SARF 100 - Scottish Aquaculture Research Forum

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Apr 16, 2015 - Ichthyophthirius multifiliis or 'Ich' is a ciliate protistan parasite of freshwater ... spots appear to be on the surface of the skin, I. multifiliis is often ...

SARF 100 - Review of freshwater treatments used in the Scottish freshwater rainbow trout aquaculture industry

A REPORT COMMISSIONED BY SARF AND PREPARED BY David Verner-Jeffreys

CEFAS

Published by the: Scottish Aquaculture Research Forum (SARF) This report is available at: http://www.sarf.org.uk Dissemination Statement This publication may be re-used free of charge in any format or medium. It may only be reused accurately and not in a misleading context. All material must be acknowledged as SARF copyright and use of it must give the title of the source publication. W here third party copyright material has been identified, further use of that material requires permission from the copyright holders concerned. Disclaimer The opinions expressed in this report do not necessarily reflect the views of SARF and SARF is not liable for the accuracy of the information provided or responsible for any use of the content. Suggested Citation:

Verner-Jeffreys, D.W., Taylor, N.J. (2015) Review of freshwater treatments used in the Scottish freshwater rainbow trout aquaculture industry. Scottish Aquaculture Research Forum Report SARF100 Title: Survey of Pacific oyster in Scotland ISBN: 978-1-907266-66-9

First published: April 2015 © SARF 2015

SARF 100 Review of Freshwater Treatments

Cefas contract report C6175

SARF 100 Review of freshwater treatments used in the Scottish freshwater rainbow trout aquaculture industry

Authors: David Verner-Jeffreys & Nick Taylor

Issue date: 16th April 2015

Centre for Environment, Fisheries and Aquaculture Science,

PageWeymouth, 1 of 51 Dorset, UK, DT4 8UB Weymouth Laboratory, Tel +44 1305 206600, Fax : +44 1305 206601.

SARF 100 Review of Freshwater Treatments

Cefas Document Control

Title:

SARF 100 Review of freshwater treatments used in the Scottish freshwater rainbow trout aquaculture industry

Submitted to:

SARF (R. Slaski & S. Gray)

Date submitted:

16/04/15

Project Manager:

D. Verner-Jeffreys

Report compiled by:

D. Verner-Jeffreys

Quality control by:

E. Peeler & N Bagwell

Approved by & date:

E. Peeler 7/11/14

Version:

3

Version Control History Author

Date

Comment

Version

D. Verner-Jeffreys

24/10/14

Submitted to internal review by E.J Peeler, N. Bagwell and S. Feist

1.0

G. Rimmer

07/11/14

Template change

2.0

D. Verner-Jeffreys

10/11/14

Update and incorporate revisions for submission to SARF

2.1

D. Verner-Jeffreys

16/4/15

Incorporate revisions 3.0 following report review by SARF

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SARF 100 Review of Freshwater Treatments

