What you should know about ferret insulinoma

by Celia Heritage

My two hobs, Jasper and Silas are now five and half years old and until last year they had been perfectly healthy. But then Silas fell sick and became so ill that he almost died. Although smaller than his brother Jasper it was Silas who was the "live wire" of the pair. It was Silas who enjoyed being taken for walks to the local wood and whom I sometimes had to run to keep up with. Jasper on the other hand was always begging to be carried!

Then last January I noticed the first signs that something was not quite right. I have to admit that at first I did not take his symptoms seriously. During his daily playtime he would occasionally appear to be deep in thought or fed up. He would just stand and stare blankly into space. After a few seconds he would carry on as normal and I honestly didn't think that there was a problem.

After a few weeks however these periods of blankness increased in length and were coupled with a lethargy that was so unlike him. If I picked him up during one of these bouts he would just lie weakly in my arms and not move. Once again this was unlike him since he would normally struggle to be put down again after a minute or so. Then one day one of his back legs gave way and he gently toppled over to one side. It was then that I finally realised that there was something seriously wrong. I had been reading and re-reading all my ferret books in order to find out what could be wrong with him but just could not find anything describing his symptoms. That night in desperation I turned to the Internet and spent two hours searching every ferret medical web site I could find. I checked illness after illness with no success, until finally I found it.


The symptoms were an almost perfect match: "staring blankly into space, episodic lethargy, hind leg weakness". The only symptom he was not showing was "foaming and pawing at the mouth". I knew then beyond doubt that this was what Silas had and my heart sank as I read that insulinomas are tumorous cells.

Basically these tumours occur in the part of the pancreas where the insulin is produced. Insulin is the hormone which lets the body cells "make use" of glucose or blood sugar. In a case of insulinoma these tumours cause the production of too much insulin, driving glucose into the body cells too fast, thus causing low blood sugar level. It is the low blood sugar level which causes the lethargy and weakness in a ferret who has insulinoma. In severe cases an untreated ferret may sink into a coma and die.

Because insulinoma usually affects ferrets in middle age, it is often not noticed by the ferret's owner as soon as it could be, since he or she attributes symptoms such as lethargy to part of the natural ageing process just like I did.

The next day I rushed Silas to the vet together with a print out on insulinoma from the Internet. Despite my brave intentions I could come out with no words other than" I think he's got this", showed her the printout and promptly burst into tears. I was sure he was going to die. She was very understanding and to my surprise said that she had come across two cases of ferrets with insulinoma in her last practice. She assured me that they were still alive, when she left there at least!

If you think your ferret has insulinoma then the first step is to get the vet to do a blood test to check the blood sugar level. My vet recommended that we test both Jasper and Silas, partly because being brothers Jasper might be in the early stages of the disease too, but also so that we could compare the readings. If Jasper were indeed healthy, as we believed, then he would provide a good indicator of what a healthy ferret's blood sugar level should be. The blood test involved shaving the fur off a portion of their necks and then inserting of a needle into their necks in just the right place for long enough to get enough blood for a sample. Needless to say this is past the tolerance point of most ferrets! Silas put up with the noisy shaver but just kept pushing the needle very firmly away with his foot! So the vet said there was no choice but to do the test under anaesthetic. I took them both down early one morning and waited anxiously until the afternoon knowing the dangers of anaesthetic and small animals. There were no problems in this respect and as usual my "boys" made lots of new fans during their morning at the surgery! When the results came back Silas' blood sugar level was surprisingly within the accepted normal level at 64mg/dl. Jasper's however was much higher at 90mg/dl (milligrams of glucose per decilitre of blood). After consulting with a ferret specialist by telephone my vet came to the conclusion that Silas definitely had insulinoma despite the blood test result. The accuracy of the blood test can be affected by various factors such as the stress of undergoing an anaesthetic or the fact that he had had "nil by mouth" before the anaesthetic. So it was lucky that we had Jasper's test to compare it with.

The information I had found on the Internet was mainly American based. There is, apparently, a far higher incident rate of insulinomas in American ferrets than in European ferrets probably caused by a more limited gene pool. Most of the information I had found on the Internet suggested an operation to remove the cancerous cells although it clearly stated that they would always grow back again fairly quickly. An operation of course always involves a risk in itself and after discussing it with my vet I decided to opt for a course of medication for Silas rather than put him through the trauma of an operation which would only remove his cancer short term. A ferret can usually live with the cancerous cells in the pancreas for up to two years or so after they occur as long as he is given medication to control his insulin level and thus maintain his blood sugar level.

The medication Silas has is a steroid called Prednicare and costs a couple of pounds for about sixty pills. Silas currently has half a pill in the morning and a whole pill at night. This amount is altered to suit the individual ferret.

So surely with the diagnosis and relevant treatment confirmed Silas should have been well on the road to being his old self again? No, in fact the worst was still to come. Silas had stopped eating and the introduction of the medication did nothing to improve this, although he no longer had his blank spells. At first he would eat little ham but refused his normal dry ferret food completely. Even covering it with gravy proved to be no incentive while offerings of fresh meat were politely put in one corner of the hutch but otherwise ignored. After a month or so he even went off the ham. The only thing he would accept was cream which I used anyway as a method of getting him to have his Prednicare (carefully crushed so he didn't know it was there). I began to despair. His body weight had dropped from his normal two pounds or so to a miserable one pound. He really did look like a ferret from Belsen and I gave him by this stage (May) only another six weeks to live.

Then one day the vet suggested I try him on jars of baby food. Off I rushed to Safeway and filled up the trolley with jars of the stuff wondering whether he would be better on baby food for babies up to four months or whether the seven month stuff would be better! Success!! Although he turned his nose up at it at first, I tried mixing it with some cream and suddenly, hey presto, he began to eat. But only if I spoon fed him! No chance of him doing it by himself. So began long months of religiously spoon feeding him twice a day, trying to get him to eat as much as possible. Here I have to thank my partner Neil who took over when I was at work despite being allergic to ferrets and also my friends Anne and Tadz who took over when we went on holiday. I would also like to thank Sheila Crompton for all her help and advice via e-mail. Gradually Silas began to put on weight and when I took him back to the vet the following month for his check up she was delighted and admitted that she had thought that when she saw us next it would be to have him put to sleep.

By the Summer he was back to his old weight of just over two pounds if a somewhat bony two pounds and after having cut his daily feed to one a day which he would by this time usually eat unassisted, I decided to try him back on dry food. He accepted it immediately and the remaining jars of baby food remain untouched in the cupboard. I kept a careful check on his weight but it remained constant.

Today he is a happy little ferret and back to his old lively inquisitive self. I still worry about him and keep a close eye on him, weighing him regularly. He suffers still from a slightly weak back leg and those long walks are now a thing of the past, but both Jasper and I are just thankful that he is still around.

(First published in the Winter 2000 issue of the NFWS News Issue 52)

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