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Aquaculture > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

When submitting a live fish sample what is it important to consider

A
  • Transport conditions - heat O2
  • Allow 2L of water per 5-10 small fish
  • Fill bags 1/4 full of water, leaving the remainder filled with air or oxygen
  • Seal and place in second bag along with ice
  • Place and seal in outer container - amount and layers of packing depend on the situation
  • If you doubt that fish will arrive alive, select samples for individual tests, especially fixed material and smears and perhaps cultures of lesions
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2
Q

When submitting freshly dead samples what is it important to consider

A
  • Submit freshly dead fish sealed in plastic bags, preferably individually wrapped and on ice
  • Ensure the fish are not in direct contact with ice or water
  • Anaesthetic overdose may cause some parasites to leave the fish so it is recommended smears for parasites be made as soon as possible
  • For organic chemical analysis, percussion stunning with a sharp blow to the head is suitable unless the brain is needed for analysis
  • Blunt force will also induce haemorrhage artefacts in the gills which may not be wanted
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3
Q

Australia post accepts biological substances under what conditions

A
  • Australian addressee much be recognised by the lab
  • The sender must
    Qualified medical practitioner
    Qualified vet surgeon
    Public hospital, clinic or lab
    A member of a commonwealth, state or territory police force
  • Triple packaging
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4
Q

How to set fish for histopathology

A

Formalin fixation - finfish are the same isotonicity as higher vertebrates, so standard vertebrates fixatives are suitable

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5
Q

What are the exceptions of histopathology

A
  1. Rapid penetration is required
  2. Tissue that tend to separate during processing
  3. Fixation of small parasites that would otherwise wash off epithelial surfaces during processing
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6
Q

What is Bouin’s fixative

A

Suitable for small specimens, especially very small fish that can be fixed and sectioned whole

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7
Q

What is Bouin’s fixative useful for

A

Skin and eyes, although eyes may be better fixed in neutral buffered formula after making a small slice in the back of the retina to aid penetration, as Bouin’s fixative may result in artefacts

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8
Q

What is Davidson’s fixative recommended for

A

Gils with suspected parasites

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9
Q

Within one week what must the tissue be trandered into from the Davidson’s fixative

A

70% ethanol within a week

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10
Q

External examination what to look at

A
  • Corneal opacity may assessing the time of death
  • (bi or uni) exophthalmia and/or hyphen is common finding with septicaemia but may also indicate gas disturbances
  • open mouth as a common finding in a group of dead fish is likely of indicate respiratory distress
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11
Q

How to perform an external examination

A
  • Lift and remove an operculum an examine gills and mouth
  • Note gill colour the extent of mucous cover, and any gill or mouth lesion and parasite
  • Gill colour is also a guide to the level of post mortem change as well as an indication of anaemia
  • Focal lesions or increased mucus may indicate parasites or other irritants
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12
Q

What may parasitised fish show

A

Few gross signs, though surface parasites are common and often in sufficient numbers to be clinically significant

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13
Q

Where are protozoa and small flukes are best observed in

A

Wet smears

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14
Q

Where to prepare smears from

A

Gills and skin surfaces

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15
Q

For lab summations what must be done to the smears

A

air dried immediately

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16
Q

How are gills examined on microscope

A

Wet smear examination for microscopic external parasites

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17
Q

How to prepare wet smears of mucus from skin and gills

A

Lightly scrape the surface of the tissue with a scalpel blade, tranfer the mucus collected to a slide and dilute with a drop or two of water and place a cover slip o

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18
Q

What is important when doing wet smear

A

Use the same source of water for dilution as that of the fish

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19
Q

How to fix gills

A

Lift or cut the gill cover and fix one or more whole gill arches from small fish or at least 1.5 cm of an arch from larger fish

20
Q

How to open the abdominal cavity

A

Using curved, blunt-ended scissors, open abdominal cavity along the mid-line to just in front of the vent (cut 1) and reflect dorsally (cut 2) or remove one abdominal wall (cut 2 and cut 3) to expose abdominal organs

