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[BANGKOK] An emerging viral disease observed in both wild and farmed tilapia could impact global food security and nutrition if biosafety measures are not introduced, the UN Food and Agriculture Organization (FAO) and other organisations warn.
The warning on the tilapia lake virus (TiLV) was contained in a special alert issued by FAO (May 26) which was first detected in Israel in 2009 but was only confirmed as a new disease in 2014. Cases have since been reported in other parts of the world.
In Sub-Saharan Africa, tilapia, in its various strains, is largely caught from traditional wild sources such as rivers, lakes and dams, according to FAO.
Tilapia, which is native to Africa, is the second most popular farmed fish globally and one of the most traded seafood commodities. It is an affordable source of protein in poor rural communities as well as in affluent urban centers.
“All countries culturing tilapia and especially those translocating live tilapia should be vigilant about the disease and take appropriate risk management measures to reduce the likelihood of imported stocks being infected with TiLV,” Melba Reantaso, aquaculture officer at the FAO, tells SciDev.Net.
“All countries culturing tilapia and especially those translocating live tilapia should be vigilant about the disease.”
Melba Reantaso, UN Food and Agriculture Organization
Tilapia is a common name for hundreds of species of the tilapiine cichlid fish and is derived from the cichlid genus Tilapia. According to scientific publications, TiLV has been reported in five countries so far: Colombia, Ecuador, Egypt, Israel and Thailand.
Outbreaks in Thailand have wiped out 90 per cent of tilapia stocks. TiLV is part of the Orthomyxoviridae family of viruses, which is related to the infectious salmon anaemia virus that has heavily damaged the salmon farming industry. The virus is not known to infect humans.
Fish infected with TiLV often display sluggishness, dermal lesions, ocular abnormalities and lens opacity. However, there are still knowledge gaps around TiLV such as whether other passive carriers transmit the disease and whether infections through frozen tilapia products are possible.
Vishnumurthy Mohan Chadag, senior scientist at WorldFish, an international non-profit research organisation, tells SciDev.Net, that countries vulnerable to the TiLV virus need to put in place monitoring and surveillance strategies.
Awareness building of TiLV in all sectors of the value chain is also important with special attention given to small-scale farmers with limited access to knowledge and information, says Chadag.
At the international level, mobilisation is already underway between various stakeholders to assist affected countries and get them to adopt biosecurity measures that include requirements to report unusual fish mortality and restrictions on the movement of live fish. Efforts are on to develop a vaccine.China, India and Indonesia are actively monitoring for TiLV. In Israel, an epidemiological survey is expected to determine factors influencing low survival rates and overall mortalities, including relative importance of TiLV.
According to FAO, tilapia is among the topmost aquaculture species in volume terms providing food, jobs and domestic and export earnings for millions of people, including many smallholders. It is the most popular farmed fish in the world after carp and salmon.
China, Indonesia and Egypt are the three leading aquaculture producers of tilapia, a fish deemed to have great potential for expansion in sub-Saharan Africa. In 2015, world tilapia production, from both aquaculture and capture, amounted to 6.4 million tonnes valued at US$9.8 billion.