EXPERIMENTAL TRANSMISSION OF POWASSAN VIRUS (FLAVIVIRIDAE) BY IXODES-SCAPULARIS TICKS (ACARI, IXODIDAE)

Transmission experiments were performed with Ixodes scapularis ticks f rom an uninfected laboratory colony. Immature and adult ticks were exp osed to Powassan (POW) viremic hamsters and rabbits, respectively. Ora l infection rates for engorged larvae, nymphs acid females fed on POW- infected hosts were 10%, 40%, acid 57%, respectively. Transstadial tra nsmission rates for nymphs exposed to POW virus as larvae, adults expo sed as larvae, and adults exposed as nymphs, were 9.5%, 10%, and 54%, respectively. Evidence of transovarial transmission occurred when two uninfected hamsters, exposed to F-2 larvae and nymphs originally expos ed to POW virus in the F-1 nymphal stage, seroconverted to POW virus w ith hemagglutination inhibition titers of 80 and 5,120, respectively; the transovarial transmission rate was 16.6%. All developmental stages were able to transmit virus orally to uninfected hosts regardless of when the ticks were originally exposed to the virus. These results sug gest that I. scapularis is a competent vector of POW virus under exper imental conditions.