Female ferrets reach sexual maturity at 4-8 months of age, typically in their first spring following birth.Female ferrets undergoing their first heat cycle may prove it to be their last heat cycle unless spayed or bred.Ferrets are induced ovulators.Induced ovulation refers to the fact that the female ferret will remain in heat or estrus until such time that they are bred or are artificially stimulated to ovulate.

Females in persistent estrus will develop estrogen toxicity.Excessive levels of estrogen effectively shut down the body’s ability to manufacture additional blood cells.This is termed a pancytopenia.Estrogen affects the hematopoietic tissue (blood producing cells), typically the bone marrow.The bone marrow is prevented from replacing worn out red blood cells with new ones, thereby causing what is termed a nonregenerative anemia.When blood levels become too low to deliver oxygen to the ferret’s body cells, death may result.

Today, most ferret producers routinely spay female ferrets before they are purchased thereby preventing the development of estrogen toxicity.When a female ferret is found to be in persistent estrus, it usually relates to a remnant of ovarian tissue being accidentally left in the abdomen at the time of the ovarian hysterectomy surgery.

Clinical signs of estrogen toxicity include anemia, weakness, swelling of the vulva and possible vulvar discharge.Severe disease may also be associated with clinical signs of bleeding secondary to thrombocytopenia (lack of platelets involved in blood clotting).Cases with concurrent thrombocytopenia may have blood in the stool (melena), or superficial hemorrhages under the skin, termed petechia or ecchymoses depending on the size of the hemorrhages.These animals may also have hair loss that is not itchy, and occurs bilaterally symmetrical (occurs relatively equally on both sides of the body).This pattern of hair loss is termed endocrine alopecia.Ferrets are typically in estrus for two months before death occurs.

A CBC or complete blood count will help in diagnosis and classification of the type of anemia that is present.

Ferrets with severe anemia may benefit from the administration of Oxyglobin®, especially if a blood transfusion is unavailable.Oxyglobin is chemically stabilized hemoglobin (the blood protein involved in oxygen transport) that will help in delivering oxygen to needy body cells when red blood cells are unavailable.The administration of 50 to 100 IU of human chorionic gonadotropin (HCG) may prove effective in reducing estrogen levels and getting the ferret temporally out of heat.HCG may be given ten or more days after the onset of estrus, with ovulation occurring 35 hours later.Clinical signs of estrogen toxicity should diminish within one week of the injection, and signs of estrus should disappear within 20 to 30 days after the injection.The only definitive treatment is the surgical removal of any ovarian tissue remaining within the abdomen.


References:

Lichtenberger, Marla DVM, Editor.Veterinary Clinics of North America, Exotic Animal Practice, Emergency and Critical Care.Volume 10. No. 2. May 2007. pp. 488-489.

Kahn, Cynthia Editor:The Merck Veterinary Manual.9th Edition. p.1475-1479.

Fox, James DVM.Biology and Diseases of the Ferret.Lea and Febiger. 1988. p186-190.