Surgery in fish

Behavioral and electrophysiological study in Colossoma macropomum treated with different concentrations of Nepeta cataria oil in an immersion bath revealed a therapeutic window for anesthesia

The purpose of this study was to characterize the activity of essential oils from Nepeta Cataria (EON) at concentrations of 125 μ L  L-1, 150 μ L  L-1, 175 μ L  L-1, and 200 μ L  L-1 on the behavior of loss of the posture reflex and recovery of the posture reflex and electrocardiographic activity and recording of the opercular beat of Colossoma macropomum during immersion bathing for a period of 5 min, in order to obtain a window for safe use during anesthesia. The fish (23.38 ± 3.5 g) were assigned to the following experiments: experiment 1 (latency to loss and recovery of the posture reflex): (a) 125 μ L  L-1, (b) 150 μ L  L-1, (c) 175 μ L  L-1, and (d) 200 μ L  L-1 (n = 9) per group. Experiment 2 (electrocardiographic and heartbeat recordings): (a) control group; (b) vehicle control group (2 ml of alcohol per liter of water), (c) 125 μ L  L-1, (d) 150 μ L  L-1, (e) 175 μ L  L-1, and (f) 200 μ L  L-1 (n = 9), per group. All the concentrations used showed efficacy in inducing loss of the posture reflex and reversibility with recovery of the posture reflex, but the electrocardiographic recordings indicated morphographic changes such as bradycardia during induction and p wave apiculation during recovery at the highest concentrations tested. In this way, we suggest a safe use window for short-term anesthesia with EON in the concentration range of 125 to 150 μ L  L-1 for juvenile Colossoma macropomum.

Treatment of Pain in Fish

This chapter provides an overview of our current understanding of clinical analgesic use in fish. Recently, the efficacy and pharmacokinetics of several analgesic drugs for use in fish have been investigated, and the most important data indicates that μ-opioid agonist drugs (e.g, morphine) are consistently effective as analgesics across fish species. In addition, bath application of some analgesic drugs may be useful, which affords multiple methods for delivering analgesics to fish. Although few published studies of non-steroidal anti-inflammatory drugs administered to fish show promise, we have much to learn about the analgesic efficacy of most drugs in this class.

Implications of comparative ventral body wall histology on selection of abdominal surgical approach and closure in 12 species of fish

A ventral midline surgical approach for fish celiotomy is commonly performed in veterinary clinical medicine and research, although the relevant ventral body wall anatomy of many fish species is not well documented. Histological evaluation of tissue samples from the ventral body wall of 12 fish species was performed to provide a reference for surgical approach and closure decisions. The width between muscle bundles running parallel to the long axis and total thickness of tissue layers varied among species. An appreciable space between longitudinal muscles of the ventral body wall and a lack of muscle, vessels and nerves on midline in all species examined supports recommendations of ventral midline incisions to spare important structures. Dense connective tissue consistent with an aponeurosis between musculature along the ventral body wall was not observed in any species evaluated. Connective tissue was concentrated within the dermis of all species evaluated, with an additional layer of collagen along the coelomic membrane in Russian sturgeon Acipenser gueldenstaedtii, koi Cyprinus carpio, goldfish Carassius auratus, black drum Pogonias cromis, black seabass Centropristis striata, tomtate Haemulon aurolineatum and scup Stenotomus caprinus. A sufficiently wide space on ventral midline for practical targeting during the surgical approach is present in A. gueldenstaedtii, C. carpio, striped bass Morone saxatilis, H. aurolineatum, P. cromis, rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta. Sand perch Diplectrum formosum, C. auratus, S. caprinus, grey triggerfish Balistes capriscus and black sea bass Centropristis striata have a negligible space between longitudinal muscles on midline. The variation in ventral body wall structure observed in this study helps inform surgical decision making for celiotomy incision and closure in these species.

