Researchers confirm a world first: Tenacibaculosis found in farmed rainbow trout, coho salmon

Published on
July 27, 2020

The pathogen tenacibaculosis has been found in farmed rainbow trout and coho salmon from the south of Chile, according to a paper published by researchers Ruben Avendaño‐Herrera, Constanza Collarte,  Mónica Saldarriaga‐Córdoba, and Rute Irgang in the “Journal of Fish Diseases.”

“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,” the researchers wrote. “Moreover, we confirm the presence of tenacibaculum species in the Chilean Patagonia.”

The diseases tenacibaculum dicentrarchi and tenacibaculum finnmarkense had previously 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.

In their investigation, the researchers collected samples from the mortalities recorded for rainbow trout and coho salmon from five marine fish farms located in the Los Lagos, Aysén, and Magallanes regions.

“The diseased fish exhibited cutaneous haemorrhages, tail and peduncle rots, and damage on the mouth and tongue,” the paper stated.

Microbiological analysis was performed on infected external tissues, yielding 13 bacterial isolates, which were then identified as members of the genus tenacibaculum through biochemical analysis.

“The success and sustainability of Chilean aquaculture largely depends on the control of endemic and emerging pathogens,” according to the paper. “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.

Chile is no stranger to having to fight fish disease. The country’s farmed fishing industry was battered from 2007 to 2010 by an infectious salmon anaemia (ISA) outbreak, leading authorities to approve a five-pillar fisheries and aquaculture law in March 2010.

These included avoiding the introduction of pathogens by controlling the import of eggs; avoiding vertical contamination by screening broodstock and disinfection of tributaries; avoiding the cross breeding of pathogens by ensuring the bio security of ships and processing plants and stipulating fallow periods; the mandatory vaccination of fish before they are put out to sea; and putting in place contingency measures and protocols if ISA or another disease occurs.

“These five pillars guarantee that salmon farming in Chile is sustainable for the future,” said Maria Eugenia Wagner, the president of SalmonChile in 2012. “The average weight of the fish is now higher and there is less mortality." The average slaughter weight has increased from about three kilograms per fish in 2009 to about five kilograms in 2012.

In total there were 44 sanitary regulations covering the whole production process. Implementation of the new production system required an investment of more than USD 500 million (EUR 430 million).

Following that crisis, Chilean salmon farming association SalmonChile acknowledged the ISA virus cannot be eradicated and that occurrences can be expected from time to time. The main issue is how the situation is addressed.

Recently, in July, Salmones Porvenir, the joint venture between Chilean salmon farming companies Nova Austral and Trusal S.A., a subsidiary of Salmones Austral – detected ISA at two of its 16 cages at the Navarro Tres center. The two affected cages contain 172,311 fish with an average weight of 430.4 grams, which are to be culled in the coming days. Navarro Tres holds a total of 1.37 million Atlantic salmon. The total loss to the JV is expected to reach USD 700,000 (EUR 613,000).

In November 2019, Chilean aquaculture authority Sernapesca announced it has notified AquaChile of suspected ISA at the company’s Caheuldao center in the Los Lagos region. The presence of the virus was detected by the authority’s ISA Virus Surveillance and Control Program, and according to Biobio Chile, 120,000 salmon were removed from the aquaculture center.

Photo courtesy of art nick/Shutterstock

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