fish and shellfish diseases

Fish and shellfish diseases

In Lelystad we have a specialized fish and shellfish diseases laboratory. This is the one complete diseases laboratory in the Netherlands for cultured fish for human consumption, ornamental and wild fish and shellfish.

Healthy aquaculture

Fish production via aquaculture is increasing strongly worldwide. One of the threats to intensive aquaculture is the occurrence of contagious fish, crustaceans and shellfish diseases, which can cause serious illness and death and thereby economic losses.

Role Wageningen Bioveterinary Research

At the specialized fish and shellfish diseases laboratory of Wageningen Bioveterinary Research, accredited and fast diagnostics are performed to identify new outbreaks at an early stage. This is the one complete diseases laboratory in the Netherlands for cultured fish for human consumption, ornamental and wild fish and shellfish. We thus make an important contribution to healthy fish in healthy aquaculture and to safe and healthy fish products for human consumption.

Our core tasks

Wageningen Bioveterinary Research has broad experience and expertise on various fish and shellfish diseases. We are consulted frequently for our diagnostic service,expertise on diseases, and as partner for collaboration in research and network projects by both national and international parties.

The fish diseases laboratory was set up in 1985, and the task on shellfish diseases was added in 2000. The laboratory has the following core tasks:

  1. Serving as a knowledge and advisory centre for the Dutch Ministry of Agriculture, Nature and Food Quality (LNV);
  2. Diagnosing diseases for the aquatic industry, and the ornamental and wild fish branches:

    1. In case of fish disease at fish farms 
    2. At suspicion of notifiable fish and shellfish diseases, in cooperation with the Food and Consumer Product Safety Authority (Voedsel en Waren Autoriteit)
    3. For certification of live fish for export, in cooperation with the Food and Consumer Product Safety Authority (NVWA).
  3. Provide expertise by consultancy for the government and the aquaculture branch regarding fish and shellfish diseases
  4. Research on fish and shellfish diseases that occur in the Netherlands.

National Reference Lab

The laboratory is the Dutch National Reference Lab (NRL) for fish and shellfish diseases for the EU. It was the first fish diseases laboratory in Europe accredited for quality standards ISO 9001 and 17025 (EN 45001). The laboratory has an impressive national and international network, in which knowledge and materials are exchanged.

Fish disease diagnostics

In case a fish culturist or owner has problems with diseased fish, live fish can be brought to Lelystad for diagnosis, at appointment, preferably via a veterinarian. Following the anamnesis, necropsy is performed, including external and internal investigation for parasites. At suspicion of a virological or bacteriological disorder, further tests are performed. For example, in the event of a bacteriological suspicion, specimens from the lesions and internal organs of the fish are inoculated onto agar. For virology organs of the fish are sampled, and in histopathology (microscopy of sections of affected tissue) pieces of tissue are put into a fixative.

Follow up tests

The inoculated agar plates are incubated at room temperature, as fish are cold-blooded animals and their pathogenic organisms have adapted to that temperature. In case a pure culture of bacteria results, an antibiogram is made, so that the fish owner can choose an appropriate antibiotic to treat the disease. In parallel to this process, the bacteria are characterized by classic and/or molecular techniques.

For virus isolation, a suspension of the fish organs is put on fish cell cultures to cultivate any virus that may be present. The morphology of the virus can be examined with an electron microscope. The virus is generally characterized with specific antibodies that neutralize the particular virus. Moreover, for various viruses PCR-tests (sensitive rapid diagnostics) are available. After the name of the virus is known, specific recommendations are made, for example regarding changes in the water temperature in the fish culture system, to inhibit clinical disease.

For histopathology, the fixed tissue is sliced and stained in such a way that it can be examined with a microscope. This makes it possible to see alterations at cell level that indicate a viral, bacteriological or other disease. This method also enables detection of very small parasites in the tissue or in cells.

Diagnosis of shellfish diseases

Shellfish from the Zeeland open water bodies is sampled twice per year in a monitoring program, to detect infections and diseases. The condition of the shellfish is determined by an autopsy, after which shellfish are sampled for histopathology and sometimes also bacteriology. Molecular techniques are also increasingly being used for diagnostic purposes.


Once the diagnostic tests have been completed, a diagnosis is made. If possible, the diagnosis includes a recommendation to the fish owner and/or the veterinarian regarding what to do. As a member of (inter-)national advisory committees, the laboratory experts also give advice to parties like the Ministry of LNV, the EU and the EFSA (European Food Safety Authority). The laboratory also publishes frequently in professional bulletins of the aquaculture and ornamental fish industry, and in international peer reviewed fish diseases journals, and books. Researchers of the laboratory present posters and oral presentations at (inter-)national meetings and conferences; they also offer a course in fish diseases: this 1-day course is intended for fish culturists, veterinarians, a.o.


