Strawberry disease is a chronic, nonlethal skin condition that affects Rainbow Trout Oncorhynchus mykiss in the United States and several European countries, where it is also known as red-mark syndrome. We provide the first identification and characterization of three strawberry disease outbreaks occurring at two aquaculture farms in southern Chile. Clinically affected fish weighing an average of 400 g presented multiple bright-red, usually raised, skin lesions on the flank, ventral surface, and dorsal surface. A PCR using Rickettsia-like-organism (RLO)-specific primers was performed on nine affected fish, and all skin samples were positive for the RLO 16S ribosomal RNA sequence. All PCR results for Flavobacterium psychrophilum and other bacterial and viral pathogens were negative. Histopathological examination of the skin lesions revealed extensive dermatitis, with severe lymphocytic infiltration in advanced cases. This report is the first to describe strawberry disease in farmed Chilean Rainbow Trout. Additional studies are needed to evaluate the risk for Rainbow Trout culture; fish challenge experiments should be performed to fulfill Koch's postulates and to demonstrate that RLO is the cause of this disease. Received December 27, 2014; accepted October 23, 2015.

Proteins present in blood samples from Atlantic salmon (Salmo salar) infected with salmon lice (Lepeophtheirus salmonis) were analyzed using liquid chromatography–high-resolution mass spectrometry. Bioinformatic analyses revealed 1820 proteins, of which 58 were assigned to lice. Among these, peroxiredoxin-2, an antioxidant protein, was found relevant with respect to blood feeding of the parasite. The three-dimensional structure analysis of the protein revealed a surface amino acid sequence of interest. A 13-amino-acid peptide was selected as a potential antigen due to its predicted solubility, antigenicity, probable non-allergenic, and non-toxic nature. This peroxiredoxin-2-derived peptide was synthesized, combined with a commercially available adjuvant, and used for vaccination. The test vaccine demonstrated a 60–70% protection rate against early-stage Lepeophtheirus salmonis infection in a challenge trial in Norway. Additionally, the vaccine was tested against salmon lice (Caligus rogercresseyi) in Chile, where a remarkable 92% reduction in the number of adult lice was observed. Thus, in combination with the selected adjuvant, the peptide showed antigenic potential, making it a suitable candidate for future vaccine development. The approach described holds promise for the development of peptide vaccines against various ectoparasites feeding on blood or skin secretions of their hosts.

Tenacibaculum maritimum is a major etiological agent of tenacibaculosis in marine fish and represents an increasing concern for Chilean salmon aquaculture; however, updated information on the phenotypic and molecular diversity of circulating isolates is limited. This study characterized 40 isolates recovered from Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), and red cusk eel (Genypterus chilensis) obtained from outbreaks between 2020 and 2024. Isolates were analyzed using biochemical and phenotypic assays, multiplex PCR targeting the O-antigen gene cluster (O-AGC), REP-PCR-based genetic fingerprinting, and experimental bath challenges in Atlantic salmon. Phenotypic characterization revealed species-consistent traits but variable gelatin and starch hydrolysis and differences in seawater tolerance. O-AGC typing identified four molecular serotypes (1-0, 3-1, 3-2, and 4-0), with serotypes 1-0 and 3-2 detected for the first time in Chilean salmonids. Genetic fingerprinting distinguished previously described profiles and two novel REP patterns (REP6 and REP7), indicating additional genomic heterogeneity within dominant serotypes. Virulence assays showed cumulative mortality ranging from 0% to 100%, with serotype 3-1 isolates generally associated with higher mortality and serotype 4-0 displaying broad intra-serotype variability. These findings document substantial phenotypic, antigenic, and genetic diversity among Chilean T. maritimum isolates and provide epidemiologically relevant information for disease surveillance and vaccine design in salmon aquaculture.

Sea lice (Caligus rogercresseyi) are major ectoparasites in Chilean salmon aquaculture, causing economic losses and increasing fish susceptibility to secondary infections. Tenacibaculosis has recently emerged as the second leading cause of mortality in farmed salmon. Understanding whether sea lice may harbor or transmit bacterial pathogens is therefore highly relevant. A sea lice survey was conducted at an Atlantic salmon (Salmo salar) farm in the Los Lagos Region, Chile. Twenty adult parasites (10 ovigerous females and 10 males) were analyzed using an integrated approach combining immunohistochemistry (IHC) with specific antibodies and conventional PCR with appropriate controls. IHC revealed positive signals for Tenacibaculum maritimum in the gastrointestinal tract and cuticle, and for Tenacibacuum dicentrarchi in the cuticle and ovigerous sac of C. rogercresseyi. A specific PCR test confirmed the presence of both pathogens, yielding amplification products of 1088 bp for T. maritimum and 284 bp for T. dicentrarchi. This study provides the first dual evidence, by PCR and IHC, of Tenacibaculum species in C. rogercresseyi. These findings suggest that sea lice may play a role in pathogen dynamics in salmon farming, highlighting the need for further research on their contribution to disease transmission within aquaculture systems.