Resistance of pearlspot larvae, Etroplus suratensis, to redspotted grouper nervous necrosis virus by immersion challenge

Abstract

Viral nervous necrosis (VNN) affects more than 120 species mostly belonging to the order Perciformes. However, none of the brackishwater species belonging to the family Cichlidae under the order Perciformes are reported to be susceptible. Hence, the present experiment was undertaken to study the susceptibility of the brackishwater cichlid, pearlspot, Etroplus suratensis to NNV. Thirty‐day‐old pearlspot larvae were infected with NNV by immersion. Mortality was recorded till 14 days post‐infection, and the infected larvae were subjected to nested RT‐PCR and histology. The virus was isolated from infected larvae using SSN‐1 cells. To study the replication of the virus in vitro, primary cultured brain cells of E. suratensis and IEK cells were infected with NNV. No mortality was observed in any of the control or experimentally infected larvae. However, the experimentally infected larvae were positive for NNV by nested RT‐PCR and the virus was isolated using SSN‐1 cells. Further, the infected pearlspot brain cells and IEK cells showed cytopathic effect at second and third passage of the virus and they were positive for NNV by nested RT‐PCR. Pearlspot is relatively resistant to VNN although the virus could replicate in the larvae and in cell culture.

Non-lethal screening of Asian seabass (Lates calcarifer) by monoclonal antibody based indirect enzyme linked immunosorbent assay for viral nervous necrosis

“…Complete inactivation of the virus was confirmed by inoculating the inactivated virus onto SSN-1 cells and observing no cytopathic effect even after 3 passages. The capsid protein gene of RGNNV was RT-PCR amplified, cloned into pET-28b(+) vector and the recombinant protein was expressed in Escherichia coli BL21 (DE3) cells as described earlier [23] . The purified recombinant capsid protein was used to coat ELISA plates.…”

“…One microgram of RNA was reverse transcribed into cDNA using iScript TM cDNA synthesis Kit (Bio-Rad, India). Nested RT-PCR for NNV was carried out using gene-specific primers [3] as described earlier [23] . The PCR products were electrophoresed on 1.5% (w/v) agarose gel and stained with ethidium bromide.…”

A natural outbreak of infectious spleen and kidney necrosis virus threatens wild pearlspot, Etroplus suratensis in Peechi Dam in the Western Ghats biodiversity hotspot, India

“…To date, there is only one published report of a systemic Iridoviral infection in E. maculatus (Armstrong & Ferguson, 1989). Though pearlspot is relatively resistant to nervous necrosis virus (NNV), it has been reported to act as a carrier of NNV that can spread the virus to other susceptible fish species (Marappan et al., 2019).…”