Fish medicine

Question 1

Role of a vet in the aquatic animal industry?

Answer 1

1. Health management & disease prevention
2. Aquaculture and food safety
3. Conservation and wildlife health
4. Regulatory and policy roles
5. Education & training
6. Ornamental fish and public aquariums
7. Research & conservation of aquatic ecosystem
8. Exotic species and zoonotic dx control

Question 2

What important consideration?

Answer 2

VENOMOUS SPECIES

Question 3

what notes on initial contact ?

Answer 3

• Advise client to send pictures of set up & history
• Ensure staff prepared -> block off time to examine +/- diagnostics
• Advise on transport & what to bring (separate bags of water, spare acquarium bags, sealed container with water, for testing)

Question 4

How can we be ‘fish ready’

Answer 4

• Willing vet/RVN
• High quality microscope
• Slides/coverslips
• Hand held lens
• Powder free gloves
• Basic surgical kit
• Water testing kit -> API freshwater master test kit

Question 5

When would we do home visits/ why?

Answer 5

● For larger set ups/outdoor ponds.
○ Full assessment easier → can see bigger picture.
■ Filtration methods → biological vs mechanical.
■ Water quality → appearance, smell, temperature, aquatic plants,
algae growth.
■ Stocking density.

Question 6

What biosecurity to remember?

Answer 6

● Remember to take microscope!
● Remember to take basic equipment for sedation for pond side diagnostics

Question 7

What biosecurity to be aware of?

Answer 7

■ Koi herpes virus (Cyprinid herpesvirus 3) → notifiable
■ Spring Viraemia of Carp → notifiable

Question 8

Quarantine ?

Answer 8

○ Isolate new fish for 30-90 days before introducing them to the main tank.
○ Use a separate tank with proper filtration and heater.

Question 9

Maintenance of water quality?

Answer 9

○ Perform regular visual inspections and water quality tests.
■ Test ammonia, nitrite, nitrate, dissolved oxygen, temp and pH levels regularly.
■ Ammonia should be 0mg/l. Nitrite should be 0mg/l.
■ Nitrate is less toxic BUT levels of 50mg/l & above may be LETHAL to some
species.
■ Nitrate is more toxic in salt water & at a low pH.

Question 10

How often to change water?

Answer 10

Perform 10-30% water changes weekly or bi-weekly, depending on set-up/species

Question 11

How to remove chlorine?

Answer 11

use water conditioners.natural emthods

Question 12

New tank syndrome?

Answer 12

• NEW TANK MUST BE CONDITIONED BEFORE ANY FISH ADDED
• ADD TOO EARLY → RAPID SPIKE IN AMMONIA, NITRITES & NITRATES = DEATH

Question 13

What to filtrations do we want?

Answer 13

Biological ->
- gravel or media within filter;
- bacteria within gravel converting ammonia -> nitrites -> nitrates

Mechanical ->
○ Use of water → water drawn in through media → traps waste
○ Must be cleaned regularly (10-14 days) with approx. 10%
water change weekly

Question 14

Water changes?

Answer 14

○ Treat new water before adding
○ Treatment to remove chlorine, chloramines & heavy metals

Question 15

How to ensure optimal filtration system?

Answer 15

○ Use of mechanical, biological and chemical filtration
(carbon).
■ If under treatment, carbon must be removed from
tanks
○ Clean or replace filter media as recommended.
○ Ensure the filter & flow rate is appropriately sized for
the tank.

Question 16

What is appropriate stocking density?

Answer 16

○ Follow the guidelines for the species (marine fish →
lowest stocking density)
■ Based on water volume & surface area + fish
species
○ Ensure fish have adequate space to swim and hide.
○ Consider the bioload when stocking the tank.

Question 17

Diet & feeding practices?

Answer 17

○ Feed a varied, species-appropriate diet.
○ Feed small portions and remove uneaten food.
○ Avoid overfeeding to prevent poor water quality.

Question 18

tank cleaning?