Executive Summary Availability of effective treatments for control of infectious diseases is a critical requirement of the Scottish and wider UK rainbow trout industry. The purpose of this project was to: identify the key diseases that affect freshwater aquaculture operations in Scotland, particularly the trout sector, and determine their relative impact; to identify the main methods used to control these diseases; identify the potential consequences if any of the main control methods were to be withdrawn; and finally, to identify any new potential treatments that could be used instead, if any of the main treatments were to be withdrawn. Producers, vets and health professionals surveyed confirmed that production was constrained by a limited group of common diseases that affected rainbow trout producers in England and Scotland. These included rainbow trout fry syndrome (RTFS) caused by the bacterium Flavobacterium psychrophilum, white spot disease caused by the endoparasite Ichthyophonus multifiliis, enteric redmouth disease (ERM) caused by the bacterium Yersinia ruckeri, proliferative kidney disease caused by the myxozoan parasite Tetracapsuoidesa bryosalmonae, red mark syndrome (RMS) and bacterial gill disease (BGD). The main treatments available to control these conditions were limited, with florfenicol reportedly used by all producers to control RTFS, formalin used extensively to control white spot and a range of parasites and chloramine T to treat bacterial gill disease. ERM was mainly controlled by vaccination, particularly via dip vaccination of fry with the Relera dual antigen vaccine. Other licensed antibiotics (oxytetracycline, amoxicillin and oxolinic acid) were used to treat sporadic outbreaks of ERM, in fish where vaccine protection had waned, and furunculosis. The major reliance of the industry on florfenicol and formalin was concerning. Firstly there were limited identified alternatives to control RTFS in the event of RTFS-causing strains of F. psychrophilum developing resistance to florfenicol. There is also pressure at an EU level to withdraw formalin from sale as a biocide. Possible alternatives to the use of formalin products purchased for biocidal applications were reviewed in the event of their withdrawal from sale. For control of white spot it may be possible to use a licensed product marketed in Spain for the control of parasites of turbot under the veterinary cascade. The bronopol containing medicine Pyceze is one identified alternative that may be used. Where systems can be engineered to allow its use, Salt (sodium chloride), either via low concentration continuous dosing for several days, or short duration high concentration flushes is also a potential treatment. Practical issues with regards either maintaining low concentrations of salt, or dealing with high concentration effluents, may limit the use of this treatment strategy though. Project staff also consulted with Danish producers who are trialing the use of peracetic acid. For control of some ectoparasites, particularly flukes (e.g. trichodina), praziquantel, either as a water-based or in feed treatment, may also be an option to explore. Review of the literature suggested that caprylic acid, green tea extract and epigallocatechin gallate (EGCG), Piscidin 2, quinine, Triclabendazole and potassium ferrate may all have some promise as alternative treatments. Selection of any alternative treatments should be guided by whether they are likely to be readily useable. In this regards, products that already have approval for use in food animal production, either as biocides, feed additives or as medicines should be preferred in the first instance.

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SARF 100 Review of Freshwater Treatments

Recommendations       

Undertake further controlled studies (laboratory and field based) on the effectiveness of peracetic acid for the control of white spot and other production diseases. Obtain further information on the margin of safety of peracetic acid at different temperatures via target animal safety studies, at both a farm and laboratory scale. Continue to support efforts to develop alternatives vaccines for the control of RTFS. Determine the effectiveness of alternative antibiotics to florfenicol to control RTFS infections caused by Flavobacterium psychrophilum. Explore practicalities of importing formalin-containing medicinal products licensed in other Ms for control of fish diseases for controlling white spot and other diseases. Investigate use of mechanical control measures to reduce the impact of white spot in rainbow trout production systems. In vivo trials are needed to follow up some of the potential alternative chemical treatments identified (e.g. caprylic acid, green tea extract and epigallocatechin gallate (EGCG), Piscidin 2, quinine, Triclabendazole and potassium ferrate).

Conclusions The survey clearly demonstrates that the rainbow trout industry is heavily reliant on a very limited range of treatment options to control major production diseases. Discussions with fish medicine producers and veterinarians also suggest that the freshwater stage of the Atlantic salmon industry is similarly reliant on a small range of similar treatments to those used in the trout industry. In particular, there is also heavy reliance on formalin to control white spot disease and Costia in some hatcheries, and similar reports that florfenicol is the only effective treatment for the control of Flavobacterium psychrophilum. They also report that formalin is used quite extensively to control saprolegniasis in vaccinated salmon smolts prior to seawater transfer. These findings are collectively concerning as either the withdrawal of formalin from sale, or the development of resistance to florfenicol in Flavobacterium psychrophilum, could affect the viability of both industries.

