Mortality in farmed European eel (Anguilla anguilla) in Italy due to Streptococcus iniae.
Bacterial septicaemia
European eel disease
Fish streptococcosis
Journal
Acta veterinaria Scandinavica
ISSN: 1751-0147
Titre abrégé: Acta Vet Scand
Pays: England
ID NLM: 0370400
Informations de publication
Date de publication:
14 Feb 2023
14 Feb 2023
Historique:
received:
09
08
2022
accepted:
01
02
2023
entrez:
15
2
2023
pubmed:
16
2
2023
medline:
17
2
2023
Statut:
epublish
Résumé
Streptococcal infections are one of the main causes of fish disease. During the last decade, Streptococcus iniae has become one of the most important aquatic pathogens worldwide, causing high losses in marine and freshwater finfish. Clinical signs in farmed fish include loss of appetite, lethargy and grouping at the bottom of the tank. Gross changes comprise darkening of the skin and haemorrhage at the basis of fins and opercula. To date, S. iniae has been isolated from several wild and farmed fish species but never in the European eel (Anguilla anguilla). In Europe, eel production from aquaculture is around 4500 tonnes and Italy is the third largest producer. This communication represents the first report of an outbreak of S. iniae infection in European eels. The outbreak occurred at an eel farm in northern Italy between May 2021 and September 2021. The outbreak caused about 2% mortality per month, resulting in the loss of about 10% of the farmed fish. The diseased eels showed apathy, lethargy, inactivity and inappetence. In July 2021, three eels were necropsied. Necropsy revealed skin and branchial hyperaemia, a few skin ulcers, and diffuse peritoneal congestion with a few haemorrhagic-like spot lesions. Swab samples for bacteriology were taken from the kidneys, liver, spleen, and brain. Additionally, four eels were opened and swap samples as above were taken. All the investigated eels were found dead. Bacteriological examination revealed growth of Streptococcus spp. from all samples. Identification of S. iniae was done by biochemical characterization, the API20STREP microsystem, 16S rDNA sequencing, and MALDI-TOF. Antimicrobial therapy (oxytetracycline and erythromycin) was ineffective. This is the first report of S. iniae infection in the European eel. Although this may be an isolated outbreak, it is of concern due to the losses associated with this pathogen in fish worldwide and because the European eel is an endangered species. Due to the difficulties of controlling the disease with antimicrobials, it is advisable to plan other effective control measures, such as improving water quality and the environmental conditions, reducing fish density, improving biosecurity, and by using immunostimulants and, when possible, vaccines.
Sections du résumé
BACKGROUND
BACKGROUND
Streptococcal infections are one of the main causes of fish disease. During the last decade, Streptococcus iniae has become one of the most important aquatic pathogens worldwide, causing high losses in marine and freshwater finfish. Clinical signs in farmed fish include loss of appetite, lethargy and grouping at the bottom of the tank. Gross changes comprise darkening of the skin and haemorrhage at the basis of fins and opercula. To date, S. iniae has been isolated from several wild and farmed fish species but never in the European eel (Anguilla anguilla). In Europe, eel production from aquaculture is around 4500 tonnes and Italy is the third largest producer. This communication represents the first report of an outbreak of S. iniae infection in European eels.
CASE PRESENTATION
METHODS
The outbreak occurred at an eel farm in northern Italy between May 2021 and September 2021. The outbreak caused about 2% mortality per month, resulting in the loss of about 10% of the farmed fish. The diseased eels showed apathy, lethargy, inactivity and inappetence. In July 2021, three eels were necropsied. Necropsy revealed skin and branchial hyperaemia, a few skin ulcers, and diffuse peritoneal congestion with a few haemorrhagic-like spot lesions. Swab samples for bacteriology were taken from the kidneys, liver, spleen, and brain. Additionally, four eels were opened and swap samples as above were taken. All the investigated eels were found dead. Bacteriological examination revealed growth of Streptococcus spp. from all samples. Identification of S. iniae was done by biochemical characterization, the API20STREP microsystem, 16S rDNA sequencing, and MALDI-TOF. Antimicrobial therapy (oxytetracycline and erythromycin) was ineffective.
CONCLUSIONS
CONCLUSIONS
This is the first report of S. iniae infection in the European eel. Although this may be an isolated outbreak, it is of concern due to the losses associated with this pathogen in fish worldwide and because the European eel is an endangered species. Due to the difficulties of controlling the disease with antimicrobials, it is advisable to plan other effective control measures, such as improving water quality and the environmental conditions, reducing fish density, improving biosecurity, and by using immunostimulants and, when possible, vaccines.
Identifiants
pubmed: 36788544
doi: 10.1186/s13028-023-00669-y
pii: 10.1186/s13028-023-00669-y
pmc: PMC9926715
doi:
Types de publication
Case Reports
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
5Informations de copyright
© 2023. The Author(s).
Références
Appl Environ Microbiol. 1998 Oct;64(10):4065-7
pubmed: 9758844
J Fish Dis. 2018 May;41(5):773-782
pubmed: 29315698
Dis Aquat Organ. 1999 May 31;36(3):177-81
pubmed: 10401583
Am J Clin Pathol. 1966 Apr;45(4):493-6
pubmed: 5325707
J Fish Dis. 2020 Apr;43(4):485-490
pubmed: 32100309
Dis Aquat Organ. 1999 May 31;36(3):227-31
pubmed: 10401588
J Fish Dis. 2005 Mar;28(3):141-50
pubmed: 15752274
J Fish Dis. 2007 Apr;30(4):233-8
pubmed: 17394525
Dis Aquat Organ. 2002 Jun 3;49(3):165-70
pubmed: 12113301
Acta Vet Scand. 2020 Jan 23;62(1):6
pubmed: 31973764
Aust Vet J. 2006 Nov;84(11):408-11
pubmed: 17092328
J Fish Dis. 2019 Nov;42(11):1509-1521
pubmed: 31452217
J Fish Dis. 2022 Jun;45(6):939-942
pubmed: 35263448
J Fish Dis. 2010 Nov;33(11):901-5
pubmed: 21504081
Dis Aquat Organ. 2006 Nov 21;73(1):77-81
pubmed: 17240756
J Fish Dis. 2013 Jul;36(7):647-56
pubmed: 23297744
J Aquat Anim Health. 2010 Sep;22(3):158-66
pubmed: 21192545
J Clin Microbiol. 2000 Jan;38(1):246-51
pubmed: 10618095
Fish Shellfish Immunol. 2020 Sep;104:654-662
pubmed: 32561456
Syst Appl Microbiol. 2015 Feb;38(1):36-47
pubmed: 25466920
Mol Cells. 2018 Jun;41(6):495-505
pubmed: 29754470
Iran J Vet Res. 2022;23(3):219-228
pubmed: 36425608
Vet Microbiol. 2007 May 16;122(1-2):1-15
pubmed: 17418985
Vet Res. 2016 Oct 4;47(1):98
pubmed: 27716438