Pet fish medicine and surgery (Proceedings)

These notes are provided as an outline and brief review of pet fish medicine with emphasis on the clinical work up and standards of care. The further reading section contains a list of references that should be helpful to the clinician interested in learning more about the practice of fish medicine and surgery. Please feel free to contact me via e-mail with any questions or requests for information. I will do my best to reply within a reasonable time frame.

Clinical Work Up

      The history

As with any sick animal a good history can be the clinician's best friend; be sure and obtain a complete one. The clinician will require such important information as: How long has the client owned the fish? How experienced is the client? What and how often are the fish fed? Have any new fish been introduced into the aquarium or pond recently and if so were they quarantined? Have the fish been treated with any medications? Developing/utilizing a medical record form tailored to the fish patient that includes the history and water quality values is recommended.

      Water chemistry

Water chemistry is the most complicated part of aquatic system management and perhaps the most important. It is necessary to have an understanding of water chemistry principles in order to successfully diagnose and correct aquarium problems.

      Water testing

Obtaining a good and durable test kit that can be purchased for between $200.00 and $300.00 is recommended. Hach Co. (www.hach.com) and LaMotte Chemical (www.lamotte.com) are two reputable manufacturers and suppliers of quality water test kits. Regardless of test kit you'll want to be able to evaluate the water for dissolved oxygen, temperature, ammonia, nitrite, nitrate, pH, hardness, and total alkalinity.

      Filtration

All successful recirculating systems have at least one type of filter and many have two or more. A filter is just what it says it is; it filters or removes harmful or unwanted components from the water.

      Anatomy and physiology

Knowledge of normal anatomy is a prerequisite for practicing fish medicine. Fortunately, the vertebrate body plan is fairly well conserved, so much of what one sees in fish will be familiar, although there are some bizarre arrangements of the familiar (e.g. sea horses and flat fish), and many differences in specifics. Please contact me via e-mail for a review of fish anatomy and physiology, and/or, refer to the reference section at the end of these notes.

      Biopsy and other sampling techniques

In many cases, and especially those dealing with a client's pet fish, the clinician may want to take some tissue samples for examination without killing the fish. Many procedures can be rapidly performed with little risk to the piscine patient. Naturally, larger fish fare better than smaller fish and the overall condition of the animal is also a factor in how it will respond to biopsy techniques.

          -      Obtaining blood samples from smaller tropical fish is challenging but not impossible. In larger fish, like koi, successful phlebotomy is safe and readily accomplished. It is difficult to do in fish less than three inches long (if you want the fish to survive). A sterile blood sample is a useful way to culture for a suspected bacteremia or septicemia. Fresh whole mount blood smears can be valuable in diagnosing protozoal blood parasites (e.g. trypanosomes) and in an overwhelming septicemia motile gram negative rods can frequently be observed darting across the microscopic field of view. Stained blood smears will reveal numerous nucleated erythrocytes, leukocytes and thrombocytes. Campbell and Ellis (2007) have published an excellent review of piscine hematology. There is a growing body of literature on reference ranges in a number of species.

          -      Performing a fecal examination on a fish is not usually at the top of a list of diagnostic procedures even though it is a relatively easy and valuable test to perform. If the owner cannot obtain a fecal sample from the bottom of the aquarium, the fish can be placed in water containing tricaine methanesulfonate. Many fish will defecate as they relax in the anesthetic solution. If time is not a factor, the fish can be placed in a plastic bag, clean jar, or small aquarium, and a fecal sample can be collected within a matter of hours in most cases.

          -      Microbiological cultures of skin and gill tissues are not especially helpful due to the ubiquitous nature of aquatic bacterial pathogens. Cultures of clinically healthy fish and clean water will commonly reveal the presence of Gram-negative bacteria. Clean blood samples are valuable in detecting and identifying septicemia. As with terrestrial animal medicine, every attempt must be made to procure sterile samples for microbiology. A popular culture site in fish is the kidney. The kidneys of fish run just ventral to the spinal column and are generally found the length of the body cavity. Many small animal clinics are not equipped to perform microbiology testing. Fish cultures can be sent out of house since many veterinary schools and state agricultural diagnostic laboratories are familiar with fish bacteriology.10

      Radiology

Here at NC State radiology is part of many a pet fish diagnostic evaluation. Radiographic findings have been instrumental in diagnosing and treating a number of fish cases. Fish are relatively easy to radiograph. Most can be handled without anesthesia by simply removing the fish from a tank or bucket, placing it on a radiographic plate (protected by a plastic bag), and making the exposure. Fish will even tolerate contrast studies, CT scans, and bone scans (see below).

      Ophthalmic examination

Ophthalmic problems in pet fish are commonly encountered. Diagnostic techniques such as ophthalmoscopic examination, fluoroscein staining of the cornea, and even electroretinography have been utilized to help diagnose ocular disorders of fish.

