Maintaining self-sustaining populations of elephants through captive breeding is a new goal of the Elephant Species Survival Plan. Most elephants available for breeding in U.S. zoos are nulliparous and aged, and their fertility is unknown. Endometrial hyperplasia has been noted in aged elephants, and this condition may affect their fertility. The purpose of this study was to better characterize the gross and histopathologic features of these lesions and assess the demographic distribution.
Clinical histories, necropsy reports, and endometrial samples from Asian elephants (Elaphus maximus) at least 20 yr of age that died from 1985 to 1999 were reviewed. Gross pathologic findings in all cases were similar and consisted of a multifocal to diffuse distribution of 1-2 cm diameter cysts in the endometrium. Pedunculated edematous endometrial polyps up to 10 cm in length also were present, projecting from the endometrial surface or free within the lumen. Some polyps were necrotic. Histologically, the endometrium was characterized by varying sized cystic endometrial glands lined by cuboidal to tall columnar epithelium. Other glands were present in small clusters and lined by hyperplastic endometrium. The endometrial polyps consisted of a core of edematous stroma containing clusters of cystic glands. Tissues expelled from the urogenital tract of another aged, nulliparous cow were also reviewed. These fragments consisted of necrotic tissue with ghost-like remnants of glands similar to endometrial glands. These fragments may represent expelled pedunculated endometrial polyps, which had become necrotic and sloughed.
These results indicate that aged nulliparous Asian elephants commonly develop cystic endometrial hyperplasia and that the pedunculated polyps may represent a more advanced form of this disease. Sloughing of these pedunculated polyps may be noted clinically and may offer information about the condition of a cow's endometrium. The effect of endometrial hyperplasia on fertility in elephants is unknown, but in other species large numbers of cysts can interfere with implantation. The prevalence of these lesions in aged elephants suggests that younger animals would be better candidates for breeding and that efforts should be made to clinically evaluate potential breeding cows for endometrial health.