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SARF 100 Review of Freshwater Treatments

Table of Contents

Cefas Document Control......................................................................................................................... 2 Executive Summary................................................................................................................................. 3 Recommendations .................................................................................................................................. 4 Conclusions ............................................................................................................................................. 4 Table of Contents.................................................................................................................................... 5 1

Introduction .................................................................................................................................... 8 1.1

2

3

4

Aims......................................................................................................................................... 8

Materials and Methods................................................................................................................... 8 2.1

Treatments survey .................................................................................................................. 8

2.2

Identification of alternative treatments ................................................................................. 9

Overview of licensing and use of medicines and other chemicals in the freshwater industry ...... 9 3.1

Medicines................................................................................................................................ 9

3.2

Biocides .................................................................................................................................10

3.3

Disinfectant testing schemes ................................................................................................10

3.3.1

Defra disinfectant approvals.........................................................................................10

3.3.2

Aquaculture disinfectant listing scheme.......................................................................11

3.4

Use of biocides for disease control purposes .......................................................................11

3.5

Discharge consents ...............................................................................................................12

Rainbow trout production: Main diseases....................................................................................12 4.1

Producers, veterinarians and health professionals surveyed...............................................12

4.2 Summary of main diseases identified in last 12 months by producers and health professionals .....................................................................................................................................13 4.2.1

Rainbow trout fry syndrome (RTFS)..............................................................................14

4.2.2

Red Mark Syndrome .....................................................................................................14

4.2.3

White spot.....................................................................................................................15

4.2.4

Bacterial gill disease (BGD) ...........................................................................................18

4.2.5

Enteric redmouth disease (ERM) ..................................................................................18

4.2.6

Furunculosis ..................................................................................................................19

4.2.7

Saprolegniasis ...............................................................................................................19

4.2.8

Costia.............................................................................................................................19

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SARF 100 Review of Freshwater Treatments 4.2.9

Other ectoparasites ......................................................................................................20

4.2.10

Proliferative kidney disease ..........................................................................................20

4.2.11

Strawberry disease........................................................................................................20

4.2.12

Puffy skin disease ..........................................................................................................20

4.2.13

Infectious pancreatic necrosis (IPN) .............................................................................21

..........................................................................................................................................................22

5

4.2.14

Bacterial Kidney Disease (BKD) .....................................................................................22

4.2.15

Cherry fin.......................................................................................................................24

4.2.16

Rainbow trout gastroenteritis (RTGE)...........................................................................24

4.3

Reported most important diseases.......................................................................................24

4.4

Estimated impact of diseases without main control strategies............................................25

Main treatments ...........................................................................................................................26 5.1

Florfenicol .............................................................................................................................26

5.2

Other antimicrobials: oxytetracycline, amoxicillin and oxolinic acid....................................26

5.3

Pyceze................................................................................................................................26

5.4

Formalin ................................................................................................................................31

5.4.1

Likely continued availability of formalin .......................................................................31

5.4.2 Use of formalin containing medicinal products in other EU Member States and internationally...............................................................................................................................31

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SARF 100 Review of Freshwater Treatments

6

5.5

Chloramine T.........................................................................................................................32

5.6

Benzalkonium chloride..........................................................................................................32

5.7

Vaccines ................................................................................................................................33

Alternative treatments..................................................................................................................33 6.1

6.1.1

Vaccines ........................................................................................................................33

6.1.2

Other antibiotics ...........................................................................................................33

6.1.3

Other treatments ..........................................................................................................34

6.2

7

Alternatives to florfenicol for treatment of RTFS .................................................................33

Alternatives to formalin for treatment of white spot...........................................................34

6.2.1

Salt.................................................................................................................................34

6.2.2

Salt: continuous dosing.................................................................................................34

6.2.3

Salt: short duration dosing............................................................................................35

6.2.4

Issues with regards use of salt to control white spot ...................................................35

6.2.5

Benzalkonium chloride..................................................................................................35

6.2.6

Bronopol........................................................................................................................35

6.2.7

Potassium ferrate..........................................................................................................36

6.2.8

Praziquantal ..................................................................................................................36

6.2.9

Copper sulphate............................................................................................................36

6.2.10

Peracetic acid ................................................................................................................37

6.2.11

Hydrogen peroxide........................................................................................................38

