Ferrets are thought to have been domesticated as early as 2000 years ago (Thomson, 1951). Although they are thought to have descended from wild polecat species, they are categorised as a separate species, Mustela (‘mouse catcher’) putorius (‘smelly’) furo (‘little thief’). Despite the extensive and well-documented experiences of using ferrets in hunting and for pest control as well as pets, there is still much to earn about their anatomy and treatments for specific illnesses. However, there is a wealth of expanding anecdotal and scientific information available for successful care of this ‘smelly thief’. After a brief review of relevant anatomical, physiological and behavioural characteristics, this article will focus on critical care nursing of the pet ferret.
Revision: the ‘ferret facts’ relevant to veterinary nurses
Anatomy
Behaviour
Handling
Suggested equipment for nursing ferrets
In the author's experience, it is advised to consider equipping a veterinary practice with some particular items to assist with caring for sick ferrets, such as small scales, baby bottle warmer, nutritional formula, microwavable heat packs, and small endotracheal tubes (2.0–4.0 mm).
What is meant by ‘critical care’ for ferrets?
The term ‘critical (or intensive) care’ tends to indicate a higher level of nursing care, which focuses on the critically ill, unstable patients or on patients that are recovering from surgeries. The term can potentially include life-saving treatments and the need for it will occur either with acute or chronic conditions (www.nhs.uk/). There are a wide variety of diseases affecting ferrets that are commonly encountered by veterinarians in practice in the UK, some of which are particular to ferrets. This article only addresses the critical nursing care skills and treatments that can be used in the commonly encountered conditions of ferrets; for further investigations, practical references are given in Table 1.
| Body system | Critical care or emergency condition | Reference |
|---|---|---|
| Gastrointestinal |
|
|
| Respiratory |
|
Pollock (2007); Barron and Rosenthal (2012) |
| Cardiovascular | Dilated cardiomyopathy | Morrisey and Kraus (2012) |
| Reproductive/urogenital |
|
|
| Endocrine |
|
Schoemaker et al (2000, 2002, 2004); Wagner et al (2001, 2005); Schoemaker (2003); Kuijten et al (2007); Pollock (2007); Rosenthal and Wyre (2012); Girling (2013) |
| Other | Heatstroke (‘the sweats’) | Pollock (2007); Girling (2013) |
Vigilance will be required, accompanied by a sense of urgency and a guarded prognosis for the ferret patient. Many of the treatments may resemble those used in supportive care from elective procedures, for example fluid and nutritional therapy, but their intensity and incident rate may increase along with more invasive treatments, such as intraosseous catheters.
Critical care nursing of ferrets
A detailed history from the owner and a complete physical examination are always of utmost importance to the veterinary team to formulate an efficient and effective treatment plan. As with dogs and cats, assessing the ferret's body condition, including both fat and muscle, allows differentiation between weight loss from anorexia and ‘cachexia’ from muscle wasting in sick animals (Zaffarano, 2010). It is also important to acknowledge that male and female ferrets experience seasonal weight fluctuations where up to 40% bodyweight is lost from subcutaneous fat during the spring (Fox and Bell, 1998). Normal values for basic biological parameters in ferrets are reported in Table 2.
| Lifespan (years) |
|
|
| Adult body weight (kg) |
|
|
| Dentition | I 3/3, C 1/1, PM 3/3, M 1/2 | |
| Respiratory rate (breaths/min) | 40–80 | |
| Heart rate (beats/min) | 180–250 | |
| Rectal temperature (°C) | 37.8–40 | |
| Total blood volume | 60–80 ml/kg | |
| Daily water intake | 75–120 ml/kg | |
| Daily food consumption | 140–190 g | |
| Duration of oestrus (days) | Until mated but possibly up to 6 months | |
| Length of gestation (days) | 41–42 | |
| Litter size | 2–14 (average 8), up to 2 litters per year | |
| Normal birth weight (g) | 6–12 | |
| Weaning age (days) | 42–56 (6–8 weeks) | |
| Sexual maturity (months) |
|
|
| Breeding season in Northern Hemisphere | March–September | |
| Activity | Nocturnal | |
| Vaccinations | Canine distemper virus (CDV) | CDV vaccine (NobivacDHPPi®, Intervet) from aged 8 weeks |
| Rabies | Rabies vaccine 1 ml from aged 12 weeks and annually thereafter if going abroad or remaining in certain countries e.g USA | |
Blood sampling
There are various sites available in the conscious ferret, including the jugular vein and cranial vena cava, which are the most commonly used for venipuncture (Quesenberry and Orcutt, 2012). The lateral saphenous and cephalic veins can also be used if a small amount of blood is needed (Figure 2), as they tend to easily collapse. In the author's experience the ventral tail artery and femoral veins are seldom used to obtain a blood sample; applying local anaesthetic preparations such as Emla® cream (lidocaine/prilocaine) can reduce reactivity from the patient, when given the manufacturer's stipulated time for effectiveness. Anaesthesia may be required in some cases. It is advised to take no more than 10% of the total blood volume (7% of bodyweight) or 1% of the bodyweight in healthy individuals, and reduce further to 0.5% from sick patients (Pollock, 2007). Blood parameters can be affected when ferrets are anaesthetised using inhalant gases, such as isoflurane, and this should be acknowledged when interpreting blood sample results as packed cell volume (PCV) and white blood cell counts will be reduced (Pollock, 2007). Normal and pathologica haemato-biochemica parameters used to assess patients in critical conditions are reported in Table 3.
