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Pathogen Ecology - FC1204

Description
Overview: Understanding the processes that control the likelihood, and duration, of infection by pathogens is key to developing surveillance, contingency and management plans. It is also of great importance when attempting to assess impact on both wild and farmed stocks of aquatic animals. This project aims to increase our understanding of the epidemic processes and impact of important aquatic animal pathogens under various environmental and husbandry conditions. The project will focus on producing experimental data that can be used to derive models to study the epidemic process of the pathogens of interest under different outbreak scenarios.

Work stream 1: Factors affecting the epidemic processes of notifiable aquatic animal pathogens.
This work stream will focus on infectious haematopoietic necrosis virus (IHNv) infections in rainbow trout, as relatively little is known about the epidemiology of this pathogen, compared to other notifiable viral pathogens such as viral haemorrhagic septicaemia (VHS). Currently there is little experimental evidence on which to base epidemiological models for this pathogen, and in order to prepare for an introduction of IHNv these knowledge gaps need addressing. Experiments conducted in this work stream aim to determine the influence of factors such as host density, temperature, water flows and co-infection with other pathogens on the following key epidemiological parameters:
a) Susceptibility and transmission rates.
b) Duration of infection and shedding.
c) Mortality rate/likelihood of recovery.
The experimental data will be used to parameterize, and further develop, epidemiological models to assess the likelihood of establishment and impact of this notifiable pathogen under a variety conditions. This information will help determine sites and locations at greatest risk from IHNv.

Workstream 2: Pathogen interactions between wild and farmed salmonid populations
Disease is one of the biggest limiting factors to aquaculture production. There is obviously bidirectional flow of pathogens between wild and farmed aquatic animals. Though farm sites may amplify pathogen numbers, the rapid rate of pathogen transmission between fish in a farm setting and the lack of host evolution, may cause virulent, but potentially highly host specific pathogen strains to emerge. Little work has been conducted to understand these processes in pathogens common to trout farming, and therefore little is understood about the processes or impacts that may occur through wild and farm pathogen interactions in this setting. This work package will focus on key diseases of rainbow trout that are known infect on wild salmonids and aims to:
a) Compare the susceptibility of wild salmonids to farm strain of IHNv to determine if their virulence to wild fish changes following adaption to aquaculture conditions.
b) Where required conduct experiments to fill knowledge gaps regarding the life-cycle of key pathogens under a variety of climate, husbandry and environmental scenarios.
c) Review current farm management practices with a view to optimising them in terms of reducing pathogen amplification by farms.
d) Assess the potential impact pathogens discharged from fish farms may have on wild fish stocks.
e) Use modelling approaches to assess practices that could be used on farm to minimise pathogen discharge.
Objective
Objective 1: Conduct experiments to estimate key epidemiological parameters for IHNv and determine the influence of factors such as host density, host size, temperature (under climate change scenarios), water flows and co-infection with other parameters.
Objective 2: Further develop epidemiological models for based on the information gained in objective 1 to assess the likelihood of establishment and impact of IHNv under a variety of husbandary conditions conditions. This information will help inform contingency planning and the proposed Defra surveillance project by identifying sites at greatest risk from IHNv.
Objective 3: Compare the susceptibility of wild salmonids to farm strain pathogens to determine if their virulence to wild fish changes following adaptation to aquaculture conditions.
Objective 4: Conduct experiments to understand the life-cycle of key pathogens used under objective 3 under a variety of climate, husbandary and environmental scenarios in order to inform models developed in objective 6.
Objective 5: Review current farm management practices with a view to identifying and prioritising factors underpinning pathogen amplification and emergence of pathogenicity / virulence on farms. This data will be used to inform the models developed under objective 6, and form the basis of advice to the aquaculture industry.
Objective 6: Produce models using the data derived from objectives 3, 4 and 5 to investigate the interaction of pathogens between farmed and wild fish populations and use these to inform practices minimise disease emergence and pathogen impact.
Time-Scale and Cost
From: 2012

To: 2015

Cost: £380,000
Contractor / Funded Organisations
C E F A S (CEFAS)
Keywords
Epidemiology              
Fish Disease              
Fish Farming              
Fish Health              
IHN