10.0 Drugs, Pesticides, and Biologics for Aquatic Animals
10.5 Reasons for Treating Animals
There are five general reasons for treating animals: water treatments, illnesses with bacteria or parasites, preventing disease, promoting weight gain and growth, and aiding or inducing reproduction. In real-life situations, these reasons are often intertwined and rarely is just one reason for treatment present.
Water Treatments
Water treatments involve altering the physical or chemical parameters of the environment to better suit the animal’s needs. Methods of water treatment are discussed in Chapter 2.3 Water Treatments. The chemicals used in these methods may be federally considered for regulation in some way. Salt is an example of when plain sodium chloride is reviewed. The FDA regards salt as a Drug of Low Regulatory Priority. The agency will not likely expend regulatory resources on oversight.
Examples of other treatments include formalin, hydrogen peroxide, Chloramine-T, salt, garlic oil, and freshwater. But any disinfectants with a specific disease claim must be FDA-approved and EPA-registered for use on fish or their water. Always read the product label carefully to ensure the product is marked as FDA approved. Formalin that is not FDA approved is not substitutable with FDA-approved products. Similarly, a formalin product with FDA approval for footbath use in sheep is not okay to use in food-fish water! Products used in food-fish production must have FDA approval for fish and for the labeled purpose. Hydrogen peroxide and Chloramine-T are other products that must have FDA approval to market a company’s product for label-specified food-fish purposes.
For ornamental fish, the FDA’s decision is to not expend regulatory resources at this time. Using a chemotherapeutant from the ornamental fish industry on food fish should not even be considered. Most drugs marketed for ornamental fish are not FDA approved for food-fish administration. Consider malachite green, an antimicrobial used for ornamental fish. This product cannot be used in food fish because it is a genotoxic carcinogen. Using this product on a food-fish farm can result in active enforcement actions from the FDA. The same can be considered for the parasiticides from ornamental fish treatment to food-fish production.
Although numerous chemotherapeutants such as antiparasiticides are available for ornamental fish that have not been FDA approved, only FDA-approved formalin (e.g., Parasite-S [Formalin]-NADA 140-989), can be legally used on food fish for labeled indications. Hydrogen peroxide in the FDA-approved product (e.g., 35% Peroxaid- NADA 141-255[1]) and Halamid-Aqua (chloramine-T)-NADA 141-423, are FDA-approved to use as external microbicides for treating external infections in food fish. Read the specific label claims permitted in treating aquatic animals to avoid violations. Of special note is the same compound, Chloramine-T, sold by the same firm as Halamid. But Halamid is not FDA approved for use on fish. It is labeled as a disinfectant! Halamid is not used on food fish as is Halamid Aqua for external bacterial diseases. Please read labels and be aware of regulations when treating aquatic food animals!
Illness with Bacteria or Parasites
Like mammals, fish can become sick. Even though the clinical signs are not specific except in a few cases, the best way to use medications is with an accurate diagnosis. The clinical signs considered here are septicemias, erosions, mortalities, and chronic diseases.
According to the FDA Center for Veterinary Medicine “Program Policy and Procedures Manual 1240.4200, Supplemental Policies, Enforcement Priorities for Drug Use in Aquaculture,” any compound determined to be a drug under FFDCA is a drug even if it has pesticide, biologic, food, or color additive properties or claims.[2] The chemotherapeutics that are considered drugs include antibiotics, antifungals, antiparasitics, clays, and herbicides when used to diagnose, cure, mitigate, treat, or prevent disease in animals. The clays and herbicides are not FDA approved but are drugs of low regulatory priority as per the Procedures Manual 1240.4200. Fullers Earth is a clay used to reduce the adhesiveness of fish eggs to improve hatchability. An herbicide, diquat, is being investigated under an INAD for treating infectious disease in fish.
Products found not to be of low regulatory priority but with regulatory action deferred pending further study include Copper sulfate and Potassium permanganate. Drugs with high regulatory priority include Chloramphenicol, Nitrofurans, Fluoroquinolones and Quinolones, Malachite Green, and Steroid Hormones.
There are four FDA-approved antibiotics for food fish (see Table 10.3).
