**The title, authors, and abstract for this completion
report are provided below. For a copy of
the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**
Development
of improved diagnostic methods for the herpesvirus
associated with epizootic
epitheliotropic disease (EED) in lake trout Salvelinus namaycush.
Ronald
P. Hedrick2, Tomofumi Kurobe2,
Susan Marcquenski3
2
Department of Medicine and Epidemiology, School
of Veterinary Medicine, University of California Davis, CA 95616
3
Wisconsin
Department of Natural Resources, Box 7921 Madison WI 53707
December 2009
Abstract
Epizootic epitheliotropic
disease virus (EEDV) has caused catastrophic losses among hatchery-reared
juvenile lake trout (Salvelinus namaycush) since the early 1980’s and remains as a
major impediment to lake trout restoration in the Great Lakes basin of the United
States. Although EEDV has been tentatively designated as a herpesvirus
based upon morphological criteria, further characterization of the virus and
development of improved detection methods has been hampered by the inability to
propagate the virus in cell culture. Recently obtained sequence data for a
region of the putative terminase gene from EEDV as well
as the related Salmonid herpesvirus
1 and 2 has permitted the development of a polymerase chain reaction (PCR)
assay for specific detection of EEDV. The new EEDV PCR demonstrated both an
excellent analytic sensitivity and specificity and detected viral DNA as
present in the skin of lake trout during periods of active viral outbreaks. In
addition, EEDV DNA was detected among healthy appearing juveniles and in the
ovarian fluids of spawning adults. A comparison of the new assay with electron
microscopy, the current “gold standard” method for virus detection,
demonstrated a greater analytical sensitivity for the PCR. An initial
assessment of virus prevalence among populations of lake trout indicates a potentially
broad geographic salmonid host range than previously
recognized. In this study we describe the development and initial validation
steps of the EEDV PCR as a replacement for current diagnostic methods which
require virus extraction from the skin, partial purification by isopycnic centrifugation and visualization of
negatively-stained virions by electron microscopy.