Health Matters 15

A mixed bag this time round! There’s been a number of suggestions and cases sent in, so many thanks to everyone, as ever.


Richard Dobson reports on his ferret, Compo.

Insulinoma in Ferrets
A Case Study

My polecat hob ‘Compo’ is a rescue ferret of about 4 years old. The first indication that he was unwell occurred when he was out playing while I cleaned out my ferret cubs. He is the noisiest of my ferrets and ‘chuckles’ almost continuously whilst he is in the exercise pen. I noticed that he was quiet and as I watched him he looked like he was falling asleep on his feet. His head started to slowly drop towards the ground and his sides twitched slightly as if he were sniffing something. He then started to fall to one side but before he fell over he suddenly came around and started to walk about and chuckle. The whole episode took no longer than about 20-30 seconds. About 4-5 minutes later the same thing occurred again.

That same day I booked an appointment with the vet and took him along that afternoon. As is often the case, whilst at the vets the symptoms did not recur. After a thorough physical examination (temperature, heart rate etc.) the vet told me that he could find nothing wrong, but that he would give him a dose of antibiotic in case it was an infection and that I should return with him after the weekend if he hadn’t improved. A few days later there was no change so I took him back. Unfortunately it was a different vet who repeated the examination and came to the same conclusion. However, he gave him a second dose of antibiotic along with a painkiller.

At this point I felt the need to talk to someone who was more familiar with ferret conditions than my vets appeared to be, so I phoned Dr June McNicholas who suggested that it sounded like Insulinoma. She explained the illness to me and also gave me some ideas about possible medication and dietary changes.

Insulinoma is a condition caused by very small tumours forming on the pancreas which, although malignant tend not to spread throughout the rest of the body. This results in increased levels of insulin being released, which suppresses the blood glucose level. The visible signs are a hypoglycaemic attack that gives the appearance of nodding off.

Fortunately my collection of ferret books contains some that deal with diseases and medicines etc. So I looked up Insulinoma and photocopied the relevant pages.

I decided to go back and see the first vet and I duly presented him with the photocopies and details of the books (just in case he wanted to buy them!). He said that although he had heard of Insulinoma in ferrets he was more familiar with the disease in cats and dogs. He suggested a blood test so he kept Compo in for an hour or two.

Later that afternoon the vet called to confirm that Compo’s blood sugar was low and that it did appear that he could have Insulinoma. He had given him an injection of Prednisolone and said that he would investigate this condition in ferrets over the next few days. I was given a prescription of Prednisolone 1mg tablets and told to give Compo a quarter of a tablet twice daily. The following week on a follow-up visit, the vet confirmed that Compo did have Insulinoma and that he would need to be on the medication for the rest of his life. He also advised that an operation to remove the tumours from the pancreas and/or part of the pancreas was possible, but life expectancy would only be about a year. However, it was not possible to predict his life expectancy without the surgery but the consensus of opinion was that it would probably be shorter than 12 months.

I’ve now changed the diet for all of my ferrets to increase the protein and fat content whilst minimising the carbohydrate content. Ferrets, being carnivores, require a diet high in protein and fat but low in carbohydrate. Carbohydrates are readily converted into glucose and too much glucose would raise the blood sugar level causing the pancreas to over produce insulin.

It has been less than a month since this first occurred but in that time Compo has improved, with his ‘attacks’ now occurring much less frequently and lasting only for about 5 seconds. However, when they do occur as an emergency measure, I rub a very small amount of honey on to his gums to increase his blood sugar level to counter the effect of his high insulin level.

I’ve spoken to Dr June McNicholas on several occasions since my initial call and I’ve found her advice and experience of tremendous help and reassurance. If I hadn’t made that call to her it is very likely that Compo’s condition would have deteriorated very quickly and he could have gone into a coma and died. I can’t thank June enough for that initial diagnosis and her ongoing advice.

The lessons for me from this experience are:
If you think that something is wrong with your ferret it probably is.

Visit your vet and if he appears inexperienced in ferret health matters or is dismissive be persistent.

Talk to others who keep ferrets to see if they have ever experienced similar symptoms in their ferrets, and research the subject in the publications available.

Then re-visit your vet, my experience showed that he was only too happy to accept other sources of information.

This is important to help UK vets increase their knowledge base since currently most information of ferret illnesses is based on experiences in the USA and Australia.

Richard Dobson
22nd July 2004

Vasectomy reversal

Using a vasectomised hob to bring a jill out of season whilst avoiding pregnancy may not be as reliable as once thought. The following piece recently appeared in Ferrets First magazine. Apologies to readers who may have already seen the article, but we think it important enough to repeat given that vasectomised hobs are frequently quite busy at this time of year.

