Fish Medicine Flashcards
What are a majority of ZCA species issues related to?
husbandry
What are the 2 major classes of fish?
- Chondrichthyes - sharks and rays
- Osteichcthyes - Actinopterygii* (ray-fins), Sarcopterygii (lobed fins)
What are the most common fish species presented to veterinarians? What are the 2 major families?
freshwater (ornamental) teleost fish
- Cyprinids = koi, goldfish
- Anabantoids = bettas
What are the major anatomical adaptations that fish have made to their environment?
different body shapes
- fusiform (torpedo)
- ribbon-like
- eel-like
- ventrally flattened
- spheroid
- laterally flattened
Where is the coelom found in laterally flattened fish?
right behind the operculum, which covers the gills
Label the following anatomical structures of the fish.
a. lateral line - sensory, venipuncture landmark
b. dorsal fin
c. caudal peduncle - cranial to caudal fin, venipuncture landmark
d. caudal fin
e. anal fin
f. vent
g. pelvic fin
h. pectoral fin
i. operculum - bony plate covering the gills
Where is the heart located in fish?
caudal and ventral to the gills
What is the physical barrier to the environment? What is it responsible for?
integument
- hydration
- osmoregulation
- other physiologic functions
What do alarm cells and chromatophores in the skin of fish do? In what 3 ways does their skin differ from mammals?
ALARM CELLS = secrete a substance when skin is penetrated to alert other fish of danger
CHROMATOPHORES = change color of skin in response to physiologic stimuli
- epidermis lacks keratin
- all layers are capable of mitosis
- minimal to no SQ space
Chromatophore action:
How are injections given concerning fish scales?
under/between —> can cause damage and infection if directly through scales
What is the cuticle of fish skin?
mucus layer on the surface of the epidermis responsible for immune defense and UV protection
- contains Igs and antimicrobials, commonly fed on by fries
What is the primary mode of respiration for fish? What 2 additional functions does this system have?
gills —> requires continuous flow of water (swimming!)
- osmoregulation
- excretion of nitrogenous waste
Gills, histology:
What is the heart and lymph system of fish like?
four chambers - sinus venosus receives deoxygenated blood, atrium, ventricle, bulbus arteriosus sends off deoxygenated blood
has an extensive system that lacks nodes
What 3 systems take part in osmoregulation and excretion in fish?
- gills
- kidneys
- digestive tracts
What are the 2 anatomical sections of fish kidneys? What are their functions?
- ANTERIOR - hematopoietic, endocrine, area for blood collection for cultures and histopath
- POSTERIOR - hematopoietic, excretory
How does osmoregulation in freshwater and marine teleost differ?
FRESHWATER - must remain hypertonic compared to the environment, so they actively uptake and retain electrolytes and produces dilute urine
MARINE - must remain hypotonic compared to the environment, so they take in more water and actively excrete concentrated urine
How does the GI system of herbivorous and carnivorous fish compare?
HERBIVOROUS = longer tract
CARNIVOROUS = shorted tract
(some fish contain a hepatopancreas + GB and lack a stomach)
What is the nervous system of fish like?
similar to other invertebrates, contain a CNS and PNS —> they feel pain!
What is the lateral line system?
sensory system containing mechanoreceptors and hair cells that is sensitive to vibrations and water displacement
- how fish are able to form such tight schools
What is head and lateral line erosion (HLLE)? How is it treated?
depigmentation and decreased function of the lateral line up towards the head, common in saltwater fish (tangs!) kept in tanks with recirculated water
improve tank water circulation system
What is the swim bladder?
organ present in some fish responsible for buoyancy, pressure, and sound production (drummed against)
What are the 2 types of swim bladders?
PHYSOSTOMOUS - contains a pneumatic duct between the esophagus and swim bladder allowing the fish to swallow and burp out air to actively alter buoyancy
PHYSOCLISTOUS - lacks a pneumatic duct, making the fish unable to quickly change buoyancy
What are common causes of buoyancy disorders in fish? How are they treated?
- granulomatous disease
- polycystic kidney disease
- fluid within the swim bladder
- poor water conditions
- congenital
- decreased temperatures
high fiber foods (peas!), mechanical devices, antibiotics, aspiration of the swim bladder
What are important aspects of a history taken during physical exams on fish?
- TANK: size, lighting, filtration, heater, feeding, decorations, length of ownership
- WATER: source, frequency of change, water quality
- TANK INHABITANTS: types, numbers, diet, frequency of feeding
- CURRENT PROBLEMS
- PRIOR TREATMENTS
What is the major cause of illness in fish in human care?
water quality issues
What are the 3 types of filters used in fish tanks?
