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FERRET NEWS for the latest news in the ferret world!!!
Watercolour paintings, photos.
By Fret Popper
It’s time to give serious thoughts to managing ferret fertility. Up to now the issue was dealt with simply - either you were allowed to breed or it was off to the clinic ‘snip snip snip’ and the matter was resolved for good - but sometimes with consequences.
Research has given a good indication - some believe proof - that surgical neutering results in the occurrence of adrenal tumours in ferrets. Adrenal tumours cause significant morbidity in ferrets. (See ‘Adrenal Disease in a Nutshell’)
The correct term for this phenomenon is ‘gonadectomy-induced adrenocortical neoplasia’ which has also been observed in mice, rats, guinea pigs and hamsters.
In ferrets with hyperadrenocorticism - or adrenal disease - following surgical neutering, the adrenal cortex has adopted features of gonadal hormone producing cells. In other words, the adrenal glands, or more correctly the adrenocortical neoplasia or tumours, mimic the role of ovaries or testes by producing sex hormones (sex steroids) giving rise to vulvar swelling in neutered female ferret, recurrence of sexual behaviour in neutered male ferrets and symmetrical alopecia in both. But sex steroids produced by adrenocortical neoplastic or tumour cells are different in their composition and plasma concentration than those produced by gonads (ovaries and testes) Thus the negative feedback function of the sex steroids to the hypothalamus is reduced.
Let me explain:
When gland X releases hormone X, this stimulates target cells in gland Y to release hormone Y. When there is an excess of hormone Y gland X senses this and inhibits its release of hormone X. This is called negative feedback. But if hormone Y is not quite the same as it is supposed to be because it’s being made by a different gland - the adrenal gland neoplasia or tumours instead of the gonads as in neutered ferrets with the disease - gland X doesn’t recognise hormone Y and keeps churning out hormone X stimulating the production of more and more hormone Y. An undesirable condition indeed!
In the ferret:
During the winter months when daylight is less than 12 hours, high melatonin (produced by the pineal gland in the brain) concentration suppresses the release of gonadotropin releasing hormone (GnRH) from the hypothalamus (also a gland in the brain). With increasing daylight this suppression is lost and GnRH is released stimulating the pituitary gland (another gland in the brain) to produce gonadotropins (luteinizing hormones [LH] and follicle-stimulating hormone [FSH] which in turn stimulate the release of oestradiol and testosterone from the gonads (ovaries and testes). This is the start of the breeding season. These hormones exert a negative feedback on the hypothalamus and pituitary glands, thereby preventing excessive secretion of GnRH, and gonadotropins LH and FSH.
But in neutered ferrets this negative feedback is reduced or lost resulting in an increased release of gonadotropins, which promote the production of sex steroids inducing adrenocortical enlargement as a consequence of chronically elevated luteinizing hormone levels.
Scientists have discovered several factors which point to a relationship between gonadotropic hormones and hyperadrenocorticism in ferrets.
First, the initial sign of adrenal disease are observed only during the breeding season when gonadotropic hormone levels are high.
Second, in countries where the neutering of ferrets is common practice, adrenal disorders are a common condition, whereas in countries where ferrets often remain entire the condition is seldom diagnosed.
Third, there is a significant correlation between the age at neutering and the age at the onset of the disease.
Fourth, the gonadotropin-releasing hormone (GnRH) analogues (leuprolide acetate and deslorelin acetate) have beneficial effects in the treatment of the disease.
And finally, scientists have detected luteinizing hormone (LH) receptors in the adrenal cortex of ferrets. In healthy entire and healthy neutered ferrets those receptors are non-functional but in neutered ferrets with adrenal disease the receptors are functional mimicking the function of the receptors in ovaries and testes.
The lines of evidence so far discovered leave little doubt that surgical neutering is a major risk for ferrets to develop adrenal disease.
