Emergency Medicine & Critical Care: Small Mammals:
Presenting problem:
Neurologic Deficits in the Ferret
Date: June 3, 2011
Key words: Stupor, paresis, ataxia, paralysis, mentation, seizure, ferret.
Introduction
Unfortunately, neurologic disease is a common presenting problem in the ferret (Mustela putorius furo). Neurologic deficits may include an altered level of consciousness, paresis, ataxia, or even pelvic limb paralysis or collapse. Vestibular disease is rare, but has been reported (van Zeeland 2009). Tremors have also be reported secondary to cerebellar disease caused by Aleutian disease virus.
Signalment
Ferrets suffering from neurologic disease may be of any age and there is no sex predilection, although some medical conditions like insulinoma are more common in middle aged to older ferrets.
History
Is the onset of neurologic signs acute or chronic? Acute disease may be associated with
trauma, toxic exposure, cerebrovascular accident, and possibly heat stroke. Consider neoplasia, infection, inflammation, and metabolic disease with a chronic or gradual onset of signs. Thiamine deficiency is another potential but rare cause of neurologic disease in the ferret (Lewington 2002). In fact, no neurologic deficits were observed in one case report on vitamin B1 deficiency (Gill 1989).
Is the ferret’s home or play area “ferret-proofed”? Is time outside of the cage supervised? If the answer is no, then the risk of toxicity or trauma increases greatly. Is the ferret taken outside? This will increase the potential for exposure to canine distemper virus through direct or indirect contact with unvaccinated dogs.
|
Altered Mentation
The stuporous ferret is extremely dull or dazed with a lack of spontaneous movement and greatly decreased responsiveness to stimulation (Fig 1). Coma is defined as a state of profound unconsciousness caused by disease, injury, or poison.
Figure 1. Altered mentation, is a common presenting problem in the domestic ferret (Mustela putorius furo). Image provided by Dr. Ariana Finkelstein.
Physical examination findings
Physical examination should include a complete neurologic examination including evaluation of the pupillary light reflex and oculovestibular reflex. Be forewarned that the menace response is normally diminished or absent in the ferret (Antinoff 2007).
Differential diagnoses
Hypoglycemia caused by pancreatic beta cell tumor or insulinoma is the most important cause of altered mentation in ferrets over 2 years of age. Additional neurologic deficits seen with insulinoma may include seizure activity, episodic lethargy, ptyalism, ataxia, and hind limb weakness. Hypoglycemia may also be seen in young kits or in older ferrets suffering severe malnutrition or starvation.
Other potential causes of dazed or stuporous mentation may include:
- Head trauma
- Brain tumors
- Severe liver or renal disease
- Sepsis
- Iatrogenic hypoadrenocorticism
Pelvic Limb Paresis, Ataxia, Paralysis
Physical examination findings
Perform a complete physical examination including a complete orthopedic exam assessing muscle tone and range of motion of each limb. Palpate the spine for evidence of pain, swelling, or asymmetry. Also palpate peripheral pulses, although saddle thrombus has yet to be reported in the ferret.
Neurologic examination should include the cranial nerve exam as well as evaluation of spinal reflexes, proprioception, and deep pain perception.
- Is there evidence of fecal or urinary incontinence? Incontinence may accompany pelvic limb paresis, and it is extremely important to check for this problem since this significantly affects quality of life as well as pet quality.
- Palpate the urinary bladder. Lesions of sacral or caudal spinal cord segments results in lower motor neuron signs including an atonic or flaccid bladder. The bladder is easily expressible and overflow incontinence may be observed. Lower motor neuron signs may also include a dilated anus with loss of sphincter tone and reflex (Macintire 2006).
Since ferrets are so low to the ground, it can be challenging to accurately assess their gait. Place the ferret on the exam room floor after completing the bulk of your examination. Allowing the animal to walk on a slippery linoleum floor may make subtle paresis or ataxia more obvious. The classic “hump” in the back may also be gone in the weak or paretic ferret.
Differential diagnoses
Pelvic limb paresis and ataxia is a common finding in the ferret. Pelvic limb paresis does not always indicate neurologic or orthopedic disease in the ferret, and instead can simply be a manifestation of profound, generalized weakness.
