Molecular identification of erythrocytic necrosis virus (ENV) from the blood of Pacific herring (Clupea pallasii)

Veterinary Microbiology
By: , and 

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Abstract

Viral erythrocytic necrosis (VEN) is a condition affecting the red blood cells of more than 20 species of marine and anadromous fishes in the North Atlantic and North Pacific Oceans. Among populations of Pacific herring (Clupea pallasii) on the west coast of North America the disease causes anemia and elevated mortality in periodic epizootics. Presently, VEN is diagnosed by observation of typical cytoplasmic inclusion bodies in stained blood smears from infected fish. The causative agent, erythrocytic necrosis virus (ENV), is unculturable and a presumed iridovirus by electron microscopy. In vivo amplification of the virus in pathogen-free laboratory stocks of Pacific herring with subsequent virus concentration, purification, DNA extraction, and high-throughput sequencing were used to obtain genomic ENV sequences. Fragments with the highest sequence identity to the family Iridoviridae were used to design four sets of ENV-specific polymerase chain reaction (PCR) primers. Testing of blood and tissue samples from experimentally and wild infected Pacific herring as well as DNA extracted from other amphibian and piscine iridoviruses verified the assays were specific to ENV with a limit of detection of 0.0003 ng. Preliminary phylogenetic analyses of a 1448 bp fragment of the putative DNA polymerase gene supported inclusion of ENV in a proposed sixth genus of the family Iridoviridae that contains other erythrocytic viruses from ectothermic hosts. This study provides the first molecular evidence of ENV's inclusion within the Iridoviridae family and offers conventional PCR assays as a means of rapidly surveying the ENV-status of wild and propagated Pacific herring stocks.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Molecular identification of erythrocytic necrosis virus (ENV) from the blood of Pacific herring (Clupea pallasii)
Series title Veterinary Microbiology
DOI 10.1016/j.vetmic.2014.08.028
Volume 174
Issue 1-2
Year Published 2014
Language English
Publisher Elsevier
Contributing office(s) Western Fisheries Research Center
Description 11 p.
First page 16
Last page 26
Other Geospatial North America, Pacific Ocean
Online Only (Y/N) N
Additional Online Files (Y/N) N