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U.S. Department of Health and Human Services

Animal & Veterinary

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CVM Approves Drug for Catfish; First New Antimicrobial for Finfish in 20 Years

FDA Veterinarian Newsletter July/August 2005 Volume XX, No IV

The Center for Veterinary Medicine (CVM) in October approved an antimicrobial drug for use in treating catfish, marking the first new antimicrobial approved in over two decades for use in a finfish species.

The drug sponsor is Schering-Plough Animal Health Corporation, Union, N.J. The product, Aquaflor® Type A Medicated Article (florfenicol), an antibiotic, was approved as a “Veterinary Feed Directive” (VFD) product for the control of mortality due to enteric septicemia of catfish associated with Edwardsiella ictaluri.

Enteric septicemia of catfish (ESC) is a serious disease for catfish producers. It has been reported that ESC accounts for 30-47 percent of all cases submitted to fish diagnostic laboratories in the southeastern United States. The disease causes high morbidity and mortality among catfish in infected ponds. Economic losses from ESC are reported to cost the catfish industry millions of dollars each year.

Channel catfish (Ictalurus punctatus) are the species most susceptible to infection with ESC, although the disease has been reported in other members of the catfish family Ictuluridae. In addition there are also occasional reports in other species of finfish. Affected fish are sometimes observed swimming in tight circles (related to the presence of intracranial bacteria), and frequently have multiple small red and white ulcers on their skin. Severely affected fish may also exhibit exophthalmia (bulging eyes), and erosions between the eyes, sometimes referred to as “hole-in-head” condition.

Second Veterinary Feed Directive (VFD) Drug Since 1996

Aquaflor® is only the second drug CVM has approved as a VFD. The first was Elanco Animal Health’s Pulmotil 90 (tilmicosin phosphate), approved in 1996 as an antimicrobial for control of swine respiratory diseases.

The Animal Drug Availability Act (ADAA) of 1996 established a new category of drugs in addition to those available over-the-counter (OTC) and by prescription. This category of drugs was specifically designed for certain medicated feeds. Prior to ADAA, there were difficulties associated with regulating medicated feeds using only the OTC or prescription categories alone. For more information about the VFD provisions of ADAA see CVM’s Guidance for Industry #120, “Veterinary Feed Directive Regulation,” at http://www.fda.gov/cvm/Guidance/guide120.doc.

Since Aquaflor® was approved as a VFD drug, it is only available upon the order of a licensed veterinarian. In order to obtain a VFD order from a veterinarian several conditions must be met. The order must be made in the context of a valid veterinarian-client-patient relationship. In other words, the veterinarian must have firsthand knowledge of the fish experiencing the disease condition and be available for follow up, such as in the case of adverse reactions. Copies of the VFD order will then go to a licensed feed mill for preparation and distribution of the medicated feed. A second copy of the VFD order will be kept on the premises by the client to be followed in administering the medicated feed to ponds of affected fish. A third copy of the VFD order will be retained by the veterinarian. Industry guidance “Veterinary Feed Directive Regulation” (Guidance for Industry #120) (http://www.fda.gov/cvm/Guidance/guide120.doc) describes in detail the responsibilities of the veterinarian, procuder.

It is important to note that VFD orders can be written only for a single site and contain an expiration date, after which further disease diagnosis must be made prior to writing another order. It is acceptable to write an order for the treatment of multiple ponds located in a single location. It is expected that all medicated feed will be utilized for a particular disease outbreak and that medicated feed will not be stored for future use.

FDA/CVM believes that such control of VFD drugs is critical to reducing unnecessary use of such drugs in animals and to slowing or preventing any potential for the development of bacterial resistance to antimicrobial drugs. Safety concerns relating to difficulty of diagnosis of disease conditions, high toxicity, or other reasons may also dictate that the use of a medicated feed be limited to use by order and under the supervision of a licensed veterinarian.

First Drug Designated Under the MUMS Act

Aquaflor® is the first drug to be designated under the Minor Use and Minor Species (MUMS) Animal Health Act of 2004. Aquaflor® was designated based on the fact that catfish are a minor species. Designation occurs prior to submission of a new animal drug application and provides certain benefits to drug sponsors to encourage them to develop drugs for minor uses and minor species.

The MUMS Act—patterned after the well known and successful human -Orphan Drug Act of 1983 – is another provision of ADAA. The MUMS Act was a response to the lack of economic incentive for drug sponsors to develop drugs for minor species and for minor uses (rare diseases) in major species. Minor species are defined as any animal other than dogs, cats, horses, swine, cattle, chickens, or turkeys.

The MUMS Act contains three key provisions to assist in the development of drugs for minor uses and minor species: designation, conditional approval, indexing. For more information on these provisions and about the MUMS Act go to CVM’s website at http://www.fda.gov/cvm/minortoc.htm.

Designation of a new animal drug, prior to its approval, provides incentives to the drug sponsor to continue its development and to seek eventual approval. The MUMS Act makes the drug eligible for grants to support safety and effectiveness testing.

Additionally, sponsors who gain approval for designated new animal drugs will be granted seven years of exclusive marketing rights, which means the sponsor will face no competition in the marketplace for the approved use of the drug for that time period.

Evaluated for Antimicrobial Resistance Risk Management Strategy

Aquaflor® is among the first new antimicrobial approvals in food-producing animals that have been evaluated under CVM’s Guidance for Industry #152, “Evaluating the Safety of Antimicrobial New Animal Drugs with Regard to Their Microbiological Effects on Bacteria of Human Health Concern” (http://www.fda.gov/cvm/Documents/fguide152.doc).

The safe use of antimicrobials in the production of food-producing animals is an important public health issue. The Guidance for Industry about evaluating the safety of antimicrobial new animal drugs (#152) provides a regulatory pathway sponsors can use to show how a new antimicrobial drug can be used in a food-producing animal without endangering public health. CVM has determined that antimicrobial resistance risk management strategies (as described in the Guidance for Industry) in place for Aquaflor® are appropriate for its proposed conditions of use in pond culture systems.

New Horizon for Aquaculture Drugs

The approval of Aquaflor® signals a new horizon for drugs for finfish and minor species. Previously, treatments for the diseases of these species have languished for lack of economic incentives to encourage drug sponsors to pursue their approval. The hurdles have been high and the path uncertain. Now, under the provisions of ADAA and MUMS together with the guidance for addressing key issues such as antimicrobial resistance, drug sponsors have a clearer path for pursuing these approvals. The Center is pleased that sponsors are pursuing approvals for drugs to treat important diseases in minor species and for minor uses (rare diseases) in major species.