[The effect of the physiological age of Dermacentor marginatus (Ixodidae) ticks on their infection with and the infiltration of the tick-borne encephalitis virus into the saliva].

The decisive effect of physiological age of ticks on the infection of their saliva was revealed by means of parenteral infection of D. marginatus females with tick-borne encephalitis virus. The virus was not found in the saliva of young individuals of instar II. Maximum number of cases of saliva infection was recorded in mature ticks of instar III (50%). It was established that the infection of saliva did not depend on the amount of virus in the tick's body. Less susceptibility to the virus of young individuals, associated probably with the way of infection, was noted. Under light microscopy there were observed no significant age differences in salivary glands of ticks of instars II and III. The infection of saliva of young individuals is, apparently, opposed by the barrier of fat body on the way of virus to salivary glands, depending on the age of ticks. The barrier is supposed to have an influence under natural transphase infection of ticks.