The laboratory has studied various fish disease subjects in more detail, with or without infection trials: the swimbladder parasite (Anguillicola crassus) in eels, common eel parasites in the open waters, eel bacteria and currently eel viruses. In addition, various molecular detection methods have been developed for KHV (koi herpes virus), HVA (eel herpes virus), Bonamia (oyster parasite) and Nocardia (shellfish bacteria). Scientific publications have appeared based on the results of these studies. The scientists collaborate with other partners in new research projects that optimally utilize the specific knowledge of all participants.

Procedure for diagnostic service of fish and shellfish diseases

Live diseased or healthy fish and shellfish can be diagnosed at appointment (after a phone call or e-mail) with the Fish and Shellfish Disease Laboratory, preferably via a veterinarian. The fish or shellfish should therefore be delivered at Edelhertweg 15, 8219 PH Lelystad. Reasonable rates are charged for diagnosis {necropsy (including parasitology), bacteriology, virology, and histopathology}. Results of necropsy, including parasitology are generally reported the same day; bacteriology results take a minimum of two days (including the antibiogram) and virology and histopathology take a minimum of two weeks. Export certification is arranged via the Dutch Food and Consumer Product Safety Authority (NVWA); a notification period of 14 days prior to this must be taken into account. After the diagnostic report has been sent, the invoice follows separately.

Publications 2012 - 2020


Gorgoglione, B., C.Bailey, M.D.Fast, D.Bass,  M. Saraiva , M. Adamek, P. Noguera, S. Ciulli, M. Palíková, I. Aguirre-Gil, L.Bigarré and O.Haenen, 2020. Co-infections and multiple stressors in fish. EAFP 19TH INTERNATIONAL CONFERENCE ON DISEASES OF FISH AND SHELLFISH SPECIAL EDITION WORKSHOP REPORT. Bull. Eur. Ass. Fish Pathol., 40(1) : 4-19.

Joosten, Lotte, Antoine Lecocq, Annette Bruun Jensen, Olga Haenen, Eric Schmitt, Jørgen Eilenberg, 2020. Insect pathogen risks for black soldier fly Hermetia illucens and guidelines for reliable production. Mini Review. Entomologia Experimentalis et Applicata. Special Issue: Insects in production, 1-16. DOI:10.1111/eea.12916 

Baron, Sandrine, Daniela Ceccarelli, Inger Dalsgaard, Sophie A. Granier, Olga Haenen, Eva Jansson, Lone Madsen, Eric Jouy, Isabelle Kempf, Emeline Larvor, Thierry Morin, Joop Testerink, Kees Veldman, Kári Karbech Mouritsen, Betty Van Gelderen, Michal Voorbergen-Laarman, Eva Säker, Eva Blomkvist, Peter Smith, 2020. Influence of incubation time on antimicrobial susceptibility testing of pathogenic Vibrio anguillarum and Vibrio vulnificus isolated from fish. Aquaculture 524, 15 July 2020, 735258. 

Haenen, Olga, Daniela Ceccarelli, Nedzib Tafro, Kees Veldman, Tina Zuidema, and Dik Mevius, 2020 in press. Potential transfer of antimicrobial resistance and zoonotic bacteria through global ornamental fish trade. FAO technical publication, in press (MSU). Expected spring 2020.

Haenen, Olga, Iddya Karunasagar, Amedeo Manfrin, Snjezana Znrcic, Celia Lavilla-Pitogo, Mark Lawrence, Larry Hanson, Rohana Subasinghe, Indrani Karunasagar, 2020 in press. Contact-zoonotic bacteria of warm water ornamental and cultured fish. FAO technical publication, in press (MSU). Expected spring 2020.


Gulla, Snorre & Bayliss, Sion & Björnsdóttir, Bryndís & Dalsgaard, Ingeri & Haenen, Olga & Jansson, Eva & McCarthy, Una & Scholz, Felix & Vercauteren, Maaike & Verner-Jeffreys, David & Welch, Timothy & Wiklund, Tom & Colquhoun, Duncan. (2019). Biogeography of the fish pathogen Aeromonas salmonicida inferred by vapA genotyping. FEMS Microbiology Letters. 366. 10.1093/femsle/fnz074.

Haenen, Olga, 2019. Major eel diseases in Europe: the past 30 years. Ch. 17 in: Eels: Biology, Monitoring, Management, Culture and Exploitation: Proceedings of the First International Eel Science Symposium, Eds. A. Don & P. Coulson. 5M Publishing, Sheffield, UK. pp. 257-279.

Haenen, O., A. Borghuis, B. Weller, J. van Eijk, E. van Gelderen, M. Boonstra, E. Weerman, L. Bonte, L. Dingboom, R. Petie, P. de Cocq, 2019. Bacteriële gezondheid in Nederlandse insectenkweek: een pilot. In: Staat van Zoönosen, 2019.

