Exotis ISSN 2398-2985

Ferrets

Prolonged estrus

Synonym(s): Persistent estrus or heat, Hyperestrogenism

Contributor(s): Cathy Johnson-Delaney, David Perpinan

Introduction

  • Cause: female ferrets are seasonally polyestrous and induced ovulators, remaining in estrus until they are mated or for as long as daylight lasts longer than 12 h.
  • Signs: alopecia, vulvar swelling, pale mucous membranes.
  • Diagnosis: history and clinical signs, hematological profile.
  • Treatment: administration of hCG, GnRH or a deslorelin implant; ovariectomy/ovariohysterectomy
  • Prognosis: good in ferrets with a PCV of >25%; fair to guarded in ferrets with a PCV of <25%.
  • Persistent estrus is a well-known endocrine condition that affects sexually mature, non-neutered female ferrets.
  • It is characterized by elevated concentrations of feminizing sex hormones such as estradiol, estriol and estrone that may result in pancytopenia.
  • Hyperestrogenism due to prolonged estrus is relatively rare in the United States and other countries where most ferrets are surgically neutered when they are 5-6 weeks of age.

Pathogenesis

Etiology

  • Female ferrets are seasonally polyestrous (breeding season lasts from March to August) and induced ovulators. As a result, they remain in estrus until they are mated, or for as long as daylight lasts longer than 12 h.
  • The prolonged estrus and associated hyperestrogenism may subsequently result in an estrogen-induced bone marrow suppression of the erythroid, myeloid and megakaryocytic cell lines, and thus pancytopenia.
  • As a result, females are at risk of developing life-threatening anemia Anemia overview Aplastic anemia and blood loss due to thrombocytopenia if estrus persists over longer periods of time.
  • On occasion, hyperestrogenism may also be encountered in neutered ferrets of both genders as a result of hyperandrogenism Hyperadrenocorticism/hyperandrogenism, or in females with remnant ovaries or ovarian tumors.
  • Bone marrow suppression associated with hyperandrogenism is generally mild.
  • Females with ovarian remnant syndrome could potentially develop prolonged estrus.
  • Not all females in estrus that have not been mated will develop prolonged estrus:
    • In those where prolonged estrus is seen, approximately 50% will develop aplastic anemia Aplastic anemia.
    • Overall, it has been reported that 30% of females in estrus will die in a reproductive season if no male is available for copulation and no treatment is done in females with prolonged estrus.

Predisposing factors

General

  • Entire female.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Van Zeeland Y R A, Pabon M, Roest J & Schoemaker N J (2014) Use of a GnRH agonist implant as alternative for surgical neutering in pet ferrets. Vet Rec 175 (3), 66 PubMed.
  • Bernard S L, Leathers C W, Brobst D F & Gorham J R (1983) Estrogen-induced bone marrow depression in ferrets. Am J Vet Res 44 (4), 657-661 PubMed.

Other sources of information

  • Schoemaker N J & van Zeeland Y R A (2017) Disorders of the Endocrine System. In: Ferret Medicine and Surgery. Ed: Johnson-Delaney C A. CRC Press, USA. pp 191-218.


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