Answer 18

○ Perform regular gravel vacuuming during water
changes.
○ Clean decorations and plants to remove algae.
○ Avoid drastic water changes that could shock the
fish.

Question 19

Stability of environment ?

Answer 19

○ Maintain stable temperature and water conditions.
○ Provide hiding spots for fish to feel secure.
○ Place tanks in quiet areas to avoid stress from noise/vibrations.

Question 20

routine health assessments?

Answer 20

○ observations for signs of illness (e.g., white spot, frayed fins, lumps/bumps).
■ Look for common signs of parasites, bacterial infections, and fungal diseases.
○ Any behavioural changes?
○ Appropriate handling – only when necessary.
■ Use a soft net and care when handling – minimise stress & physical damage.
■ Isolate and treat any sick fish in a quarantine tank.

Question 21

History pt 1 ?

Answer 21

Question 21

History pt 2?

Answer 21

Question 22

History pt 3?

Answer 22

Question 23

Describe how to do water testing?

Answer 23

○ API master kit → ammonia, nitrite, nitrate, pH, oxygen content
■ Ideally water should be tested onsite but if not possible get
client to bring a sealed, filled (clean) container of water.
■ Specific guidelines → measured volume added to
measured amount of chemical → colour change →
compare to chart
■ Don’t forget the temperature!
○ Low oxygen and poor water quality can stress fish and contribute
to disease.

Question 24

Waterborne pathogen testing?

Answer 24

Culture, Colony, count, bacterial population, microscopy

Question 25

Describe skin scrapes?

Answer 25

● Skin scrape → microscopy slide → scrape in direction of
scales to collect mucus →apply coverslip → examine
immediately.
● Collect from several areas to include under fins and the
underside of the fish
● Non invasive procedure
● Skin scrapes to identify parasites, fungi, or bacteria.
● Ideally perform without sedating
○ Immersion in anaesthetic agent may affect culture
and parasite observation

Question 26

Gill clip procedure?

Answer 26

● Diagnostic procedure → under anaesthesia
● Healthy gills should be red
● Lift operculum and take a small sample of gill
filaments.
● Examine under microscope immediately.
○ Assess for parasites
○ Assess structure and cellularity of gills

Question 27

Blood sampling approach?

Answer 27

Ventral or lateral approach to caudal vein
○ Lateral approach → insert just below lateral line angled
towards the head.
○ Ventral approach – ventral midline caudal to anal fin

Question 28

how to do blood sampling ?

Answer 28

● Clean with dilute povidone iodine
● Insert needle between scales
● Fresh blood smears & heparin tube
● Haemolysis occurs readily in fish → use as little vacuum as
possible.

Question 29

microsopic exam on faecal exam?

Answer 29

○ Normal faeces are dark green/brown (varies with
species/diet)
○ Normally break off after emerging from vent (freshwater) vs
not formed & disperses in water (marine fish)
○ Abnormal colouration → pale, white, yellow, mucoid
○ Abnormal → long, stringy and trails from vent.
○ Abnormal → may float to surface. may see blood.

Question 30

what might we see on fresh smears?

Answer 30

Fresh smears → microscopic examination → Capillaria ova,
flagellate protozoans & coccidia depending on species

Question 31

radiography?

Answer 31

○ Under sedation – orthogonal views
○ Useful for determining coelomic swellings/look for causes of buoyancy
problems
○ Great at visualising skeletal anatomy and position of swim-bladder
○ Can use contrast media – barium or iohexol for Gi tract (species
dependent – approx. 5ml/kg)

Question 32

US in fish?

Answer 32

○ Differentiates soft tissue structures → organ size, location &
pathological changes
○ 7.5-10 MHZ transducer
○ Leave fish in water → no need for acoustic gel → use glove
○ Care!!! Electrical equipment & water – residual current device must be
used.

Question 33

PME eval?

