Abstract:
BACKGROUND : The native porcine zona pellucida (pZP) vaccine has been successfully used for
immunocontraception of wild horses, white-tailed deer and approximately 90 zoo species for
more than 25 years.
OBJECTIVES : To provide proof of concept and test contraceptive efficacy of pZP in African
elephants. Once completed, test the population and behavioural effects on cows in the Greater
Makalali Private Game Reserve (GMPGR). Following the GMPGR, test efficacy, population
effects, safety and reversibility in 25 reserves with populations ranging from 9 to 700 elephants.
METHOD : Histological sections were reacted with anti-pZP antibodies to provide proof of
concept. From 1996 to 2000, 21 and 10 cows were treated with pZP vaccine in the Kruger
National Park (KNP) and monitored for pregnancy. Population effects of pZP with Freund’s
adjuvants (three vaccinations in Year 1 with one annual booster) were studied on 18 cows in
the GMPGR. Another six game reserves with a total of 90 cows were added to the project. The
project was then expanded to include another 18 reserves.
RESULTS : Binding of anti-pZP antibodies to elephant zona proteins was demonstrated in vitro.
The KNP provided efficacy results of 56% and 80%, respectively. The contraceptive efficacy in the
GMPGR and additional six reserves was 100% following calving of pregnant cows. Safety and
lack of impact on social behaviour were demonstrated. In larger populations, efficacy was > 95%.
CONCLUSION : Contraceptive efficacy and safety of pZP vaccine could be demonstrated in small
to large populations. The methodology is now being implemented in approximately 800 cows
on 26 reserves across South Arica.
