A report released Wednesday by Fisheries and Oceans Canada, says there is minimal risk to the wild Fraser River sockeye salmon population due to the transfer of IHNV from Atlantic salmon farms in the Discovery Islands.
The report is the first in a series of risk assessments that will be looking at pathogens known to occur in the area and the relationship between the pathogens, the environment, farmed Atlantic salmon and Fraser River sockeye salmon.
“Our assessment concluded that IHNV attributable to salmon farms in the Discovery Islands, poses minimal risk to sockeye salmon abundance and diversity,” said Jay Parsons, director of the aquaculture, biotechnology and aquatic animal health branch of Fisheries and Oceans Canada. “This is because, under the current fish health management practices, including an effective vaccination program, it is very unlikely that this virus will cause disease on Atlantic salmon farms in the Discovery Islands.”
Samples for the research were collected by DFO agents and the findings were reviewed by 39 national and international experts from various disciplines.
According to the Canadian Food Inspection Agency infectious hematopoietic cerosis virus is a contagious virus that can be spread through infected water or equipment as well as infected live or dead fish.
“IHNV is a naturally occurring virus that is found throughout the whole west coast of B.C. and the United States,” Parsons said. “Both Atlantic and sockeye salmon are susceptible to IHNV, although sockeye salmon are less susceptible compared to Atlantic salmon.”
Though it is not a risk to human health finfish species pinks, chums, cohos, chinooks, sockeyes and Atlantic salmon, as well as others, can all be infected. At the moment there is no treatment for the disease, only a vaccination to prevent infection.
“When it does occur it can potentially have quite an impact on both farmed and wild salmon, but as a result of vaccination…there hasn’t been an outbreak on farms in Discovery Islands area since 2013,” Parsons said.
The vaccination for IHNV was licensed and approved by the food inspection agency in 2005.
“IHNV has not occurred on any vaccinated salmon farm since the companies have started using the vaccines,” Parsons said.
Though aquaculture licenses do not require the IHNV vaccination for operation, Parsons said that fish health management plans, that ensure the overall health of the farmed fish, including preventing disease from occurring and preventing it from spreading if it does occur, is mandatory.
“All the companies do have an agreement among themselves to vaccinate all of their fish for IHNV,” he added.
This risk assessment was an important step in addressing B.C. Supreme Court Justice Bruce Cohen’s recommendations made in 2012 through the Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River.
One of the many recommendations made at the time was to determine what pathogens Fraser River sockeye salmon encounter on their migratory route and whether or not farmed salmon are infecting the wild salmon.
IHNV was the first of 10 pathogens which cause disease in sockeye salmon and have been identified to have caused outbreaks in the Discovery Islands region.
“Part of the reason for this interest is the susceptibility of Atlantic salmon to this virus,” said Ingrid Burgetz, national manager of aquaculture regulatory sciences for Fisheries and Oceans Canada. “It has caused disease in the past and also because it is endemic in B.C. and there have been outbreaks in fresh water systems where sockeye salmon in the freshwater system, at the juvenile stage, have been susceptible and it has caused mortality.”
The next series of risk assessments will be on four bacterial pathogens that result in similar symptoms.
Though the risk assessment for IHNV as well as the effectiveness of the vaccinations is promising, the results cannot be applied to other concerning pathogens such as PRV.
“PRV is quite different than IHNV,” said Kyle Garver, a DFO research scientist based in Nanaimo.
At the moment there is no vaccine for PRV but experimental vaccines are in preliminary trials in Norway.
“Whether vaccination will be part of the disease management for PRV is yet to be determined because of other research that is ongoing,” Garver said.