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.