Aquatic Ambulatory Practice

Ambulatory aquatic veterinary medicine allows examination of a patient's environment and identification of potentially sick animals. Common clients to use ambulatory service are owners of large koi and aquaculture facilities, but any aquatic animal owner could benefit from on-site services. This practice limits stress from handling and transporting large or critically sick or injured aquatic animals. Additional skills must be practiced to attain proficiency in capturing potential patients. Most diagnostics are available to practitioners in an ambulatory setting and follow-up care must be thoroughly discussed with clients.

Intramuscular infiltration of a local anesthetic, lidocaine, does not result in adverse behavioural side effects in rainbow trout

Fish are a useful animal model for research, but our improvement in some aspects of their welfare has not kept pace with their increased popularity for this use. For example, researchers rarely use analgesics. We evaluated the side effects of lidocaine, a local anesthetic widely used in human and veterinary medicine. We infiltrated lidocaine on each side of the dorsal fin (total 20 mg/kg) of young rainbow trout (15 fish per group) compared with infiltration with an equal volume of saline. We monitored behaviour of individual trout during the 4-hour trial. Food was presented 5 times during the trial (30 min, 1 h, 2 h, 3 h, 4 h after infiltration) and we analyzed behaviour for 1 minute before and after food presentation. Behaviour of Saline-Infiltrated trout compared with trout that received no infiltration showed that infiltration in and of itself had no statistically significant effects on trout behaviour. However, there were many statistically significant effects of Lidocaine-Infiltrated trout compared with Saline-Infiltrated trout; none of the side-effects were adverse.

Evaluation of tissue changes following intramuscular infiltration of lidocaine in rainbow trout Oncorhynchus mykiss

Rainbow trout Oncorhynchus mykiss were infiltrated with either saline or lidocaine adjacent to the dorsal fin to assess histopathological changes. Infiltration was done as if it were being used as a local anaesthetic. Tissue lesions and associated tissue healing were examined over a period of 30 days. Most changes occurred at the cranial site of where the solution was first infiltrated. The infiltration of a dose of 10 mg kg^-1 of lidocaine appears to have damaged the skeletal muscle and connective tissues more than a similar volume of saline, especially during the first 15 days. The primary changes included haemorrhage, inflammation and muscle degeneration and necrosis. By day 30 post-infiltration inflammatory lesions were either nearly or completely absent, signs of myofibre regeneration were noted in only one fish. This experiment shows local anaesthetics and saline can produce localized tissue damage, especially during the first 2 weeks post infiltration. Care should be taken to allow the fish to heal for at least 30 days and probably more, no matter the solution administered, especially if giving repeated injections or infiltrations at the same site.

Guidelines for the Care and Welfare of Cephalopods in Research -A consensus based on an initiative by CephRes, FELASA and the Boyd Group

This paper is the result of an international initiative and is a first attempt to develop guidelines for the care and welfare of cephalopods (i.e. nautilus, cuttlefish, squid and octopus) following the inclusion of this Class of ∼700 known living invertebrate species in Directive 2010/63/EU. It aims to provide information for investigators, animal care committees, facility managers and animal care staff which will assist in improving both the care given to cephalopods, and the manner in which experimental procedures are carried out. Topics covered include: implications of the Directive for cephalopod research; project application requirements and the authorisation process; the application of the 3Rs principles; the need for harm-benefit assessment and severity classification. Guidelines and species-specific requirements are provided on: i. supply, capture and transport; ii. environmental characteristics and design of facilities (e.g. water quality control, lighting requirements, vibration/noise sensitivity); iii. accommodation and care (including tank design), animal handling, feeding and environmental enrichment; iv. assessment of health and welfare (e.g. monitoring biomarkers, physical and behavioural signs); v. approaches to severity assessment; vi. disease (causes, prevention and treatment); vii. scientific procedures, general anaesthesia and analgesia, methods of humane killing and confirmation of death. Sections covering risk assessment for operators and education and training requirements for carers, researchers and veterinarians are also included. Detailed aspects of care and welfare requirements for the main laboratory species currently used are summarised in Appendices. Knowledge gaps are highlighted to prompt research to enhance the evidence base for future revision of these guidelines.