| Sample | Measurement | Normal parameters | Parameter use in diagnosis of illness |
|
|---|---|---|---|---|
| Indicated conditions implied | Abnormal parameters | |||
| Blood analysis | Packed cell volume (PCV) | 46–61% |
|
>61% <40% |
| Total protein | 45–62 g/l | Aleutian disease | 80 g/l | |
| Blood glucose | 6.66–7.99 mmol/l (if fasting) | Hypoglycaemia, insulinoma | <4 mmol/l | |
| Blood urea nitrogen | 6.42–11.42 mmol/l | Renal disease | If increased 3.5–16.1 mmol/l | |
| Reticulocyte counts |
|
Regenerative anaemia | 10–12% | |
| Alanine aminotransferase | 48–292 IU/I | Renal disease, lymphoma, hepatic disease | >275 IU/I | |
| Creatinine | 0.1–0.3 mg/dl (or <0.5 mg/dl) | Azotaemia | 0.7–1.0 mg/dl | |
| Calcium | 1.9–2.4 mmol/l | Renal disease | 2.0–3.0 mmol/l | |
| Urine analysis | Urine specific gravity | 1.015–1.048 | Chronic renal failure | 1.050–1.115 |
| Daily production | 25–30 ml/kg | Dehydration, renal failure | <20 ml/kg | |
| pH | 5.5–6.5 (acidic owing to diet) | More alkaline | Urolithiasis | |
Hospitalisation
When planning to house a ferret in a hospital environment, it is important to ensure enclosures are ‘ferret-proofed’ by considering a ferret's size and determination to squeeze through small gaps (1″ diameter) or to tenaciously chew through thin plastic carriers (Pollock, 2007). In the author's experience, they should be placed in a metal or hard plastic animal enclosure with either vertical-bar doors or Perspex fronts, but still with adequate ventilation to avoid overheating. Additional consideration should be given to their predator and prey response, where their ability to scare other patients (e.g. small birds, rabbits and rodents) with their smell or to be scared themselves by other patients (e.g. dogs and cats) should dictate their location in the hospital (Fisher, 2006).
Fluid therapy
Ferrets will normally drink between 75–120 ml/day, and when considering supportive fluid therapy they require a maintenance rate of 100 ml/kg/day (4 ml/kg/hour) (Moody et al, 1985; Girling, 2013). As with other mammals, hydration status should be assessed with each physical examination by observing if the mucous membranes are tacky, the eyes are sunken and the cornea is desiccated or if skin pinches (‘tenting’) remain in place (Figure 3). During procedures requiring anaesthesia, they should be supported with at least 10 ml/kg/hour with fluid types that are suitable for ferret patients depending on the condition being treated. Crystalloids (compound sodium lactate or lactated ringers) may be used for rehydration and if hypovolaemia or hypoproteinemia are present (Girling, 2013). Fluids containing dextrose (2.5–5%) can be used in hypoglycaemic cases, after confirmation of blood glucose levels. Colloids may be required to increase fluid volume and oncotic pressure (Girling, 2013). If a patient is showing a PCV<25% or thrombocytopenia, blood transfusions are possible without the need for cross matching between donor and recipient (Girling, 2013). Collected blood should be mixed at a rate of 1 ml of anticoagulant to 6 ml of blood, and administered intravenously or intraosseously at a rate of 6–12 ml/kg/hour (Girling, 2013).
