Multi-Year Antibody Titers from a Single-Dose pZP Vaccine in Captive African Elephants (Loxodanta africana)
African elephants are locally overabundant in parts of southern and East Africa, where they often come into conflict with humans. Controlling numbers by culling is increasingly unacceptable, which leaves contraception as the most attractive option. Immunocontraception has great potential to control fertility, but conventional porcine zona pellucida (pZP) vaccines require annual boosters, which limits application to populations in small game reserves. For example, in the Makalali Private Game Reserve, South Africa, 82% of the female elephants have received pZP vaccinations annually since 2001, and 2 years after initiation of these trials, 0% population growth was achieved.1 ImmunoVaccine Technologies (IVT) in Halifax, Canada, produces SpayVac®, the only pZP vaccine with proven single-dose, multi-year contraceptive efficacy, which makes it practical and economical for broad-scale field application.2 In this study, we inoculated captive African elephants with one of two SpayVac® formulations and then followed antibody titers for several years.
Seven non-reproductive captive African elephants were given a 2-ml intramuscular injection of SpayVac®/Modified Freund’s Adjuvant (MFA) aqueous emulsion (n=3) or SpayVac®/MFA non-aqueous (n=4). Serum was collected prior to vaccination, then weekly for 2 months, bi-weekly for another 2 months, every 4 weeks for 5 months, and then annually. Serum titers of pZP antibodies were determined by ELISA. The non-aqueous vaccinates had significantly higher antibody titers than did the aqueous vaccinates (p<0.0001), and titers were sustained for several years post-vaccination. Field research to test contraceptive efficacy of the SpayVac®/MFA non-aqueous formulation is planned.
The authors thank staff at the Nashville Zoo, Cheyenne Mountain Zoo, Bowmanville Zoo, Sedgwick County Zoo, San Antonio Zoo, and Wildlife Safari for collecting samples and participating in this study. This research was supported by grants from the International Elephant Foundation and Elephant Care International.
1. Delsink, A.K., J.J. van Altena, D. Grobler, H. Bertschinger, J. Kirkpatrick, and R. Slotow. 2006. Regulation of a small, discrete African elephant population through immunocontraception in the Makalali Conservancy, Limpopo, South Africa. South African Journal of Science 102:403–405.
2. Fraker, M.A. and U. Bechert. 2007. SpayVac®—a long-lasting, single-dose pZP contraceptive vaccine for practical wildlife population control. Paper presented at the 6th International Conference on Fertility Control for Wildlife, 3–5 September 2007, York, UK.