      Computed tomography (CT)

This imaging modality is being utilized for fish diagnostics with more frequency and several publications describe techniques and results (see Further Reading section). As machines become "faster," imaging fish with CT becomes easier and safer since time out of the water is greatly reduced.

      Magnetic resonance imaging (MRI)

Although not yet commonly used for imaging pet fish, MRI units have been installed in a number of veterinary schools and referral practices, allowing for better access and consequently more opportunities for pet fish application.

      Endoscopy

This technique is gaining in popularity as more equipment and experienced operators become established. Endoscopy can be minimally invasive (exploring the oral or opercular cavities) or surgically invasive (laparoscopy). More details can be found in the Further Reading section and the University of Georgia School of Veterinary Medicine offers a short course on fish endoscopy.

      Necropsy procedures

On some occasions, a full necropsy is the best way to arrive at an accurate diagnosis. Necropsies have several obvious advantages over biopsy procedures. Tissues can be looked at thoroughly and completely. Any and all tissues and organs are available for both gross and histopathological inspection as well as microbiological testing. If possible, the clinician should obtain a moribund fish and quickly euthanatize it for examination. An overdose of tricaine methanesulfonate (over 400 mg/liter for 15 minutes) followed by a rapid cut with a scalpel at the base of the cervical spine will quickly dispatch a fish.

Standard of care

(Abbreviated version of a 2005 North American Veterinary Conference Proceedings, Lewbart, GA and Stamper, MA)

      Introduction

With regards to the Standard of Care (SOC) for this group of animals, koi, goldfish, and all commonly kept freshwater and marine bony fishes should be included. Sharks and other elasmobranchs, while occasionally kept in the home aquarium, are more frequently managed by aquarium and zoo veterinarians.

          -      As our knowledge of fish diseases, therapeutics and water quality increase, more and more veterinarians will be qualified to responsibly work with these animals. Peer-reviewed articles on the clinical management of pet fish issues now appear in many veterinary journals. Nearly every major veterinary conference includes fish medicine in the program and several veterinary schools now offer continuing education courses on this subject. In addition, a growing number of textbooks and review articles contain valuable information on pet fish medicine. All veterinarians, even if they have never worked on a fish, have a broad understanding of disease processes, diagnostics, animal husbandry, and chemotherapeutics. The opportunity to apply this knowledge to a client's pet fish problem can be a rewarding experience. Currently, some clinicians report that 10% or more of their income is generated by fish patients.

      Hospital physical plant

Hospitalizing fish patients can be a challenge but will be necessary on occasion. A variety of aquarium support equipment and supplies including tanks, pumps, filters, nets, siphons, heaters, and water conditioners are required. In many situations the owner of the fish can provide some or all of the necessary materials, including conditioned biological filter substrate, for the hospitalized patient. A room or portion of a room dedicated to fish life support is ideal. Some of the references contain supply lists, or, I'm happy to provide you with an electronic version via e-mail or flash drive.

      Procedures

          -      The following procedures, while not applicable in every case, should be available and the practitioner should be comfortable with utilizing them or alternatively know where/when to refer.

          -      Anesthesia/sedation; cloacal lavage; celiotomy; coelomic lavage; enucleation; eye aspiration; fin biopsy; gas bladder lavage; gastric lavage; gill biopsy; intracoelomic (ICe/IP) and intramuscular (IM) injection sites; microbiological sample collection (frequently kidney, spleen, liver); necropsy; skin biopsy; surgical wound repair; tube-feeding; venipuncture.

Drugs

          -      The majority of the current information on chemotherapeutics used in aquarium fish has been extrapolated from the aquaculture literature. There are a number of reasons for this, most of which revolve around funding for sound pharmacokinetic research. There are currently no drugs approved by the FDA for use in pet fish (although the FDA's Minor Use Minor Species Act is addressing this matter) in the United States. Many commonly employed veterinary compounds, including antibiotics, parasiticides, and disinfectants, should be on hand and available for use with pet fish patients. The fish practitioner should also be aware of the wide use of over-the-counter (OTC) drugs by pet fish hobbyists. An effort should be made to learn about these OTC compounds and have a basic understanding of their ingredients and impact on the patient and its environment.

          -      There are currently only three available antibiotics approved for use in fish intended for human consumption (Romet-30®—sulfadimethoxine/trimetoprim; Terramycin for Fish®—oxytetracycline; Aquaflor®—florfenicol). Much of the literature dealing with antibiotic usage in aquarium fish is empirical and anecdotal. For a thorough review refer to Reimschuessel et al., 2005. Fortunately, the veterinarian treating aquarium fish can apply current extra label drug use regulations when selecting and initiating antibiotic therapy.

          -      Please refer to the reference section of these notes for more details. I can also provide an electronic formulary via e-mail for those interested.

