Amid concerns of antibiotics overuse contributing to the development of drug-resistant superbugs, American consumers are increasingly demanding antibiotic-free meat and fish. That’s bad news for Chilean salmon farmers who are facing a bacterial outbreak and treating their fish with record levels of antibiotics — and losing the business of Costco and others.

Chile is the world’s second-largest producer of salmon, pumping out 895,000 metric tons of the fish in 2014. At the same time, Reuters reports that salmon farmers in the South American nation used 1.2 million pounds of antibiotics (up 13% from the previous year) in an effort to fight off the Piscirickettsiosis (or SRS) bacteria, which causes lesions, hemorrhaging, swollen kidneys and spleens, and ultimately death in infected fish.

While the farmers insist that the fish treated with the antibiotics are safe, U.S. retailers — especially Costco — are moving away from Chilean salmon.

Costco purchases some 600,000 pounds of salmon each week to fill its warehouse stores around the country, and until recently 90% of that came from Chile.

But in recent months, the company has moved to cut that by more than half to 40%. The majority (60%) of Costco’s salmon will be coming toward Norway, which produces more salmon (1.3 million metric tons in 2013) and uses virtually no antibiotics (2,142 lbs. total in 2013).

And Costco is just the latest to look for alternatives to Chile. Whole Foods, and Trader Joe’s have already phased out antibiotic-treated Chilean salmon.

“The whole industry is starting to shift,” explains the Costco exec who oversees fresh foods to Reuters. “If I was to ask you your biggest concern on produce, you might say pesticides. When we ask people in protein, generally it’s going to be hormones or antibiotics.”

The situation in Chile is slightly different from the usual debate about antibiotics in farm animals. In most cases here in the U.S., cows, pigs, and chickens are provided continual, low-dose amounts of antibiotics, primarily for growth promotion.

Following recent guidance to drug-makers from the Food and Drug Administration, farmers now claim they use the drugs for “disease prevention,” even though this prophylactic, sub-therapeutic approach to antibiotics is exactly the kind of practice that physicians and scientists say engenders the development of drug-resistant pathogens.

But in Chile, the farmers claim that the antibiotics to prevent SRS infection are medically necessary.

“This is only something given to sick fish so they don’t die. It’s not something preventive,” the CEO of salmon producer Camanchacha tells Reuters.

And much like farm animals are weaned off antibiotics to minimize the chance of drug residues in meat products, the Chilean salmon go through a detox period before being harvested. And the FDA says its inspections since Oct. 2014 of these fish have not turned up any unapproved drug residues.

However, the issues of drug residues is different from the conversation about drug-resistant pathogens. Even though the fish may be cleansed of the antibiotics by the time they hit store shelves, the constant use of the drugs in salmon farms still can result — and has resulted — in the development of resistant bacteria.

In 2014, a Chilean government report noted antibiotic-resistant strains of SRS turning up in the country’s salmon farms. And they will likely continue to pop up so long as farmers keep using the same antibiotics.

Farmers say that without a vaccine to treat SRS, they have no choice but to continue with the antibiotics treatments.

Addicted to antibiotics, Chile’s salmon flops at Costco, grocers [Reuters]

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