[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.