Experimental challenge of Chinook salmon with <i>Tenacibaculum maritimum</i> and <i>Tenacibaculum dicentrarchi</i> fulfils Koch’s postulates
Notice bibliographique
Résumé
Abstract The bacterial skin disease tenacibaculosis, caused by Tenacibaculum species, can compromise numerous species of economically important marine fish, including salmonids. While tenacibaculosis is a known threat to Atlantic salmon ( Salmo salar ) aquaculture, the pathogenesis of Tenacibaculum maritimum and Tenacibaculum dicentrarchi on Chinook salmon ( Oncorhynchus tshawytscha ) has not yet been investigated. In this study, three molecular O-AGC types of T. maritimum (O-AGC Type 3-0, Type 2-1 and Type 3-2) and T. dicentrarchi isolated during a disease outbreak of farmed Chinook salmon in Aotearoa New Zealand were assessed for their ability to induce tenacibaculosis in salmon smolts under controlled conditions. Naive Chinook salmon were exposed to T. maritimum or T. dicentrarchi by immersion. Clinical signs of tenacibaculosis were apparent post-exposure and observed in 100% of all three molecular O-AGC types of T.-maritimum -challenged fish, with 100% morbidity in O-AGC Type 2-1 and Type 3-2 and 60% in O-AGC Type 3-0. Chinook salmon exposed to T. dicentrarchi showed characteristic clinical signs of disease in 51% of the challenged population, with 28% morbidity. Common gross pathological signs observed for both Tenacibaculum species were congruent with observations on farmed fish in the field, including scale loss, erythematous skin lesion, skin ulcers, fin necrosis, mouth erosion and gill ulceration. Exophthalmia was observed only in T. maritimum -challenged fish, while skin ulcers appeared grossly more severe with exposed musculature in T. dicentrarchi -challenged fish. Pure T. maritimum and T. dicentrarchi cultures were reisolated from the skin and gills of the challenged fish and their identity was confirmed by species-specific PCR and molecular O-AGC typing. Challenge experiments and associated field surveillance (for T. maritimum ) did not show the presence of culturable T. maritimum cells in the anterior kidney. This provides compelling evidence that tenacibaculosis in farmed Chinook salmon is an external infectious disease, and that Tenacibaculum is a marine obligate organism that is unable to survive in fish body fluids and does not cause septicaemia. This has repercussions for approaches to experimental challenges with Tenacibaculum species, which must occur by immersion rather than intraperitoneal or intramuscular inoculation, to replicate the natural transmission pathway and to ensure a successful challenge model. This study fulfilled modernised Koch’s postulates for the three molecular O-AGC types of T. maritimum and single strain of T. dicentrarchi as aetiological agents of tenacibaculosis in Chinook salmon that cause mortalities with considerable external abnormalities. Author summary Chinook salmon, Oncorhynchus tshawytscha , is the most significant species of Pacific salmon for its large size and nutritional content which makes it a premium choice for aquaculture. In Aotearoa|New Zealand, Chinook salmon is the only marine salmon species farmed. For a decade, the industry was impacted by an undiagnosed skin disease resulting in high mortalities. Disease susceptibility in Chinook salmon is scarcely studied and added to the challenge for a timely diagnosis. This novel research provides insight on disease susceptibility of Chinook salmon and confirms Tenacibaculum species identified in New Zealand pose a high threat to the aquaculture industry. This research has global implications and contributes valuable insights and approaches to disease management that can be applied in British Columbia and Canada where Chinook salmon populations are in decline.
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Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,001 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
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Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».