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September 25, 2015
A hepatitis B-like virus has been found for the first time in fish. A team of USGS researchers found the virus in white sucker from the Great Lakes Region using gene-sequencing technologies.

A hepatitis B-like virus has been found for the first time in fish. A team of USGS researchers found the virus in white sucker from the Great Lakes Region using gene-sequencing technologies.

How the recently discovered hepatitis B-like virus is transmitted between fish is not yet understood, and it is unlikely to be communicable to humans.

“To date, a hepatitis B virus has never been found before in fish and we now have evidence that it infects fish in geographically distant river systems in the Great Lakes region,” said lead author Cassidy Hahn, a USGS scientist and graduate student at the University of West Virginia. “This new virus is similar, but also very different from hepatitis B-like viruses found in mammals and birds, and may be a new genus.”

The hepatitis B virus is a small, spherical, enveloped virus, previously known only in two groups--one that infects humans and other mammals including orangutan, gibbons, gorillas and chimpanzee; and the other that infects birds.

The white sucker is considered an indicator species, which is native to river systems in the Midwestern and Northeastern United States. Their widespread distribution and life-history have made them a target species in numerous contaminant monitoring and effects studies. White sucker are bottom feeders, spending most of their lives in close proximity to the bottom of rivers, because of this they are in contact with contaminants associated with the river bottom.

The DNA of an organism is like a recipe book for making all of the proteins necessary for life. Those instructions are coded as genes and are conveyed to protein making factories in the cell via messenger ribonucleic acid molecules. In order to develop tools to evaluate how these fish were utilizing their DNA (responding to their environment), the RNA from liver tissue was sequenced using contemporary high throughput RNA-sequencing methods. This approach allows for decoding the usage of this blueprint.

In general, hepatitis-B viruses have a narrow host range and infection manifests in various ways. In mammals, these viruses infect and multiply in liver cells and are typically associated with acute and chronic liver diseases including fibrosis, cirrhosis, bile duct cancer, and hepatocellular carcinoma. It is estimated that 350 million people are chronically infected with HBV. Hepatitis B viruses in birds are not normally associated with these liver diseases. The potential effects on fish are currently unknown.

According to the research team, the hepatitis “B-like” virus found in the fish is about as similar to the human hepatitis B virus as it is to the bird hepatitis B viruses.

“This new virus may improve our understanding of the evolutionary history of hepatitis B-like viruses,” said USGS biologist Luke Iwanowicz, study coauthor.  “There have been considerable scientific efforts focused on identifying the origins of hepatitis B -like viruses. The genome of this new virus has features not present in any known virus from this family. It is a very exciting discovery.”

According to the researchers, the study may offer the opportunity to develop a new model system to investigate host – pathogen interactions and benefit human medical research.

Part of a joint U.S. Fish and Wildlife/USGS Great Lakes Initiative Project, the study, Characterization of a Novel Hepadnavirus in the White Sucker (Catostomus commersonii) from the Great Lakes Region of the USA, by Cassidy M. Hahn, Luke R. Iwanowicz, Robert S. Cornman, Carla M. Conway, James R. Winton, and Vicki S. Blazer is available in the Journal of Virology online.

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