Abstract
With limited space for individual species among zoological institutions, reproduction must often be controlled and maintaining non-reproductive females is common. This is achieved either through separation from males, pharmacological contraception, or surgical sterilization; however, preventing pregnancy may have serious unintended consequences. Individual cases of cystic endometrial hyperplasia (CEH) and life-threatening pyometra in different wild canid females have been reported.1,6,9,11,12 CEH and pyometra are common conditions in older, nulliparous, intact female domestic dogs.15 A review of medical records and pathology reports of the seven managed canid species in North American zoos showed that African painted dogs (Lycaon pictus) and red wolves (Canis rufus) are at especially high risk for development of CEH and pyometra.4 Occurrence of these conditions was positively correlated with non-reproductive years and the use of deslorelin (Suprelorin®, Virbac Animal Health, Carros cedex, France) as a contraceptive agent. Suppressing the initial surge in gonadotropins after deslorelin implant placement by administering megestrol acetate, however, reduces the risk of CEH and pyometra with deslorelin use.3 Clearly, the chronic, non-pregnant state predisposes the endometrium to disease in many canid species. Observations suggest that this may also be true in other taxa, such as stingray, bats, felids, elephants, rhinoceros, wildebeest, and equids.2,8,13,14
Ultrasound has shown some promise for diagnosis of more advanced cases of CEH,5 but lacks the sensitivity to detect early stages of CEH, requires high-quality imaging, a skilled operator, and cannot detect fibrosis or inflammation, which may also cause significant subfertility in domestic canids10. Transcervical endometrial biopsy (TCEB) in domestic dogs can provide histopathological diagnoses of fibrosis, inflammation, and early stages of CEH which correlate well with full-thickness biopsy sample results from the same uteri.7 In canids, it is recommended to perform TCEB outside of diestrus to avoid potentially inducing pyometra.7 A similar technique is standard practice in fertility evaluations of domestic horses.16 TCEB also requires specialized equipment and skill, but avoids surgery and can diagnose different types of uterine pathology at early stages of disease. This promising diagnostic tool may help identify individual zoo animals in at-risk categories that have endometrial disease before obvious clinical signs are present. Targeted treatments for infectious or inflammatory conditions include systemic and local (transcervical) antibiotics and anti-inflammatory medications. Treatment for cystic endometrial hyperplasia includes suppression of estrus/diestrus, or prolongation of anestrus, followed by breeding for pregnancy on the next estrous cycle. Early diagnosis and targeted treatment of these animals may save lives and prevent more serious infertility.
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