Carp edema virus in Germany and differences in

susceptibility of common carp strains

- results from an epidemiological studies and

experimental infections.

Mikolaj Adamek1*, Max Helling1, Felix Teitge1, Verena Jung-Schroers1, David

Gela2, Veronika Piackova2, Martin Kocour2, Jerzy Adamek3, Dieter Steinhagen1

1Fish Disease Research Unit, Institute for Parasitology, University of Veterinary Medicine, Hannover, Germany

2Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia Ceske

Budejovice, Vodnany, Czech Republic 3Experimental Fish Farm in Zator, The Stanislaw Sakowicz Inland Fisheries Institute in Olsztyn, Poland

;

4th International Carp Conference 2017

Plan

What is carp edema virus?

Has CEV any significance in aquaculture?

Does CEV cause „Koi Sleepy Disease“?

Are there any differences in susceptibility of common carp strains to CEV?

What makes a fish sleep and die in „Koi Sleepy Disease”?

What are the recommendations?

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Koi sleepy disease / Carp edema virus

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CEV in common carp

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CEV in the world

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Japan 1976 (1974) USA 1997 (1996)

UK 2013 (1990`)

NL 2014

A 2015 (2014)

F 2015

CZ 2014

I 2014

PL 2016 (2013)

DE 2015 (2007)

HU 2017 (2016)

China 2017

India 2017

CEV genogroup I vs CEV genogroup IIa

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CEV genogroup IIa (Koi lineage)

CEV genogroup I (Carp lineage)

CEV genogroup IIb (mixed lineage)

KSD / CEV in Germany

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• Preliminary results from epidemiological studies

• 2007 - Archival samples (common carp)

• 2009 - Archival samples (Koi)

• 2009 - First detection in imported Koi

• 2014 - First disease outbreak in Koi

• 2015 - First disease outbreak in carp farm

Monthly distribution / Water temperature

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Clinical signs

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Clinical signs vs virus load

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Are other fish species involved?

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CEV experimental cohabitation

(i) Virus load and viral mRNA expression

(ii) Behavioural changes

(iii) Pathohistological changes

(iv) Mortality

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Is CEV infection causing „Koi Sleepy Disease”?

The target organ/tissue for CEV

The target organ/tissue for CEV replication is gill

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Differences in susceptibility of common carp strains to CEV

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Donor fish: common carp n=13 Recipient fish: Koi (Koi) Prerov scaly (PS) Ropsha (Rop) Amur wild carp (AS) (n=8/n=8/n=8/n=8) 10-12°C flow through 6d, 11d post exposure 4 fish per time point Gills

Cohabitation II (Genogroup I [Carp])

Donor fish: Koi n=3 Recipient fish: Koi (Koi) Prerov scaly (PS) Ropsha (Rop) Amur wild carp (AS) (n=8/n=8/n=8/n=8) 11-13°C flow through 6d, 11d post exposure 4 fish per time point Gills

Cohabitation IV (Genogroup IIa [Koi])

Differences in susceptibility of common carp strains to CEV

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DNA RNA

Genogroup I

Co II

Genogroup Iia

Co IV

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KSD (behavioural)

VS

Cohabitation

experiment

CEV genogroup Development of KSD (behavioural)

Carp strain

Koi PS Rop AS

Co II Genogroup I KSD KSD * -

Co IV Genogroup IIa KSD - - -

Cohabitation

experiment

CEV

genogroup

Observation

day

Development of KSD clinical signs (no. of fish)

Carp strain

Koi PS Rop AS

Co II Genogroup I 11 7/7 7/7 2/7 0/7

Co IV Genogroup IIa 11 4/4 0/4 0/4 0/4

Differences in the susceptibility of common carp strains to CEV

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Cohabitation

experiment

CEV

genogroup

Observation

day

Severity of histological changes

Carp stain

Koi PS Rop AS

Co II Genogroup I 11 +/++ ++/+++ ++ +/++

Co IV Genogroup IIa 11 +/++ +/++ +/++ ++

Cohabitation

experiment

CEV genogroup Development of KSD (gill histology)

Carp strain

Koi PS Rop AS

Co II Genogroup I mild / moderate moderate / severe moderate mild / moderate

Co IV Genogroup IIa mild / moderate mild / moderate mild / moderate moderate

KSD (gill histology)

CEV genogroup I is more virulent for

some strains of common carp

CEV genogroup IIa is more virulent

for Koi

Differences in the susceptibility of common carp strains to CEV

Genogroup IIa Genogroup I

Mortality

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Temp. 18 °C

n=10 (2-5 g)

Genogroup IIa Genogroup I *

Temp. 16 °C

n=5 (5-10 g)

*

Summary

• CEV is widely distributed in common carp aquaculture and was/is a cause for some idiopathic

disease outbreaks related to losses

• Significant differences in the virulence between CEV genogroups

• higher virulence towards the same fish group (common carp or koi) as the donor fish

• Amur wild carp are more resistant to an infection with CEV and do not develop clinical signs for

KSD

• Prerov scaly carp (in CEV genogroup I) and Koi carp (in CEV genogroup IIa)

developed high virus loads and clinical KSD

• Significant differences in virulence and genetics and strain separation (at least in Germany) of

CEV genogroups rise questions about a better separation of these viruses by nomenclature

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Recommendations

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We can recommend using resistant strains of carp (Amur wild carp) in

breeding programs which could limit potential losses caused by this

disease in aquaculture

Control your fish in the winter / spring time if they are apathetic / lying at

the bottom of the tank – do not blame it on NH3 intoxication – check them

for CEV (also in archival samples)

Keith Way Centre for Environment, Fisheries and Aquaculture

Science (CEFAS)

Acknowledgements

Faculty of Fisheries and Protection of Waters,

University of South Bohemia Ceske Budejovice,

Vodnany, Czech Republic

David Gela

Veronika Piackova

Martin Kocour

Fish Disease Research Unit,

University of Veterinary Medicine

Ilka Baumann

Max Helling

Felix Teitge

Verena Jung-Schroers

Dieter Steinhagen

Clinic for Swine and Small Ruminants,

University of Veterinary Medicine

Martin Ganter