Industry hails FDA approval of new antibiotic to fight ESC in catfish; first drug to clear under MUMS

WASHINGTON, DC – It has been a long wait for US fish farmers, but in October the US Food and Drug Administration (FDA) approved the first new in-feed antibiotic for finfish in more than two decades.

Aquaflor® (florfenicol) was licensed by FDA for the treatment of enteric septicemia (ESC) in farm-raised catfish.

“This is a real breakthrough for our industry,” said Hugh Warren, executive vice president of the Catfish Farmers of America (CFA).

“Having a safe, new-generation antibiotic available gives catfish farmers a new tool for improving profitability while delivering a safe, wholesome product to today’s health-conscious consumers,” Warren said.

The antimicrobial is also the first drug approved under changes put in place by the Minor Use and Minor Species Animal Health Act (MUMS), which passed Congress and was signed into law in 2004.

Schering-Plough Animal Health Corp. of Kenilworth, NJ, Aquaflor’s developer, began shipping the premix product to feed mills immediately following the FDA approval.

ESC costly disease

According to Schering-Plough, Aquaflor is “a highly palatable, fast-acting antibiotic proven worldwide to be effective against a wide range of bacteria in several aquatic species.”

New to the US market, the drug has been used successfully for nearly 15 years in aquaculture applications in Japan, Europe, and Latin America to treat diseases in other farm-raised aquatic species.

“We gave priority to securing a claim for (treatment of) ESC in catfish because of high death losses associated with the disease – more than $13 million a year according to a US Dept. of Agriculture (USDA) estimate,” said Dr. Robert Simmons, vice president, pharmaceutical research for Schering-Plough Animal Health, in an Oct. 28 press release from the company.

ESC, sometimes referred to as “hole in the head” disease, erodes the frontal bone of channel catfish. In its acute form, it can cause rapid mortalities in a pond, in some cases killing up to 50 percent of the population within days.

Industry experts say that bacterial diseases account for about half of all fish mortality in the catfish industry annually, with ESC being near the top of the list. Obviously, the economic benefit to catfish producers of having better therapies for management of ECS is potentially huge.

“With early diagnosis and proactive management, we think Aquaflor will raise the bar for several (catfish) industry standards, including fish survival, stocking rates, and profitability,” Simmons said.

Effective, good palatability

Unlike sulfa drugs and tetracyclines, the new antibiotic was developed specifically for use in food animal species.

Aquaflor can be used in catfish over the entire growth cycle, from fingerling to market-sized food fish, with no resulting setbacks in feed consumption or growth rates.

In tank trials at Mississippi State University (MSU), the drug proved highly effective in reducing mortalities among young catfish infected by the ESC bacteria. Sick, untreated fingerlings experienced a death rate of 60 percent, compared to mortality rates of less than one percent (.08) among fish treated with Aquaflor.

The drug’s effectiveness against the spread of infection during tank trials was also impressive. Untreated “control” fish experienced an infection rate of over 72 percent, vs. an infection rate of just 1.7 percent among treated fingerlings.

Dr. Pat Gaunt, MSU associate professor of aquatic animal health and a veterinary toxicologist, knows the drug and is impressed by it. She began studying the use of florfenicol to treat ESC more than five years ago.

“The stack of data generated by our group was over four feet tall. This was submitted to the FDA along with many more volumes from Schering-Plough Animal Health,” she said in an MSU press statement.

“We only have two other antibiotics for treating channel catfish. Palatability problems have been reported with one, and the other is most often formulated as a sinking feed and producers can’t tell if the fish are eating it or not,” Gaunt said.

“Aquaflor has proven to be safe and highly effective, with good palatability, and it is a floating feed,” she said, “so we have high hopes for it in the catfish industry.

“Producers have to realize that it’s not a silver bullet, however. As with any therapy, Aquaflor must be combined with diagnostics and good management.”

Schering-Plough recommends using feed medicated with Aquaflor as the sole ration for 10 consecutive days for best results. Treatments should be discontinued 12 days before marketing, the company said, and the drug is not approved for use in breeding stock.

Vet’s order

Aquaflor Type A Medicated Article is also the first drug in this industry to be classified by FDA as a veterinary feed directive (VFD) drug.

VFD is a relatively new category, established by the FDA in 1999, to help the agency more closely control new therapeutic drugs, primarily antimicrobials, and their use in food animals.

“The VFD allows us to continue adding new drugs to our health tool box,” said Richard Sellers of the American Feed Industry Association (AFIA).

Catfish producers may obtain VFD drugs through normal feed distribution channels, but they will require a signed veterinary feed directive from a licensed veterinarian. The vet must visually inspect one or more of the affected fish and keep copies of the paperwork for a minimum of two years.

Broader impacts

While the immediate impact of FDA’s approval of the new drug will be confined to the US farm-raised catfish industry, many see this as having broader implications for domestic aquaculture.

“The approval of florfenicol is a significant event for all of aquaculture, and indeed, animal agriculture,” said Randy MacMillan, vice president of Clear Springs Foods Inc. and president of the National Aquaculture Association (NAA).

“It signifies that if an antimicrobial drug can be scientifically shown to be safe and effective – including demonstration of no significant risk to humans because of antimicrobial resistance, and in spite of significant opposition to aquaculture or to the veterinary use of drugs from various activist groups – the FDA will approve the drug.”

Dr. Rod Getchell, who works in the Aquatic Animal Health Program at Cornell University’s College of Veterinary Medicine and is the Fish Health Notes columnist for Fish Farming News, concurred.

“The approval of Aquaflor is an encouraging sign for the aquaculture industry as a whole, particularly because this is the first aquaculture drug approved under MUMS,” Getchell said.

“Also, the addition of this antimicrobial should reduce the chances of antibiotic resistance developing that catfish farmers and their veterinarians are fighting to keep under control,” he added.

MacMillan hopes this approval has a ripple effect.

“This approval hopefully sends a significant, positive message to other potential sponsors of drugs that domestic aquaculture is worth pursuing for therapeutic agent approvals,” he said.

“Of course, the MUMS provisions further sweeten the deal, providing the potential for market exclusivity and, hopefully, grant money, to support various aspects of the approval process.”

MacMillan helped spearhead a multi-year, multi-industry effort that ultimately led to passage of the MUMS legislation.

“We, in the NAA, and all of domestic aquaculture, applaud the efforts of Schering-Plough, the scientists involved in the approval process, the FDA, and Roz Schnick, the national coordinator for aquaculture new animal drug applications,” MacMillan said.

“We all look forward to additional approvals, not only for florfenicol, but for the many and varied therapeutic agents under investigation.”

Schering-Plough said that it will pursue Aquaflor approval from the FDA for use in treating other (non-ESC) disease-causing pathogens in catfish and eventually other species.

Rick Martin

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