Blood sampling: Ferret
Approaches for sampling blood in the ferret, covering non-surgical, surgical and terminal techniques.
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General principles
Jugular vein (non-surgical)
Technique
Sampling from the jugular vein is quick and simple as the vein is superficial and easily accessible. It is appropriate for small and large blood samples. Fur should be shaved from the sampling site to allow better visibility and aseptic technique must be used throughout.
Ferrets should be habituated to handling and restraint; this will improve the experience of the animal and handler and will lead to obtaining a better-quality blood sample. Treats such as FerretviteTM or malt paste can be used during the procedure to distract the animal, and following the procedure to help with habituation.
For manual restraint, wrapping the animal in a soft cloth or towel can assist to prevent twisting of the body and hindlimbs during the procedure. An assistant can then hold the wrapped body between their upper arm and body, whilst using their hands to assist with positioning of the forelimbs and head. The ferret’s forelimbs should be drawn downwards, and the head upwards, to gently expose the neck. Holding the forelimbs over the edge of a workbench can assist with this positioning. An alternative method is to position the ferret in lateral recumbency, with the forelimbs drawn towards the hindlimbs, and the head drawn away from them, to expose the neck. In either position, the person sampling should now be able to easily visualise the neck.
If animals have not been well handled, such as with juveniles, anaesthetic or sedation may be needed to enable safe venepuncture. Care should be taken with the choice of agent to ensure it does not impact on blood parameter being investigated. Any treats given to conscious animals also need to be checked to make sure they will not affect results such as blood glucose levels. Where sedatives contain peripheral vasodilators, doses should be low to avoid prolonged bleeding from the puncture site.
The jugular vein is raised by compression in the jugular grove, just cranial to the thoracic inlet. The vein is situated more laterally than would be seen in the cat or dog but is still superficial. A 25-gauge needle would be appropriate in most cases, with 23-gauge being suitable in some larger males. The skin is thick around the neck of a ferret meaning increased pressure may be required to puncture the skin, compared to other sampling sites. The needle can be placed cranially in the vein or caudally, depending on the positioning of the ferret and preference of the sampler. Pointing the needle up towards the head is generally the easier direction if the animal is in ventral recumbency, but if the animal is in lateral recumbency either direction can suit.
If blood does not flow once the needle is inserted into the vein, the head may have been drawn too far upwards, leading to flattening of the vein. Gentle lowering of the head should allow blood to flow easily. A maximum of 3 needle sticks should be attempted per sampling procedure. If after this, insufficient blood has been obtained, the animal should be released and given appropriate time to recover before any new attempt is made.
Pressure should be maintained at the jugular groove throughout sampling then removed once sampling is finished. The head should be lowered, and light finger pressure put at the sampling site immediately as the needle is withdrawn, to prevent bruising. Pressure should remain here for approximately 30 seconds.
The volume of sample taken will depend on the weight of the animal, sampling frequency and scientific justification. If frequent sampling is performed, always sample at the caudal aspect of the vein and work cranially. Alternate sides should also be used to limit bruising and aid recovery.
Summary
| Number of samples | Up to eight in any 24-hour period dependent on volume |
| Sample volume | 2-4 ml depending on the size of the ferret. |
| Equipment | 25G (preferably 5/8" long) needle |
| Staff resource | Two people are required to blood sample; one for restraining and one for raising the vein and taking the blood sample. |
| Adverse effects |
|
| Other | Stress associated with the technique can be minimised by training and acclimatising the ferrets to manual restraint and the sound of the clippers beforehand. A reward can be used during to procedure as a distraction and should be given after each procedure. |
Resources and references
- Smith SA et al. (2015). Hematology of the Domestic Ferret (Mustela putorius furo). Clinics in Laboratory Medicine 35(3): 609-16. doi: 10.1016/j.cll.2015.05.009
- Quesenberry KE and de Matos R (2020). Basic Approach to Veterinary Care of Ferrets. In: Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery (Eds. Quesenberry KE, Orcutt CJ, Mans C and Carpenter JW), 4th edition. Elsevier Health Sciences.
- Wolfensohn S and Lloyd M (2013). Handbook of Laboratory Animal Management and Welfare, 4th edition. Wiley-Blackwell.
