[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. At the same time, the ratio of the formed blocks and lumps was much lower, which points to the instability of the formed masses. This is supported by the detection of specimens with partial blocks only among the fleas infected with L-forms. The reversed bacterial form was exceeded in the rate of formation of lumps by the original and L-forms. This may be associated with the reversion of L-forms on the nutrient medium rather than in the vector. At the same time, the revertant formed stable blocks in shorter periods than did L-forms and caused a generalization of the infection in plague-infected mice, which may be important for further transmission 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. In winter fleas survived without the feeder under artificially created conditions of an uninhabited nest for long-tailed souslik. After each feeding, the ectoparasites were microscopically examined, by taking into account the individuals with aggregated agent - bacterial lumps, complete or partial blocks of the proventriculus. The experimental data showed with a high degree of significance that the females had survived the cold season better. Both before and after hibernation of the insects, the plaque agent in the aggregated state was also more frequently recorded in the females than in the males though the proportion of fleas with conglomerates significantly decreased in either sex during that time. If the best female survival and a higher proportion of females with Yersinia pestis are borne in mind, it should be recognized their greater role than that of males in conserving the plague agent during winter.

[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)]. / Sezonnye osobennosti dinamiki agregirovannogo sostoianiia vozbuditelia chumy v organizme 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. An analysis indicated that estimation of the parameter "the proportion of infected insects containing the causative agent at the aggregated state" is of greater informative value than is the recording of only sporadic gizzard "blocks". In experiments on fleas of a breeding of the current year, the conglomerates of the causative agent of plague were more frequently observed in males. All things being equal, the greatest efficiency of transmission of the microbe to the carriers of infection and the highest block formation in the fleas were observed in summer. The proportion of specimens with microbial conglomerates drastically increased in autumn during the preparation of the body of imagoes for hibernation. At this state, the microbe survived in the organism of a dormant carrier during winter. In spring, in the imagoes infected during the previous season, bacterial conglomerates were observed during the first feeds ten times more frequently than those in the insects of a breeding and infection of the current year.

[Relationships of parasitic triad co-members in a Tuva natural plague focus: environmental and physiological aspects (experimental studies)]. / Ekologo-fiziologicheskie aspekty vzaimootnoshenii sochlenov parazitarnoi triady v tuvinskom prirodnom ochage chumy (po éksperimental'nym issledovaniiam).

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.

[Results of the bacteriological work of the specialized epidemic brigade of the Stavropol Research Institute for Plaque Control]. / Osnovnye itogi bakteriologicheskoi raboty spetsializirovannoi protivoépidemicheskoi brigady Stavropol'skogo Nauchno-Issledovatel'skogo Protivochumnogo Instituta.

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 brigade sent to its mission should be given concrete tasks with a view to ensure the adequate supply of the bacteriological section with diagnostic preparations, materials and equipment.

[The survival of the causative agent of plaque in the long-tailed suslik from a Tuva natural focus in wintertime]. / O sokhranenii vobuditelia chumy u dlinnokhvostogo suslika iz Tuvinskogo prirodnogo ochaga v zimnii period.

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. Inoculation and placement of the animals and fleas into the bunker were accomplished in the September to early October. The rodents and ectoparasites were examined after their hibernation in the late April to early May of the following year. The duration of the experiment was 7.5 months. It has been found that the long-tailed souslik can be infected with the causative agent of plague before hibernation through transmission. There were no cases of plague microbial infection through the bite of fleas in sousliks following hibernation. Low infection rates of the fleas hibernating with their host were notified. The causative agent was found to survive in the mummified carcasses of sousliks for 7.5 months (the follow-up period).

[An experimental study of the possibility for the preservation of the causative agent of plague in the nest substrate of the long-tailed suslik]. / Eksperimental'noe izuchenie vozmozhnosti sokhraneniia vozbuditelia chumy v substrate gnezda dlinnokhvostogo suslika.

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 experiment used 25 sousliks, 56 albino mice, and 3256 fleas. Two hundred and ninety flea carcasses were individually explored. Y.pestis was ascertained to survive in the nest substrate infected with flea feces and carcasses. The pathogen may be preserved as a mutant in the flea carcasses, as evidenced by the isolation of 6 Y. pestis cultures from flea carcasses as a L-form. There is evidence for the fact that healthy animals may be infected on their contact with the contaminated substrate.

