Fisheries Research Services is an agency of the Scottish Executive

FRS Marine Laboratory PO Box 101 375 Victoria Road Aberdeen AB11 9DB UK

tel +44 (0)1224 876544 fax +44 (0)1224 295511

enquiries@marlab.ac.uk http://www.frs-scotland.gov.uk

Fisheries Research Services

Epidemiology at Fisheries Research Services

IntroductionEpidemiologists study the spread of diseases to find ways

of eliminating or reducing resultant problems. At Fisheries

Research Services (FRS), epidemiologists work on diseases

of wild and farmed fish, and investigate the potential for

interactions between these two groups. This work is

conducted in collaboration with a range of wild fish

interests and aquaculture bodies, as well as other

government organisations in Scotland, the rest of the UK,

and elsewhere.

Key Diseases and Pathogens StudiedInclude:

Infectious Pancreatic Necrosis (IPN)

Infectious pancreatic necrosis (IPN) is the most damaging

viral disease of farmed salmon production present in the

EU. Routine data collected by FRS Fish Health Inspectors

have been used to describe the prevalence and dynamics

of IPN virus (IPNV) in salmon farms. A case - control study

has been carried out to identify factors associated with

sites that have clinical IPN disease cases. Experimental

work on infection and on virus shedding by infected fish

is being conducted. Data gathered from both groups of

experiments will be used in hydrographic models of

currents. These models will inform on separation of farms

to minimise infection risks. Epidemiology has contributed

to a government-industry report on IPN control policy,

recently submitted to the Scottish Executive and available

o n o u r w e b s i t e a t : h t t p : / / w w w . f r s -

scotland.gov.uk/FRS.Web/Uploads/Documents/

IPNSubgroupReport.pdf

IPNV has also been surveyed in wild fish in both marine

and fresh water. Generally, prevalence has been found

to be very low and not increasing, but IPNV has been

detected in several species of fish in which it has not

previously been reported in Scottish waters. A pilot survey

of fry in wild redds near rainbow trout farms, carried out

in collaboration with the Atlantic Salmon Trust, found no

evidence of IPN infection. Gene sequencing is used to

further the understanding of the link between viruses in

wild and farmed fish.

Infectious Salmon Anaemia (ISA)

Between 1998 and 1999 a major epidemic of infectious

salmon anaemia ( ISA) occurred in Scotland. The need to

understand and control this disease (which cost an

estimated £25M to eradicate) led in part to the

development of epidemiology at FRS. Scientists at FRS

worked in collaboration with the industry to develope

basic epidemiological principles of movement restriction,

culling and control, and surveillance zones for the control

of ISA. To prevent further outbreaks, current work includes

field studies of ISA in the Faroe Islands, experimental

studies of infectious salmon anaemia virus (ISAV)

shedding and infection dose, analysis of data from the

Scottish epidemic (particularly risk analysis of harvesting

and well boat movements) and surveillance of wild fish.

The aim of this closely targeted research is to prevent ISA

returning to Scotland, or to contain it should it recur.

Culling during the ISA epidemic

Fisheries Research Services is an agency of the Scottish Executive

FRS Marine Laboratory PO Box 101 375 Victoria Road Aberdeen AB11 9DB UK

tel +44 (0)1224 876544 fax +44 (0)1224 295511

enquiries@marlab.ac.uk http://www.frs-scotland.gov.uk © Crown copyright

Fisheries Research Services

Sea Lice

Sea lice are a major pest of farmed salmon and wild

salmonids. Scientists and epidemiologists at FRS Marine

and Freshwater Laboratories, are studying sea lice

dynamics in an intensive study of Loch Torridon and

elsewhere. Epidemiological and hydrodynamic modelling

of dispersal of larval lice is helping to understand the

transmission of the parasite.

New Species in AquacultureThe growing interest in diversification in aquaculture has

resulted in the production of species such as cod and

halibut on an increasing scale. As little is known about

the diseases which may emerge in this sector, FRS is

conducting a programme of strategic research aimed at

identifying and minimising the risk of diseases. Surveys

of wild gadoid fish for viruses, bacteria and parasites

have begun with the aim of obtaining ‘baseline’ data.

Future surveys will use these data to help quantify changes

as aquaculture increases, and possible problem

pathogens can be identified at an early stage. Historical

patterns of disease emergence in salmon and other

established aquaculture species and theoretical methods

such as virulence evolution theory and risk analysis are

being used to develop best practice to minimise disease

emergence. This work will shortly be published in a

government-industry report, which will be available via

our website.

The FutureEpidemiologists at FRS have a range of skills in

surveillance and analysis of disease of wild and farmed

fish. This experience was developed during the control

of ISA and is being applied to obtain an increasing

understanding of existing disease, particularly IPN, and

used in a predictive way to reduce likely disease problems

particularly in new species. Focus will change as different

disease problems emerge. To address these, new methods

such as risk analysis, contact structure modelling,

improved surveillance methods, and genetic epidemiology

are being applied.

AAAH13|05|04

Surveillance for pathogens of wild fish on RV Clupea

Sea lice infestation and damage