Antibiotic Resistance Strikes $15 Billion Ornamental Fish Industry

But the transmission of disease from fish to humans is rare, researchers said.

SATURDAY, Feb. 2 (HealthDay News) -- Antibiotic resistance is taking a toll on the $15 billion ornamental fish industry, according to a new study.

The findings raise concerns that treatments for these fish, which are often raised and sold as pets for personal aquariums, may not be effective if the fish catch bacterial diseases.

Researchers in Oregon cautioned that this resistance could continue and more fish could be lost to bacterial diseases as antibiotics lose their effectiveness. Although this increased resistance to some commonly prescribed antibiotics doesn't pose a major threat to humans, the study's authors noted that people with weak immune systems or those who work with tropical fish are at greater risk.

Around the world, there are few restrictions on treating ornamental fish with antibiotics. The researches said antibiotics are regularly given to the fish during transport, regardless of whether they appear sick.

"We expected to find some antibiotic resistance, but it was surprising to find such high levels, including resistance in some cases where the antibiotic is rarely used," Tim Miller-Morgan, a veterinary aquatics specialist with Oregon State University, in Corvallis, said in a university news release. "We appear to already have set ourselves up for some pretty serious problems within the industry."

In conducting the study, which was published online this month in the Journal of Fish Diseases, the researchers tested 32 freshwater fish from Colombia, Singapore and Florida for resistance to nine different antibiotics, including the commonly prescribed drug tetracycline.

Although they found some resistance to all of the antibiotics, tetracycline met the highest level of resistance, at 77 percent.

"The range of resistance is often quite disturbing," the researchers said in the news release. "It is not uncommon to see resistance to a wide range of antibiotic classes."

Although many of the bacterial infections identified among the fish -- including Aeromonas, Pseudomonas and Staphylococcus -- could also occur in people, the study's authors noted that the transmission of disease from fish to humans is unlikely.

The researchers advised, however, that anyone in contact with tropical fish wear gloves and wash their hands after working with them. People should also avoid cleaning fish tanks if they have cuts or open sores on their hands. Sick fish should be removed from tanks immediately, and antibiotics should never be used on tanks unless the bacteria is identified.

"We don't think individuals should ever use antibiotics in a random, preventive or prophylactic method," Miller-Morgan said. "Even hobbyists can learn more about how to identify tropical fish parasites and diseases, and use antibiotics only if a bacterial disease is diagnosed."

The ornamental fish industry involves the trade of more than 6,000 species of freshwater and marine fish from more than 100 countries. The researchers suggested that the industry needs to improve screening methods, and quarantines -- not antibiotics -- should be used to reduce fish disease.

The researchers added that concerns about antibiotic resistance are on the rise. Resistance to antibiotics can cause the drugs to lose some or all of their effectiveness against bacterial infections.

More information

The U.S. Centers for Disease Control and Prevention provides more information on antibiotic resistance.