ACIPENSER IRIDOVIRUS-EUROPEAN (AcIV-E): EMERGING PROBLEM IN STURGEON FARMS?

It's known that viruses are one of the main causes of mortality in farmed sturgeons: despite this, there's still little knowledge on etiological agents of these infectious diseases. Iridoviridae are viruses belonging to the Nucleocytoplasmic Large DNA Viruses (NLDV) known to cause diseases in sturgeons in North America. Several etiological agents have been isolated over the years in the USA: white sturgeon iridovirus (WSIV), Missouri River sturgeon iridovirus (MRSIV), Namao virus (NV). In Europe, iridovirosis has become an emerging issue for sturgeon farms. The etiological agent, called Acipenser Iridovirus-European (AcIV-E), has been identified in several sturgeon species (Acipenser gueldenstaedtii, A. baeri, A. naccarii and Huso huso). This work presents the data on AcIV-E monitoring in sturgeons farmed in northern Italy between January and August 2019.

Five farms in Northern Italy were sampled, for a total of 210 sturgeons analysed: 80 (38,1%) from Farm 1, 89 (42,4%) from Farm 2, 1 (0,5%) from Farm 3, 20 (9,5%) from Farm 4 and 20 (9,5%) from Farm 5. The subjects were necropsied under aseptic conditions and gill were sampled for AcIV-E DNA detection. A real-time PCR protocol targeting the Major Capsid Protein (MPC) gene described by Bigarré et al. (2017) was used to analyse the DNA previously extracted by a commercial kit.

The monitoring results are listed in table below.

Specific real-time PCR for MPC allowed to identify 68 (32,4%) positive sturgeons. Russian sturgeon A. gueldenstaedtii was the species with the greatest number of positive. Ten (4,8%) hybrid sturgeons were positive for AcIV-E: it must be considered that these fish are crosses with A. gueldenstaedtii (e.g. hybrids BAGU and GUBA), which appears to be the most susceptible species. Sterlet A. ruthenus was also positive to PCR: the low numbers sampled on this species need future investigation.

This monitoring allowed to clarify the risk represented by AcIV-E in Italian and European sturgeon farms, particularly for A. gueldenstaedtii, but the susceptibility of other sturgeon's species should be investigated. Complete viral genome sequencing, isolation on sturgeon cell cultures and identification of specific clinical signs will be critical points on which to plan future research.

Bibliography

Bigarré L., Lesne M., Lautraite A., Chesneau V., Leroux A., Jamin M., Boitard P.M., Toffan A., Prearo M., Labrut S., Daniel P. (2017) Molecular identification of iridoviruses infecting various sturgeon species in Europe. Journal of Fish Diseases 40:105-118.