|
Administration Route |
Drug |
Use |
|
Immersion |
Halamid Aqua (Chloramine- T) |
Read current label for species and specific bacteria to be treated |
|
Formalin |
External parasites and fungal pathogens on fish, fish eggs, and shrimp |
|
|
Hydrogen peroxide |
Read current label for species and specific bacteria to be treated |
|
|
Oxytetracycline hydrochloride |
Skeletal marking[3] |
|
|
Tricaine methanesulfonate |
Anesthetic Immobilization of fish (off-label use in euthanasia) |
|
|
Injectables |
Chorionic gonadotropin |
Improve spawning in broodstock fish |
|
Medicated feed |
Florfenicol |
Read current label for species and specific bacteria to be treated |
|
Oxytetracycline dihydrate |
Read current label for species and specific bacteria to be treated |
|
|
Sulfadimethoxine/ormetoprim |
Read current label for species and specific bacteria to be treated |
|
|
Sulfamerazine |
FDA approved but not marketed at this time |
However, only three of these antibiotics are marketed at this time: Aquaflor, Romet, and Oxytetracycline. There are so few because of the lack of commercial sponsors to provide the drugs. Oxytetracycline is one of the most commonly used antibiotics in human medicine. This simultaneous human and animal use creates greater potential for antimicrobial resistance to develop in treated individuals.[4]
Prevention of Disease
“An ounce of prevention is worth a pound of cure” is an adage for those working with disease control. The scenario has changed, though, in recent times. Growing incidents of antimicrobial resistance have caused federal regulations to be promulgated to restrict antibiotics used in food animals and are no longer considered a safe preventative measure. Now preventative measures focus on biosecurity and vaccinations, as these methods do not commonly lead to resistance to pathogens.
Other methods for prevention outside of these two main biologics and drugs are biosecurity, complete nutritional management, water treatments and exchange, better management plans, selective breeding programs, and certain immune-stimulating feed ingredients when other measures fall short.
Promote Weight Gain and Growth
Producers tend to be very cognizant of production costs, especially feed and utilization efficiency. In order to be more efficient, the feed conversion rate is one characteristic most focused on at the producer’s level. Several antimicrobial agents were frequently used prior to the FDA restricting antibiotic use in food fish. The FDA has removed the use of antimicrobials for promoting weight gain and growth. There are no specific FDA-regulated products for enhancing animal production gains, and antibiotics are prohibited as promoters of weight gain. Aspects like cleanliness, nutrition, husbandry, and other management techniques can be done to improve feed conversion, resulting in increased weight gain and growth.
Regarding marketing products, where a need is unmet, someone will soon offer a product to correct it, complete with glossy trade literature to support the claims. This type of marketing paradigm can be difficult to anticipate and regulate. There is interest in topics and products such as probiotics and prebiotics that are being studied and commercialized. Weight gain trials or health improvement studies, as in other livestock, will clarify some confusion about using these products in aquatic livestock production. In conclusion, it can be stated that, for example, many published reports (peer-reviewed) of essential botanical oils can do many things. Some are in commercial use in other countries. All that can be clearly stated is for the producer to do their homework and find actual field trials and other supporting evidence sources.
Aid in or Induction of Reproduction
In any breeding facility, the timing of spawning is imperative for efficiently utilizing the farm’s resources. Proper timing/coordination of spawning can result in raised fecundity, increased egg hatching, higher fry survival, and off-season spawning. Adjusting the spawning time will improve cost efficiency or reposition the harvest to better meet market demand.
Aquatic livestock production has some capability in some species to generate gender control of a population or timing of the reproductive effort. Some reasons for this are to prevent uncontrolled reproduction, like in tilapia, which sexually mature and procreate before they have achieved harvest size; to reduce territorial aggression; or to ensure that animals grow at similar rates. Many strategies include hormones, lighting, specific feed availability, or temperature variations.
An FDA-approved hormone product is Chorulon, a drug used for preventing partial ovulation and spawning, enhancing egg quality, milt production, sperm volume, and motility.[5] What is unique about this drug is that it is a preparation of human freeze-dried chorionic gonadotropin.
Ovaprim injectable is an FDA-indexed drug for ornamental fish—not food fish. The product is an ovulating/spermiating agent in a liquid peptide preparation. The product contains an analog of gonadotropin-releasing hormone (GnRHa) from salmon and a dopamine inhibitor. This level of detail may be difficult to understand if you have not studied fish reproductive physiology. Therefore, the discussion will end with the statement that this strategy causes the release of stored gonadotropins from the pituitary and inhibits dopamine release, lowering the release of GnRHa. This action initiates influence on the reproduction cycle.
- Syndel. (2019 January). 35% PEROX-AID package insert. https://syndel.com/wp-content/uploads/2019/01/Perox-Aid-Insert-ver.-062519.pdf ↵
- Federal Drug Administration. (2011). Enforcement Priorities for Drug Use in Aquaculture. Program Policy and Procedures Manual 1240.4200. https://www.fda.gov/media/70193/download ↵
- Fish marking examples can be seen at https://www2.dnr.mi.us/Publications/pdfs/ifr/i frlibra/technical/reports/2002- 1tr.pdf ↵
- Leal, J. F., Santos, E. B., & Esteves, V. I. (2019). Oxytetracycline in intensive aquaculture: water quality during and after its administration, environmental fate, toxicity, and bacterial resistance. Reviews in Aquaculture, 11(4), 1176-1194. ↵
- Merck Animal Health. (2014 April revised). Chorionic gonadotropin product label. https://www.merck-animal-health-usa.com/product/chorulon ↵
