Aquatic diagnostics - the problem of new and emerging disease

Aquatic diagnostics - the problem of new and
emerging disease
Dr Stephen W. Feist
Cefas Weymouth
What are we protecting?
• The environment, fisheries (wild stocks), aquaculture, shellfish,
other…………
Emerging disease
‘A disease which has a significant impact resulting from a) a
change of known pathogenic agent or its spread to a new
geographic area or species; or b) a newly recognised or
suspected pathogenic agent’ (adapted from the OIE Aquatic Animal
Health Code)
• Aquaculture has its share!
• Causes – intensification, diversification, human intervention, evolution, the
aquatic continuum, bad luck?
• Rapid recognition and characterisation is key (-ologies and omics combined)
• Seeing is believing------------------------------------------------------------
Emerging or emerged disease in aquaculture examples
• Acute Hepatopancreatic Necrosis Disease (AHPND) (= Early Mortality
Syndrome, EMS) in shrimp – 2009 ‘a game changer for the future development of
aquaculture’ T. W Flegel DAA9 2014’
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Oyster herpesvirus (OsHV -1 µvar) in oysters - 2008
Francisellosis in cod - 2004
Red Mark Syndrome in trout - 2003
Heart & Skeletal Muscle Inflammation (HSMI) caused by piscine
orthoreovirus (PRV) in salmon – 1999
New disease in rainbow trout similar to HSMI & PRV (2013)
White Spot Syndrome Virus (WSSV) – c1992
Bonamia exitiosa in oysters – 1985 (NZ), 2007 (Spain), 2010 (UK)
Salmonid gill poxvirus (2008)
Histopathological diagnosis in fish (and shellfish)
• Histopathology is a front-line tool for the diagnosis of disease.
• Provides data on the severity of a condition and can be
prognostic.
• An important approach to establish links between the presence of
pathology and pathogens in situ – co-infections & toxicity.
• Classical methods still provide the standards by which other
histological techniques are judged.
• Ability to apply selective and specific markers for pathogen
identification and molecular/biochemical markers of cellular
pathology.
Specialists
Specialists don’t always make the most impact in their field: Wolf,
K. & Markiw, M. E. (1984) Biology contravenes taxonomy in the Myxozoa: new discoveries show
alternation of invertebrate and vertebrate hosts. Science 225: 1449-1452.
Increasing need to work together – integration of techniques
and approaches
Increasing interdisciplinary approaches required
Specialists will always be needed!
‘Phenotype anchoring’
• External disease and (particularly) histopathology provides a ‘phenotypic anchor’ to
understand co-factors (intrinsic host and external environmental influences) affecting
expression of disease.
Beware co-infections!
New approaches need collaboration
• Microscopic lesions
• Gene/protein/metabolite profile
changes
• Pathogenesis and pathogen
characterisation
Laser Capture Micro-dissection
A tool for many aspects of aquatic animal disease –
single cell (or pathogen) isolation possible
Laser-capture dissection and immunohistochemistry reveals chloride
and mucous-cell specific gene expression in gills of seawater
acclimated Atlantic salmon Salmo salar. B. Nowak, K. Cadoret, S.W.
Feist and T.P. Bean (2013) J. Fish Biol.,83: 1459-1467.
Emerging fish disease?
• Cherry fin
- In larger fish characterised by large red mass in pectoral region
(occasionally dorsal)
- No Increased mortality, behavioural changes
- No changes in feeding rate
- No pathology of internal organs seen at necropsy
- A progressive condition
Histological features of sections through early ‘cherry fin’ lesions in
fingerlings.
A. Low power view showing the base of the pectoral fin and associated fin ray with
a marked inflammatory response (*); B. Section through bone showing chronic
inflammation (*) affecting region between the bone and adjacent cartilage.
