Producers Assess New Weapon Against ESC


Enteric septicemia (ESC) is nothing new to the U.S. catfish industry.  Producers have been battling outbreaks of this costly bacterial disease for the last 20 years.   And, according to USDA’s National Animal Health Monitoring System data, the industry now loses some $13 million a year to ESC.

Producers have tried everything from antibiotics and vaccination to restricted feeding to bring the disease under control, all with varying levels of success.  Now, after years of trial and effort, they are rethinking their strategy and evaluating a few new approaches to combating ESC — not only to reduce fish mortality, but also to keep them on feed, increase efficiency and make their operations more profitable.

“We have a couple of medications that have been around for a good number of years,” says Tim Saxton, a partner in Five Mile Fisheries, Belzoni, Mississippi. 

“You’d feed one for four or five days and the fish would stop dying — and that was good.  But then, when you stopped the treatment and put the fish back on their regular feed, you’d go right back to where you started — more ESC.”

Clayton Miller, a catfish farmer in Brooksville, Mississippi, experienced the same thing. “The antibiotics would work. But oftentimes, as soon as you quit, you’d be back to the same problem you had before,” he says. “It was very frustrating.”

Producers don’t necessarily fault the drugs themselves.  The problem, they say, is that fish simply weren’t eating the medicated feed. “And if the fish don’t eat the medicine, you’re just wasting your money,” Miller says.
 
The situation perturbed producers for many years — so much, in fact, that some fish health specialists recommended taking fish off feed to reduce activity and the spread of the disease.

While that strategy was effective on some operations and didn’t require any additional expense, producers and researchers acknowledge that it went against the basic tenet to optimize fish growth and feed efficiency. The non-feeding days during an ESC disease outbreak were considered “lost days” and could not be recovered later in the growing season.  As a result, five-inch fingerlings were the best producers could expect in a typical year.

New weapon

This season catfish producers are rethinking their approach to ESC management — partly because they’ve endured enough economic loss already.  Many are being more proactive with diagnostics and trying to get an earlier start treating outbreaks.  Having a new weapon in their arsenal has also made them more optimistic about winning the battle against ESC.
 
Miller and Saxton say the arrival of AQUAFLOR® Type A Medicated Article (florfenicol) — an antibiotic now in its first full season after FDA approved it last fall for control of catfish mortality due to enteric septicemia (ESC) associated with Edwardsiella ictaluri — is already going a long way toward solving their ESC problems.

“I normally see outbreaks with ESC in the spring and the fall,” says Carl Jeffers of Top Cat Fishery, Portland, Arkansas. But, he says, ESC can pop up throughout the summer or anytime the water temperature is between 68 to 82 degrees Fahrenheit.

“This past spring I had an ESC outbreak in what was probably the heaviest stocker pond in our 2,000-acre operation,” he reports  “We’d been feeding about 200 pounds per acre per day, but then over about four days’ time, feed consumption dropped down to about 50 pounds per day.”

Jeffers says experience taught him to move fast. “We had the fish analyzed, and we identified ESC as the problem,” he says.

At the advice of his consulting veterinarian, Jeffers used AQUAFLOR at the recommended dose rate of 10 mg florfenicol per kg of fish for 10 consecutive days.

Fewer dead

 “We started seeing the effects of the treatment almost immediately – fewer dead fish – and within three days our feed consumption was back up to 200 pounds (of feed) per acre per day.  Exceptional results.”

Jeffers says he feels as if he dodged a bullet. “It could have been a devastating situation. There was probably $150,000 worth of fish in that pond.  To have them treated, back on feed, growing and healthy within three days, that was exceptional,” he says.

Mississippi producers also have been impressed with the speed of the new therapeutic.

“Some of the bugs we have in those ponds are real hard, fast-working bacteria, especially in warm weather,” says Five Mile Fisheries’ Saxton. “If it’s real hot and you let them get going, they can wipe out a pond in 48 hours. We’ve had real good results using AQUAFLOR to clear up the ponds.”

Brooksville’s Miller says he, too, has obtained good results using the new therapeutic. “We’re basically a food fish operation here,” he says, “but we do have two ponds with fingerlings, which we grow to eight inches or so. We get ESC along with a lot of mixed infections.”
 
While ESC can cause trouble in any size catfish, he says fingerlings get hit really hard.  “Those little fish seem like they’re a lot more susceptible to disease,” Miller adds.  “ESC infection runs heavy in those ponds.”

Miller says that during a recent outbreak, he saw 50 to 100 sick fish and immediately started feeding AQUAFLOR. “The next day we had about a dozen dead fish, then the next day only two or three, and on the fourth day, none.”

Makes more sense

The early field experience by producers mirrors results of a trial conducted at Mississippi State University.  Fingerlings challenged with ESC and treated with AQUAFLOR had a cumulative death rate of only 0.8 percent, compared to 60 percent for challenged, untreated fish. In the same study, treated fingerlings showed an infection rate of only 1.7 percent, compared to 72.3 percent for untreated controls.

Another study showed that feed containing AQUAFLOR was as palatable as unmedicated feed.  As a result, fish stay on feed throughout treatment period.  This in turn minimizes wasted feed while maximizing antibiotic intake and growth potential.

In the end, producers need to weigh the benefits of the additional income from increased number and longer length of treated fingerlings versus the increased costs of medicated feed.  If receipts outweigh the costs, producers using this new option for ESC control will see a larger return than the traditional non-medicated approach.

Miller believes that even with the cost of the drug, it makes a lot more sense than restricting feed. Jeffers agrees.
 
“In my mind, the only thing you’re doing when you stop feeding is prolonging the problem,” he says.  “As soon as you start the food up again the ESC comes back.  And all you’ve done is lose time when you could have been growing the fish.”

All growers interviewed say they were particularly impressed with the way treated fish stayed on feed. “I fed AQUAFLOR to three ponds and the fish were very aggressive on the feed, and they stayed aggressive on it,” Miller reports.

Schering-Plough Animal Health Corporation, the company that developed the broad-spectrum antibiotic and markets it in worldwide, is seeking more claims for other disease-causing bacterial infections pathogens in catfish and farmed aquatic species farms in the United States.

“We gave priority to securing a claim for ESC in catfish because of high death losses associated with the disease,” says Richard Endris, Ph.D., Aquaculture Research Program Manager for the company.

 “Along with early diagnosis and proactive management, it’s our hope that AQUAFLOR and the increased feed consumption that goes with it will help producers raise the bar for fish survival, stocking rates and profitability,” he adds.

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