- MECHANICAL - foam/sand physically removes/traps particles and debris
- BIOLOGICAL - bacteria in the filter breaks down nitrogenous waste (drugs used in tank can kill these bacteria)
- CHEMICAL - ion exchange with carbon and UV lights sterilize the tank
What are the 7 basic water quality parameters measured during physical exams?
- temperature
- dissolved O2
- ammonia
- nitrite, nitrate
- pH
- salinity, hardness
- chlorine, chloramine
What are 4 abnormal behaviors that can be observed in fish?
- flashing - rubbing against substrates or decorations = parasites!
- piping - gasping for air = O2/water quality problems!
- clamped fins - not moving and keeping fins close to body = uncomfortably, not systematically well!
- isolation or congregation
What external lesions are commonly seen in sick fish?
- pigment changes
- lesions
- deformities
How can obesity be differentiated from ascites (Dropsy)?
ascites will cause scales on dorsum to protrude
What are the 2 major routes of administration of anesthesia for fish?
- immersion - dip, continuous
- injections - IV, IM, intra-ceolomic
What aspect of monitoring is most important for fish anesthesia? What else is commonly monitored?
respiratory rate
- heart rate: Doppler
- muscle tone: stiff, reacting to stimuli
- swimming behavior
- equilibrium
What is the most common immersion drug used for anesthesia in fish? How is it created for a tank?
tricaine methanesulfonate (MS-222)
a stock solution of 100 mg/mL is created, but due to its acidity, it needs to be buffered with sodium bicarbonate 1:1
What 3 things influence uptake of tricaine methanesulfonate (MS-222)?
- temperature
- hardness/salinity
- crowding
What is an alternative anesthetic compared to tricaine methanesulfonate (MS-222)?
eugenol (clove oil) —> not completely soluble in water, recovery is commonly prolonged
- diluted 1:10 in 95% ethanol for stock solution of 100 mg/mL
What are some other immersion, oral, and injectable anesthetic options for fish?
IMMERSION - Metomidate, Quinaldine, 2-Phenoxyethanol, Ketamine + Xylazine, Medetomidine, Propofol, Alfaxalone
ORAL - Metomidate, Diazepam, Ketamine, Telazol
INJECTABLE - Ketamine, Medetomidine, Xylazine, Telazol, Propofol, Alfaxalone
What should be worn by physicians before performing a physical exam on a fish?
non-powdered gloves
What is the primary target for many infectious agents of fish? How is it commonly evaluated?
integument
skin scrape - use a blunted scalpel blade, glass slide, or overslip and scrape behind the pectoral fin towards the tail, then add water and a coverslip to evaluate for bacterial, fungi, algae, or parasited
What must be done before performing microbiology and cultures? What stains are commonly used?
rinse area with sterile saline or water - an infectious should have an overabundance of that organism, be aware that it is commonly contaminated by what else is in the tank
- Gram’s stain
- acid-fast stain (Mycobacteria)
- Diff Quik
How are gill preparations performed?
- gently lift the operculum (patient sedated!)
- use iris/suture scissors to sample the tip of a few primary lamellae (bleeding common, these can regenerate)
- add a drop of water, apply a cover slip, and examine
What is a common artifact of clipping during gill preparations?
- telangiectasia
- hypertrophy due to trauma
What is important to communicate with owners prior to fin biopsies? How is it performed?
development of permanent defects to the fin
use iris scissors cut out a sample between rays
What are the 2 major options for venipuncture in fish? How much blood is able to be taken? What are they most commonly collected in?
- CAUDAL VEIN - lateral or ventral approaches, ventral to the vertebral column in the tail
- CARDIAC
0.5-1% of BW
heparin (green) tubes
How does blood smears in fish compare to other species?
nucleated, elliptical RBCS
What is used for contrast studies in fish?
iodine
- barium is harmful to gills
What can commonly interfere with performing ultrasounds in fish?
swim bladder
What is the most common infectious agent responsible for disease in fish in human care?
bacteria
- commonly also secondary opportunistic infections
What are the most common types of bacteria that infect fish? What do they cause?
Gram -
acute, septicemic infections
What kind of diseases do Gram-positive bacteria cause in fish?
chronic, granulomatous lesions
What are the most common clinical signs for bacterial disease in fish? How are they treated?
- lethargy, anorexia
- reddened fins/oral cavity
- exophthalmia
- ulceration
- distended fin vasculature
- disequilibrium
assess environment and husbandry for underlying causes + antibiotics based on antimicrobial sensitivity
How does Aeromonas salmonicida affect salmonids and carp/koi? What does it cause in both?
- SALMONIDS - furunculosis (necrotic swellings in the muscle tissue)
- CARP/KOI - ulcerative disease
septicemia
How do Edwardsiell tarda and ictalurid compare?
