Detection of Erythrocytic Inclusion Body Syndrome (EIBS) Virus (Piscine orthoreovirus 2) from Ovarian Fluid of Coho Salmon Survivor

Virucidal Effect of Disinfectants against Erythrocytic Inclusion Body Syndrome (EIBS) Virus <i>Piscine orthoreovirus</i> 2

“…Coho salmon juveniles (mean body weight 38 g) obtained from the Miyagi Prefecture Freshwater Fisheries Experimental Station (MPFFES) were used for bioassays after injection with disinfectant-treated virus suspension. The occurrence of EIBS has never been observed in MPFFES, and we have confirmed by RT-PCR that the lot used in this experiment was not infected with PRV-2, which we have reported in previous study (Kumagai et al, 2019). The experiment with each disinfectant used 15 naïve coho salmon juveniles that were interperitoneally injected with 0.1 mL of disinfectant-treated virus suspension and together reared in a 20-L tank with flowing water (5 L/min) at 8 ± 1°C and fed a commercial diet.…”

“…Next, 30 fields of view in each stained blood smear were examined for the presence of cytoplasmic inclusion bodies under a light microscope at 1000× magnification. Spleen (50 mg) taken from each fish was also tested for the presence of PRV-2 virus RNA (L1 genome segment) using RT-PCR as described previously (Kumagai et al, 2019).…”

“…PRV-2 was detected in ovarian fluid samples of EIBSexperienced coho salmon spawners (Kumagai et al, 2019), indicating that PRV-2 in the ovarian fluid contaminates the surface of eggs. In Japan, a method of disinfecting fish eggs with povidone-iodine (50 ppm for 15 min) was developed in the 1970s to prevent IHNV; this method is still widely applied in salmonid hatcheries to prevent not only IHNV but also the transmission of bacterial pathogens such as Aeromonas salmonicida and Flavobacterium psychrophilum into the hatchery via infected egg surfaces (Yoshimizu, 2009).…”

Piscine orthoreovirus: Biology and distribution in farmed and wild fish

“…Although the primary mode of PRV transmission is almost certainly horizontal, it is probable, given the systemic nature of PRV infections, that PRV contamination of sexual fluids permits the potential for egg‐associated vertical transmission from parent to offspring. Fish in freshwater hatcheries in North America, Europe and Japan have become infected presumably via this method (Kumagai et al., 2019; Løvoll et al., 2012; Polinski et al., 2019); however, a study following a population of Norwegian Atlantic Salmon brood fish and progeny from 2008 to 2011 found that PRV was not isolated in or on eggs collected from infected brood fish following a Buffodine ® disinfection treatment (Wiik‐Nielsen et al., 2012). Similarly, neither PRV‐1 in juvenile Atlantic Salmon from British Columbia nor PRV‐3 in Rainbow Trout from Denmark could be detected after being reared from iodine disinfected eggs even though the brood fish supplying the respective hatchery facilities carried high systemic RNA loads of PRV (M. Polinski, K. Garver and N. Vendramin, unpublished data).…”

“…There are currently no strategies that have shown effectiveness at eliminating PRV once established in a population or facilitating resistance in naïve fish. However, egg‐surface disinfection presents a promising means of limiting PRV spread and prevalence in at least confined land‐based aquaculture systems (Kumagai et al., 2019; Wessel et al, 2020; Wiik‐Nielsen et al., 2012). A combination of molecular testing, fallowing and disinfection has also been used to remove PRV from a confined aquaculture system in Pacific Canada (D. Morrison, personal communication), a strategy that may be particularly valuable for recirculating aquaculture systems that maintain fish over an entire production cycle in a closed environment.…”