Important causes of generalized weakness in the ferret include severe renal or hepatic disease, cardiovascular disease (Kottwitz 2006), iatrogenic hypoadrenocorticism, severe anemia caused by hyperestrogenism, and hypoglycemia caused by insulinoma.
| Pelvic limb paresis can be a clinical manifestation of generalized weakness in the ferret. |
Insulinoma or pancreatic beta cell tumors, should always be considered in ferrets over 2 years of age. Insulinoma may cause a constellation of signs ranging from episodic lethargy, profound weakness to neurologic problems like seizures.
| Degenerative | Intervertebral disc disease is rare. |
| Anomalous | |
| Metabolic | Insulinoma or systemic diseases causing generalized weakness |
| Neoplasia | Chordoma, plasma cell myeloma, lymphosarcoma l |
| Infection | Aleutian disease virus, canine distemper virus, rabies virus |
| Inflammation | Disseminated idiopathic myofasciitis, Myasthenia gravis (Couturier 2009) |
| Infarct | Thromboembolism (saddle thrombus) has never been reported in the ferret. |
| Trauma | Head trauma, spinal trauma |
| Toxin | Pesticides, heavy metals, metronidazole toxicity |
Pelvic limb paresis may be the only clinical sign seen with rabies virus infection. The cerebellar lesions caused by rabies virus can also manifest as acute onset paralysis (Niezgoda 1998; Niezgoda 1997).
If the ferret appears reluctant to move and appears to be in pain when the rear limbs are palpated, consider disseminated idiopathic myofasciitis. The index of suspicion should be highest in a young ferret less than 1 year of age with a high fever (Garner 2010).
Although there are no reports in the literature of metronidazole toxicity in the ferret this medication is frequently administered as part of combination therapy for Helicobacter gastritis. In dogs, doses exceeding 50-60 mg/kg/day may cause an acute onset of neurologic signs including vestibular signs, ataxia, seizures, and/or blindness. Lower doses may cause neurologic signs with liver disease (Macintire 2006).
Seizure Activity
Physical examination findings
Certain cardiovascular abnormalities may be noted after seizure activity such as tachycardia, red mucous membranes, and a rapid capillary refill time (Jasani 2011) so these findings would be expected in the post-ictal ferret in addition to elevated body temperature. Also perform a complete neurologic examination keeping in mind that the animal may be pre- or post-ictal, which may confuse the results.
Differential diagnoses
Pancreatic beta cell tumors should be considered in seizuring ferrets over 2 years of age.
| Extracranial |
Hypoglycemia typically caused by insulinoma |
| Intracranial |
Trauma |
Rare or potential causes are written in italics.
Keep in mind that owners may also misinterpret other behaviors observed, such as syncope or severe acute vestibular disease, as seizure activity.
Diagnostics
- Measure the patient’s blood glucose level as soon as possible.
- After the patient has been stabilized, a small mammal veterinarian may perform additional testing based on the history and physical exam findings:
–Fundic examination
–Serum protein electrophoresis when Aleutian disease virus is suspected.
–Immunofluorescent assay to confirm canine distemper infection.
–Echocardiography to evaluate the heart.
–Abdominal ultrasonography may be indicated when metabolic disease is suspected.
–Use myelography, CT, MRI, and/or cerebrospinal fluid analysis if brain or spinal disease is suspected.
Normal fasting blood glucose is at least 90 mg/dL in most ferrets while postprandial levels are typically around 120 mg/dL. It is generally unnecessary to fast the neurologic ferret, before measuring blood glucose, but when fasting is performed this should be done for no more than 3-4 hours and the ferret should be monitored very closely.
Remember that seizure activity may increase intracranial pressure during and after the episode so avoid jugular vein occlusion when collecting blood whenever possible.
A minimum database may help to elucidate other potential causes of neurologic disease or generalized weakness:
–Complete blood count
–Biochemistry panel
–Urinalysis
–Survey whole-body radiographs
Consider infectious or inflammatory disease when leukocytosis is recognized such as disseminated idiopathic myofasciitis.
Therapy
Specific treatment will vary with the underlying cause of disease.
Hypoglycemia
Treat hypoglycemia promptly. If you are unable to collect blood initially but hypoglycemia is strongly suspected, provide conservative empirical glucose therapy such as rubbing Karo syrup or 50% dextrose on the gums. In confirmed cases, administer 0.25-0.5 ml (2-4 ml/kg) of 50% dextrose 1:1 with saline. Administer dextrose intravenously slow bolus over at least 5 minutes to effect. If there is no response, then see Pancreatic beta cell tumors in the ferret for additional advice. If the patient is alert and stable enough to eat, feed a small amount of highly digestible, easily absorbable food like Emeraid Carnivore. Alternatively a high protein product like warm chicken baby food may be offered.
