TiLV, AN EMERGING NEW VIRAL DISEASE OF  TILAPIA SPP.

In Summer 2009, massive losses of Tilapia were observed in several fish farms in Israel.   Very high mortality of Tilapia was described in all sizes. The disease outbreak was transferred readily from one pond to the next one indicating to be highly contagious. Most important, morbidity and mortality was limited only to Tilapia species and hybrids (Oreochromis niloticus X O. aureus hybrid). Tilapia that survived the initial outbreak in the same ponds appeared to be more resilient than naïve Tilapia if exposed to further infections.  

Gross lesions were characterized mainly by unilateral or bilateral ocular alterations (cataracts). Other lesions, observed in diseased pond-raised Tilapia included skin erosions and moderate congestion of the spleen and kidney.    

Eyngor et al. (2014) isolated successfully from diseased fish the etiological agent responsible for massive mortality in Tilapia. The virus was designated Tilapia Lake Virus (TiLV).  

Disease outbreaks are frequently characterized by secondary Bacterial and Parasitic infection, leading to mortality rates of over 50% in juvenile Tilapia populations.

The existence of fish that survived the TiLV disease strongly suggests that an effective immune response against this pathogen can be mounted. This has important applications for future disease containment strategies.

Reports of similar clinical symptoms and very high mortality rates have been reported by Tilapia producers in Colombia and Ecuador during these last few months.

This disease process may endanger the rapidly developing Tilapia industry, worldwide.