Live and freshly dead samples of fish can be brought directly to the Institute for examination. Post-mortem examination will then be carried out by the veterinary staff. Please contact us beforehand to arrange suitable times.
If fish cannot be brought to the Institute then, in many cases, samples can be taken on site and the samples can be transported to Stirling by courier or post.
A history should always accompany specimens, placed in a separate plastic bag and giving brief details plus contact details. We strive whenever possible to report submissions of urgent clinical cases within 24 hrs of receiving the samples, otherwise we are usually able to report most clinical cases within two days of receiving the samples. Providing some sort of identification number usually helps with cross referencing: if supplied, this is always included in our reports.
The information below outlines some of the normal sampling procedures to be followed when sampling a fish on site and submitting samples for analysis.
Should further details or assistance be required please contact us.
Samples for histology must be taken as soon as possible after death, but preferably from moribund animals, and fixed immediately, usually in 10% Neutral Buffered Formalin. Tissues should be placed in at least 10 times their volume of fixative i.e. one part tissue to ten parts fixative. The tissue can be kept in formalin for prolonged periods but they should be stored in such a way as to avoid any portion of the tissues remaining out of the fixative.
|10% Neutral Buffered Formalin Recipe|
|Sodium phosphate, monobasic (NaH2PO4.H2O)||4g|
|Sodium phosphate, dibasic (Na2HPO4)||6.5g|
Dissolve in 750ml of water, add 100ml of formaldehyde (37-40% HCHO), and make up to 1000ml with water
Please use this recipe referenced from J.A. Kiernan, ‘Histological and Histochemical Methods’, Theory and Practice, 4th edition
Use properly labelled pots where we are able to supply these if required before hand.
Fry can usually be fixed whole, without the need for dissection.
Fingerlings - The best approach is to remove an operculum, open the abdominal cavity, and move the viscera to allow proper penetration of fixative. Unless lesions are present, the tail posterior to the vent can usually be removed and discarded to save space. These fish can then be mailed whole without the need for dissection.
Larger Fish - Individual organs will need to be dissected out and placed in fixative
The organs sampled depend on the nature of the problem but in most cases all the major organs are sampled: Gill, Skin, Heart, Liver, Pancreas / Gut, Spleen, Kidney. It is usually best to keep fish separate, using one container per fish.
The dissected organs should be in small pieces and not as whole organs prior to immersing in NBF.
Samples should be taken from the kidney and spread out onto an agar plate using the streak plate method. Tryptone Soya Agar (TSA) is a suitable medium for freshwater fish and Marine Agar or TSA + 1.5% salt is suitable for marine fish.
Pre-prepared agar plates are commercially available from a number of suppliers including Oxoid, Cherwell Labs, E&O Labs, Technical Services Consultants, Beckton Dickinson. We are able to supply general purpose and selective agar to those wishing to take samples for bacterial recovery.
Direct inoculation from kidney, spleen, or a lesion itself, is the most common method of sampling for bacteriology. Care must be taken to use sterile loops and aseptic technique during sampling.
Owing to the need to get cells ready, it is best to inform us ahead of time before sending samples - usually 2-3 days notice is sufficient.
Samples should only be taken from recently killed fish. Very little tissue is required. The total samples from all the organs should not exceed 1g of tissue.
Fry: Remove and discard heads and tails from just posterior to the vent. Retain the remaining portion of the body.
Fingerlings: Open the body cavity and remove the viscera, including kidney, by cutting and scraping. Retain these tissies for examination.
Larger Fish: Remove and retain a portion of the kidney, spleen, caecae-pancreas, liver and gill in the weight ratio of approximately 3:1:1:1:1 In certian situations, however, it is sufficient to sample only kidney material.
Tissues from a maximum of 10 fry or fingerlings may be pooled and treated as one sample. When larger fish are sampled, tissues from a maximum of 5 fish may be pooled and treated as one sample. You need take no more than 1g of tissue in total from each fish.
Wear latex gloves when sampling fish.
Each fish / pool must be sampled using a separate sterile scalpel blade. Tissue to be taken depends on the virus being tested for.
The sample must be small. The ideal sample is 0.5 x 1.0 x 1.0 cm.
Samples must be freshly taken, so ideally live fish should be brought to Stirling for analysis.
Samples can be taken on site and placed in a solution of RNA later then transported to Stirling on ice.
It is extremely important that samples send via the postal service or via a courier are packaged properly to protect the sample during the transport process and also that they conform with UK transport regulations.
Contact us if in doubt.