New research by scientist Dr. Emiliano Di Cicco shows that piscine orthoreovirus (PRV), a disease-causing agent infesting B.C.’s Atlantic salmon farms, first showed up in B.C. approximately 30 years ago, coinciding with the arrival of fish farm companies.
Dr. Emiliano Di Cicco recently spoke to the House of Commons Standing Committee on Fisheries and Oceans (FOPO). The committee is currently conducting an investigation into the state of Pacific salmon and will report to Parliament with its findings and recommendations.
Dr. Di Cicco has extensive experience in salmon pathogens, including viruses and bacteria and spoke on new research that highlights the disease risks of open-net salmon farms and hatcheries.
Some key takeaways from his testimony:
- The research Dr. Di Cicco is involved in, is the most comprehensive investigation of infection and diseases ever undertaken in wild salmon.
- Piscine orthoreovirus (PRV) affects the condition and survival of chinook and coho salmon.
- PRV was introduced to B.C. from the Atlantic Ocean about 30 years ago and is currently prevalent in salmon farms.
- Wild salmon sampled within 30 kilometres of a salmon farm showed the highest rate of infection by PRV.
- A bacterium called Tenacibaculum maritimum appears to be responsible for significant mortality on salmon farms and can affect the health and survival of wild sockeye salmon, chinook and coho.
- Hatcheries can play a role in disease spread and evolution in wild salmon.
Here is his introductory testimony in its entirety:
Thank you, Chair, and thank you to all the members of the committee for inviting me here. It’s a big honour for me to be here today to attend this session.
I’ve been told to say my statement is going to take five minutes and 50 seconds, so hopefully I’ll be able to say it all.
I would like to introduce myself. I’m Emiliano Di Cicco. I’m a doctor of veterinary medicine and I have a Ph.D. in fish pathology. I have worked in this field for over 15 years, and for the past six years in British Columbia.
In 2015, I was hired as a fish pathologist and project manager for the strategic salmon health initiative, also known as SSHI. The primary objective was to assess the contribution of pathogens and diseases to the decline of Pacific salmon.
We have evaluated more than 50 infective agents across 30,000 salmon sampled over the last decade as the basis of the most comprehensive investigation of infection and diseases ever undertaken in wild salmon. We have identified several infectious agents that appear to impact the health of salmon in the wild, with effects that can be as great as the well-known effects of sea surface temperature.
Just to give you a few examples, we found that piscine orthoreovirus, also known as PRV, is associated with condition and survival in chinook and coho salmon. This virus, introduced to B.C. from the Atlantic Ocean about 30 years ago, is also prevalent in salmon farms. This is an important aspect to keep in mind, because viruses carry the potential to rapidly evolve, and just like the current situation with the coronavirus, the availability of a high number of hosts favours viral replication and facilitates the development of more dangerous variants.
As a pathologist working in the SSHI, I led the two main studies on the effect of PRV infection in British Columbia. The first study identified the disease called heart and skeletal muscle inflammation, also called HSMI, associated with the PRV in farmed Atlantic salmon in B.C.
Considering that the weight of evidence worldwide indicates that PRV causes HSMI in Atlantic salmon, we therefore recommend that PRV be treated as a pathogenic agent regulated under the Fisheries Act.
In the second study, we found that PRV can also induce a related disease in chinook salmon, called jaundice anemia. This disease has also been described in Chilean coho, and our wild salmon carrying a high abundance of PRV develop similar pathology to what we described on farms. Finally, B.C. salmon sampled within 30 kilometres of a salmon farm showed the highest rate of infection by PRV.
A similar situation has been revealed for another bacterium, called Tenacibaculum maritimum. It appears to be responsible for significant mortality on salmon farms and likely plays a role in the health and survivorship of sockeye salmon, chinook and coho.
Importantly, this bacterium has been found to be abundant in the water around active salmon farms during outbreaks, and the risk of infection in Fraser River sockeye salmon is highest as they pass by farms in the Discovery Islands.
One of the 15 salmon viruses newly discovered by our team is the nidovirus, which is related to coronaviruses. It infects gills—the respiratory tissue of salmon. We see this virus most commonly in fish released by our federal hatcheries. Preliminary results indicate that this virus may play an important role in the survival of juvenile salmon upon entry into the marine environment.
However, there are some agents that impact the survival of wild salmon that are naturally present in their ecosystems. An example is a small skin parasite that causes white spot disease in juvenile Pacific salmon in fresh water and appears to have a significant carryover effect upon ocean survival.
The agents I just mentioned are not the only ones posing a risk to our wild salmon, but they are among the most significant and consistent across species.
In recommending management actions, we can only mitigate factors that we can control, most of which will be anthropogenic. When it comes to diseases in salmon, the main lever we can control is cultured fish, including salmon farms and hatcheries. We have the power to control when and how cultured salmon are grown and their abundance relative to wild salmon. We can regulate the type and level of infection that would be tolerated. In this context, a closed containment system for salmon farms is strongly recommended.
Furthermore, there is a risk associated with hatcheries releasing a large number of Pacific salmon, which may not only compete for a dwindling food supply with wild salmon, but could represent an additional source of transmission and evolution of diseases. Therefore, proactive monitoring and regulation of the health and condition of hatchery fish before release into the ocean is essential. All testing should be available publicly to provide confidence in our management system.
As my last remark, I would like to say that the expression of disease associated with a pathogen is often triggered by environmental conditions that a fish experiences. We should expect that diseases will increase in frequency and impact as the climate situation worsens. The cumulative impacts of stress and diseases are likely not simply additive, and there is no doubt that the direct and indirect effects of climate change are impacting the survival of salmon in freshwater estuaries and the ocean. This is why rapid action to deal with fish pathogens and diseases is not only recommended but necessary. We have no time to waste. We need mitigation and restoration now.
Watch Dr. Emiliano Di Cicco’s presentation.
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