New Zealand rickettsia‐like organism (NZ‐RLO) and Tenacibaculum maritimum: Distribution and phylogeny in farmed Chinook salmon (Oncorhynchus tshawytscha)

Abstract

A total of 777 fish from three growing regions of New Zealand Chinook salmon farms comprising of five sites were tested. Quantitative PCR was used to determine the distribution of New Zealand rickettsia‐like organism and Tenacibaculum maritimum. Genetic information from these bacteria were then compared with strains reported worldwide. Using this information, suggested associations of pathogens with clinically affected fish were made. NZ‐RLO was detected in two of the three regions, and T. maritimum was detected in all regions. Three strains of NZ‐RLO were identified during this study. Based on analysis of the ITS rRNA gene, NZ‐RLO1 appears to be part of an Australasian grouping sharing high similarity with the Tasmanian RLO, NZ‐RLO2 was shown to be the same as an Irish strain, and NZ‐RLO3 was shown be closely related to two strains from Chile. Based on multi‐locus sequence typing, the New Zealand T. maritimum was the same as Australian strains. NZ‐RLOs were detected more frequently in fish with skin ulcers than fish without skin ulcers. While additional research is required to investigate the pathogenicity of these organisms, this is the first time that NZ‐RLOs have been associated with the development of clinical infections in farmed Chinook salmon.

Review of infectious agent occurrence in wild salmonids in British Columbia, Canada

“…Many wild and cultured fish species host this bacterium (Toranzo, Magarinos, & Romalde, ). Among salmonids, T. maritimum‐ related infection has been reported in Chinook salmon in the USA (Chen, Henry‐Ford, & Groff, ) and recently New Zealand (Brosnahan, Munday, Ha, Preece, & Jones, ), farmed Atlantic salmon in western Canada (Ostland, Morrison, Ferguson, & H., ), Australia (Soltani, Munday, & Burke, ), Ireland (Downe et al, ; Fringuelli et al, ) and Chile (Apablaza et al, ). Disease caused by this agent has some species‐specific pathological differences.…”

Case definitions for skin lesion syndromes in chinook salmon farmed in Marlborough Sounds, New Zealand

“…There are several farming areas in the South Island of New Zealand, including Marlborough Sounds, Canterbury and Stewart Island. While the industry has not been affected by any of the major production diseases seen internationally, skin lesions have been recorded with an increase in prevalence from 2012 onwards in the Marlborough Sounds and were associated with elevated summer mortalities on farms in 2015 (Brosnahan et al., 2019).…”

Ultrastructure of intracytoplasmic Rickettsia-like infection of the gills of the teleost Archosargus probatocephalus (Sparidae) in northeastern Brazil

“…Intracellular prokaryotes have frequently been described in different aquatic species and in several geographical locations, as: Ruditapes decussatus (Mollusca, Bivalvia), collected in Portugal (Azevedo, 1989); Venerupis rhomboides, from Spain (Villalba et al, 1999); juvenile Atractoscion nobilis, collected in the California (USA) (Chen et al, 2000); Mytella guyanensis from, Bahia (Brazil) (Ceuta & Boehs, 2012); Crassostrea gasar, cultivated in northeastern Brazil (Silva et al, 2015) and Oncorhynchus tshawytscha, from farms in New Zealand (Brosnahan et al, 2019).…”