Comparative analgesic efficacy of morphine sulfate and butorphanol tartrate in koi (Cyprinus carpio) undergoing unilateral gonadectomy

OBJECTIVE

To identify pain-related behaviors and assess the effects of butorphanol tartrate and morphine sulfate in koi (Cyprinus carpio) undergoing unilateral gonadectomy. Design-Prospective study.

ANIMALS

90 adult male and female koi.

PROCEDURES

Each fish received saline (0.9% NaCl) solution (which is physiologically compatible with fish) IM, butorphanol (10 mg/kg [4.5 mg/lb], IM), or morphine (5 mg/kg [2.3 mg/lb], IM) as an injection only (6 fish/treatment); an injection with anesthesia and surgery (12 fish/treatment); or an injection with anesthesia but without surgery (12 fish/treatment). Physiologic and behavioral data were recorded 12 hours before and at intervals after treatment.

RESULTS

Compared with baseline values, the saline solution-surgery group had significantly decreased respiratory rates (at 12 to 24 hours), food consumption assessed as a percentage of floating pellets consumed (at 0 to 36 hours), and activity score (at 0 to 48 hours). Respiratory rate decreased in all butorphanol-treated fish; significant decreases were detected at fewer time points following morphine administration. In the butorphanol-surgery group, the value for food consumption initially decreased but returned to baseline values within 3 hours after treatment; food consumption did not change in the morphine-surgery group. Surgery resulted in decreased activity, regardless of treatment, with the most pronounced effect in the saline solution-surgery group. Changes in location in water column, interactive behavior, and hiding behavior were not significantly different among groups. Butorphanol and morphine administration was associated with temporary buoyancy problems and temporary bouts of excessive activity, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol and morphine appeared to have an analgesic effect in koi, but morphine administration caused fewer deleterious adverse effects. Food consumption appeared to be a reliable indicator of pain in koi.

Fish Surgery: Presurgical Preparation and Common Surgical Procedures

Fish surgical procedures are commonplace in aquaria, zoos, laboratory facilities, and pet clinical practice. To incorporate fish surgery into a clinical setting, an understanding of anatomic differences between mammals and fish, bath anesthetics, and recirculating anesthesia techniques must be developed; a system or different size systems to accommodate anesthesia and surgery of particular species of concern at an institution or practice constructed; and familiar mammalian surgical principles applied with some adaptations. Common surgical procedures in fish include coeliotomy for intracoelomic mass removal, reproductive procedures, gastrointestinal foreign body removal, radiotransmitter placement, and integumentary mass excision.

Evaluation of the effects of tricaine methanesulfonate on retinal structure and function in koi carp (Cyprinus carpio)

OBJECTIVE

To determine whether repeated exposure to clinically relevant concentrations of tricaine methanesulfonate (MS-222) would alter retinal function or induce histologically detectable retinal lesions in koi carp (Cyprinus carpio).

DESIGN

Prospective, controlled, experimental study.

ANIMALS

18 healthy koi carp.

PROCEDURES

2 fish were euthanized at the start of the study, and eyes were submitted for histologic evaluation as untreated controls. Anesthesia was induced in the remaining fish with 200 mg of MS-222/L and maintained with concentrations of 125 to 150 mg/L for a total exposure time of 20 minutes daily on 1 to 13 consecutive days. On days 1, 7, and 13, electroretinography of both eyes was performed in all fish remaining in the study, and 2 fish were euthanized immediately after each procedure for histologic evaluation of the eyes. Median b-wave amplitudes were compared among study days for right eyes and for left eyes via 1-way repeated-measures ANOVA with a Bonferroni correction for multiple comparisons.

RESULTS

Median b-wave amplitudes on days 1, 7, and 13 were 17.7, 20.9, and 17.6 μV, respectively, for right eyes and 15.1, 16.9, and 14.3 μV, respectively, for left eyes. No significant differences in b-wave amplitudes were detected among study days. No histopathologic abnormalities were identified in the retinas of any fish treated with MS-222 or in control fish.

CONCLUSIONS AND CLINICAL RELEVANCE

Short-term exposure of koi carp to clinically relevant concentrations of MS-222 daily for up to 13 days was not associated with changes in retinal structure or function as measured in this study.

