Tilapia Lake Virus (TiLV) disease: Current status of understanding

Abstract

Tilapia Lake Virus (TiLV) disease is an emerging and transboundary disease of tilapia cultures, causing mortality up to 90% globally. TiLV is a negative sense single stranded RNA virus belongs to family Amnoonviridae, genus Tilapinevirus and species Tilapia tilapinevirus. The first TiLV outbreak to fishes was reported from Israel followed by other countries viz., Ecuador, Colombia, Egypt, Thailand, Chinese Taipei, India, Malaysia, Bangladesh, Uganda, Tanzania, Peru, Mexico, Philippines, Indonesia, and USA. All the life stages of Tilapia (belonging to the family Cichlidae) are vulnerable to TiLV infection. However, river barb and giant gourami have also been found susceptible to TiLV infection. The virus infects the vital organs of the fish, including eyes, brain, and liver. The notable pathological finding of this disease includes syncytial cell formation and massive hepatocellular necrosis with pyknotic and karyolytic nuclei in the liver cells of infected fish. The disease is very contagious and spreads through both horizontal and vertical transmission. Several sensitive and rapid molecular diagnostic tools like reverse transcriptase polymerase chain reaction (RT-PCR), RT-quantitative PCR (RT-qPCR), loop-mediated isothermal amplification (LAMP) have been developed for early detection of the virus. Till date, no comprehensive control measures have been developed throughout the globe, although aggressive work on this line is going on. Implementations of strict good management practices, including quarantine protocols, are the only available option to combat the outbreak and spread of the disease. This review emphasizes the etiology, occurrence and distribution, mode of transmission, pathology and pathogenesis, diagnosis, possible control measures, and challenges of TiLV disease.