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Courtesy of NAA:

The U.S. Department of Agriculture, Animal and Plant Health Inspection Service, organized a conference call yesterday, May 6, 2019, to present information describing the first documented case of Tilapia Lake Virus (TiLV) in the United States.
 
Background Information:
The agency’s goal is to prevent the TiLV from negatively impacting U.S. commercial tilapia facilities. They are working closely with State partners and conducting an epidemiologic investigation to determine how the disease entered the country and if any additional facilities may be impacted.
 
TiLV was first reported in 2014 and is found in Asia, Africa, Central America and South America. It was also reported in aquaculture production facilities in six Mexican states. Veterinarians and scientists are working to fully understand the disease and how to best manage it. Current scientific evidence suggests that TiLV spreads through direct contact with affected fish. Researchers are also investigating the role of disease transmission from parent to offspring.
 
TiLV can be deadly to farmed and wild tilapia, with death rates between 10-90 percent. Younger fish may be more affected by the disease. Signs of the disease may include: cloudy or bulging eyes, skin lesions such as darkening, bruising, ulcers or protrusion of the gills, and abdominal swelling. Fish may be slow-moving and off feed.
 
The agency reported during the conference call:

• TiLV was initially found at an Idaho farm in Nile tilapia imported from Thailand. The imported fish suffered about 20% mortality in young fish. The Idaho producer sells fingerlings and 1 to 2-pound live fish for human consumption. To clear the farm, the farmer will be allowed to continue to sell to the live market.
• Samples of infected fish were ultimately submitted to the National Veterinary Services Laboratory for confirmation. Following testing on April 26, the animals tested negative for TiLV. The facility has been released from quarantine by the Idaho State Veterinarian. Idaho will be declared free of TiLV once the Index facility disinfects. 
• Infected fish were traced to two cases, one in Wyoming and one in Colorado, in farms that grow and sell tilapia to live markets. They will be allowed to clear their farms by selling market-ready fish to their live markets.
• To date no states have instituted, except Michigan, TiLV testing; however, that state has delayed TiLV testing pending establishment of diagnostic standards.  
• There will likely be restriction on future imports and exports but this remains to be determined. The agency will begin negotiations with countries that receive live tilapia from the United States. These negotiations will occur within the framework of bilateral trade agreements which will take time. Most likely receiving countries will have different testing requirements.
• The World Organization of Animal Health (OIE) and Canada were notified yesterday that the United States is no longer free of TiLV.
• The agency noted there is considerable work to complete. There is not a standard test for TiLV. It is not clear if frozen products can carry the virus (some say yes, others say no). The agency commented there remains a need to determine what the U.S. tilapia farming community wants to occur going forward.

The NAA’s Aquatic Animal Health Committee is working on this issue and for additional information or to provide comment, tilapia farmers should contact the NAA Office at naa@thenaa.net.  

The United Nations Food and Agriculture Organization has published a Tilapia Lake Virus rapid risk assessment. Visit their website for a description of the pathogen, fish species that are susceptible, and biosecurity practices farmers should adopt.