Solving a fishy mystery

 “Something started killing farmed Atlantic salmon in Chile in about 2007,” says Dr. Fred Kibenge, Professor of Virology at UPEI’s Atlantic Veterinary College. “And it was thought to be a bacterial disease, so they treated with antibiotics. But the fish kept dying.”

Until this point, Chile was the number two producer of farmed Atlantic salmon in the world, and well on track to becoming number one.

“We tested samples for a disease known as infectious salmon anaemia, or ISA, and it was confirmed,” says Kibenge. “The effect has been terrible. Production in Chile is now barely 30 per cent of what it was just three years ago.”

Dr. Fred Kibenge: Photo from Fish Information & Services (click for article)Dr. Fred Kibenge: Photo from Fish Information & Services (click for article)

Kibenge’s findings, and how he came to them, read like a script for the television program C.S.I. But instead of finding a murderer, he’s tracked the route of a virus that jumped an ocean to decimate the Chilean aquaculture industry.

ISA virus is a blood-borne virus in salmon that literally bleeds the fish to death. The disease was first reported in 1984 in salmon farms in Norway. More than a decade later, it was confirmed in farms in the Bay of Fundy off New Brunswick.

“But while the diseases were similar, the viruses were genetically distinct,” says Kibenge, “which means the disease wasn’t spread from one place to another. These two viruses evolved separately, literally, an ocean apart.”

Kibenge’s lab quickly developed expertise in ISA, and in May of 2004 was named an official reference lab by the World Organization for Animal Health, or OIE.

“There are reference labs all over the world with specialties in different diseases,” says Kibenge. “For example, if a country suspects it has cases of avian influenza, it must seek confirmation from a specific OIE laboratory. We are one of two labs for ISA—the first being a government lab in Norway.”

Kibenge’s confirmation of ISA in Chile created a few more questions: Where did it come from? How did it get there? And, when did it happen?

“I had been working with Dr. Yingwei Wang in the Computer Science department of UPEI since 2006,” says Kibenge. “We developed a computer program that compared genetic sequences of different samples of the virus with startling results.”

The program, called BACKTRACK, was able to confirm the ISA virus in Chile came from Norway. The samples taken in Chile in 2007 were most similar to samples taken in Norway in 1996.

“Which was surprising, because the virus didn’t become a problem for more than a decade,” says Kibenge. “But BACKTRACK was also able to show the ISA virus in Chile underwent a mutation in 2005. It wasn’t until that point that it was able to spread to Chile’s salmon farms.”

The OIE recently awarded a contract to Kibenge’s lab to help train a Chilean lab at the Pontificia Universidad Católica de Valparaíso. Over the next two years, a team from AVC will travel twice to Chile to help bring the lab’s protocols and practices up to date. Representatives from Chile will also visit AVC.

“The hope is these exchanges will prepare the Chilean lab to become an OIE reference lab for Latin America,” says Kibenge.

The first AVC workshop in Chile will be this coming October. Check back with the ORD Blog for updates on this story.

Top photo: Electron micrograph of infectious salmon anaemia virus particles in cell culture.