Inter-species transmission of viral hemorrhagic septicemia virus (VHSV) from turbot (Scophthalmus maximus) to rainbow trout (Onchorhynchus mykiss)

Successful viral infection is a complex mechanism, involving many host–pathogen interactions that developed during coevolution of host and pathogen, and often result in host-species specificity. Nevertheless, many viruses are able to infect several host species and sporadically cross species barriers. The viral hemorrhagic septicemia virus (VHSV), a rhabdovirus with high economic impact on the aquaculture industry, has developed an exceptionally wide host range across marine and freshwater environments. Transmission of VHSV between host species therefore represents a potential risk for aquaculture, which currently is not addressed in biosecurity managements. The objective of this study was to investigate the inter-species transmission potential of VHSV and evaluate whether infected marine wild fish pose a potential risk on marine cultured rainbow trout. A cohabitation infection trial with turbot as donor and rainbow trout as recipient host species was conducted. Turbot were intraperitoneally injected with either a marine-adapted (MA) or a trout-adapted (TA) VHSV isolate and subsequently grouped with naïve rainbow trout. Both VHSV isolates were able to replicate and cause mortality in turbot, while only the TA isolate was able to cross the species barrier and infect rainbow trout with fatal outcome. The results demonstrate that a marine fish species can function as reservoir and transmitter of TA VHSV isolates.