TARDA = emphysematous putrefactive disease of catfish (ZOONOTIC)
ICTALURID = enteric septicemia of catfish
What causes Redmouth in salmonids?
Yersinia ruckeri
(+ septicemia)
What lesions are caused by Flavobacterium columnare?
necrotic skin and gill lesions
What bacterial disease is most commonly transmitted to humans after handling fish? How do they affect the fish?
Mycobacterium marinum = fish tank granuloma on hand
- chronic disease in striped bass
- granulomatous disease
How does Psiciricketssia salmonis affect fish?
necrosis/granulomatous inflammation of the kidneys, liver, and intestines
- high mortality rate
How does Renibacterium salmoninarum affect fish?
bacterial kidney disease in salmonids
What is the most common cause of integumentary mycosis (water mold) in fish? What lesions do they cause?
- Saprolengia
- Achyla
- Aphanomyces
- Leptolegmia
(commonly opportunistic, affecting open wounds)
white cotton-like lesions on fins and skin
How is integumentary mycosis confirmed? Treated?
skin scrape shows branching, non-septate hyphae
- potassium permanganate dip
- Malachite green dip
What are the most common causes of Ich in freshwater and saltwater fish? What lesions do they cause?
- FRESHWATER = Ichthyophthirius multifilis
- SALTWATER = Crytptocaryon irritans
(protozoa)
while dots on fin, body, and tail; fish will commonly flash
How is Ich diagnosed? Treated?
skin scrape
- FISH = topical disinfectants, bath/dip
- ENVIRONMENT = water change/disinfection, increased water temperature
What causes velvet disease? What lesion does it cause? How is it treated?
Amyloodinium ocellatum
velvet sheen to the skin, giving it a dusty, brownish-gold color
prolonged treatment with Chloroquine
How does Iridovirus affect fish?
lymphocytosis and hypertrophied dermal fibroblasts form nodules
What fish is most commonly infected with Retrovirus? What lesion does it cause?
Angelfish
lip fibromas
How are quarantines carried out for new fish?
30-day quarantine with isolation in separate tanks to minimize aerosolization and fomites
- small and easy to clean
What are some common surgical procedures performed on fish?
- external/internal biopsy
- wen trimming - overgrown skin that impedes vision
- ocular procedures
- exploratory laparotomy
- FB, mass removal
- reproductive surgery
- wound repair
How are surgical sites prepared for procedures in fish? How can the skin be kept moist?
- dilute povidone-iodine (1:20) or chlorhexidine (1:40)
- clear plastic drapes
spray bottles
What sutures are used for closing the skin of fish? What is avoided? What is the closing layer?
absorbable
surgical adhesives - cause dermatitis
skin/dermis
Does the ID of a pathogen always warrant treatment?
NO - need a full clinical picture, should have a diagnosis and resistance pattern
What considerations are used for marine vs. freshwater fish with regards to treatment?
- efficacy in each environment
- medications can be toxic to invertebrates - shrimp!
What dosing is commonly used with waterborne medication administration? What are the 4 major durations?
ppm (mg/L)
- DIP - short time, high concentration
- BATH - longer time, lower concentration
- FLOW THROUGH - flow washes through system
- PROLONGED - long duration, compound decomposes over time
How are oral medications given to fish? Why are these not as common?
food formulation - quantity over a treatment period should be 0.5-5% of BW/day
- many sick fish are anorexic and do not want to eat (can gavage)
- difficult to determine if the fish is actually eating it
What are the 2 locations used for injectable medications in fish?
- IM - epaxial muscles, lift up scales
- intra-coelomic - dorsal recumbency to displace other organs toward the spine
What medication is commonly used for euthanasia in fish? What are 4 other secondary methods?
MS-222 (not commonly enough alone)
- ICe KCL
- ICe Pentobarbital
- cervical/spinal dislocation
- pithing, captive bolt
Select the letter that corresponds to the operculum:
B
Select all the acceptable venipuncture sites in fish:
a. ventral abdominal vein
b. caudal vein
c. lateral line
d. heart
B, D
You visit a client to assess their koi pond. The client noted they have has an issue with an algal blood recently and have observed fish piping. Which diagnostic are you most interesting in?
a. radiographs
b. skin scrape
c. basic water quality including DO
d. CBC
e. culture and sensitivity
C —> piping indicative of oxygen quality issues
Which of the following is an approved immersion for sedation/anesthesia and is FDA approved for the use in fish.
a. ketamine
b. tricaine methanesulfonate
c. medetomidine
d. propofol
B
True or false: the abdominis rectus sheath is the holding layer when performing a celiotomy on a fish.
FALSE —> dermis (skin)
