Scientists find virus behind tilapia die-offs in Israel, Ecuador

An international team of researchers said Tuesday that they have identified a new virus behind massive die-offs of farmed tilapia in Israel and Ecuador in recent years.

A paper in the U.S. journal mBio described the tilapia lake virus (TiLV), which threatens the 7.5-billion-U.S.-dollar global tilapia industry.

"Tilapia is one of the most important fish industries worldwide," first author Eran Bacharach, a molecular virologist at the Tel Aviv University in Israel, said in a statement.

"Moreover, because they eat algae, they are ecological gatekeepers for freshwater and they are an inexpensive, important source of protein in poorer countries."

Various countries in Asia, South America and the Middle East are the largest tilapia producers and the United States is the largest importer, consuming 225,000 tons of the fish each year.

Since 2009, Israel has seen sharp declines in the world's second most farmed fish, with annual yields plummeting as much as 85 percent -- highly unusual considering the fish is known to be relatively resistant to viral infections. Similar die-offs have been seen in Ecuador and Colombia.

The researchers used high-throughput sequencing to determine the genetic code of the virus from tissue taken from diseased fish in Israel and Ecuador and found what they had represented an entirely new virus, which they named TiLV.

When healthy fish were exposed to TiLV cultured in a laboratory, the resulting disease matched with what was seen in those countries: in Israel, the fish had swollen brains; in Ecuador, liver disease.

But how the virus traveled between Israel and Ecuador, and in which direction, is still a mystery, they said.

The findings, said the researchers, provided the genomic sequences necessary for TiLV detection, containment, and vaccine development.

The team included 18 researchers from the Center for Infection and Immunity and the New York Genome Center in the U.S., Tel Aviv University and Kimron Veterinary Institute in Israel; the University of Edinburgh, Scotland; and St. George's University, Grenada, West Indies. Enditem