Vasectomised Hobs - are they all they are cut up to be?!

Some disturbing news has come to light on the subject of vasectomised hobs. Firstly, it seems that there is sometimes a little confusion about the differences between a vasectomised hob and a castrated hob, and what this means for an owner and any other ferrets in the family. Secondly, it may be that using a vasectomised hob on an in-season jill is not a totally reliable method of avoiding unwanted litters, as a number of readers have reported this spring.

Let’s take the differences between vasectomy and castration first. A vasectomy in a male ferret involves the severing of the ducts that transports the fertile sperm from the testicles to the penis. The ferret will still, technically, be fertile in that he is producing viable sperm. The only difference is that the sperm does not reach the penis and so mating a jill should not result in pregnancy. In all other respects, the hob will look, smell and behave as if he is an entire, sexually active male. This means he will be totally preoccupied with looking for jills in the spring and summer months; he may be aggressive to other males, and he will probably have a fairly pungent pong. He will completely willing and able to mate with jills, despite the fact that he cannot impregnate them.

Castration, on the other hand, involves the removal of the testes and thus the production of the sex hormones. A castrated hob becomes sexually inactive, uninterested in jills, and loses most, if not all, of the inter-male aggression associated with rivalry for mating jills. Indeed, he is incapable of making a jill pregnant. Lack of sex hormones also leads to less smell, a cleaner coat and, generally, a ferret who is more sociable and playful with people and other ferrets. Castration does not, however, reduce working ability.

Until recently, vets were more accustomed to being asked for a hob ferret to be vasectomised than castrated. This is simply because it has been long recognised that jills need to be brought out of season to avoid the risk of aplastic anaemia, a potentially fatal condition of unmated jills left in season. Since it is the act of mating that brings about ovulation in the jill, a mating with a vasectomised hob ends her season but does not result in pregnancy. The jill may go through a phantom pregnancy and, six weeks later (the end of a normal pregnancy), will usually come back into season and need to be mated again to the vasectomised hob.

Problems can occur when an owner simply asks for a hob ferret to be ‘neutered’. The owner may want the ferret to be castrated, the vet may assume it is in for vasectomy. Technically, of course, mistakes like this shouldn’t happen but it has been known. Several rescues have reported owners coming to find companions for their ‘neutered hob’ only to find it was a sex-mad vasectomised hob with a lot more than a plutonic friendship on its mind! Entire and vasectomised hobs do not make easy companions for jills or other hobs during the mating season.

In most cases, the situation is that an owner has requested that a hob be vasectomised because he is to be used to bring jills out of season. Indeed, most ferret welfare organisations will recommend this as an alternative to a jill jab or a permanent spay (ovariohysterectomy) operation on the jill. The caveat here is that many vasectomies can and do reverse themselves.

This year, I have had five incidents reported of vasectomised hobs apparently becoming fertile. Two have been in Scotland, one in the North of England, one in the south east, and one in the Midlands. All resulted in unwanted litters. In two cases the hob was lent out to other owners as a means of bringing jills out of season, resulting in even more unwanted litters. Aside from the fact that every year there are too many ferrets and too few caring homes, there is the embarrassment of rescues who advise the use a vasectomised hob and then find that they are indirectly responsible for dozens of unplanned kits.

Alarmingly, vasectomy reversal is more common than many people realise. After speaking to a number of rescues and vets, some feel the reversal rate may be as high as 70% in the two years following vasectomy. This was far higher than I had ever thought, and although we have no hard statistics for the rate as yet, it offers some indication of the number of unplanned kits born each year as a result.

Why does it happen? One vet suggested that while the surgical procedure is, technically, quite uncomplicated, it is often difficult to ensure that the sperm ducts are sufficiently cut and tied adequately to be permanent. After all, you are talking about tiny, tiny, pieces of tissue. Some will re-grow enough to rejoin, and so the hob is again entire. Even if only one sperm duct rejoins, ‘firing on one cylinder’ is enough to make a jill pregnant.

So what are the options for bringing a jill out of season without producing a litter? The safest and most permanent is to have your jill spayed. If you feel that you never want to breed from your jill, do please consider this. If your vet is reluctant or quotes a price higher than, say, that charged for spaying a female cat, contact your local ferret club, the NFWS or me, and maybe we can put you in contact with vets who routinely spay jill ferrets at a reasonable rate.

