Scientists identify farmed tilapia virus


Tilapia is the world's second most frequently farmed fish and an inexpensive source of protein for millions of people worldwide. So it was a major source of concern to the fish industry when tilapia farmers started seeing massive die-offs of their fish starting in 2009.

Now, an international team of scientists led by Columbia University's Mailman School of Public Health and Tel Aviv University have discovered the cause of the casualties: an illness they've dubbed tilapia lake virus (TiLV). Their discovery was published in a recent edition of the journal mBio, according to a press release from Columbia.

"Gumshoe epidemiology, molecular gymnastics and classical microbiological methods were required to link this new virus to disease," said Ian Lipkin, senior author, director of the Center for Infection and Immunity and a professor of epidemiology at the Mailman School in the release.

To uncover the cause of the die-offs, the team took tissue samples from deceased tilapia in Israel, where it's known as St. Peter's fish, and Ecuador. They then used high-throughput sequencing to map the virus' genetic code, at which point they discovered that it was unlike any other known virus. So by employing mass spectroscopy, they scrutinized the proteins that caused the virus to grow. When they exposed healthy fish to the new virus, they knew they had found their culprit, because the fish developed symptoms identical to those seen on the affected farms, according to the release.

TiLV is most closely related to a family known as orthomyxoviruses, which cause some strains of the flu. Although the biology of these viruses is not well understood, the scientists believe they have learned enough about the newly discovered bug to develop products that will protect the $7.5 billion global tilapia industry. "We are shifting our focus now to implementing diagnostic tests for containment of infection and to developing vaccines to prevent disease," said Avi Eldar of the Kimron Veterinary Institute in Bet Dagan, Israel, in the release.

As the worldwide demand for high-protein foods grows, so does the animal health industry's interest in developing new products for aquaculture uses. Zoetis ($ZTS) made a big bet on aquaculture last November, when it laid out $765 million to acquire Pharmaq, a leading maker of fish vaccines. Phibro Animal Health ($PAHC) has also boosted its presence in the fish industry, citing vaccines as a major growth opportunity.

The discovery of TiLV was a multinational effort that also included the New York Genome Center and the Center for Infection and Immunity, which had previously identified a virus that wiped out European salmon farms in 2010.

- here's the press release
- access the tilapia paper here