AFBINI meeting F
ish health professionals, vets and leading produc- ers from the aquaculture industry gathered at the AFBINI Veterinary Sciences Division laboratories in Belfast at the end of last
year for a comprehensive review and discussion on diagnostic and monitoring techniques for identifying and managing pancreas disease (PD). The one-day seminar, hosted by AFBINI and sponsored by MSD Animal Health, provided a broad spectrum of 40 professional and commer- cial delegates with a panel of leading speakers on the disease. The objective of the programme was to bring together the latest knowledge and experience and to understand how the various disciplines and techniques can help drive suc- cessful diagnostic and management practices. Simon Doherty, Veterinary Research Officer
at AFBINI, opened the seminar and together with David Graham (formerly also from AFBINI) provided an introduction to the topics and an overview of the day.
BUILDING A DIAGNOSIS
The first speaker was Marian McLoughlin MVB PhD MRCVS, from Aquatic Veterinary Services, whose presentation ‘Differential Diagnosis of common viral diseases of Marine Atlantic Salmon’ started by explaining the life cycle and production timeline for salmon. She then highlighted at which stages the risk period from a number of diseases such as Infectious Pancreatic Necrosis (IPN), Pancreas Disease (PD), Heart and Skeletal Muscle Inflammation (HSMI) and Cardiomyopathy syndrome (CMS) were understood to be at their greatest and where epidemiological and clinical events and observations corresponded. Dr McLoughlin then explained the limitations of reaching a diagnosis by purely histological examination by highlighting that many of the diseases presented common responses to challenge and that concurrent infections can and do occur. The presentation included field and experimental data to demonstrate the progression of PD challenge as confirmed through histopathology, PCR and blood analy- sis. Dr McLoughlin also detailed the limitations of RT-PCR testing by explaining that, while RT-PCR can confirm the presence of a specific infection, a positive result did not necessarily indicate disease. The concluding message was that, with PD, it is possible to obtain a more accurate picture by looking at specific blood and tissue samples but limitations exist and for a more conclusive diagnosis the complete historical, clinical and epidemiological profile is needed with supporting veterinary advice.
THE ROLE OF RT-PCR TESTING
A presentation, entitled ‘The pros and cons of RT-PCR testing’, from David Graham MVB PhD MRCVS followed by looking in more detail at how RT-PCR testing has evolved to become a ‘Next Generation’ diagnostic tool used widely across animal health and production. The ad- vantages of availability, relative speed and accuracy were explained. Dr Graham highlighted how the technique had been particularly useful in confirming alphavirus subtypes of PD from salmon production sites in the UK
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and Ireland. Vets and producers had benefited through an increased ability to interrogate groups of results and un- derstand the progression of the disease in terms of subtypes, instances and frequency. Continuing the theme developed by Dr McLoughlin a number of points were made relating to the danger in accepting the use of RT-PCR as an absolute diagnostic tool. Positive results can result from salmon that have had SAV inactivated vaccines. RT-PCR testing is also not necessarily able to distinguish between in- fectious and non-infectious virus. It is accepted that, while highly valuable in identifying and mapping the virus both individually and collec- tively, the key benefit is in utilising the technol- ogy as part of a broader diagnosis strategy.
Opposite page: delegates at the Belfast meeting. Top: Lene Hoegest, MSD’s Technical Manager Aquaculture. Above: Keith Morris, MSD’s Commercial Manager
UNDERSTANDING DIAGNOSTIC AND SAMPLING OPTIONS As a useful conclusion to the first session Simon Doherty BVMS, MRCVS, Veterinary Research Officer at AFBINI, presented a detailed and practical guide in his presentation ‘Best practice for surveillance and diagnostic sampling’. He started with the fundamental point, what is the question that we are we try- ing to answer by sampling – the prevalence of infection or the presence of disease? Once the objective was understood Simon then mapped out the logical thought process with which to determine the merits and functions of the ap- propriate tools, tests and techniques to use. As an example the timing for using specific tests in relation to the stage of a disease outbreak was explored (eg testing blood by PCR after the acute SAV viraemic phase was a waste of time). The protocol for which individual fish to sample and what samples to take from how many fish
were all detailed and when it was appropriate to pool samples (pooled samples for SAV antibody or crea- tine phosphokinase analysis are not useful, while pooled tissue for SAV RT+PCR could be useful). The process for the appropriate and safe handling of samples was illustrated with clear guidelines on how to complete and transport submissions. The concluding message was that the AFBINI is a dedicated agency that is in a position to assist the whole diagnostic process and that the skills and experience within the organisation are actively available to support producers and vets.
For a more conclusive diagnosis
a complete profile is needed
NORWEGIAN FIELD STUDY
The results from an extensive PD field study ‘PDfri’ in Norway were presented by Mona Jansen from The National Veterinary Institute of Norway. The PDfri project was established in 2007 with aims of reducing the spread, outbreaks and impact of PD in farmed salmon. 337 sites, which accounted for 99% of the targeted sites, agreed to participate and fund the project at a cost of €1250 each. Production, health and vaccination data was recorded and reported monthly. With the comprehensive data collection it was possible to report very directly on a number of parameters which included cumulative levels of poor growth, discards and mortality at both infected and non-infected sites and for vaccinated and non-vacci- nated fish. The information presented confirmed that the
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