Lewin, Neil C., Amy J. Reading, Joanna James, Jo Cable, Gareth D. Davies, Derek Evans, Claude Belpaire, Alan M. Walker, Keith Way, Olga L. M. Haenen, Dave Hoole, and Chris F. Williams, 2019. Silver service: a standard protocol for eel health examinations. Ch. 20 In: Eels: Biology, Monitoring, Management, Culture and Exploitation: Proceedings of the First International Eel Science Symposium, Eds. A. Don & P. Coulson. 5M Publishing, Sheffield, UK. pp 305-313.


Haenen, O., L. Bigarré, T. Ito, J.-C. Avarre, N. Vendramin, 2018. Workshop Neglected viral diseases of freshwater fish farming. EAFP Bulletin 38, 3: 105-115.

Saucedo, Bernardo, Joseph Hughes, Annemarieke Spitzen-van der Sluijs, Natasja Kruithof, Marc Schills, Jolianne M. Rijks, Mónica Jacinto-Maldonado, Nicolás Suarez, Olga L. M. Haenen, Michal Voorbergen-Laarman, Jan van den Broek, Maarten Gilbert, Andrea Gröne, Steven J. van Beurden & M. Hélène Verheije, 2018. Ranavirus genotypes in the Netherlands and their potential association with virulence in water frogs (Pelophylax spp.). Emerging Microbes & Infections, 7, 56.


Ceccarelli, Daniela, Alieda van Essen-Zandbergen, Kees T. Veldman, Nedzib Tafro, Olga Haenen, Dik Mevius. 2017. Chromosome-encoded blaOXA-48-like variants in Shewanella spp. from food-producing animals, fish and the aquatic environment. Antimicrob. Agents Chemother. February 2017, 61, 2: e01013-16.

Cieslak Michael, Thomas Wahli, Nicolas Diserens, Olga L. M. Haenen, Heike Schütze, 2017. Phylogeny of the Infectious Hematopoietic Necrosis Virus in European Aquaculture. PLoS One 12, 9. - ISSN 1932-6203.

Haenen, O., L. Bigarré, T. Ito, J.-C. Avarre, N. Vendramin, 2017. Workshop Neglected viral diseases of freshwater fish farming. EAFP Bulletin 38, 3: 105-115.

Ito T, Kurita J, Haenen O, 2017. Importation of CyHV-2 infected goldfish into the Netherlands. Dis. Aquat. Org. 126: 51–62.

Saucedo B, Hughes J, van Beurden SJ, Suárez NM, Haenen OLM, Voorbergen-Laarman M, Gröne A, Kik MJL. 2017. Complete genome sequence of Frog virus 3, isolated from a strawberry poison frog (Oophaga pumilio) imported from Nicaragua into the Netherlands. Genome Announc 5:e00863-17.

Way K., O. Haenen, D. Stone, M. Adamek, S.M. Bergmann, L. Bigarré, N. Diserens, M. El-Matbouli, M.C. Gjessing, V. Jung-Schroers, E. Leguay, M. Matras, N.J. Olesen, V. Panzarin, V. Piačková, A. Toffan, N. Vendramin, T. Veselý, T. Waltzek, 2017. The emergence of carp edema virus (CEV) and its significance to European common carp and koi, Cyprinus carpio. Dis.Aquat.Org. 126: 155–166.


Michael Cieslak, Susie S. Mikkelsen, Helle F. Skall, Marine Baud, Nicolas Diserens, Marc Y. Engelsma, Olga L. M. Haenen, Shirin Mousakhani, Valentina Panzarin, Thomas Wahli, Niels J. Olesen, Heike Schütze. 2016. Phylogeny of the viral hemorrhagic septicemia virus in European aquaculture. PLoS One 11: e0164475. doi:10.1371/journal.pone.0164475. WOT-01-002-004.02

Haenen O.L.M., H. Schuetze,  M. Cieslak, S. Oldenburg, M.A.H. Spierenburg, I. Roozenburg-Hengst, M. Voorbergen-Laarman, M.Y. Engelsma  and N.J. Olesen, 2016. First evidence of Infectious Hematopoietic Necrosis Virus (IHNV) in the Netherlands. J. Fish Dis. 39: 971-979. Doi 10.1111/jfd.12434. WOT-01-002-004.02

Gittenberger A, Voorbergen-Laarman M, Engelsma MY. 2016. Ostreid herpesvirus OsHV-1 μVar in Pacific oysters Crassostrea gigas (Thunberg 1793) of the Wadden Sea, a UNESCO world heritage site. J. Fish. Dis. 39: 105-109. WOT-01-002-004.03

van Beurden, S.J., Voorbergen-Laarman, M.A., Roozenburg, I., van Tellingen, J., Haenen, O.L.M., Engelsma, M.Y. 2016. Development and validation of a real-time PCR assay for the detection of anguillid herpesvirus 1. J. Fish Dis. 39: 95-104. WOT-01-002-004.02


Engelsma MY, Culloty SC, Lynch SA, Arzul I, Carnegie RB. 2014. Bonamia parasites: a rapidly changing perspective on a genus of important mollusc pathogens. Dis. Aquat. Org. 110: 5-23.

