Epidemic Risks associated with high-temperature replicating infectious hematopoietic necrosis virus (IHNV) field isolates: from molecular characterization to host pathogen interactions

Thermotolerant IHNV field isolates RtNag0a and SA-22 replicate at elevated temperatures (>20{degrees}) in cell culture and are linked to distinct virulence and antiviral responses in zebrafish larvae at 21.5 and 23.5{degrees}.

• Why it matters: Climate warming may select for thermotolerant IHNV strains and alter salmonid immune responses, but the replication and host-pathogen effects of high-temperature field isolates remain unclear.
• What they did: Replication kinetics of IHNV reference strain N61 and two field isolates were measured in EPC and RTG-2 cells at 14, 20 and 22{degrees}, then virulence and antiviral host responses were tested in zebrafish larvae using microinjection and bath immersion at 21.5 and 23.5{degrees}.
• The result: In vitro results showed distinct thermal replication profiles, separating thermosensitive from thermotolerant isolates with dependence on the cellular environment, and waterborne infection was effective, enabling zebrafish larvae as a relevant model for virulence assessment of field isolates.

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