Australasian Veterinary Examination (AVE), formerly the National Veterinary Examination (NVE) · Australia / New Zealand · Australasian Veterinary Boards Council (AVBC)
Original practice questions written to the published syllabus · not past papersDiseases of fish and crustaceans, the role of water quality, aquaculture biosecurity, and the residue rules for therapeutants used in food fish.
In the exams: NAVLE aquatics 1%; China runs a separate aquatic-animal category of its national exam
How our questions for Australasian Veterinary Examination, formerly the National Veterinary Examination spread across the units of Aquatic Animal Diseases, Health Care & Management. Difficulty: 20 easy, 28 medium, 3 hard.
| Water-quality diseases | 7 | |
| Biosecurity in aquaculture | 7 | |
| Parasitic diseases of fish and shrimp | 6 | |
| Bacterial diseases of fish and shrimp | 5 | |
| WOAH-listed aquatic animal diseases | 5 | |
| Therapeutants and residues | 5 | |
| Diagnosis of aquatic animal disease | 4 | |
| Viral diseases of fish and shrimp | 4 | |
| Fungal diseases of fish | 4 | |
| Degree-day withdrawal periods | 4 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Fresh water at 25 °C holds 8.26 mg/L of dissolved oxygen at saturation. A pond at 25 °C reads 5.0 mg/L. What is the percent saturation?
A. About 61%
% saturation = 5.0 / 8.26 × 100 = 60.5%, about 61%. 165% inverts the ratio (8.26/5.0); 50% assumes saturation is 10 mg/L; 3.3 is the deficit in mg/L (8.26 − 5.0), not a percentage.
Further reading: Boyd & Tucker, Pond Aquaculture Water Quality Management; Emerson et al. (1975)
Fish in a recirculating system have chocolate-brown blood and gasp despite adequate dissolved oxygen. Which measure directly reduces uptake of the likely toxicant across the gill?
B. Adding sodium chloride to raise chloride
Brown blood is methaemoglobinaemia from nitrite. Nitrite enters by the gill chloride-uptake pathway, so raising chloride competitively reduces its uptake. Raising pH increases ammonia toxicity rather than helping; thiosulphate neutralises chlorine; more feed raises ammonia and nitrite production.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
Why are salmonids and carp called physostomous?
C. The swim bladder stays connected to the gut by a pneumatic duct
Physostomous fish keep a duct from swim bladder to gut and can gulp or release air. A closed bladder filled by a gas gland and rete mirabile is the physoclistous arrangement. Labyrinth organs belong to anabantids such as gouramis.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
For a laboratory investigation of a fish mortality, which animals are the best samples?
A. Live, moribund fish showing typical signs
Fish tissues autolyse within hours of death and secondary bacteria overgrow the primary pathogen; freezing ruins histology. Moribund fish give the best chance of finding the cause; a few healthy fish are useful only as comparison.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
Which quick farm-side test finds most external parasites of fish?
D. Wet mount of skin scrapings and a gill clip
A wet mount in the fish's own water, examined within minutes, shows ciliates, flagellates, monogeneans and crustacean parasites. Blood culture at 37 °C is wrong for most fish bacteria; serology and faecal flotation do not detect ectoparasites.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
Farmed tilapia at 30 °C swim erratically in spirals, with exophthalmia and corneal opacity; the brain yields Gram-positive cocci in chains. What is the likely agent?
C. Streptococcus iniae or S. agalactiae
Meningoencephalitis with exophthalmia in warm-water tilapia and Gram-positive cocci points to streptococcosis. The other organisms are Gram-negative rods, and F. psychrophilum is a cold-water pathogen.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
Crayfish plague is caused by:
D. Aphanomyces astaci
A. astaci causes crayfish plague, a WOAH-listed disease that devastated native European crayfish. A. invadans causes EUS in fish.
Further reading: WOAH Aquatic Animal Health Code, chapter 1.3; WOAH Manual of Diagnostic Tests for Aquatic Animals
A flattened, disc-shaped crustacean moving freely over the skin of pond carp and feeding with a preoral stylet is:
B. Argulus
Argulus (the fish louse) is a mobile branchiuran. Lernaea females embed their heads in the host; Ergasilus attaches to gills; Gyrodactylus is a monogenean flatworm, not a crustacean.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
Which one of the following diseases of carp and trout appears on the WOAH list?
C. Koi herpesvirus disease
Koi herpesvirus disease is listed. Columnaris, carp pox (cyprinid herpesvirus 1) and enteric redmouth are not.
Further reading: WOAH Aquatic Animal Health Code, chapter 1.3; WOAH Manual of Diagnostic Tests for Aquatic Animals
Tricaine methanesulfonate is used as a fish anaesthetic. Why is it usually buffered with sodium bicarbonate?
A. It acidifies the water, especially soft water, which stresses the fish
Tricaine methanesulfonate is acidic and lowers pH in poorly buffered water, so it is buffered. It is active without buffer; availability and withdrawal requirements vary by country — confirm against the product label and your national formulary.
Further reading: Roberts (ed.), Fish Pathology, 4th ed.; Noga, Fish Disease: Diagnosis and Treatment, 2nd ed.
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