APPLICATIONS OF PIG ZONA-PELLUCIDA IMMUNOCONTRACEPTION TO WILDLIFE FERTILITY-CONTROL

A unique application of pig zona pellucida (PZP) immunocontraception i s the control of wildlife populations. A native PZP vaccine has been s uccessfully applied to wild horse and donkey populations. A single ann ual booster inoculation was capable of maintaining contraception. Seve n consecutive years of PZP treatment in wild mares resulted in no dete ctable debilitating side effects, and reversibility of contraception h as been documented among mares treated for up to 4 consecutive years. Long-term treatment (5-7 years) is associated with some ovulation fail ure and depressed urinary oestrogen concentrations. Complex social beh aviours in horses were unaffected by treatment. PZP immunocontraceptio n has also been successfully applied to white-tailed deer, with no det ectable changes in ovarian histology after 2 years of treatment. Seven ty-four species of captive zoo animals have been treated with the PZP vaccine, with documented success in 27 species, including members of t he orders Perissodactyla (Equidae), Artiodactyla (Cervidae, Capridae, Giraffidae, Bovidae), and Carnivora (Ursidae, Mustelidae, Felidae). Im munocytochemistry studies have demonstrated a high degree of crossreac tivity between anti-PZP antibodies and African elephant zona pellucida . The need for a one-inoculation form of the vaccine has led to the in corporation of PZP into lactide-glycolide microspheres, which cause a delayed release of the PZP. PZP immunocontraception of wildlife has po tential because of (1) > 90% effectiveness, (2) the ability for remote delivery, via darts, (3) reversibility after short-term use, (4) a wi de breadth of effectiveness across many species, (5) a lack of debilit ating side-effects even after long-term treatment, and (6) minimal eff ects upon social behaviours.