For small fish, abdominal exposure is best made by one curved incision from in front of the anus curving towards the spine but remaining ventral to the kidney and extending forward to the gill arch (cut 2 and 3)

The abdominal flap can then be retracted ventrally to provide a sterile surface for handling tissues

21
Q

What to look for in the abdominal cavity

A

Major organs and note size, colour, friability, haemorrhages, nodules, necrosis or parasites present in the organ

22
Q

What is a good indicator of conditions

A

Level of abdominal or pancreatic fat

23
Q

What may the presence of fluid in the abdominal cavity or swim bladder and/or serial congestion or petechiae indicate

A

Viral or bacterial diseases

24
Q

What is the spleen

A

Major haematopoietic, lymphoid and phagocytic organ

25
Q

If the spleen is typically enlarged what can it indicate

A

Infection or stress

26
Q

How many chambers in the heart do fish have

A

2 chambers

27
Q

How to expose the heart

A

Is exposed by cutting the diaphragm above the liver

28
Q

What should the pericardial sac be like

A

Smooth

29
Q

What fills much of the lumen

A

Myocardium trabeculae

30
Q

What does poor heart morphology indicate

A

Developmental changes, nutritional imbalances or inactivity is relatively common and may result in rounder/more globular shape

31
Q

What is the kidney

A

A dark organ closely apposed to the dorsal wall of the abdomen; retroperitoneal and covered but the swim bladder

32
Q

What does the kidney contain

A

Haematopoietic tissue and tissue breakdown pigment as well as the nephrons

33
Q

What is the Corpuscles of Stannius

A

A small place endocrine gland

34
Q

How is the pancreas usually found

A

usually found as microscopic glandular clusters within the fat between the pyloric caeca in salmonids, through in some species e.g. Barra, pancreatic tissue is restricted to the liver in the hepatopancreas

35
Q

How is the brain exposed

A

Expose the brain by slicing off the top of the skull
Alternatively, section through the head posterior to the eyes, grasping the fish firmly behind the head and cutting through the head transversely a short distance behind the eyes
Continue cutting until the oropharynx is reached
The incision for the for large fish is best made with culinary or butcher’s knife between 15-20cm ling that has finely serrated cutting edge to the clade or use as hack-saw

36
Q

What is standard pathology practice

A

Fix samples for histopathology in 10x their volume of fixative
Samples should me no more than 0.5-1.0 cm thick in two dimensions

37
Q

What is the preferred fixative to improve penetration of intact skin

A

Bouin’s fixative

38
Q

What must be done before fixing whole

A
  1. The abdomen must be opened
  2. An abdominal flap and gill cover removed
  3. Preferably the swim bladder deflated
39
Q

Fish should not be fixed unless

A

Internal organs are well exposed

40
Q

How to sample for virology

A

Method of choice fro diagnosis of fish viral disease is virus isolation using fish cell lines

Other techniques, used aline or in combination with this, include, histopathology, direct visualisation by electron microscopy and PCR techniques

41
Q

What is needed for testing for freedom of disease - OIE

A

A minimum number of 10 moribund fish or 10 fish exhibiting clinical signs of the disease in question

42
Q

How to take samples for virology

A

5mm3 of liver, kidney and spleen, collected aseptically have been traditionally collected for virus isolation and are sufficient to detect most viruses, but heart and encephalon are now more generally included

43
Q

Why don’t you pool organs such as skin, gut, gills with internal organs

A

They have high natural bacterial flora

44
Q

What is the recommended sample number per pool

A

5 fish per pool

45
Q

What is important when collecting sterile samples

A

Use separate sets of instruments for opening the fish and for collection of tissues

46
Q

What must tool be cleaned of before soaking it in ethanol

A

Residual blood and tissue

47
Q

What does the OIE recommend with small yolk sac fry

A

Be sampled whole if the yolk sac is removed

Aquaculture (11 decks)

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