New salmonid hosts for Tenacibaculum species: Expansion of tenacibaculosis in Chilean aquaculture

Abstract

The success and sustainability of Chilean aquaculture largely depends on the control of endemic and emerging pathogens, including several species of the genus Tenacibaculum. Tenacibaculum dicentrarchi and “Tenacibaculum finnmarkense” have been detected and confirmed in Chilean Atlantic salmon (Salmo salar). However, no outbreaks of tenacibaculosis in rainbow trout (Oncorhynchus mykiss) or coho salmon (Oncorhynchus kisutch) have been reported, either in Chile or globally. The aims of this study were to determine whether the mortalities recorded for rainbow trout and coho salmon from five marine fish farms located in the Los Lagos, Aysén, and Magallanes Regions could be caused by Tenacibaculum spp. The diseased fish exhibited cutaneous haemorrhages, tail and peduncle rots, and damage on the mouth and tongue. Microbiological analysis of infected external tissues yielded 13 bacterial isolates. The isolates were identified as members of the genus Tenacibaculum through biochemical analysis (e.g. Gram‐stain negative, straight rods, filamentous cells and motile by gliding), but differences existed in biochemical results, making species‐level identification through biomolecular tools essential. The 16S rRNA analysis found that the majority of isolates were more closely related to “T. finnmarkense” than T. dicentrarchi, while the phylogenetic trees resulting from multilocus sequence data recovered the four main clades (clades I to IV) identified by Olsen et al. (2017, Veterinary Microbiology, 205, 39). This is the first documented occurrence of clinical tenacibaculosis in farmed rainbow trout and coho salmon globally, and it extends the known host distribution of this pathogen in Chile. Moreover, we confirm the presence of Tenacibaculum species in the Chilean Patagonia. These findings highlight the importance of establishing preventative measures to minimize the spread of this disease within the Chilean marine aquaculture industry, as well as the need for monitoring initiatives worldwide in these farmed fish species.

Quantitative PCR for Tenacibaculum dicentrarchi and T. finnmarkense

“…The phylogenetic placement of T. finnmarkense AYD7486TD has recently shifted because AYD7486TD had greater similarity to T. finnmarkense based on complete genome comparisons (Bridel et al. 2018) and multilocus sequence analysis (Avendaño‐Herrera et al., 2020). The DICEN assay can still be used for its intended function; however, other genes (i.e.…”

Proximity ligation strategy for the genomic reconstruction of microbial communities associated with the ectoparasite Caligus rogercresseyi

“…We further explored the Tenacibacullum cluster, as it is a genus known to comprise different pathogenic species that are relevant for Chilean aquaculture 25 . Based on all the 16S genes fully annotated in the genome, we were able to identify this particular cluster as T. ovolyticum (Fig.…”

Phylogenetic analyses of Norwegian Tenacibaculum strains confirm high bacterial diversity and suggest circulation of ubiquitous virulent strains

“…from sick fish followed by morphological, biochemical, and serological characterization of the bacteria and analysis of their antimicrobial susceptibility profiles [ 8 ]. MultiLocus Sequence Analysis (MLSA) has, however, been increasingly used for bacterial genotyping [ 17 , 23 , 28 , 36 , 37 ] and has become an important tool for diagnosis and studies of epizootics. The results from the current study confirm the large diversity of Tenacibaculum spp.…”

“…It is interesting to note that all the STs from Clade III except one (LIM064, isolated in Rogaland) have been isolated at least once in Troms or Finnmark. To note, Tenacibaculum finnmarkense has also been isolated outside of Norway, from Chilean Atlantic salmon, coho salmon, and rainbow trout ( Oncorhynchus kisutch ) [ 27 , 36 , 40 ]. Tenacibaculum dicentrarchi strains and the strains closely related to T .…”