An alternative to surgical neutering - Depot GnRH agonist
In recent years deslorelin acetate a gonadotropin releasing Hormone agonist (GnRH agonist) has been tested on ferrets in Europe. (SAFA News June 2008, ‘Cutting Edge Ferret Medicine’, p 9, and April 2009, ‘An Update on the GnRH Implant - Suprelorin) In Australia the drug is available under the brand name ’Suprelorin’ registered for the use in dogs to suppress reproductive function by stopping the production of the sex steroids. The drug is given in the form of a slow release depot lasting on average 2 or 4 years in ferrets depending on the size of the implant given.
Initially the GnHR agonist implant increases the production of gonadotropic hormones. This increase if followed by a desensitisation of the gonadotropic receptors. As a result luteinizing hormone (LH) plasma concentrations decrease and ovaries or testes are not stimulated into producing sex steroids.
Many American veterinarians are now getting FDA approval to import these same implants to use them in their clients’ ferrets.
Non-surgical neutering is expected to decrease the incident of adrenal disease significantly, however, we have to keep in mind that there are still cases of disease in intact ferrets.
An advantage of using the implant is that - as I see it - non-surgical neutering is reversible. Once the drug has worn off the ferret is expected to be fertile again.
Please watch your implanted ferrets carefully when you think the implant has run its course.
If there are signs of sexual behaviour and you don’t want to breed with him or her,
it’s high time for another implant!
If the guys don’t get the implant in time females are at risk developing prolonged oestrus with deadly consequences and males become smelly and testy and may get stomach ulcers and become even testier - not nice at all.
‘Hyperadrenocorticism in ferrets’, Nico Johannes Schoemaker, Utrecht
Universiteit Utrecht, Faculteit Diergeneeskunde,
‘Gonadectomy-induced Adrenocortical Neoplasia in the Domestic Ferret
(Mustela putorius furo) and Laboratory Mouse’ M. BIELINSKA, S. KIIVERI, H. PARVIAINEN, S. MANNISTO, M. HEIKINHEIMO, AND D. B. WILSON,
Vet Pathol 43:97–117 (2006) http://www.vetpathology.org/cgi/content/abstract/43/2/97
‘Use of a gonadotropin releasing hormone agonist implant as an alternative for surgical’castration in male ferrets (Mustela putorius furo).’ Abstract, http://linkinghub.elsevier.com/retrieve/pii/S0093691X08001398
CUTTING EDGE FERRET MEDICINE
An Update on the GnRH Implants (Suprelorin)
By Stephenie Baas*
The Netherlands, February 2009
Our ferret boys Moon and Shadow were three years old last August and have had the implant since they were three months old. I am very happy with the results.
The implant is still in the experimental period. At this moment, so we do not know for sure that it will stop adrenal disease, we are pretty sure but not yet 100% positive.
What we know now is that some female ferrets can have a phantom pregnancy and can get a little aggressive until the implant kicks in. We advise keeping them away from other ferrets until the implant kicks in. Some dominant males will still be dominant despite the implant. The implant takes about 2 to 3 weeks to really start working but once it's started it seems to work well.
You do need to watch the ferrets when you think the implant has run its course because ferrets do become sexually active again. No one has tried it yet, but we presume they can also reproduce again.
There is also the stress factor to consider; ferrets playing too rough because of returning hormones. That can happen when the owner does not recognize the problem for what it is and is not quick to get a new implant. I nearly missed the signs myself. (One of my boys needed a new one within two years; the other took longer).
Stress is one of the biggest death factors with ferrets held in large groups and groups that have not been desexed. Stress causes helicobacter and helicobacter causes ulcers, and if not treated will lead to internal bleeding and death.
When Dr Schoemaker started the experiment, he started with the 2-year version, and then went to the 4-year version. He imported the implants from Australia. Then, unluckily for the experiment, the implant was legalized for dogs in Holland. This made it possible for all vets in Holland to use it. Consequently Dr Schoemaker lost his hold on the experiment because people can now go to any vet for the 2-year version. He can no longer import the 4-year version from Australia because the university has stopped his grant and the money costs were too high for him to pay himself.
