Researchers have discovered a previously unknown hepatovirus in harbor seals (Phoca vitulina) that is the closest known relative of the human hepatitis A virus, according to a new study published today online in the journal mBio.
Harbor seal infected liver tissue. Top: liver section from animal, stained with hematoxylin; the image includes bile duct (A), hepatic vein (B), and hepatic artery (C); no inflammation is observed in the infected tissue. Bottom: distribution of phopivirus in liver using fluorescent in situ hybridization, with higher-magnification insets demonstrating clear cytoplasmic infection. Image credit: S.J. Anthony et al.
According to the study, hepatitis A and the new virus, named phopivirus, share a common ancestor, which means that a spillover event must have occurred at some point in the past.
“It raises the question of whether hepatitis A originated in animals, like many other viruses that are now adapted to humans,” said Dr Simon Anthony of Columbia University, who is the lead author on the study.
Dr Anthony and his colleagues from the United States and the UK discovered the phopivirus while investigating a strain of avian influenza that killed over 150 harbor seals off the coast of New England in 2011. In an effort to determine what viruses might co-occur with influenza, they performed deep sequencing of all the viruses present in three of the animals.
A harbor seal (Phoca vitulina) colony in Helgoland, Germany. Image credit: Andreas Trepte / CC BY-SA 2.5.
An analysis of additional marine mammals living off the coast of New England (29 harbor seals, 6 harp seals and 2 grey seals) identified phopivirus in seven more individuals.
It is unclear whether the virus spilled over from humans to seals, vice versa, or from a third (unrelated) host that has not yet been identified.
However various factors, including the fact that the phopivirus was found in different species of seals, suggest that the virus has been present in seals for a fairly long time.
“Until now, we didn’t know that hepatitis A had any close relatives and we thought that only humans and other primates could be infected by such viruses,” Dr Anthony said.
“Our findings show that these hepatoviruses are not in fact restricted to primates, and suggest that many more may also exist in other wildlife species.”
The team next plans to look at species that have close interactions with seals to see if they can find other wildlife reservoirs of hepatitis A-like viruses.
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S.J. Anthony et al. 2015. Discovery of a Novel Hepatovirus (Phopivirus of Seals) Related to Human Hepatitis A Virus. mBio, vol. 6, no. 4, e01180-15; doi: 10.1128/mBio.01180-15