Answer 33

● In some circumstances (group) may need to
euthanise one.
● Aquased → 10 pumps/litre
● Perform PME within 1 hour
● Gill snips/skin scrapes/gross lesions
● Full post mortem – incision ventral midline
● Histopathology/culture & sensitivity testing

Question 34

what is white spot?

Answer 34

(Ich) (Ichthyophthirius multifilii) common rotozoan parasitic infection in freshwater fish species

Question 35

what do we see with white spot?

Answer 35

• Small, white spots over body.
• Excess of mucus and thickened epithelium
• Advanced disease → extensive gill damage. Typically introduced to aquariums through
  infected fish or plants.

Question 36

Life cycle of Ich?

Answer 36

• Free-swimming stage (theront) → locates host → penetrates the epidermis →
  develops into a ciliated trophont → WHITE SPOT → breaks through epidermis and
  becomes an encysted tomont → this attaches to tank furniture/plants → division →
  release of infective theronts
• Life cycle = 10-15 days at 15°C & 6 days at 27°C

Question 37

marine equivalent of Ich?

Answer 37

Cryptocaryon irritans → Life cycle identical

Question 38

Tx for ìch?

Answer 38

→ if identified before infective stages released → remove fish & quarantine
* Only the free-swimming stage is susceptible to chemical treatment → repeat treatments
needed at approx. 5-10 day intervals. Treatment intervals are temp dependent

Question 39

what is ‘dropsy’?

Answer 39

non-specific term →oedematous conditions
in a fish.

Question 40

what might we see with dropsy?

Answer 40

• Abdominal distension → ascites
• Cutaneous oedema → scales protrude
• Exophthalmos may be seen.

Question 41

Causes / tx of Dropsy?

Answer 41

• A symptom of underlying issues, typically related to
  failure of osmoregulation → gill or kidney disease.
• Need to address underlying cause → if bacterial
  infection may respond to antibiotics.
• Polycystic kidneys/neoplasia – poor prognosis

Question 42

What is Fin Rot?

Answer 42

affects their fins and in severe cases, can
progress to the body → peduncle disease.
* Often caused by bacterium Flavobacterium
columnare → affects debilitated fish

Question 43

what do we see with fin rot?

Answer 43

Hyperaemia of the fins often seen → caused by
septicaemic infections.

Question 44

Tx of fin rot?

Answer 44

→ treat underlying cause, remove
stressors, water changes, antibacterials if indicated,
?aquarium salt

Question 45

surgical considerations?

Answer 45

● Thermoregulation, osmoregulation, and other water quality
parameters must be maintained.
● Postoperatively, depending on species and procedure, may want
to add salt to the water concentration of 3-5ppt (species variation)
for freshwater species → reduces osmotic stress.

Question 46

Suture material in fish?

Answer 46

If using suture material, absorbable suture will remain for a longer
period of time → lower environmental temperatures

Question 47

mass removal?

Answer 47

● Indication for surgery should
ideally be confirmed, before the
procedure as some masses will
regress spontaneously (cyprinid
herpesvirus 1 infection)
● External mass incisional or
excisional biopsies are similar to
that in mammals.

Question 48

enucleation in fish?

Answer 48

Anaesthetise → lidocaine block → dissect and transect
periorbital tissue, conjunctiva and oculomotor muscles
off the globe.
● Transect and remove the globe.
● Ligate retro-orbital vessels, apply digital pressure and a
haemostatic gel if available.
● Leave the orbit open to heal by secondary intention

Question 49

wound management?

Answer 49

Follow same principles as a more
familiar species.
● Culture and sensitivity
● Debride necrotic tissues, remove
detached scales
● Lavage wound
● Apply thin layer of gel

Question 50

Dentals in fish medicine?

Answer 50

● Oral surgery and incisive plate
adjustments to aid in food prehension if
there has been insufficient wearing of
the dental plates or an oral mass.
● Pufferfish
→ continuously growing
incisor plates (normal!). If overgrown,
under a GA trim with a dental burr or
rotary tool.
● Care not to overheat the incisor plates ● Address diet to prevent this reoccurring