6.2.12

Chloramine T .................................................................................................................38

6.2.13

Caprylic acid ..................................................................................................................39

6.2.14

Green tea extract and epigallocatechin gallate (EGCG)................................................40

6.2.15

Piscidin 2 .......................................................................................................................41

6.2.16

Quinine..........................................................................................................................41

6.2.17

Mechanical and other management methods .............................................................43

Summary .......................................................................................................................................44 7.1

Recommendations ................................................................................................................44

8

Acknowledgements.......................................................................................................................44

9

References ....................................................................................................................................45

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SARF 100 Review of Freshwater Treatments

1 Introduction Effective and safe chemical, pharmaceutical and vaccine treatments for the control of diseases are a critical requirement for aquaculture operators in both the freshwater and marine environments. Without access to such treatments disease can affect the economic sustainability of operations directly via mortalities, reduced growth rates and adverse effects on product quality. As diseases found in farmed fish can also potentially affect wild fish (e.g. sea lice (Boxaspen, 2006)), indirect effects on wild populations can adversely affect the environmental sustainability of the industry as well.

1.1 Aims The purposes of this survey and review are to: Identify the key diseases that affect freshwater aquaculture operations in Scotland, particularly the trout sector, and determine their relative impact Identify the main methods used to control these diseases Identify the potential consequences if any of the main control methods were to be withdrawn Identify any new potential treatments that could be used instead, if any of the main treatments were to be withdrawn.

2 Materials and Methods 2.1 Treatments survey A range of respondents who had knowledge of the trout industry in Scotland and the rest of the UK were surveyed for information on the types of diseases they were dealing with and what treatments they were using. An electronic Excel-based survey form was devised to elicit information on: •

The main diseases affecting producers



The main treatments used to control these diseases



The reported efficacy of these treatments



Possible alternative treatments

Respondents were questioned either in person or via telephone. This also included project staff attending the aquaculture UK trade show in Aviemore Scotland in May 2014.

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SARF 100 Review of Freshwater Treatments

2.2 Identification of alternative treatments Literature searches were conducted through the use of the scientific publications database, Scopus. Records between 1960 and present day were searched using keywords relevant to the control, treatment and management of the diseases where there were identified issues with regards availability of effective treatments. Internet search engines were used to identify grey literature associated with similar key word searches.

3 Overview of licensing and use of medicines and other chemicals in the freshwater industry 3.1 Medicines Veterinary medicines used in fish are controlled under Directive 2001/82/EC as amended by Directive 2004/28/EC. Article 1.2 of the Directive defines a "VMP" as:  

Any substance or combination of substances presented as having properties for treating or preventing disease in animals; or any substance or combination of substances that may be used in, or administered to, animals with a view either to restoring, correcting or modifying physiological functions by exerting a pharmacological, immunological or metabolic action, or to making a medical diagnosis.

With limited exceptions, any medicine needs to have a Marketing Authorisation before it can be used to treat farmed fish. In the UK, the Veterinary Medicines Directorate is the Government agency responsible for granting Marketing Authorisations (MAs) for veterinary medicines; and regulating the manufacture and distribution of veterinary medicinal products and animal feedingstuffs containing veterinary medicines and specified feed additives. It is also responsible for surveillance of Adverse Events (AE). The processes for applying for an MA are outlined under Directive 2001/82/EC, as amended by Directive 2004/28/EC, but in essence, the manufacturer needs to demonstrate the product is of acceptable quality, effective and safe towards the user, consumer, target animal and the environment. When used in food producing species, such a farmed trout, it is also a requirement to demonstrate the product will not harm the consumer. A practical distinction can be drawn between the authorisation of pharmaceutical products, where there is a requirement to set maximum residue limits and appropriate withdrawal periods, and for the authorisation of immunological products (vaccines) where there is typically less of a requirement to demonstrate environmental and consumer safety (as they pose less relative risk to either). Exceptions would include where an immumnological product contained other substances, such as certain adjuvants where MRL may be required. In such cases, as per pharmaceuticals, a Phase I assessment will be required to determine if a phase II (which

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SARF 100 Review of Freshwater Treatments is a very comprehensive assessment) 1997)(EMEA/CVMP/074/95FINAL).

is

required.

