Cichlids endemic to India are not susceptible to Tilapia Lake virus infection

Infection with Tilapia tilapinevirus, also known as Tilapia Lake virus (TiLV) is responsible for high mortalities in tilapia and its hybrid species and presents a significant threat to the tilapia farming industry. Till date, TiLV infections have not been reported in other cichlids that are co-cultured with tilapia. Nonetheless, as natural host switch is a frequent phenomenon among fish viruses, the current study was undertaken to check the susceptibility of three Indian cichlid species, viz. pearlspot (Etroplus suratensis), orange chromide (Pseudetroplus maculatus), and canara pearlspot (E. canarensis), to TiLV vis-a-vis a susceptible host, Nile tilapia (Oreochromis niloticus) using in vivo and in vitro methods. The experimentally-infected Etroplus spp. did not exhibit any clinical signs of infection. Nile tilapia, on the other hand, exhibited a cumulative mortality of 75% at 12 days post challenge, with clinical signs typical of TiLV disease. Three cell lines derived from Etroplus spp. namely, orange chromide fin (OCF), canara pearlspot fin (CPSF), and pearlspot fin (PSF) cell lines did not show any cytopathic effects (CPE) even after 5 blind passages upon inoculation with TiLV-positive tissue homogenate from tilapia. CPE were apparent in the O. niloticus liver (OnlL) cell line after 72 h and the presence of TiLV was confirmed by RT PCR. Thus, the absence of clinical signs and TiLV-specific amplification in the liver and brain tissues of the experimentally infected Etroplus spp., as well as the absence of CPE and the presence of TiLV genome in the three Etroplus cell lines confirmed that Indian cichlids are not susceptible to TiLV infection.