Risk factors for escalating saprolegniosis outbreaks in salmon farms (RIFE-SOS)

Fish diseases are a huge threat for the aquaculture industry and for global food security. Some of the most important disease-causing organisms in aquaculture are part of the oomycetes or watermoulds, in particular Saprolegnia parasitica, Saprolegnia diclina and Saprolegnia australis are causing serious fish losses. Collectively, these fungal-like organisms are responsible for at least 10% annual mortalities in most salmon hatcheries and freshwater sites. Consequently, Saprolegnia ranks among the most important pathogens of Atlantic salmon.

Unfortunately, over the last few years the incidences of saprolegniosis outbreaks in Scottish farms have significantly increased. Indeed, some sites have had very high losses due to saprolegniosis. Whereas other farms have remained largely disease free. The reasons as to why some farms are badly affected and others seem to avoid disease outbreaks, with apparent identical welfare standards and husbandry management practises, are at present completely unclear and form the main rational for the current application.

Our hypothesis is that several risk factors (pertaining to fish, pathogens and the environment) are playing a synergistic role in suppressing immunity in fish towards Saprolegnia, which lead to outbreaks of saprolegniosis. Therefore, we propose a concerted industry-wide, industry-led and industry-supported research programme to discover, map, model and understand the main drivers, risk factors, that allow saprolegniosis outbreaks.

A "big data" resource will be created that will be scrutinised with statistical methods to identify the main risk factors and conditions for outbreaks of saprolegniosis. Undoubtedly, identifying the main, or a combination of, risk factors will greatly aid the salmon aquaculture industry to pre-empt any future outbreaks and would lead to an integrated approach to saprolegniosis management, which would result in increased welfare standards, improved fish health, fewer losses and a reduction in production and treatment costs.

Fish diseases are a huge threat for the aquaculture industry and for global food security. Some of the most important disease-causing organisms in aquaculture are part of the oomycetes or watermoulds, in particular three Saprolegnia species are causing serious fish losses.

Our hypothesis is that several risk factors (pertaining to fish, pathogens and the environment) are playing a synergistic role in suppressing immunity in fish towards Saprolegnia, which lead to outbreaks of saprolegniosis. Therefore, we propose a concerted industry-wide, industry-led and industry-supported research programme to discover, map, model and understand the main drivers, risk factors, that allow saprolegniosis outbreaks.

We will investigate for Fish: the genetic & historical background, developmental stage / age, size of fish, (anti-microbial) gene expression, immune status, cortisol production, mucus viscosity and quality, vaccination status, formalin treatment after vaccination, stock densities, feed and feeding practices and handling of fish / grading, mortality / moribund removal. For the Pathogen we will study: presence / absence of pathogen, spore load, species/strain, effectivity of formalin treatment, salt tolerance. For the Environment we will investigate: temperature (changes), oxygen levels, CO2 levels, toxic metals quantities, peat / organic content in water, salt concentration, pH and flow rate of water and microbial community.

A "big data" resource will be created that will be scrutinised with statistical methods to identify the main risk factors and conditions for outbreaks of saprolegniosis. Undoubtedly, identifying the main, or a combination of, risk factors will greatly aid the salmon aquaculture industry to pre-empt any future outbreaks and would lead to an integrated approach to saprolegniosis management, which would result in increased welfare standards, improved fish health, fewer losses and a reduction in production and treatment costs.

Who will benefit from this research?

(1) Pharmaceutical, biotechnology industries, the aquaculture industry (fish farmers), stake holders.
How will they benefit?
With the proposed project we will provide novel knowledge on the Saprolegnia-host interaction, in particular we will develop a risk prediction tool for saprolegniosis that would be extremely valuable for the farmers. Furthermore, we will investigate several parameters that might be important for disease initiation for two consecutive years. For example, we will determine several environmental parameters, the immune status of fish before and during an infection, investigate the quality and quantity of mucous production before and during infection, perform gene expression analysis in the skin, determine which Saprolegnia species are present in the farms, quantify spore levels, uncover microbial communities on the fish. All the data will be analysed with statistical and PCA modelling to determine what the main risk factors are for saprolegniosis.
The results of our study will allow farmers to anticipate better when to intervene with control measures. This should minimize the use of chemicals, because a more targeted and integrated approach can be implemented, which is good for the environment, good for the farm workers and also increases profitability for the fish farm companies.

What will be done to ensure that they have the opportunity to benefit?
We will have quarterly RIFE-SOS management meetings where we will communicate our results and discuss better husbandry methods to reduce saprolegniosis outbreaks.
Furthermore, we will present our results at appropriate scientific meetings, and make reagents generated as part of this project available to other researchers under structured material transfer agreements. We will take advantage of natural liaison opportunities that emerge from our membership of BBSRC Networks. We will also work together with the Research and Innovation unit at the University of Aberdeen to identify findings that have clear potential for commercial exploitation. We will proactively inform all our partners about our findings by giving seminars for fish farm health managers. The PI currently gives such seminars on a very regular basis at several of the companies involved in the current application and at other stakeholder workshops (i.e. RSPCA, SSPO meetings).

(2): The public
How will they benefit?
The general public will benefit from this research in a number of ways because our work will ultimately safeguard food production. We will ensure that the public is informed about our research, forming part of a national effort by the science community to ensure greater scientific literacy among the general population. Our data will be published in open access journals.

What will be done to ensure that they have the opportunity to benefit?
Ensuring public awareness of our research and allowing a public education impact to be made, we will use our groups' web sites to communicate our science to the public. Key research outcomes from this proposal will be communicated as press releases by the University of Aberdeen, SAIC, RSPCA and SSPO Communication sections after agreement with all our partners.

(3) Policy makers and (non)-government bodies
How will they benefit?
Legislators and (non)-government bodies involved in fish farming (such as RSPCA, DEFRA, SEPA, SSPO, the British Trout Association etc.) will be able to use some of our generated data to better inform the public policy makers and legislators about saprolegniosis outbreaks in the UK.

What will be done to ensure that they have the opportunity to benefit?
We have excellent links with several representatives of these organisations and we will actively approach them to consider our findings.

(4) Fish
How will they benefit?
With our risk prediction tool, we hope that we will ultimately reduce mortality of salmon and contribute to better fish welfare.