Treatments to prevent prolonged oestrus in female ferrets, in the absence of Delvosteron

4 September 2024

Earlier this year, Delvosteron, commonly known as the ‘jill jab’ and used to chemically stop the signs of oestrus in female ferrets, was discontinued. Female ferrets that are not artificially stimulated to ovulate or mated will stay in a constant state of season and can become ill or die due to associated complications. Therefore, it’s essential to prevent prolonged oestrus and related illness. There are many alternative options to Delvosteron that veterinary professionals should be aware of, which are evaluated in an article in the latest Veterinary Nursing Journal by Anna Mercer APVN, RVN1, and summarised here.

Ferret reproductive biology

Ferrets are seasonal breeders and are stimulated to come into season by lengthening daylight hours. In the UK, the breeding season generally begins in March and can run until September. Common signs of a jill being in season are a swollen vulva, vulval discharge and an oily coat. Female ferrets are induced ovulators and will stay in oestrus until they are mated or artificially stimulated to ovulate. The persistently high oestrogen levels in unmated jills can cause hyperoestrogenism and life-threatening bone marrow aplasia, unless they are brought out of oestrus.

Alternative options to Delvosteron

  • Surgical neutering

Ovariohysterectomy (spaying) should ideally be performed when the ferret is not in season, as there is an increased risk of bleeding at that time, although successful neutering of jills in season is possible.

Neutering ferrets can make them more likely to develop hyperadrenocorticism (adrenal disease), though this can also occur in entire ferrets. To reduce this risk, surgical neutering should be done after a ferret reaches puberty, as there is a correlation between the age at neutering and age at diagnosis. The risk of hyperadrenocorticism should be discussed with clients, so an informed decision can be made.

  • Mating with a vasectomised hob

‘Sham’ mating jills with a vasectomised hob can be used to bring them out of season. Both ferrets should be in good health to reduce disease transmission risk, and the hob should be loaned from an experienced owner or reputable rescue centre. The best time to place the ferrets together is around 2 weeks into the jill’s season, and it’s important that vasectomised hobs are not used for 7 weeks after vasectomy.

There are risks of mating with a vasectomised hob, including the possibility of injuries and stress, especially if the jill is not receptive, and the induction of pseudopregnancy, causing the jill to display nesting behaviour and aggressive behaviour towards the owner.

  • Deslorelin (Suprelorin) implants

Deslorelin (Suprelorin) implants can be used in both females and males to suppress sex hormone production and bring a jill out of season. The implant, slightly larger than a microchip, can be implanted in conscious ferrets, with the use of topical local anaesthetic cream and salmon oil or whisked raw egg as a distraction, although sedation may be required in some animals. Studies have shown that the implant can suppress oestrus for 1.5-2 years when using a 4.7mg implant, and 3-4 years when using a 9.4mg implant. It’s recommended that replacing the implant every other year may be sufficient in the majority of ferrets.

Care is needed if the jill has been in season for some time, as an initial hormonal surge can occur that can prolong oestrus and bone marrow suppression, or if using the implant in an in-heat jill, if she presents with early signs of hyperoestrogenism and hypoplastic anaemia.

  • Human chorionic gonadotropin

Human chorionic gonadotropin (hCG) can be used to stimulate ovulation in ferrets, by stimulating the corpus luteum of the ovary to produce progesterone. Ovulation occurs 35 hours after administration and oestrus terminates within 7 days, followed by anoestrus and pseudopregnancy in the majority of jills. A repeat dose may be needed in some cases.

Gonadotrophin-releasing hormone (GnRH) can be administered to stimulate endogenous luteinizing hormone release. This will induce pseudopregnancy and the jill will subsequently return to season. After treatment with hCG or GnRH, medical or surgical treatment will need to be considered to prevent ovarian activity.

Take home message

There are various options available to prevent prolonged oestrus and associated illness in female ferrets. Veterinary professionals should be able to discuss treatment options with clients, taking into consideration the risks associated with each treatment, the client’s situation and duration of season in the ferret.

BSAVA related resources

Ferrets: urogenital and reproductive system disorders – in the BSAVA Manual of Rodents and Ferrets

Ferrets: biology and husbandry – in the BSAVA Manual of Rodents and Ferrets

Ferrets and hormones: an update on endocrinology and reproduction – webinar

Reference

1Mercer A (2024) Alternative treatments in the absence of Delvosteron to avoid prolonged oestrus in female ferrets. Veterinary Nursing Journal. 39 (4), 36-51. DOI: https://doi.org/ 10.56496/FXAV3117