So now there are only a few people who are still willing to work with him to see what the long-term effects will be. One of them is me. But we will not know for a few more years yet, what the full extent of this experiment will be but it seems very promising. We do however know that most ferrets with adrenal disease do seem to react very well to the implant, as they do for Lupron. The big difference here is that Lupron needs to be repeated every few months while the implant only has to be replaced every two years. This in itself is much less stressful for the ferret and a lot cheaper in the long run for the owner. Well if I have any more news on the implant I will keep you all informed.
*Stephenie Baas is president of ‘Stichting de Fret’ and a friend of Dr N. Schoemaker.
ALTERNATIVE TO CASTRATION AND SPEYING
(Since the end of August 2007 new and larger implants are being used!)
For some time the University of Utrecht has been engaged in research into adrenal gland tumours in ferrets and the possibility to prevent them. Earlier research has shown that castration and speying probably play a role in the emergence of adrenal gland tumours. Over the past 3 years Nico Schoemaker has tried to find alternatives to surgical castration and speying.
At the university uncastrated males are being treated with a GnRH ( gonadotropin-releasing hormone) implant. This implant suppresses the production of sex hormones. It appears that this implant works very well. The odour of ferrets with the implant is less than the odour of those who are castrated. And behaviour tests have shown that ferrets with the implant are more social than their castrated counterparts. Because of these positive results the trials will continue with privately owned ferrets.
Nico Schoemaker has a number of implants available. The implants used are registered in Australia for use in male dogs as an alternative to surgical castration. So far no serious side effects have been reported. Only in a few females who were in heat pseudopregnancies occurred (see below). The implants were effective at least for 2 years. But the new implants used since the end of August 2007 are expected to be effective longer, approximately twice as long.
In uncastrated male ferrets the treatment is simple. When the smaller implants were used blood testosterone levels were measured in summer following the implantation. With the larger implants this is no longer necessary. Dr Shoemaker will contact you asking about the odour, the size of the testicles and the behaviour of the ferret towards you and other ferrets.
We also want to test the implants on female ferrets. After inserting the implant females came into heat for one week. This is not a problem for the animal because of the short duration. Females who are already in heat at the time of implantation might suffer a pseudopregnancy. These females could then be treated with the drug Galastop ® (cost to owner). Obviously it is best to treat females before they come into heat.
It is important that you watch the vulva of your jill closely. If its size increases contact Nico Schoemaker or Hanneke Moorman.
For our European Readers
Would you like to participate?
If you are interested get in contact with the Frettenkliniek or Nico Schoemaker. We asked you make a contribution of Euro 120, - which includes consultation, health check and the implant.
5704 NZ Helmond
Nico Schoemaker en Andrea Kuijten
Afdeling Vogels en Bijzondere Dieren
Universiteitskliniek voor Gezelschapsdieren
The 'Ferret Enthusiasts of Tasmania' offer free advice on all ferret matters. We are an informal network of interested people exchanging information on feeding, housing, handling, behaviour and everything else concerning ferrets (Mustela putorius furo) in Australia. We communicate mainly by telephone and e-mail.
OUR AIM IS TO PROMOTE THE WELLBEING OF ALL FERRETS.
We are in regular contact with SAFA (South Australian Ferret Association). We also have many other interstate and overseas contacts including vets specialising in ferret health.
The 'Ferret Enthusiasts of Tasmania' (FET) are in their tenth year of continuous operation. Our service is free of charge but we would very much appreciate donations to help us to pay for posters, fact sheets, phone calls and postage.
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!!! A T T E N T I O N !!!
Prepare yourselves for the 2011 Ferret Fantastic!
26th January 2011
at the Latrobe 'Henley on the Mersey' Show. Latrobe Tasmania, of course!
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Thanks to the support of so many Ferret Enthusiasts and their ferrets THE 2010 FERRET RACES WERE AN OUTSTANDING SUCCESS. See photo under 'Downloadable Files'.
See you all in 2011!
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