- Otto G et al. (1993). Practical venipuncture techniques for the ferret. Laboratory Animals 27: 26-9. doi: 10.1258/002367793781082322
Cranial vena cava (non-surgical)
Technique
Sampling from the cranial vena cava of a ferret can be performed with manual handling when working with animals acclimatised to handling. Ferrets can be given treats during restraint to distract them, such as FerretviteTM or malt paste. This will help reduce stress and limit movement during the procedure. They can also be rewarded with treats after the procedure, to assist with training, if repeat sampling is expected. If animals have not been well handled, such as with juveniles, anaesthetic or sedation may be needed to enable safe venepuncture. Care should be taken with the choice of anaesthetic to ensure it does not impact on blood parameter being investigated. Any treats given to conscious animals also need to be checked to make sure they will not affect results such as blood glucose levels.
Sampling from the cranial vena cava allows a single large blood sample to be collected. Due to the size of the vessel, this site carries an increased risk of haemorrhage compared to sampling from the jugular, with bleeding potentially occurring into the anterior thoracic cavity. As with all blood sampling, animals should be monitored after sampling for any adverse effects.
For manual restraint, two assistants may be required unless the animal is well acclimatised to the procedure. Wrapping the animal in a soft cloth or towel can assist to prevent twisting of the body and hindlimbs during the procedure. The animal should be held in dorsal recumbency with forelimbs drawn downwards, and the head upwards, to gently expose the neck. Depending on circumstance, one person can hold the hindlimbs, with the second holding forelimbs and head, or one person can hold fore and hindlimbs, whilst the second assistant holds the head and is able to gives treats when appropriate. Either way, the person sampling should now be able to easily visualise the neck.
Fur should be clipped from the sampling site to ensure aseptic technique can be followed. The cranial vena cava cannot be visualised, so sampling is performed ‘blind’ through anatomical knowledge and correct technique. A 25-gauge needle should be used attached to a 1 – 3 ml syringe, or appropriately sized vacutainer, if bigger samples are required. The needle should be inserted into the thoracic cavity cranial to the first rib and lateral to the manubrium, aiming towards the opposite hindlimb or caudal rib. The needle should be inserted to the hub, at an angle of 30 – 45o to the body wall. Once inserted, pull the plunger back on the syringe slightly, to create negative pressure, and slowly withdraw the needle until blood begins to fill the syringe. At this point, hold the needle steady and pull the plunger back until the full sample is collected. The needle can now be withdrawn. No pressure needs to be applied to the sample site as the vessel is too deep for this to be effective.
If the animal becomes distressed or struggles, quickly remove the needle, reduce restraint and calm the animal before reattempting to sample. Continuing to sample can risk damage to the vessel and internal haemorrhage. A maximum of 3 needle sticks should be attempted per sampling procedure. If after this, insufficient blood has been obtained, the animal should be released and given appropriate time to recover before any new attempt is made.
The volume of sample taken will depend on the weight of the animal, sampling frequency and scientific justification.
Summary
| Number of samples | Usually a maximum of once per seven days. |
| Sample volume | Up to 14 ml (depending on the size of the ferret) |
| Equipment | 25G (preferably 5/8" long) needle. |
| Staff resource | Two to three people are required to blood sample; one to two for restraining and one for taking the blood sample. |
| Adverse effects |
|
| Other | Stress associated with the technique can be minimised by training and acclimatising the ferrets to manual restraint and the sound of the clippers beforehand. A reward can be used during to procedure as a distraction and should be given after each procedure. |
Resources and references
- Quesenberry KE and de Matos R (2020). Basic Approach to Veterinary Care of Ferrets. In: Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery (Eds. Quesenberry KE, Orcutt CJ, Mans C and Carpenter JW), 4th edition. Elsevier Health Sciences.
- Wolfensohn S and Lloyd M (2013). Handbook of Laboratory Animal Management and Welfare, 4th edition. Wiley-Blackwell.
- Brown C (2006). Blood collection from the cranial vena cava of the ferret. Lab Animal 35 (9): 23-2. doi: 10.1038/laban1006-23
Blood vessel cannulation (surgical)
Technique
Cannulation should be considered when repeated samples are required as it avoids multiple needle entries at any one site and can therefore minimise distress in potentially aggressive animals such as ferrets. It is suitable for use in all strains of ferret and can be used to take blood from the carotid artery and femoral vein. Surgery is required and appropriate anaesthesia, analgesia and aseptic technique should be used to minimise pain. Ferrets should be allowed to regain their pre-operative body weight before blood samples are taken.