Seizure activity
It is important to control seizure activity since prolonged convulsions may result in permanent deficits. Place an intravenous or intraosseous catheter to provide central access. Stop seizure activity with the administration of an anticonvulsant and provide supplemental oxygen. Manage hypoglycemia as needed.
| Drug | Dose | Route | Comments/th> |
|---|---|---|---|
|
IM: intramuscular; IV: intravenous; CRI: constant rate infusion; h: hour |
|||
| Diazepam | 1.0 mg/kg | Rectal | |
0.5-1.0 mg/kg
| IV, IM |
Repeat up to three times or begin constant rate infusion (0.5-1.0 mg/kg/h) |
| |
| 0.5-1.0 mg/kg | CRI IV | ||
| Dexamethasone sodium phosphate OR | 1.0-2.0 mg/kg | IV | Administer if cerebral edema is suspected. |
| Prednisolone sodium succinate | 10 mg/kg | IV | Administer if cerebral edema is suspected. |
| Mannitol | 0.5-1.0 mg/kg | IV over 20 minutes | Administer if cerebral edema is suspected. |
Supportive care
- Provide fluid therapy and nutritional support as needed.
- Restrict exercise if spinal disease is suspected.
- Although ferrets are small and relatively lightweight, they can develop decubital ulcers so provide them with thick, dry, well-padded bedding. Turn the patient regularly every 2-4 hours.
- If the patient is unconscious or stuporous, lubricate the eyes every 4-8 hours to prevent corneal drying and ulceration.
- Provide appropriate bladder management by gently expressing the bladder every 4-8 hours.
References
Antinoff N. Musculoskeletal and neurologic diseases. In: Quesenberry KE, Carpenter JW (eds). Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery, 2nd ed. St. Louis, MO: Elsevier; 2007. Pp. 115-120.
Couturier J, Huynh M, Boussarie D, etal. Autoimmune myasthenia gravis in a ferret. J Am Vet Med Assoc 235(12):1462-1466, 2009.
Ehrhart N, Withrow SJ, Ehrhart EJ, Wimsatt JH. Pancreatic beta cell tumor in ferrets: 20 cases (1986-1994). J Am Vet Med Assoc 209(10):1737-1740, 1996.
Fox JG. Mycotic diseases. In: Fox JG (ed). Biology and Diseases of the Ferret, 2nd ed. Baltimore; Lippincott, Williams, and Wilkins; 1998. Pp. 375-391.
Garner MM. Diseases of domestic ferrets (Mustela putorius). Proc Annu Conf Assoc Avian Vet; 2010. Pp. 209-219.
Gill J. An outbreak of a possible thiamine deficiency in farmed ferrets. Surveillance Vol 16(4): 16-17, 1989.
Hanley CS, Wilson GH, Frank P, etal. T cell lymphoma in the lumbar spine of a domestic ferret (Mustela putorius furo). Vet Rec 55(11):329-332, 2004.
Jasani S. Saunders Solutions in Veterinary Practice: Small Animal Emergency. Churchill Livingston Elsevier; New York; 2011. Pp. 83-86, 102-107.
Kottwitz JJ, Luis-Fuentes V, Michael B. Nonbacterial thrombotic endocarditis in a ferret (Mustela putorius furo). J Zoo Wildl Med 37(2):197-201, 2006.
Lewington JH. Ferret husbandry, medicine and surgery. Edinburgh: Elsevier, 2002.
Macintire DK, Drobatz KJ, Haskins SC, Saxon WD. Neurologic emergencies. In: Macintire DK, Drobatz KJ, Haskins SC, Saxon WD (eds). Manual of Small Animal Emergency and Critical Care Medicine. Ames; Blackwell Publishing; 2006. Pp. 251-278, 415.
Niezgoda M, Briggs DJ, Shaddock J, etal. Pathogenesis of experimentally induced rabies in domestic ferrets. Am J Vet Res 58(11):1327-1331, 1997.
Niezgoda M, Briggs DJ, Shaddock J, Rupprecht CE. Viral excretion in domestic ferrets (Mustela putorius furo) inoculated with a raccoon rabies isolate. Am J Vet Res 59(12):1629-1632, 1998.
Oglesbee BL. The 5-Minute Veterinary Consult: Ferret and Rabbit. Ames, Iowa; Blackwell Publishing; 2006. Pp. 11-12, 79-80.
Pye GW, Bennett RA, Roberts GD, Terrell SP. Thoracic vertebral chordoma in a domestic ferret (Mustela putorius furo). J Zoo Wildl Med 31(1):107-111, 2000.
van Zeeland Y, Schoemaker N, Passon-Vastenburg M, Kik M. Vestibular syndrome due to a choroid plexus pailloma in a ferret. J Am Anim Hosp Assoc 45(2):97-101, 2009.
Related topics
Assessing the sick ferret
Cardiac disease in ferrets
Pancreatic beta cell tumors in the ferret
Physical examination of small exotic mammals
Presenting problem: Trauma in the ferret
Written by Christal Pollock, DVM, Dipl. ABVP-Avian; Lafeber Company veterinary consultant.