Carnegie, R.B., Engelsma, M.Y. 2014. Microcell parasites of molluscs: introduction to DAO Special 7.Dis. Aquat. Org. 110: 1-4.

Hine PM, Carnegie RB, Kroeck MA, Villalba A, Engelsma MY, Burreson EM. 2014. Ultrastructural comparison of Bonamia spp. (Haplosporidia) infecting ostreid oysters.Dis. Aquat. Org. 110: 55-63.

Tilmans, M., Mrugala, A., Svoboda, J., Engelsma, M. Y., Petie, M., Soes, D. M., Nutbeam-Tuffs, S., Oidtmann, B.. Roessink, I., Petrusek, A. 2014. Survey of the crayfish plague pathogen presence in the Netherlands reveals a new Aphanomyces astaci carrier. J. Invertebr. Pathol. 120: 74-79.

Haenen OLM, van Zanten E, Jansen R, Roozenburg I, Engelsma MY, Dijkstra A, Boers SA, Voorbergen-Laarman M, and Möller AVM. 2014. Vibrio vulnificus outbreaks in Dutch eel farms since 1996, strain diversity and impact. Dis. Aquat. Org. 108: 201-209. WOT-01-002-004.02

Marc Y. Engelsma, Keith Way, Melanie J. Dodge, Michal Voorbergen-Laarman, Valentina Panzarin, Miriam Abbadi, Mansour El-Matbouli, Helle Frank Skall, Søren Kahns, David  M Stone, 2014. Detection of novel strains of Cyprinid herpesvirus closely related to koi herpesvirus. Dis.Aquat.Org. 107: 113-120. WOT-01-002-004.02


Haenen, O.L.M., J.J. Evans, and F. Berthe, 2013. Bacterial infections from aquatic species: Contact zoonotic potential and prevention. Rev. sci. Epiz. 32 (2): 497-507.

Noèlia Carrasco, Ineke Roozenburg, MichalVoorbergen-Laarman, Naoki Itoh, Marc Y. Engelsma. 2013. Development of a real time PCR for detection of the oyster pathogen Nocardia crassostrea based on its homogeneous16S-23S rRNA intergenic spacer region. J. Invertebr. Pathol. 114:120-127.Project BAS nr: WOT-01-002-004.03.

Van Beurden, S.J., Peeters, B.P.H., Rottier, P.J.M.,Davison, A.J., Engelsma, M.Y. 2013. Genome-wide gene expressionanalysis of anguillid herpesvirus 1. BMC Genom. 14: 83

Lynch, S. A., Villalba, A., Abollo, E., Engelsma, M.,Stokes, N. Culloty, S. C. 2013. The occurrence of haplosporidian parasites, Haplosporidiumnelsoni and Haplosporidium sp., in oysters in Ireland. J. Invert.Pathol. 112: 208-212.


Steven van Beurden, Derek Gatherer, Karen Kerr, JulieGalbraith, Pawel Herzyk, Ben Peeters, Peter J. Rottier, Marc Engelsma, andAndrew Davison. 2012.Anguillid herpesvirus 1 transcriptome. J. Virol. 86: 10150-10161.

Carrasco,N., Villalba, A., Andree, K.B., Engelsma, M.Y., Lacuesta, B., Ramilo, A.,Gairin, I., Furones, M.D. 2012. Boanamia exitiosa (Haplosporidia) observedinfecting the European flat oyster Ostrea edulis cultured on the Spanish Mediterranean coast. J. Invert. Pathol. 110: 307-313.

Galinier,R., van Beurden, S., Amilhat, E., Castric, J., Schoehn, G., Verneau, O., Fazio,G., Allienne, J-F., Engelsma, M., Sasal, P., Faliex, E. 2012. Complete genomesequence and toxonomic position of Eel virus European X (EVEX), a rhabdovirus ofEuropean eel. Virus Res. 166: 1-12.

Van Beurden, S.J., Engelsma, M.Y. 2012. Herpesviruses of fish, amphibians andinvertebrates. In: Herpesviridae, pp 217-242. Intech Open Acces Publishers,december Croatia. ISBN978-953-51-0186-4. Ed. G.D. Magel. Project BAS nrs WOT-01-001-003 enWOT-01-002-004.02

Haenen, Olga en Marc Engelsma, 2012. Zoönosen. Aquacultuur2012, 1: 24-28

Publications before 2012