For recovery work the cannula is exteriorised at the nape of the neck and secured by a crepe bandage. Ferrets cannulated using a traditional approach are usually housed singly. The caging, bedding and environmental enrichment needs to be appropriate to prevent the bandage becoming entangled and the wound contaminated. The use of a vascular access port or button should be explored since these can eliminate the need for the bandage and can allow for group housing. For terminal work, the cannula is not exteriorised.
Small cannulas will increase the risk of blood clotting (however, large cannulae can abrade the blood vessel wall). To prevent this, the cannula requires regular maintenance (e.g. regular flushing with an appropriate lock solution. See our preventing thrombosis section for more information).
Blood should be collected aseptically. Usually, 0.1 - 0.5 ml can be taken per sample. Depending on the sample volume and scientific purpose, up to six samples over a two hour period or up to 20 samples over a 24-hour period may be taken. Sterile saline with anticoagulant should be flushed into the cannula after blood sampling to prevent the blood from clotting. A pin is then inserted into the exteriorised end of the cannula, which stops the blood from flowing. A sterile locking solution can be used to lock the cannula after a series of samples have been taken, allowing flushing to be avoided for a number of days.
The following should be checked daily
- The bandage should be checked for tightness.
- If a jacket is used, this should be checked for tightness and the skin in contact with the jacket checked for abrasion.
- Wound sites should be checked for infection/bruising/swelling/haemorrhage.
- The cannula should be checked for patency (without blockage).
- The weight of the ferret should also be monitored.
Changes in any of the above may require veterinary advice or treatment, or may indicate that a humane endpoint has been reached and appropriate action should be taken.
Summary
| Number of samples | Up to 20 samples may be taken in a 24-hour period, depending on the sample volume. |
| Sample volume | Up to 0.5 ml |
| Equipment | 19G cannula |
| Staff resource | Two people are required: one to take the blood sample and another to restrain the ferret. |
| Adverse effects |
|
| Other | Ferrets should be at their pre-operative weight before blood sampling starts. |
Resources and references
- Parasuraman S et al. (2010). Blood sample collection in small laboratory animals. Journal of Pharmacology and Pharmacotherapeutics 1(2): 87-93. doi: 10.4103/0976-500X.72350
- Quesenberry KE and Orcutt C (2011). Ferrets: Basic Approach to Veterinary Care. In: Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery (Eds. Quesenberry KE and Carpenter JW), 3rd edition. Elsevier Health Sciences.
- Gunaratna PC et al. (2004). An automated blood sampler for simultaneous sampling of systemic blood and brain microdialysates for drug; absorption, distribution, metabolism and elimination studies. Journal of Pharmacological and Toxicological Methods 49(1): 57-64. doi: 10.1016/S1056-8719(03)00058-3
Cardiac puncture (terminal)
Technique
Cardiac puncture should not be used if the peritoneum needs to be lavaged to harvest cells, as this technique can cause blood to escape into the peritoneal cavity.
Cardiac puncture is a suitable technique to obtain a single, large, good quality sample from a euthanised ferret or a ferret under deep terminal anaesthesia if coagulation parameters, a separate arterial or venous sample or cardiac histology are not required.
A sample of 20 ml of blood can be obtained depending on the size of the ferret and whether the heart is beating. Blood samples are taken from the heart, preferably the ventricle, which can be accessed either via the left side of the chest, through the diaphragm or by performing a thoracotomy. Blood should be withdrawn slowly to prevent the heart collapsing.
Summary
| Number of samples | One |
| Sample volume | Up to 20 ml |
| Equipment | 19-21G needle |
| Staff resource | One person is required to take the blood sample. |
Resources and references
- Parasuraman S et al. (2010). Blood sample collection in small laboratory animals. Journal of Pharmacology and Pharmacotherapeutics 1(2): 87-93. doi: 10.4103/0976-500X.72350
- Quesenberry KE and Orcutt C (2011). Ferrets: Basic Approach to Veterinary Care. In: Ferrets, Rabbits and Rodents - Clinical Medicine and Surgery (Eds. Quesenberry KE and Carpenter JW), 3rd edition. Elsevier Health Sciences.
- Smith SA et al. (2015). Hematology of the Domestic Ferret (Mustela putorius furo). Clinics in Laboratory Medicine 35(3): 609-16. doi: 10.1016/j.cll.2015.05.009
You should read the general principles of blood sampling page before attempting any blood sampling procedure.