Intravenous (IV) catheterisation
Although catheterising conscious ferrets can be a challenge, with good handling and routine venepuncture technique this can be achieved. The cephalic or saphenous veins are the sites more commonly and easily used (Pollock, 2007; Quesenberry and Orcutt, 2012). The jugular veins are seldom used for catheter placement (Pollock, 2007). A 26 G catheter is usually required, and the patient may be more amenable if a local anaesthetic is applied to the intended site(s) (e.g. Emla cream® (lidocaine/prilocaine), 30–45 minutes before any attempts, according to manufacturers’ instructions). Catheter insertion technique resembles that used for dogs and cats, although ferret skin can be tough, especially in entire males; a conservative ‘cut-down’ technique, using a scalpel blade or needle parallel to the vessel, may avoid catheter sheath crimping or discomfort for the ferret (Pollock, 2007). In the author's experience, most sick ferrets will not chew on the catheter once placed, but an Elizabethan or ‘neck-brace’ collar may be required in some cases. Performing a general anaesthetic solely to place an IV catheter should be avoided where possible in sick and weak patients (Quesenberry and Orcutt, 2012).
Intraosseous (IO) catheterisation
The IO route should be considered if the IV access is not possible and/or the patient requires immediate administration of emergency fluids or medications (Pollock, 2007). Insertion points are usually the proximal tibia (Figure 4) or proximal femur. The site should be aseptically prepared (clipped and disinfected with chlorehexidine then alcohol, or similar) and a local anaesthetic (lidocaine/bupivacaine) injected into the periosteum (Pollock, 2007). In the author's experience, in anaesthetised or collapsed patients a syringe driver can be attached for constant rate infusions, especially if administering glucose. If critically ill patients are still relatively active or capable of acquiring food and water, then care must be taken that IV or IO catheters do not jeopardise the patient's welfare, for example by getting caught on bedding and being pulled out, causing haemorrhage or trauma (author's experience).
Subcutaneous bolus injections
If IV or IO catheterisations are not viable options then, in the author's opinion, the subcutaneous route should be used, such as when first examining critically ill patients to restore a hydration status to allow venepuncture. Adding hyaluronidase to crystalloid fluids, such as compound sodium lactate (1:1000 dilution), improves the permeability of fluids to the tissues, which may avoid creating a potentially uncomfortable lump at the site of administration and allow for large volumes to be administered (Morrisey, 2009).
As most ferrets have thick skin, the administration of fluid boluses can be uncomfortable; therefore, minimising the incident rate of subcutaneous fluid treatments is preferable. The use of butterfly catheters (23 G) can be helpful when administering large volumes, especially if the ferret is not docile (author's experience) (Figure 5).
Nutritional therapy
There are various liquid critical care formulas that are commercially available and suitable for ferrets; some examples are Hills Prescription diet A/D®, Oxbow Critical Care Carnivore®, Vetark Critical Care Formula®, Labefer's Emeraid Nutritional care system Carnivore® and Royal Canin Convalescent support®. It is advisable to offer these formulas at 8–12 ml/kg (Quesenberry and Orcutt, 2012). Unlike rabbits and rodents, most ferrets will readily eat these feeds, and they could even be used to distract the animal when giving other treatments. If syringe feeding ferrets is necessary, care should be taken not to overfill the mouth to prevent aspiration pneumonia (author's experience).
Thermo/heat therapy
As with other mammals, collapsed and recovering ferrets will require careful monitoring of their body temperature to ensure that either hypothermia or hyperthermia do not occur. There is almost an inexhaustible list of heat therapy strategies that could be used in collapsed patients, where the most popular are incubators, microwavable heat packs (Snugglesafe® and cherry-stone heat packs) and water-circulating heat pads (Lichtenberger and Lennox, 2012). Care should be taken to ensure that devices are not scalding hot as surface burns can occur. Hot water bottles and ‘hot-hands’ can be an inexpensive alternative, but they are likely to cool down relatively quickly, drawing heat away from the ferret (author's experience).
Medication: drugs and route of administration
Ferrets can be administered antibiotics or other drugs via different routes (Ramsey, 2011). Most oral medications should preferably be in a liquid form as ferrets can prove a challenge to a ‘pill ’, unless the drug is crushed and added to a tasty paste such as Hills A/D® or meaty baby food (author's experience). When syringing liquids to reluctant ferrets, it can help to hold them by the scruff to access the mouth. Ferrets will react to unpalatable substances by hyper-salivating and pawing at their mouth.
