[Abundance levels of populations of the virus carriers and vectors in a focus of tick-borne encephalitis].

In 10 altitude-belt complexes of Dzhoysky ridge (West Sajans) during the summer period of 14-17 years the abundance of small mammals and imago of the taiga tick and the abundance of engorged larvae and nymphs of I. persulcatus was studied. The obtained results have shown that fluctuations in abundance of mammals and imago of ticks are not, as a rule, beyond the limits of a range of critical levels of abundance, which is defined as ee = 15.15. Fluctuations in the abundance of nymphs can cover two ranges and those of larvae up to three ranges. The amplitude of fluctuations in abundance of all groups of animals in question is minimum in optimal altitude-belt complexes and rises with an increasing effect of limiting factors. The decrease in the amplitude of fluctuations of nymphs as compared to larvae and that of imago as compared to nymphs can be, apparently, explained by a stabilizing effect of larval diapause on the abundance of nymphs and larval and nymphal diapause on the abundance of imago. Critical levels of abundance are assumed to be used as criteria of co-members stability in a parasitic system of the tick-borne encephalitis nidus and for classification of nidi with a regard for this character.