If a permanent spay is not what you want for your jill, then a jill-jab is another option. This is an injection of a hormone which will suppress the jill’s season, usually for the whole summer, although this may depend on how early you get her injected. The price of a jill jab can vary widely, though. I have heard of prices ranging from a pound or two per jill to over £10 per jill. Again, it may be worth contacting your local ferret club or NFWS to find out what their vets charge. Some clubs have arrangements which vastly reduce costs of these injections. A word of advice, though. Some people (including myself) have had some odd reactions in jills after a jill-jab. Some lose coats, others seem lethargic, others just are generally ‘off’ for a while. In many cases this may be down to the dose of hormone being a little too generous. The standard dose of the hormone used (proligesterone) is 0.5ml per kg and many owners and vets simply register the 0.5ml as a dose. However, there are lots of jills who weigh a good deal less than a kilogram so it is worth weighing your jill and asking your vet to adjust the dose pro-rata to her weight. This may help avoid some of the minor reactions to the jab.

But are vasectomised hobs a waste of time? No, I don’t think so, but we have been a bit too complacent in believing them totally reliable. There are a few golden rules to follow which may help. Firstly, if you have a newly vasectomised hob, do not allow him near the jills for at least six weeks after the op. There is likely to be enough residual sperm in his interior plumbing to make a jill pregnant. After 6-8 weeks the severing of the ducts should mean that he can no longer transport viable sperm into the jill on mating. He will be highly likely to be effective for his first year. It is from the second year onwards we start to get reports of vasectomy reversals. Here a possible safeguard is to limit the use of a hob until you are sure he is not fertile that year. This may mean not lending him out to other people until you are sure, or maybe only using him on a one of your jills at first. If this means paying out for a couple of jill jabs for others in season, look on it as insurance cover. It costs more to rear unwanted litters for 6-8 weeks than it does to pay for a couple of jill-jabs!

If any of you have also had experiences of unplanned litters as a result of putting your jills to a vasectomised hob, please let me know. I, and NFWS, are interested in compiling reports to try and identify how, why and when reversals are most likely to occur. In this way, we may be able to help avoid future accidents.

NFWS help wanted for important veterinary research into ferret health

(Request from vet, Nico Schoemaker, for help in important research into ferret health.)

Vet Nico Schoemaker, author of the British Small Animal Veterinary Association’s Manual of Exotic Pets, has contacted June to ask for help in recruiting UK ferret owners in an important study on the health of jill ferrets.

Nico would like owners of jills born in 2003 onwards to take part in a study. He is interested whether jills who are spayed, jills who have a ‘jill-jab’ or jills put to a vasectomised hob have different likelihoods for developing specific health problems. His primary interest is the adrenal disease, hyperadrenocorticism.

He writes:

As you may know I have been doing research on hyperadrenocorticism in ferrets for the last 6 to 7 years. The results of this research indicate that spaying of jill ferrets plays an important role in the development of this disease. This might also explain why this disease seems to be less common in the UK compared to the USA and the Netherlands. I have heard, however, that more and more ferrets are being spayed in the UK.

I have started a prospective study in the Netherlands in which ferret owners provide me with data on their ferrets after they have chosen either for spaying their jills, or using the ‘jill-jab’ proligestone (Delvosterone) for oestrus prevention. This is the only way to obtain data on the advantages and disadvantages of either method. As you may realise, a lot of owners have to participate in such a study if I want to be able to conclude something at the end.

I would therefore like to ask if you could help in contacting UK owners of jill ferrets to request their participation in the study.

June has had numerous discussions with Nico on the research and would like to encourage all owners of jills born since 2003 onwards to help Nico in this important piece of research which may help us understand more about the pros and cons of choosing spaying, jill-jabs or a vasectomised hob and the subsequent benefits to later health of our jills.

Your help in such research will take only a little of your time but will help enormously in advancing veterinary understanding of ferret health. If you have a jill born during or after 2003 please contact Nico on

Please pass on details of this research to all your ferret owning acquaintances, clubs and societies, and your vets, too, and urge then to take part. This is exactly the sort of research we need to help increase veterinary knowledge of ferret health.

Nico regrets that he cannot comment on other ferret health issues but he will give us information on the progress of his study.

If you would like any further details on the study, please contact June on 01854 633796 or and she will pass these on to Nico.


Many thanks to everyone for their contributions. I apologise for having to leave some case studies and suggestions until later issues. They will be covered, I promise. I’m just not allowed to fill the whole newsletter on Health Matters!

Please continue to send all your reports and suggestions to:

Dr June McNicholas
Croit Cullach
4 Durnamuck
IV23 2QZ.
Tel 01854 633796

Health Matters