Advertising

The Seattle Times Company

NWjobs | NWautos | NWhomes | NWsource | Free Classifieds | seattletimes.com

Health


Our network sites seattletimes.com | Advanced

Originally published Monday, May 30, 2011 at 10:01 PM

Comments (0)     E-mail E-mail article      Print Print      Share Share

Dog virus a clue to track origins of hepatitis C

Hepatitis C is shrouded in mystery. Typically spread through drug injections, blood transfusions and sexual contact, hepatitis C can quietly cause liver damage for 20 years or more before victims become aware that they are ill.

The New York Times

No comments have been posted to this article.
Start the conversation >

advertising

Hepatitis C is shrouded in mystery. Typically spread through drug injections, blood transfusions and sexual contact, hepatitis C can quietly cause liver damage for 20 years or more before victims become aware that they are ill.

An estimated 200 million people are infected. Some of them will suffer cirrhosis, liver cancer and even death.

"Worldwide, it's causing devastation," said Brian Edlin, an epidemiologist at SUNY Downstate Medical Center in Brooklyn.

Its origins are even more puzzling. Hepatitis C is a distinct disease from hepatitis A and B; it belongs to an entirely different virus family that includes diseases like West Nile fever and yellow fever. Scientists have searched for years for related viruses in animals to figure out how it evolved into a human disease.

"Identifying the species reservoir of hepatitis C — one of the most common and deadly of all human viruses — has been something of a holy grail in studies of viral evolution," said Dr. Eddie Holmes, a virologist at Penn State University.

Now scientists have gotten an important clue, finding a close relative in an unexpected host: dogs.

The discovery, published in Proceedings of the National Academy of Sciences, "represents a major step forward," said Holmes, who was not involved in the research.

The finding came as a surprise to all the scientists involved. Researchers at Pfizer were investigating virus outbreaks in dogs in shelters across the United States. They swabbed the noses of dogs sick with respiratory diseases and searched for viruses. In some cases they could not isolate a known virus, so they sent samples to the Center for Infection and Immunity at Columbia University, where researchers specialize in finding new viruses.

The center found that six of nine dogs in one outbreak and three of five in another shared the same unknown virus. Nasal swabs from 60 healthy dogs showed no sign of it.

Dr. Amit Kapoor, a Columbia virologist, compared the genetic material of the new virus to known ones. His analysis revealed it was closely related to the hepatitis C virus (HCV for short). "I was not expecting anything like HCV," Kapoor said. Like many researchers, he assumed it had evolved from a primate virus, because chimpanzees can be experimentally infected with hepatitis C.

But as Kapoor and Peter Simmonds of the University of Edinburgh analyzed more genetic data, the link continued to hold. Kapoor and his colleagues have called the new virus canine hepacivirus, or CHV for short.

The Columbia researchers collaborated with hepatitis C experts at Rockefeller University in New York to compare the two viruses. Canine hepacivirus infects the airways of dogs and is present at low levels in the liver.

Based on the genetic similarity of the two viruses, the scientists estimate that they share a common ancestor that lived 500 to 1,000 years ago. "It's really quite rough," said W. Ian Lipkin, director of the Center for Infection and Immunity and an author of the journal article. "This is not something that happened recently, but it didn't happen hundreds of thousands of years ago."

The researchers see three possibilities for the origin of the viruses. The least likely is that dogs acquired hepatitis C from humans. Another possibility is that dogs and humans both acquired the virus from an unknown animal.

A third possibility — one favored by Kapoor — is that the virus started in dogs, and then evolved into a liver-infecting disease in humans.

To test these alternatives, Kapoor and his colleagues plan to search for hepatitis C-like viruses in dogs from other countries, as well as in foxes and other species of carnivorous mammals.

Even before that mystery is resolved, however, researchers expect to see some benefits from the discovery of canine hepacivirus. Researchers now may be able to study CHV in dogs to get insights into hepatitis C in humans. There now is no commercially available hepatitis C vaccine.

Comments (0)     E-mail E-mail article      Print Print      Share Share

News where, when and how you want it

Email Icon




Advertising