A Review of the Current Use of Gonadotropin-Releasing Hormone Vaccines for Reproductive Management of European and North American Zoo Animals
The use of gonadotropin-releasing hormone (GnRH) vaccines in free-living wildlife is well documented. There is an increasing trend of their use in zoo animals given the relative ease of delivery of these products; however, there are few published reports of GnRH vaccine efficacy in zoo species and whether successes and failures are as a result of dosage, frequency of booster vaccination, or due to variation in species physiology. Reversibility of contraception and a return to full fertility after GnRH vaccination for individuals in captive breeding programs is crucial, but mostly unknown. Using the Association of Zoos and Aquariums (AZA) Reproductive Management Center (RMC) and European Association of Zoos and Aquaria (EAZA) Group on Zoo Animal Contraception (EGZAC) Contraception Database, we reviewed the use of GnRH vaccines (Improvac®/Improvest®, GnRH conjugate vaccine, Zoetis®, Parsippany, NJ, USA) in European and North American zoos over the last 10 years. In total, 686 bouts of vaccination were recorded in 148 (56:92) individuals, comprising 47 different species. Vaccines were principally used in ungulates (88% of records), but were also used in elephants (9%), pinnipeds (1.3%), rodents (0.6%), felids (0.3%), and macropods (0.2%). Vaccines were primarily used for contraception of male (121 records) and female (386 records) animals, but also for aggression management (82 records) and for the therapeutic treatment of reproductive tract disorders (97 records). Full contraceptive reversal was documented with live births in three out of nine animals that were allowed to breed; however, several more conceived due to contraception failure or incorrect product use. The review has helped identify successful contraception as well as causes of failure and our current understanding of how best to use GnRH vaccines in different zoo species.
The authors thank the institutions that have entered their data on the EAZA Group on Zoo Animal Contraception and the AZA Reproductive Management Centre websites, information that has anonymously contributed to this study.