Citation Kirkpatrick JF, Lyda RO, Frank KM. Contraceptive vaccines for wildlife: a review. Am J Reprod Immunol 2011; 66: 40–50 Wildlife, free‐ranging and captive, poses and causes serious population problems not unlike those encountered with human overpopulation. Traditional lethal control programs, however, are not always legal, wise, safe, or publicly acceptable; thus, alternative approaches are necessary. Immunocontraception of free‐ranging wildlife has reached the management level, with success across a large variety of species. Thus far, the immunocontraceptive research and management applications emphasis have been centered on porcine zona pellucida and gonadotropin‐releasing hormone vaccines. Contraceptive success has been achieved in more than 85 different wildlife species, at the level of both the individual animal and the population. At the population management level with free‐ranging species, the primary focus has been on wild horses, urban deer, bison, and African elephants. The challenges in the development and application of vaccine‐based wildlife contraceptives are diverse and include differences in efficacy across species, safety of vaccines during pregnancy, the development of novel delivery systems for wild and wary free‐ranging animals, and the constraints of certain non‐contraceptive effects, such as effects on behavior. Beyond the constraints imposed by the public and a host of regulatory concerns, there exists a real limitation for funding of well‐designed programs that apply this type of fertility control.

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Non-lethal management methods are required for wild equids that are protected by law and for deer inhabiting areas where lethal controls are not legal or safe. Single or multiple inoculations of porcine zona pellucida (PZP) vaccine have been delivered to wild horses and deer by means of darts. Contraceptive efficacy in horses after two inoculations ranged from 90% to 100%, and after a single inoculation ranged from 19% to 28%. Mares given a controlled-release form of the vaccine had foaling rates ranging from 7% to 20%. No detectable changes in social organization or behaviours among treated horses occurred. Contraceptive effects were reversible after 4 consecutive years of treatment but 5-7 years of treatment resulted in ovulation failure and decreased urinary oestrogen concentrations. Among deer, two inoculations were 70-100% effective in preventing fawns, but one inoculation yielded a contraceptive efficacy of < or = 20%, with pregnancies occurring late in the breeding season; a single annual booster inoculation reduced fertility to 20% in the second year. Energy costs of extended breeding seasons were less than those resulting from pregnancy. After two years of treatment, ovaries appeared normal. These studies suggest that PZP immunocontraception can be successfully applied to certain free-roaming populations of wild horses and deer.

Summary. Ten feral mares free-roaming in Maryland, USA, were inoculated with porcine zonae pellucidae (PZP)