April 12, 2016

New virus causing tilapia die-offs in Israel, Ecuador

A new virus is causing the massive die-offs of farmed tilapia in Israel and Ecuador, an international team of researchers has found.

Called TilV, the virus was responsible for the 85% decrease in the annual yields of the world's second-most farmed fish in Israel since 2009. This was considered unusual as tilapia is known to be relatively resistant to viral infections.

The researchers determined the genetic code of the virus from the tissue taken from diseased fish in Israel and Ecuador and when the healthy fish were exposed to TiLV cultured in a laboratory, the resulting disease matched with what was seen in Israel, where the diseased fish had swollen brains, and in Ecuador, where the affected fish had liver disease.

The 18 researchers--connected with the Center for Infection and Immunity and the New York Genome Center in the US, Tel Aviv University and Kimron Veterinary Institute in Israel; the University of Edinburgh, Scotland; and St. George's University, Grenada, West Indies--were baffled as to how the virus travelled from Israel to Ecuador and in which direction.

One of the researchers, Eran Bacharach, a molecular virologist at the Tel Aviv University, stressed the importance of tilapia as "one of the most important fish industries worldwide".

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

Asia, South America and the Middle East are the largest producers of tilapia while the US is the biggest importer, consuming 225,000 tonnes of the fish yearly.