(European

Medicines

Agency,

COMMISSION REGULATION (EU) No 37/2010: In selecting any alternative treatments that may be used to replace existing treatments, such as formalin (See Section 5), particular attention should be drawn to EU Regulation 37/2010 (EU, 2010). Any pharmacologically active substance that is to be applied to food producing fish, such as rainbow trout, must be listed as an allowed substance in Table 1 under EU Regulation 37/2010. This regulation repeals and replaces the earlier Council Regulation (EEC) No 2377/90 that previously listed substances for which an MRL has been established (Annex I), those for which an MRL does not need to be established (Annex II), those for which a provisional MRL has been set (Annex III) and those for which no MRL could be established because residues from that substance, at whatever limit, constitute a threat to human health. Under the new Regulation, substances previously listed under Annexes I-III are now collectively listed as allowed substances (Table 1) and those in Annex IV as prohibited substances (Table 2). Where a substance is not listed in either Table 1 or 2, detection of its residues in meat destined for human consumption would constitute an offence. A practical example here would include malachite green, although not listed in either Table 1 or Table 2, the UK authorities, through VMD, undertake surveillance to ensure farmed UK fish are free of malachite green, as well as levels of other drug residues that may exceed their permitted levels.

3.2 Biocides Disinfectants are vital tools for effective farm biosecurity, used to inactivate potentially pathogenic micro-organisms on surfaces of equipment, tanks and clothing, or suspended in effluent. They are also used in the rainbow trout and salmon industries to disinfect gametes, principally ova. The industry typically uses a variety of different biocides and their continued availability remains important. In terms of information available to guide their use for aquaculture applications, the industry is largely reliant on marketing literature from the companies supplying the biocides.

3.3 Disinfectant testing schemes 3.3.1 Defra disinfectant approvals Defra has in place a statutory mechanism under The Diseases of Animals (Approved Disinfectants) (England) Order 2007 (www.legislation.gov.uk/uksi/2007/448). This allows veterinary disinfectants to be placed on an approved list for the control of different diseases if they demonstrate efficacy in laboratory testing and comply with the requirements of the Biocidal Products Regulation. The Animal Health and Veterinary Laboratories Agency (AHVLA) deliver the scheme on behalf of Defra (http://www.defra.gov.uk/ahvla-en/tests-and-services/disinfectant-approvals). Testing is done to demonstrate the effectiveness of dilutions of disinfectant against the following diseases: 

Foot and mouth disease

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SARF 100 Review of Freshwater Treatments 

Swine vesicular disease



Diseases of poultry and the avian influenza and influenza of avian origin in mammals



Tuberculosis



General (testing is performed against Salmonella)

Effective dilutions are listed against the particular diseases.

3.3.2 Aquaculture disinfectant listing scheme http://www.gov.uk/aquaculture-disinfectant-listing-scheme-apply-or-view#listed-disinfectants There is also now a voluntary scheme running whereby manufacturers can demonstrate the effectiveness of their products against aquaculture-relevant bacterial and viral pathogens. Testing against the bacterial and viral pathogens follows modified CEN standards. Table 1. Listed disinfectant products and their effective dilutions as demonstrated under the mandatory test conditions of 4°C ± 1°C test temperature, with a 30 minute ± 30 second contact time.

