Comprehensive pathogen diagnostics in wild fish populations using blood-based molecular strategies: an Atlantic herring case study

Caza, France; Fronton, Fanny; Ennia, Lina; Robert, Dominique et St-Pierre, Yves ORCID: https://orcid.org/0000-0002-1948-2041 (2025). Comprehensive pathogen diagnostics in wild fish populations using blood-based molecular strategies: an Atlantic herring case study Scientific Reports , vol. 16 , nº 1:34. pp. 1-36. DOI: 10.1038/s41598-025-28653-8.

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Résumé

Climate change affects marine ecosystems by promoting pathogens that threaten key fish populations. To protect these, monitoring programs must adapt to manage threats and sustain fisheries. Here, we combined traditional PCR methods and transcriptomic analysis from a single drop of blood stored on FTA cards to determine the prevalence of erythrocytic necrosis virus (ENV) and the Ichthyophonus parasite in the Atlantic herring population. Across 2023–2024, 33% of individual blood samples tested positive for ENV and 10% for Ichthyophonus by PCR, with ENV-positive fish more frequently found in estuarine and coastal areas. Spatial analyses revealed a clustered distribution for ENV and a more sporadic occurrence of Ichthyophonus. RNA-Seq detected viral RNA fragments in ENV PCR-positive fish, revealing high levels of viral transcripts consistent with active viral replication. However, no significant changes were observed in the host blood transcriptome between infected and uninfected individuals, suggesting that ENV replication may proceed with limited systemic host transcriptional response under subclinical conditions. Overall, our study provides the first comprehensive baseline on the prevalence and molecular activity of ENV and Ichthyophonus in Atlantic herring, demonstrating the power of FTA-based RNA-Seq diagnostics to uncover hidden infections and informing future surveillance and management of wild fish populations.

Type de document:	Article
Informations complémentaires:	This research was performed with the logistical support of Fisheries and Oceans Canada (DFO)
Mots-clés libres:	Ichthyophonus; Atlantic herring; Erythrocytic necrosis virus; FTA cards; Pathogens; Transcriptomics
Centre:	Centre INRS-Institut Armand Frappier
Date de dépôt:	16 juin 2026 14:55
Dernière modification:	16 juin 2026 14:55
URI:	https://espace.inrs.ca/id/eprint/16792

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