Antibiotic treatment 'works for fish and the environment'

Producers’ organisation Salmon Tasmania has said the first suite of results on the use of the antibiotic florfenicol in the Australian state’s salmon farms contains good news for fish health and the environment.

Florfenicol is being tested for efficacy and impact on the environment after an “unprecendented mortality event” at salmon farms last summer. Salmon Tasmania said at the time that Piscirickettsia salmonis - the bacterial causative agent of salmon rickettsial septicaema (SRS) – had been responsible for disease that had devasted several farms in the D’Entrecasteaux Channel.

Salmon Tasmania chief executive John Whittington said today that the results confirm that florfenicol is the most effective treatment, is safe for consumers and the best option for the environment.

A textbook response

“The salmon that have been treated with florfenicol are healthy, it’s the textbook response expected with this gold-standard treatment,” Whittington said in a press release.

“This is great news for our salmon farmers who have been working hard to have every tool in the toolbox to try to ensure last summer’s mortality event doesn’t happen again.”

Salmon Tasmania said the most rigorous environmental monitoring of its kind, designed by the independent Environmental Protection Authority (EPA) and Public Health, has also been rolled out across leases where florfenicol is used.

The monitoring programme conducted by third-party experts examines the levels of florfenicol in sea floor sediment, the water column, and wild fish at various distances from the lease, prior to treatment, during treatment and post treatment on day one, seven, 14 and 21.

Consistent results

The results are in for day one and day seven post treatment at the first two leases where florfenicol was used, and day one at the third lease where florfenicol was used – all near Dover, in the south of the island state.

Salmon Tasmania said the results are markedly consistent across all three lease sites, including:

• Sea floor sediment: There was no detectable florfenicol.
• Water column: Extremely low levels, the equivalent of 20 grains of salt in an Olympic swimming pool the day after treatment, then quickly disappearing because florfenicol breaks down rapidly in seawater.
• Wild fish: Every fish caught was safe to eat, by Australian food standards. There was no detectable florfenicol in 286 fish, one fish recorded a negligible trace, and another recorded a trace, but was still safe to eat. For example, based on this data, an adult would have to catch and eat more than 1,000 servings of fish in a week to come anywhere near the Acceptable Daily Intake.

Safe to catch and eat fish

Given the high level of consistency of results, the data suggest that sampling of future treatments would deliver similar results that clearly demonstrate no environmental or public health concerns, said Salmon Tasmania.

“I understand that some people are nervous about the use of antibiotics in Tasmania’s waters, that’s why I am sharing these results now that they are available,” Whittington said.

“What these results show is that it is safe to catch, safe to eat and safe to swim in our waterways.”

All monitoring results are submitted to the EPA and Public Health, and will inform future public health advice.