-transformation in the resistant organism of a warm-blooded host (a guinea pig), as well as L-form revertants obtained on nutrient media substantially lost their ability to get acclimatized in the vector and to form a proventricular block. The capacity to form lumps did not greatly differ in L- and original form of the microbe.

[Conservation of Yersinia pestis in winter by Citellophilus tesquorum altaicus females and males].

Intersexual differences have been established in Citellophilus tesquorum altaicus Ioff (1936) from a Tuva natural focus in the accumulation of Yersinia pestis in fleas in autumn and its conservation during winter. The ectoparasites were infected and fed on the natural feeder - long-tailed Siberian souslik (Citellus undulates). Small wild animals and insects were infected with the strain Yersinia pestis 1-3226 typical of the focus.

[Relationships of parasitic triad co-members in a Tuva natural plague focus: environmental and physiological aspects (experimental studies)].

Long-term experimental studies of the environmental and physiological aspects of relationships of parasitic triad co-members, performed in a Tuva natural plague, by using Citellophilus tesquorum altaicus fleas, their natural feeder--a long-tailed Siberian souslik (Citellus undulatus), and the Yersinia pestis strain I-3226 that is typical of the focus were analyzed. A complex of biotic (the environmental features of a causative agent, avector, and a carrier) and abiotic (air temperature and moisture, atmospheric pressure, and seasonal changes) factors that ensure the existence of the enzootic disease plague in this area has been shown to exert a considerable impact on the pattern of relationships of parasitic triad co-members.

[Seasonal features of the time course of changes in the aggregated state of the causative agent of plague in the organism of Citellophilus tesquorum altaicus (Siphonaptera)].

The data of experiments made in a Tuva natural plague focus with the main vector of the flea C. lesquorum altaicus during different seasons are analyzed. Ectoparasites were infected with the plague microbial strain typical for the focus and fed on natural nourishment, such as long-tailed sousliks.

[Results of the bacteriological work of the specialized epidemic brigade of the Stavropol Research Institute for Plaque Control].

The experience of use of efforts and resources by the bacteriological section of the specialized antiepidemic brigade of the Stavropol Research Institute for Plague Control in the Chechen Republic during the period of 1999-2000 under the conditions of the emergency situation, formed as the consequence of carrying out the antiterrorist operation, is summarized. The work load falling of the bacteriological section in different shifts, the structure of bacteriological investigations, as well as some problems arising in the process of work, were analyzed. The experience showed the necessity of the complete accommodation of the bacteriological laboratory in specialized motor-vehicle modules having all necessary equipment for investigation works, disinfection, sterilization.

[The survival of the causative agent of plaque in the long-tailed suslik from a Tuva natural focus in wintertime].

The survival of the causative agent of plague in the long-tailed souslik in the Tuva natural focus in winter was experimentally studied. They were made in a special bunker laboratory just in the focus. The experimental conditions were close to the hygrothermal parameters of a long-tailed souslik's burrow.

[An experimental study of the possibility for the preservation of the causative agent of plague in the nest substrate of the long-tailed suslik].

How long Yersinia pestis can preserve in the nest substrate of Spermophililus undulatus and whether it can infect the animals contacting with the substrate infected with flea feces and carcasses were studied in a Tuva natural focus. The infected material was kept in special niches of a bunkering laboratory, which imitated a souslik nest. Biological, serological, and bacteriological studies were conducted after different storage periods.

[The duration of the persistence of the plaque microbe in the body of the flea Citellophilus tesquorum altaicus].

Experiments have established that the plague bacillus persists long in the flea C. tesquorum altaicus in the Tuva natural foci. Experimentally, 64.

[The variability of Yersinia pestis in the body of the flea].

Changes in the morphology and ultrastructure of Y.pestis cells at different periods of their stay in the body of fleas (Citellophilus tesquorum altaicus) have been studied. The study, carried out by means of optical and electron microscopy, as well as with the use of a culture medium for the isolation of L-forms, has revealed that in the body of fleas Y.

[Radioimmunological analysis in studying the persistence of the plague antigen in the body of rodents and ectoparasites in natural foci in Siberia].

To study the persistence of Y. pestis capsular antigen, or fraction 1 (F1), in the body of less important plague carriers in the Mountain Altai and Transbaikal natural foci, as well as in experimentally infected ticks, the liquid-phase competitive radioimmunoassay (RIA) was used for the first time. In this study RIA showed, due to its sensitivity, doubtless advantages over traditional methods, such as the passive hemagglutination (PHA) test and the antibody neutralization (AN) test, and made it possible to detect F1 in picogram amounts.

[The seasonal dynamics of blocking in the flea Citellophorus tesquorum altaicus from the Tuva natural plague focus].

Seasonal changes in the frequency of block formation have been established in C. tesquorum altaicus from the Tuva natural plague [correction of plaque] focus. Distinctions have been observed in the blocking of fleas born in different calendar years.

[Histological study of Xenopsylla cheopis fleas infected with the ulegeic subspecies of the plague microbe, Yersinia pestis ulegeica].

The plague microbe of the Ulegei subspecies is able to cause the stable infection of fleas of X. cheopis, which is accompanied by the formation of "block" in most individuals. The preservation of the plague agent in these ectoparasites is characterized by its variation in the number that undergoes cyclic changes depending on the feeding rate and digestion.

[Paradoxopsyllus scorodumovi (Aphaniptera) flea, an effective vector of plague in a Gorno-Altai natural focus].

A study was conducted on the fleas of P. scorodumovi and five local strains of the plague microbe, one of which is typical of the strains of the Altai subspecies and four are non-typical of this nidus. The fleas of this species are capable to transmit not only the plague agent of the strains typical of this nidus but also non-typical ones which differ in some biological properties and are avirulent for most carriers but Pallas's pika.

[Epizootiological importance of Frontopsylla hetera (Siphonaptera) fleas in the Gorno-Altai natural plague focus].

Experiments conducted during all seasons have established that F. hetera, one of the mass species of fleas in Mountain Altai, can be infected both by the strain of selective virulence typical to this nidus and by the non-typical non-virulent mountain-altai strain of plague agent. The non-virulent strain does not form in fleas the block of proventriculus and within 1.

[Flea Ceratophyllus fasciatus as the vector of the Altai-mountain strain of plague microbe].

The work was conducted with a typical strain of the plague agent, which is virulent to white mice and little virulent to guinea pigs (subcutaneous infection), and with C. fasciatus. The fleas of this species can be infected, form the block of proventriculus within 4 to 35 days, transmit the agent during bloodsucking to healthy animals and cause the death both white mice and guinea pigs.