Hyperoestrogenism - Ferret

Introduction

Female ferrets (jills) are induced ovulators. Ovulation occurs 30-40 hours after copulation. Failure to mate can result in a prolonged oestrus for the duration of the breeding season. The high levels of oestrogens produced may cause bone marrow suppression with leucopenia, thrombocytopenia and aplastic anaemia.

All jills develop a mild anaemia at some point during oestrus and up to 50% of jills with prolonged oestrus will develop aplastic anaemia. If animals remain in oestrus for more than 1 month they are at risk of developing hyperoestrogenism and the reduction in platelet count can lead to haemorrhage and death.

Clinical Signs

Bilaterally symmetrical alopecia around the ventrum and tail, weight loss, pale mucous membranes, tachypnoea, ecchymotic and petechial haemorrhages enlarged vulva and a serous or mucopurulent vaginal discharge.

Diagnosis

History and clinical signs are suggestive.

Haematology:

Low PCV (normal 46-61%)

Pancytopenia: non-regenerative anaemia, thrombocytopenia, leucopenia

Treatment/Prevention

PCV values can be used to guide treatment and are a good prognostic indicator.

Jills with PCV values above 25% have a good prognosis and ovariohysterectomy is the fastest way to remove the source of oestrogens. Hormone treatments such as proligestone, HCG or GnRH injections can be used to induce ovulation. Signs of oestrus will abate within 10-11 days but it might take up to 4 months for the anaemia to resolve.

PCV values between 15 and 25% hold a guarded prognosis, and supportive care such as fluids and blood products need to be put in place before any surgery is attempted. Hormone injections can also be considered.

The outlook for jills with a PCV below 15% is poor and intensive treatment including prophylactic antibiotics and multiple blood transfusions will be necessary for several months.

Prevention: Ovariohysterectomy at 6-8 months of age is recommended for jills that are not to be bred. Entire female ferrets should not remain in heat longer than a month and ovulation should be induced by mating with a vasectomised male or by the use of hormones such as a proligestone injection before the start of the breeding season.

References

Hubrecht, R. (2010) The UFAW Handbook on the Care and Management of Laboratory and other Research Animals, John Wiley and Sons

Jepson, L. (2009) Exotic animal medicine: a quick reference guide, Saunders

Lewington, J. (2000) Ferret husbandry, medicine and surgery, Elsevier Health Sciences