Absence of vertical transmission of infectious salmon anemia virus (ISAV) from individually infected Atlantic salmon Salmo salar.

Atlantic salmon S a h o salar L. eggs were colversity of Bergen, pers. comm.). The only existing lected from grilse that were individually identified as ISAVreDort dealin= sDecificallv this issue is that of ~ h ~ 2 1 positive based on the detection of pathogen in ovarian fluid rui & Djupvik (1988), In' the latter study, the authors by RT-PCR. The eggs were fertilised, disinfected and reared under auarantine conditions. To address the ~ossibilitv of the injection of 45 g with vertical transmission, fertilised eggs, alevins and parr were homogenates prepared from eggs collected at a site screened for the virus by SHK-1 cell culture and RT-PCR. known to have been infected with ISAV. However, In addition, ISAV-negative parr were injected with homocontributing broodstock were not individually genates of potentially infected eyed eggs. ISAV was not detected in eyed eggs, alevins or parr. No mortalities screened for infection. No mortalities or evidence of occurred among fish injected with the egg homogenates. subclinical infection were reported, These observations suggest the absence of a vertical transSince the identification of the virus in Canada for the mission route for ISAV infection. first time in 1997 (Lovely et al. 1999), and in Scotland the following year (Rodger et al. 1998), there are