Bilateral intraocular malignant neuroectodermal tumors in a telescope goldfish (Carassius auratus)

Abstract A 5-year-old male telescope goldfish (Carassius auratus) developed buphthalmia of the left eye. An enucleation was performed and a diagnosis of a neuroectodermal tumor was made on histological examination. Although the fish initially recovered, it was killed 49 days postsurgery due to a severe decline in its condition. On histological evaluation of postmortem tissue samples, it was determined that the fish also had a neuroectodermal tumor of the right eye with local invasion of the brain. On immunohistochemistry, the neoplastic cells were positive for S-100. To the authors' knowledge, this is the first published case of naturally occurring bilateral intraocular neuroectodermal tumors in a fish.

Emergency and critical care of fish

Most fish emergencies are the result of inappropriate environmental conditions and primary or secondary infectious disease or trauma. The immediate response should be to increase aeration, provide suitable water, and decrease stressors. A thorough history, evaluation of the fish and their environment, and some rapid diagnostic tests (particularly direct and stained cytology) often provide the information needed to make a diagnosis and render appropriate treatment. When cohorts are at risk and the patient is unlikely to recover, euthanasia and necropsy are recommended to reach a definitive diagnosis. Some common emergencies include ammonia and nitrite toxicity; low dissolved oxygen; copper and chlorine toxicity; gas supersaturation; and certain bacterial, protozoal, and viral diseases.

Ulcerative skin disease in a group of koi carp (Cyprinus carpio)

A case report detailing the presenting clinical signs, diagnostics, and treatment of ulcerative skin disease in a group of koi carp (Cyprinus carpio) is presented.

Viruses of pet fish

Investigation of a fish kill should begin with water quality analysis and use of standard necropsy techniques to rule out the role of parasites or bacteria. The presence of a virus does not mean necessarily that it is a pathogen. Another point to consider is the potential influence of water temperature on pathogenicity; this may be an important factor in developing disease. A list of laboratories that is approved by the USDA to conduct diagnostic testing of aquaculture species can be found at: http://www.aphis.usda.gov/vs/nvsl/labcertification/aquaapplab.htm.

Neoplasia in fishes

Similar to higher vertebrates, neoplasia is not an uncommon disease in fishes, which are the largest group of vertebrates. However,neoplasia in fishes is generally a benign condition with relatively few exceptions of malignant disease. The objective of this discussion is to provide an overview of neoplasia and the various neoplastic disease conditions in fishes according to organ system,including the few neoplasms of species that are familiar to the aquatic animal or exotic animal practitioner. The discussion also considers the various nonneoplastic lesions in fishes that may be confused with neoplasms, and treatment of neoplastic disease in fishes that is generally restricted to surgical intervention.

Reproductive medicine in koi (Cyprinus carpio)

Each year more veterinarians are seeing ornamental fish patients and our knowledge of how to manage the pet fish patient is increasing at a rapid pace. A large percentage of these patients are nishikigoi (Cyprinus carpio) which are taxonomically an ornamental carp. In this country and in many parts of the world we refer to these fish as koi. Reproductive medicine problems are well documented in koi and a thorough knowledge of this subject will aid the fish practitioner in diagnosis and treatment.

Surgical removal of a seminoma from a black sea bass

An adult black sea bass was examined because of abdominal distention and decreased appetite. A large abdominal swelling was evident and was firm on palpation. Differential diagnoses included neoplasia, abscess or granuloma, hematoma, or swim bladder abnormality. Diagnostic tests included survey radiography, positive-contrast radiography, and computed tomography. The sea bass was anesthetized with tricaine methanesulfonate. A ventral midline abdominal incision was made, and adhesions to the mass were gently dissected. The fish recovered without complications. Radiography was repeated 8 weeks after surgery, and there was no evidence of mass regrowth. To the authors' knowledge, this is the first report of a barium enema being performed in a fish. Although surgical procedures are performed more commonly on fish for research, a few reports of clinical surgical cases have been described. Our experience supports the conclusions of other reports that certain surgical procedures can be performed safely in fish.