Product name

Product physical form

Company name

Company address and contact details

Albyn House, Union St, Inverness, IV1 1QA; www.aquatic.as Brierley Rd, Walton Summit, Preston, Lancashire, PR5 8AH; www.evansvanodine.co.uk Brierley Rd, Walton Summit, Preston, Lancashire, PR5 8AH; www.evansvanodine.co.uk 22 Carsegate Road, Inverness, IV3 8EX; www.fishvet.co.uk

Aqua Des

Liquid

Aquatic Hygiene Ltd

FAM 30

Liquid

Evans Vanodine International PLC Evans Vanodine International PLC Fish Vet Group Ltd

Vanoquat Liquid New Formulation Virasure® Aquatic

Pink powder

Bacterial diseases of aquaculture relevance* (Test Standard EN1656 Modified) 1 to 200

Viral diseases of aquaculture relevance* (Test Standard EN14675 Modified) 1 to 200

1 to 100

N/A

1 to 100

N/A

1 to 100

0.7 to 100

* Effective dilution for liquids expressed as 1 part product to x parts water, or for solids expressed as 1 gram product to x mls water. † The disinfectant does not need to be diluted.

3.4 Use of biocides for disease control purposes There are some chemicals that are marketed and available general purpose biocides that are used to control particular disease problems on farms. These include chloramine T and formalin. There is requirement for all products marketed as biocides to be registered through the Biocidal Products Regulation (BPR, Regulation (EU) 528/2012). Most of the biocide chemicals used in aquaculture are registered with the BPR, with the exception of formalin (see Section Y).

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SARF 100 Review of Freshwater Treatments

3.5 Discharge consents Release of chemicals from aquaculture facilities is regulated in the UK by SEPA in Scotland and the EA. In Scotland these are regulated under the Water Environment (Controlled Activities) (Scotland) Regulations 2011 (CAR). SEPA aims to protect the environment by limiting the amount of certain medicines that can be administered and discharged. Also of importance here are wider obligations under European legislation to protect the aquatic environment, in particular the Water Framework Directive (EU, 2000). Obviously this means that any aquaculture medicine that is likely to be used on a freshwater rainbow trout farm, particularly one that discharges to natural water courses, will have to demonstrate limited environmental impact if the appropriate discharge consents are to be granted. A practical example here would include copper sulphate. Although this chemical is widely available as a swimming pool treatment (algicide) and can be effective for the control of white spot and other diseases, its use in the rainbow trout industry has been discontinued as copper based products are deemed to present significant environmental risks under the WFD and other environmental regulations (6.2.9 ).

4 Rainbow trout production: Main diseases 4.1 Producers, veterinarians and health professionals surveyed A total of 8 different producers were questioned as part of the survey. These covered three Scottish producers (one vertically integrated business that produced its own fry that it on grew in both freshwater and marine production units), one that predominantly grew juveniles for supply to on growers and another company that grew on trout, again mainly for large trout production in sea and freshwater loch cage systems. Total annual production from the two ongrowers questioned was in excess of 7000 tonnes per year and the juveniles supplier produced more than 2 million fingerlings per year. This likely represents more than 90% of total Scottish production, based on recent farm survey information (http://www.scotland.gov.uk/Publications/2013/09/9210/3#tb1a). Four English producers were also questioned, covering a major supplier of trout for the restocking (angling) trade and three other producers who mainly produced table trout. Total production represented by these producers was collectively approximately 2400 tonnes per year. This figure is equivalent to approximately 37% of annual total English production (http://www.cefas.defra.gov.uk/publications/finfishnews/FFN15.pdf). One of the producers also reared more than 4 million rainbow trout fry per year. A major egg and fry producer from Northern Ireland was also questioned. Two veterinarians were surveyed, one from a major practice who works with a number of the major Scottish producers, and an independent veterinarian who works with a number of English and Welsh producers, including major Southern English table trout producers. A fish health expert who works for a major feed company, who has extensive knowledge of the industry across England and Wales, was also questioned.

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SARF 100 Review of Freshwater Treatments

4.2 Summary of main diseases identified in last 12 months by producers and health professionals Table 2 Diseases recorded by producers within the last 12 months

Disease

Number of producers observing clinical disease

Rainbow trout fry syndrome

8

Red Mark Syndrome

7

Life stages affected (range)

Main treatments used

Estimated impact (production costs) with present treatment options

1-50g (mainly smaller fish
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