Infectious Diseases of Aquaculture: Piscirickettsia salmonis Insights

Piscirickettsia salmonis, a facultative intracellular gammaproteobacterium, is the aetiological agent of piscirickettsiosis, a multisystemic disease of salmonid fish that inflicts considerable mortality and economic losses in global aquaculture. Characterised by granulomatous lesions in key organs—liver, kidney and spleen—this pathogen evades host defences by manipulating macrophage function, subverting inflammatory signalling and residing within intracellular compartments. Conventional control measures, including antibiotic regimens and inactivated vaccines, have yielded limited long-term efficacy and have precipitated concerns over antimicrobial resistance and environmental impact. In response, research efforts have pivoted towards an integrated understanding of P. salmonis biology: from genomic diversification and population structure, through molecular mechanisms of host–pathogen interaction, to innovative diagnostic and therapeutic strategies. Insights into strain-specific virulence factors, such as secretion systems and surface antigens, underpin efforts to predict emergent lineages and tailor management practices. Concurrently, studies of host innate immunity reveal opportunities to bolster cellular defences via nutrient-deprivation pathways, immunomodulation and novel delivery systems. The global significance of P. salmonis necessitates a One Health approach that marries genomic surveillance, rapid field diagnostics and alternative antimicrobials to enhance the sustainability of salmon farming.

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Infectious Diseases of Aquaculture: Piscirickettsia salmonis Insights publication trend

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Technical terms

Piscirickettsiosis: systemic disease of salmonid fish caused by infection with Piscirickettsia salmonis.

Genogroup: a genetically distinct lineage within a species, often associated with differences in virulence or geographic distribution.

Transposase: enzyme that catalyses the movement of transposable elements within and between genomes, driving genetic diversification.

iNOS: inducible nitric oxide synthase, an enzyme in host cells that generates nitric oxide as an antimicrobial effector.

LAMP: loop-mediated isothermal amplification, a nucleic acid amplification method performed at a constant temperature for rapid pathogen detection.

References

1. Ongoing diversification of the global fish pathogen Piscirickettsia salmonis through genetic isolation and transposition bursts. The ISME Journal: Multidisciplinary Journal of Microbial Ecology (2023).
2. Blends of Organic Acids Are Weaponizing the Host iNOS and Nitric Oxide to Reduce Infection of Piscirickettsia salmonis in vitro. Antioxidants (2024).
3. Advancements in rapid diagnostics and genotyping of Piscirickettsia salmonis using Loop-mediated Isothermal Amplification. Frontiers in Microbiology (2024).
4. Transcriptional response of Atlantic salmon families to Piscirickettsia salmonis infection highlights the relevance of the iron-deprivation defence system. BMC Genomics (2015).
5. Evidence of the Presence of a Functional Dot/Icm Type IV-B Secretion System in the Fish Bacterial Pathogen Piscirickettsia salmonis. PLOS ONE (2013).
6. Extended antibiotic treatment in salmon farms select multiresistant gut bacteria with a high prevalence of antibiotic resistance genes. PLOS ONE (2018).