Repro-BLOC® gonadotropin-releasing hormone (GnRH) vaccine (Amplicon Vaccine LLC, Pullman, WA) is effective at suppressing estrous cyclicity in heifers.3,8 The production of antibodies to a GnRH fusion protein neutralizes GnRH, thereby preventing follicle-stimulating hormone and luteinizing hormone (LH) release from the anterior pituitary, leading to sterility in both genders. GnRH vaccines have been evaluated as a management tool in horses, ruminants, cervids, swine, dogs, and cats.2,5-7,9 GnRH vaccination has been used in male African4 and Asian (Thomas Hildebrandt, personal communication) elephants to decrease aggression.
Repro-BLOC® was administered to a geriatric female Asian elephant for management of suspected uterine leiomyomas associated with anemia and hemorrhage, although leiomyomas are not uncommon in this species and typically benign.1 We speculated that GnRH vaccination would be effective at suppressing ovarian activity in female elephants and would thereby reduce the size of the leiomyomas and minimize the risk of further hemorrhage. Five vaccinations in increasing doses from 3 to 30 mg were administered over 20 months before efficacy was documented. Serial serum analyses showed estrous cycle suppression in association with a rise in GnRH antibody binding and a decrease in progesterone and LH. Ultrasonographic examinations were performed to evaluate uterine changes. The hematocrit normalized soon after the initial hemorrhage with no recurrence of anemia. To the authors’ knowledge, this is the first reported use of a GnRH vaccine in a female elephant. GnRH vaccination in elephants shows great potential for reversible contraception and management of uterine pathology in older females and warrants further investigation.
We would like to thank Drs. Jerry Reeves, Valeria Conforti, Dennis Schmitt, and Thomas Hildebrandt, as well as the National Zoo’s elephant keeper and curatorial staff for their invaluable assistance with this case. We would also like to thank Amplicon Vaccine for their generous donation of the Repro-BLOC® vaccine and for covering the costs of GnRH titer analysis.
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