Hypoglycaemia means low blood glucose and clinical signs can present as unsteadiness, fatigue, exercise intolerance, muscle twitching , shaking , abnormal behaviour such as staring into space , depression, signs of nausea such as pawing at the mouth and ptyalism (excessive saliva).
In serious cases the ferret may collapse and in rare cases seizuring may occur.
So what causes hypoglycaemia?
- Insulinomas which are pancreatic islet tumours of the beta cells (cells that produce insulin) and can be in the form of beta cell adenomas (benign) or beta cell carcinomas (malignant) These tumours cause the cells to produce an excess of insulin.
- Other neoplasia (abnormal growth of cells or tissues in the body)
- Liver disease
- Sepsis (the body’s overwhelming response to an infection that can damage its own tissues and organs)
- Starvation
- As a result of vomiting and diarrhoea as nutrient absorption is impaired.
- Pregnancy toxaemia which usually develops in the late stage of pregnancy. This can occur with large litters excessive calorie demands, not enough food or unusual loss of appetite.
- Xylitol poisoning. This sweetener found in many commercial foods is toxic to ferrets.
Unfortunately insulinomas are one of the most common tumours found in middle aged to older ferrets.
So lets talk about Insulinomas….
So why are tumours of the insulin producing cells so serious?
Insulin has an effect on numerous cells in the body . These cells include muscle cells, red blood cells, and fat cells. In response to insulin, these cells absorb glucose from the blood.
These tumours cause an increase in insulin production. This continuous hyperinsulinemia (high levels of insulin in the blood ) cause the tissues to increase their uptake of glucose. causing hypoglycaemia.
In normal animals hypoglycaemia triggers the glucoreceptors in the hindbrain to release hormones that act to increase blood glucose concentration. The hormones do this by stimulating gluconeogenesis (process in which glucose is generated) and glycogenolysis ( carbohydrate glycogen is broken down into glucose) in the liver and also inhibit the use of glucose in the tissues. This feedback system is inoperative when a ferret has an insulinoma and blood glucose concentrations continue to decrease.
The signs of hypoglycaemia tend to present when the ferret has not eaten for sometime and they usually resolve once food is provided. This makes early signs more difficult to pick up by the owner especially if the ferret has constant access to food.
Diagnosis
If the ferret is currently showing signs of a suspect insulinoma-
- Test immediately
- Glucose below 75mg/dl or 4.16 nmol/l confirms insulinoma
- Glucose within a normal range ( 4.44-6.49 nmol/l or 80-117 mg/dl) in a fasted animal suggests insulinoma is not likely the cause of current clinical signs
- Glucose within a normal range in a non fasted ferret does not rule out insulinoma. The ferret may have insulinoma along with another concurrent disease
If the ferret is currently exhibiting no signs suggesting insulinoma –
- Test the blood glucose after 4 hour fast (monitoring for signs if hypoglycaemia) If the blood glucose is between 3.3 – 5 nmol/l then starve for a further 2 hours and re test.
- If the blood glucose is less <3.4 nmol/l or 60mg/dl after a 4 hour starvation period and the ferret is displaying signs of insulinoma then this can be considered diagnostic.
- If symptoms suggesting insulinoma appear at any time during the starvation period test immediately.
Sites to take a blood sample include the saphenous vein or an ear/foot prick. Some clinicians may suggest cutting the nail to the catch the quick but this is somewhat out dated and can be used as a last resort. Silver nitrate can be used to stop the nail bleed if this sampling technique is to be used.
Digital point of care glucometers manufactured for human patients are very practical but may yield false results. The glucose concentration measured from venous plasma by an official laboratory is considered gold standard.
This is an interesting study on the use of POC glucometers versus laboratory analysis –
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4137928/
Insulinomas are usually 0.5- 2mm in size and an be found in multiple places in the pancreatic tissue. Ultrasonography, CT scan with contrast or MRI scan with contrast can be used to diagnose however due to the small size of the tumours this is not routinely advised.
Treatment
Surgery is considered the best therapeutic treatment option although some tumours may be to small and remain undetected. In some cases they may not be able to be removed if they are near the pancreatic ducts in the body of the pancreas.
If too much of the pancreas is removed this can cause diabetes.
Going down the surgical route can provide a mean disease free post surgery time of 1 year and a survival time of 22 months.
Medical treatment is another option available. The use of Prednisolone (to aid gluconeogenesis) and diazoxide (inhibits insulin release) are routinely used.
Medical treatment has shown to be sufficient to control hyperglycaemia for 6-18 months.
To note – IF A FERRET SUDDENLY COLLPASES OR SEIZURES IMMEDIATLEY RUB HONEY OR CORN SYRUP ONTO THE GUMS . Be careful of injury via biting.
Case Study – Meet Enoki
Enoki is a handsome boy who is nearly 7 years old. He has been diagnosed with insulinoma just two weeks ago and I am going to be following his story.
Lisa who is Enoki’s owner (who happens to run a ferret rescue) noticed some changes in his behaviour. He began periods of head bobbing with episodes of lethargy . This was also alongside noticeable weight loss.
His glucose was checked at home with a POC glucometer and it read at 33mg/dl .Knowing that this indicated a problem she immediately called the vet and Enoki was seen that night.
A comprehensive blood panel was run to rule out any other issues.
He was starved for two hours (vets own protocol ) and blood glucose reading was taken of 39mg/dl.
Lisa’s suspicion of insulinoma was confirmed.
He was stared on Prednisolone at a dose of 2 mills ( 15mg/5ml ) and Diazoxide 25 mills (50mg/mill) both every 12 hours.
He is fed a diet of raw meat and ferret kibble. He also gets supplemented with ferret soup ,commonly known in the ferret world as ‘soupies’.
So far he has received two weeks of treatment and he is responding well. His appetite has increased along with his activity levels. He is also much brighter.
Lisa will also be adding Pepcid to reduce the side effects of the prednisolone on the gastrointestinal tract.
I will be catching up with Lisa regularly to follow this little guys treatment experience.
Sources of information for my above article-
BSAVA Manual of rodents and ferrets
Hillyer/Quesenberry ‘Ferrets, Rabbits and Rodents’ clinical medicine and surgery
Just exotics CPD webinar ‘Hypoglycemia in Ferrets’ online
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4137928/ ‘Comparison of a human portable glucometer and an automated chemistry analyzer for measurement of blood glucose concentration in pet ferrets ‘