[The duration of the persistence of the plaque microbe in the body of the flea Citellophilus tesquorum altaicus]. / Dlitel'nost' sokhraneniia chumnogo mikroba v organizme blokhi Citellophilus tesquorum altaicus.

Experiments have established that the plague bacillus persists long in the flea C. tesquorum altaicus in the Tuva natural foci. Experimentally, 64.2 to 77.3% of the fleas inoculated in autumn survived winter. More than one-half preserved the plague bacillus. From 0.7 to 19.4% of the inoculated fleas survived from one summer to another. The plague persisted in 30% of the insects. Individual C. tesquorum altaicus females survived two winters, preserving the bacillus for 21.5-22.0 months. The fact that the fleas has survived both one and two winter periods in coma transmitted the plague bacillus to healthy sousliks has been recorded. Rather late periods (278-411 days) of blocking the fleas after the insects' inoculating feeding have been defined.

[The variability of Yersinia pestis in the body of the flea]. / Izmenchivost' Yersinia pestis v organizme blokhi.

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.pestis cells undergo the effect of processes leading to their L-transformation. As the result of L-transformation, the infective agent may take altered forms, including L-like variants. Such forms are retained in hungry insects and are capable of prolonged survival in the body of the carrier.

[Radioimmunological analysis in studying the persistence of the plague antigen in the body of rodents and ectoparasites in natural foci in Siberia]. / Radioimmunologicheskii analiz pri izuchenii persistentsii chumnogo antigena v organizme gryzunov i u éktoparazitov prirodnykh ochagov Sibiri.

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. RIA revealed that F1 persisted in Siberian long-tailed gophers for up 14 months after the infection of the animals in diffusion chambers and for 7 months after their infection by subcutaneous injection. Experiments on Daurian pikas confirmed that, in comparison with the PHA and AN tests, RIA ensured fourfold effectiveness in the detection of antigen F1. The study of infected mites revealed that antigen F1 could be retained in them for more than a year and detected by RIA techniques in 10% of cases. The data obtained in this investigation indicate that the persistence of microorganisms should be studied mainly with the use of new-generation tests, and RIA, being one of the most sensitive techniques, deserves wide approval and introduction into the practical work of institutions intended for plague control.

[The seasonal dynamics of blocking in the flea Citellophorus tesquorum altaicus from the Tuva natural plague focus]. / Sezonnaia dinamika blokoobrazovaniia u blokhi Citellophorus tesquorum altaicus iz Tuvinskogo prirodnogo ochaga chumy.

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. "Young" fleas born the current year block more frequently than old ones born the previous year.

[Histological study of Xenopsylla cheopis fleas infected with the ulegeic subspecies of the plague microbe, Yersinia pestis ulegeica]. / Gistologicheskoe issledovanie blokh Xenopsylla cheopis, zarazhennykh chumnymi mikrobami uglégeiskogo podvida Yersinia pestis uglegeica.

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. The bloodsucking is accompanied by the excretion of some microbes and by the reproduction of the remaining ones in the midgut and proventriculus which lasts the whole 1 st stage while dense clots of erythrocytes are preserved in the intestine. In the course of blood digestion the reproduction of microbes is replaced by their dying off and when the digestion is over the quantity of microbes increases again. In this period small cocci, which form dense clots in the midgut and proventriculus, are the dominant form of microbes.

[Paradoxopsyllus scorodumovi (Aphaniptera) flea, an effective vector of plague in a Gorno-Altai natural focus]. / Blokha Paradoxopsyllus scorodumovi (Aphaniptera)--éffektivnyi perenoschik chumy v Gorno-Altaiskom prirodnom ochage.

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. Biological peculiarities of fleas of P. scorodumovi in addition to their high efficiency as vectors of the plague microbe enable us to associate the more active autumn epizooty with fleas of this species.

[Epizootiological importance of Frontopsylla hetera (Siphonaptera) fleas in the Gorno-Altai natural plague focus]. / Epizootologicheskoe znachenie blokh Frontopsylla hetera v Gorno-Altaiskom prirodnom ochage chumy (Siphonaptera).

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 1.5-2 months they become free from the microbe. At the infection with the typical strain of the altai subspecies rare transmissions of the agent to Pallas' pika can take place as well as its long preservation in fleas.

[Flea Ceratophyllus fasciatus as the vector of the Altai-mountain strain of plague microbe]. / Blokha Ceratophyllus fasciatus kak perenosnik gornoaltaiskogo shtamma chumnogo mikroba.

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.