Non-surgical methods of contraception and sterilization.

The Humane Society of the United States estimates that each year between 8 and 10 million dogs and cats enter shelters and 4-5 million of these animals are euthanized due to lack of homes. Many veterinarians within the United States recommend surgical sterilization for population control in dogs and cats. However, there are non-surgical methods to control reproduction. Pharmacologic methods of contraception and sterilization can be safe, reliable and reversible. Hormonal treatments using progestins, androgens, or gonadotropin releasing hormone (GnRH) analogs act to either directly block reproductive hormone receptor-mediated events, or indirectly block conception via negative feedback mechanisms. Immunocontraception, via vaccination against GnRH, the luteinizing hormone receptor or zona pellucida proteins, is also possible. Intratesticular or intraepididymal injections provide a method for non-surgical sterilization of the male dog and cat. Additional methods have been employed for mechanical disruption of fertility including intravaginal and intrauterine devices and ultrasound testicular ablation. Alternative approaches to surgical sterilization will be reviewed.