The tilapia lake virus (TiLV) is a newly emerging virus associated with significant mortalities in farmed tilapia. Since the first discovery of the virus in Israel in 2014, cases have been reported in Columbia, Ecuador, Egypt and Thailand. Now that screening tools are available and can be accessed by fish disease diagnostic/research labs, the number of reported TiLV cases is expected to rise. There has been no report of any human health-related issues linked to the consumption of affected tilapia from any of the affected countries since the emergence of TiLV. Looking at fish viruses overall, including TiLV, there is no evidence for a fish virus causing disease in humans.
The emergence of TiLV is the first-ever major disease epidemic reported in tilapia aquaculture, and puts the global industry at risk. Irresponsible trade in live aquatic animals and intensification without biosecurity considerations significantly compound this risk. Tilapia is one of the most widely-cultured species in the world. It is hardy and can be farmed under diverse farming systems with little environmental impact, making it an important aquatic food source contributing to global food and nutritional security. Tilapia has been domesticated and, now, several strains of genetically improved tilapia are farmed around the world. Global production of tilapia is estimated at 6.4 million metric tons (MMT). In 2015, the top three producers were the People’s Republic of China (1.78 MMT), Indonesia (1.12 MMT) and Egypt (0.88 MMT). Other leading producers include Bangladesh, Vietnam and Philippines (FAO 2017)
What are the clinical signs of infection with TiLV?
Mass mortalities of farmed tilapia (20–90 percent) are an indicative sign of infection with TiLV. Gross signs include dermal lesions and ulcers, ocular abnormalities, opacity of lens, loss of appetite, slow movement, gathering in the pond bottom and reduced schooling behavior.
How can infection with TiLV be diagnosed?
Presently, histopathology and PCR (RT-PCR and semi-nested RT-PCR) have been described and used to detect and confirm TiLV. Considering the seriousness of infection with TiLV, it is suggested that samples from mortality events be screened for TiLV. WorldFish also recommends that tilapia breeding programs and multiplication centers/hatcheries include mandatory TiLV screening for their seed before selling to hatcheries or grow out farmers.
See Attogene for information of the Real Time PCR kit for TLV or services (firstname.lastname@example.org) for surveillance.