*
Emerged fish disease
• Red Mark Syndrome (RMS) (= US SD)
• Skin affected to sub-dermal layer (full thickness lesion)
• Moderate to marked inflammatory response
• Downgrading of carcasses
• Now present in a number of European countries
• Significant economic impact in market sized fish
• Recently associated with RLO - molecular and visualised by EM
Wild fish and shellfish stocks
- sentinels of environmental change and source of disease threats
Declining monitoring activities
•
Advice to Government Departments (e.g. combating causes
and reducing impacts of pollution)
•
Meeting international commitments (e.g. OSPAR JAMP,
MSFD)
•
Disease recorded as a biological end-point of historical
exposure to contaminants.
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Emerging disease of potential public health concern.
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Population level effects.
Threats to aquaculture from wild fish
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VHS in herring (Dixon et al., 1997)
Francisellosis in cod (Zerihun et al., 2011)
Parasites – Myxozoans (Feist & Longshaw, 2006)
•
Zoonotic pathogens
- Anisakis (Nematode)
- Helminths
- Kudoa (Myxozoan) !!
Rationale and approach
• Sentinel flatfish (dab, flounder) sampled annually.
• ‘Commercial’ fish species examined (opportunistic basis only).
• Integrated cruise (external disease, pathology, biomarkers,
chemistry).
• Multiple stations are sampled.
• Data contributes to national Marine Environment Monitoring
Reports.
• Quality assured process via ICES and BEQUALM.
• Data for international environmental quality assessments.
eDNA approach for pathogen diversity and
disease risk
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Novel biodiversity and parasite assemblages
Improved understanding relationship between presence in the environment
and infection in host(s)
Potential for mapping distribution of pathogens
Assessing potential emerging disease risks for aquaculture and wild species
eDNA for pathogen
investigation:
Who, where, what,
how
Ecological &
epidemiological
approaches
Phylogenetic
approaches
Genomic
approaches
Visualisation &
pathology
‘ground-truthing’
Integrated science. Pathogen
ecology for assessing disease risk
and mitigation
Productive, complementary
collaborations
Policy relevance
Stentiford, G.D., Feist, S.W., Stone, D.M., Peeler, E.J., Bass, D. (2014). Policy,
phylogeny and the parasite. Trends in Parasitology 1-8.
Networking and training
• Workshops – e.g. ‘Histopathology workshops’ at the
EAFP Conferences and Cefas.
• Courses – e.g. ‘Toxicologic pathology of fish’ (includes
infectious disease aspects) held at Cefas and University
of Bern, Switzerland.
• Crustacean EURL
• OIE Collaborating Centres
• On-line facilities (proficiency testing.)
• Cefas ISO 17025 accredited
• Conferences!
Developing approaches
• Evolving threats need innovative science and partnership
• Don’t ‘trade-off’ one technique against another
• Understand the limitations of each
• Work towards a biological basis to discriminate between a disease-causing
taxon and non disease-causing relatives
• Cascade of data for pathogen identification (Ecology, Pathology, Morphology,
ribosomal gene sequence, alternative gene sequence, multi-gene phylogeny,
eDNA for pathogen divergence (Stentiford et al., 2014).
• Needs specialists working together.
We are a community
Take home points
Understanding the threat
Technical needs
Improved management
1.
Emerging diseases are a continuing and prominent threat.
2.
Lack of information on pathogen ecology/lifecycles.
3.
Lack of knowledge of pathogen diversity (threat).
4.
Lack of knowledge of disease occurrence in wild populations (threat to cultured
stocks).
5.
6.
7.
8.
Diagnostic challenges require innovative solutions and rapid
development.
Integrated diagnostic and risk assessment approaches
essential.
Lack of histopathologists and taxonomists.
Rapid response to emerging disease occurrence needed at all levels of
management.
Most of these are not new but associated problems persist!
Acknowledgements
The workshop organisers for the invitation to give this presentation
Department for Environment and Rural Affairs contract FB002 –
Surveillance, detection and investigation of new and emerging.
Exotic and notifiable diseases of aquatic animals
Thanks!