      Laboratory support

Fish clinicians should identify a laboratory that is familiar and comfortable handling fish samples, especially those related to clinical pathology and microbiology. In some cases this may require more than one laboratory.

      Miscellaneous

With literally hundreds of species kept in captivity from a variety of (sometimes) unrelated families, it is understood that the clinician will not be familiar with every species of fish with which they are presented.

      Fish clinicians should

          -      Be familiar with zoonoses and be able to speak intelligently to their clients on this topic

          -      Cultivate a list of colleagues to share information and seek consultation

          -      Have a thorough understanding of the natural history, anatomy, and physiology of the major groups of pet fishes (eg. goldfish, koi, cichlids, livebearers, anabantoids).

      Summary

Fish medicine is a growing and rewarding area of our profession. Many fish owners have strong emotional bonds to their fish and they seek state-of-the science care and support for their sick or injured pets. The fish medicine knowledge base is small compared to that of small animals or even some of the other exotic taxa. All fish practitioners are encouraged to contribute to this base of knowledge, either by publishing their findings or sharing information and discoveries with colleagues. Any Fish Practice SOC document is not comprehensive or permanent and will continue to change, grow, and develop over time.

Further reading (not inclusive)

Campbell, T.W. and Ellis C. 2007. Hematology of Fish. In: Avian & Exotic Animal Hematology & Cytology. Blackwell Publishing, Ames, IA, pp. 93-111.

Evans D.H. 1998. The Physiology of Fishes (ed.) 2nd. Ed. CRC Press, Boca Raton, FL.

Gratzek, J.B, and Matthews, J.R. 1994. Aquariology: The Science of Fish Health Management. Tetra Press, 330 pp.

Ferguson H.W. 1989. Systemic Pathology of Fish. Iowa State Press, Ames, IA, 263 pp.

Hughes Hartman K., Yanong R.P.E., Harms C.A., and Lewbart G.A. 2006. The future of training for aquatic animal health veterinarians. Journal of Veterinary Medical Education, 33:389-393.

Johnson, E.J. 2006. Koi Health and Disease. Johnson Veterinary Services, 3805 Robinson Rd., Marietta, GA 30068, 204 pp.

Jurk I. 2002. Ophthalmic disease of fish. Veterinary Clinics of North America: Exotic Animal Practice, 5(2):243-260.

Lewbart G.A. Fish; Exotic Animal Formulary, J. Carpenter editor, Elsevier Publishing, 2005; 5-29.

Murray M.J. 1998. Endoscopy in Fish. In Murray MJ, Schildger B, and Taylor M (eds), Endoscopy in birds, reptiles, amphibians, and fish. Endo-Press, Tuttlingen, Germany, pp. 59-75.

Noga, E.J. 2000. Fish Disease Diagnosis and Treatment. Iowa State University Press, Ames, IA, 367 pp.

Ostrander, G.K. (Ed.). 2000. The Laboratory Fish. Academic Press, New York, NY, 2000. 678 pp.

Plumb J.A. 1999. Health Maintenance and Principal Microbial Diseases of Cultured Fishes. Iowa State Press, Ames, Iowa, 328 pp.

Reimschuessel R, Stewart L, Squibb E, Hirokawa K, Brady T, Brooks D, Shaikh B, Hodsdon C.

Fish Drug Analysis—Phish-Pharm: A Searchable Database of Pharmacokinetics Data in Fish. AAPS Journal, 2005; 07(02): E288-E327. DOI: 10.1208/aapsj070230

Roberts R.J. 2001. Fish Pathology, Third Ed. WB Saunders, Philadelphia, PA, 472 pp.

Roberts, H.E. (ed.). 2009. Fundamentals of Ornamental Fish Health. Wiley-Blackwell, Ames, IA, 244 pp.

Saint-Erne N. 2003. Advanced Koi Care. Erne Enterprises, Glendale, AZ, 194 pp.

Spotte, S. 1992. Captive Seawater Fishes; Science and Technology. Wiley & Sons, 942 pp.

Stoskopf, M.K. 1993. Fish Medicine. Saunders Co., 882 pp.

Treves-Brown KM. Applied Fish Pharmacology. Kluwer Academic Publishers, Dordrecht, The Netherlands, 2000.

Wildgoose W. 2001. British Small Animal Veterinary Association Manual of Ornamental Fish 2nd Edition, BSAVA, Gloucester, UK, 304 pp.

www.aquavets.com (Aquatic Veterinarians and Disease Diagnostic Laboratory Resources)

www.aquavets.org (Aquatic Veterinary Association)

www.iaaam.org (International Association for Aquatic Animal Medicine)

A version of the diagnostics/water quality section originally appeared in the 2007 AVMA Annual Conference Proceedings and have been modified and updated from: Lewbart, G.A. 1992. Basic diagnostic procedures for tropical fish. Journal of Small Exotic Animal Medicine, 1(4):182-187.)