Filtration, concentration and detection of salmonid alphavirus in seawater during a post-smolt salmon (Salmo salar) cohabitant challenge

Abstract

Currently, the prevalence of salmonid alphavirus (SAV) in Norwegian Atlantic salmon farms is largely surveyed via sacrificing fish and sampling of organ tissue on a monthly basis. However, a more cost-efficient, straightforward, rapid, reliable, reproducible and animal welfare friendly method based on the detection of SAV in water could be considered as an alternative method. In the present study, such a method was developed and optimized through a 6 wk cohabitant challenge trial, using post-smolt Atlantic salmon Salmo salar L challenged with high or low doses of SAV subtype 3 (SAV3). Tank water and tissue samples from cohabitant fish were collected at 16 time points. SAV3 was concentrated from the water by filtration, using either electronegative or electropositive membrane filters, which were subsequently rinsed with one of 4 different buffer solutions. SAV3 was detected first in tank water (7 d post-challenge, DPC), and later in cohabitant fish organ tissue samples (12 DPC). The electronegative filter (MF-Millipore™) and rinsing with NucliSENS® easyMAG® Lysis Buffer presented the best SAV3 recovery. A significant positive correlation was found between SAV3 in the tank water concentrates and the mid-kidney samples. Based on these results, detection of SAV3 in filtrated seawater is believed to have the potential to serve as an alternative method for surveillance of SAV in Atlantic salmon farms.

Persistence of Tilapia tilapinevirus in fish rearing and environmental water and its ability to infect cell line

“…Comparably, the recovery of adenovirus was 29%–66% using the electronegative charge filter membrane together with membrane elution by NaOH (pH 10.8) to concentrate the virus in an environmental water sample (Li et al., 2010). Therefore, the application of filter membranes with different elution buffers or pre‐acidification of water samples could improve the recovery rate of the virus (Bernhardt et al., 2021; Kongprajug, Chyerochana, et al., 2021; Li et al., 2010; Weli et al., 2021). The application of a filtered membrane to trap viruses in water is a common protocol to study the persistence of human and aquatic viruses (Ahmed et al., 2020; Haramoto et al., 2020; Joiner et al., 2021; Kongprajug, Chyerochana, et al., 2021; Kongprajug et al., 2021; Weli et al., 2021).…”

“…The application of a filtered membrane to trap viruses in water is a common protocol to study the persistence of human and aquatic viruses (Ahmed et al., 2020; Haramoto et al., 2020; Joiner et al., 2021; Kongprajug, Chyerochana, et al., 2021; Kongprajug et al., 2021; Weli et al., 2021). For example, the electronegative charge filtered membrane was used in the study of the persistence of infectious salmon anaemia virus (ISAV) and salmon alphavirus (SAV) in seawater (Bernhardt et al., 2021; Weli, Tartor, Spilsberg, Dale, et al., 2021). Moreover, Sangsanont et al.…”