Tilapia collection. (Photo: FIS)

FAO warns about tilapia lethal virus spread

FAO's Global Information and Early Warnings System (GIEWS) has warned the outbreak of tilapia lake virus (TiLV), a highly contagious disease, is spreading among farmed and wild tilapia.

Though not a human health risk, the virus is deemed to have large potential impact on global food security and nutrition, as tilapia is the most significant fish for human consumption worldwide.

So far, the disease has been confirmed in five countries on three continents: Colombia, Ecuador, Egypt, Israel and Thailand.

The FAO points out that the outbreak should be treated with concern and countries importing tilapias should take appropriate risk-management measures, such as intensifying diagnostics testing, enforcing health certificates, deploying quarantine measures and developing contingency plans.

In its alert, the entity informed that it is not currently known whether the disease can be transmitted via frozen tilapia products, but it is likely that TiLV may have a wider distribution than is known today and its threat to tilapia farming at the global level is significant.

The FAO recommends tilapia producing countries to be vigilant, and should follow aquatic animal-health code protocols of the World Organisation for Animal Health (OIE) when trading tilapia. Besides, they should initiate an active surveillance programme to determine the presence or absence of TiLV, the geographic extent of the infection and identify risk factors that may help contain it.

Furthermore, countries are encouraged also to launch public information campaigns to advise aquaculturists - many of them smallholders - of TiLV's clinical signs and the economic and social risks it poses and the need to flag large-scale mortalities to biosecurity authorities.

Currently, actively TiLV surveillance is being conducted in China, India, Indonesia and it is planned to start in the Philippines. In Israel, an epidemiological retrospective survey is expected to determine factors influencing low survival rates and overall mortalities including relative importance of TiLV. In addition, a private company is currently working on the development of live attenuated vaccine for TiLV.

FAO will continue to monitor TiLV, work with governments and development partners and search for resources that can be explored in order to assist FAO member countries to deal with TiLV, as requested and as necessary.

The organisation stressed that more research is required to determine whether TiLV is carried by non-tilapine species and other organisms such as piscivorous birds and mammals, and whether it can be transmitted through frozen tilapia products.

The disease shows highly variable mortality, with outbreaks in Thailand triggering the deaths of up to 90 percent of stocks. Infected fish often show loss of appetite, slow movements, dermal lesions and ulcers, ocular abnormalities, and opacity of lens.As a reliable diagnostic test for TiLV is available, it should be applied to rule out TiLV as the causal agent of unexplained mortalities.

In early May, the Network of Aquaculture Centres in Asia-Pacific (NACA) released a TiLV Disease Advisory and the OIE released a Disease Card. The WorldFish Center also released a Factsheet: TiLV: what to know and do, this month.

 
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