Intramuscular injections tend to be used only when administering sedation to reduce the risk of inflicting uncomfortable treatments, especially in cachectic animals with reduced muscle mass (author's experience); epaxial muscles in lumbar or cervical regions or the biceps femoris (front of the thigh) are generally selected (Morrisey, 2009). The use of an unblunted 25 G needle is recommended by the author.
Subcutaneous injections can be a challenge to administer in entire males, as the skin over the scruff or dorsum can be tough. However, this is usually an easy route for injectable treatments and most ferrets can be distracted with meat-based diets simultaneously (author's experience).
The intraperitoneal route of fluid and/or drug administration into the lower right abdominal quadrant can offer a site for rapid fluid uptake if other routes are inaccessible, but it is considered a risky technique in ferrets; even in collapsed ferrets it is possible to inadvertently puncture organs (Saunders and Whitlock, 2012). For this reason, it may be preferable to use other routes such as the subcutaneous or oral ones.
Recognising pain in ferrets and administering analgesia
Pain management is of utmost importance to ensure optimal welfare of patients and to improve recovery from surgical procedures. It can be particularly challenging to recognise pain and thus create a pain management plan in such stoic species, but it is vital to err on the side of caution and assume discomfort with obvious trauma, e.g. fractures or conditions that may be painful in other species. Ferrets do, however, offer a few key clinical signs that indicate pain (Fisher, 2006; Pollock, 2007; Johnson-Delaney, 2009), such as:
Signs of nausea (pawing at the mouth, head pressing in the corner of enclosures or frothing at the mouth) can also be associated with the ferret patient experiencing pain (Pollock, 2007) (Figure 6).
Where possible, analgesia should be administered pre-emptively and/or continued post operatively. Many analgesics commonly used in other species (e.g. opioids, alpha-2 agonists, non-steroidal anti-inflammatory drugs (NSAIDs) and local anaesthetics) may be effectively used, alone or in combination, in ferrets (Thompson and Bament, 2013). Nevertheless, some drugs should be used with caution as they can have adverse effects; for example, NSAIDs can cause gastrointestinal ulceration, and like cats, ferrets are susceptible to acetaminophen and ibuprofen toxicity (Pollock, 2007; Dunayer, 2008; Oostrom et al, 2011).
Nebulisation
Nebulisation may be required when clinical signs indicate respiratory congestion, as seen in ferrets suffering with influenza. Ferrets can be nebulised with saline vapour, antibiotics (enrofloxacin), antifungals (itraconazole) and disinfectants (F10®). However, efficacy of this route of drug administration is anecdotal in many small mammal species (Goodman, 2009; Morrisey, 2009). Treatment involves placing the ferret in a partially sealed enclosure with a container holding the treatment secured to the side and connected to an ultrasonic or compressed-air nebuliser outside the enclosure (author's experience).
Oxygen therapy and intubation
Oxygen should be administered to ferrets showing signs of respiratory distress. In ferrets that are still responsive it may be sufficient to observe them in an oxygen-rich enclosure, such as an incubator with humidified oxygen administered (at approximately 40%), until repeat physical assessments are due (Chitty, 2009; Lichtenberger and Lennox, 2012). In more severe cases, direct oxygen administration may be required via a breathing circuit, face mask or intubation (author's experience) (Figure 7).
Intubation of ferrets is similar to cat intubation, and applying lidocaine (Intubeaze®) to the larynx 30 s before intubation can prevent laryngospasm (Longley, 2008). The intubation procedure is as follows:
Emergencies
Responses to ferrets suffering from respiratory or cardiovascular complications should follow the same principles (airway → breathing → circulation) as that used for dogs and cats and other small mammals.
Conclusion
Veterinary nurses already possess the skills required for successful treatment of critically ill ferrets, drawing on experiences from other more common mammal species, such as cats and dogs. However it is vital to understand the specific ‘ferret facts’, such as those anatomical, physiological and behavioural characteristics that are a feature of this species. This is extremely important as it will enable appropriate and correct nursing care planning when ferrets are presented with commonly encountered illnesses.
The aim of this article is to offer a useful review from the most recent literature and provide practical suggestions that may help the veterinary team in the assessment and care of critically ill ferret patients.