More About Immunocontraception

Humane Society International

  • Elephant populations can be controlled humanely. Icarus Images/iStockphoto

Immunocontraception uses the body’s immune response to prevent pregnancy. Wild female mammals are vaccinated annually, just like we receive vaccinations. A syringe and needle are attached to a dart that is shot into the female from a dart gun, either from the ground or from the air.

How it works

The female produces an egg to be fertilized by sperm from a male. In order for the sperm to fertilize the egg, it must first attach to proteins—called zona pellucida proteins—found on the outside of the egg. Scientists figured that if they could block the sperm from attaching to these proteins, it would prevent pregnancy, so they developed a vaccine using zona pellucida proteins from pigs. When the female is injected with the vaccine, her body reacts to the foreign pig proteins by producing antibodies that attach to the zona pellucida proteins on the outside of the egg, preventing sperm from attaching and thus blocking fertilization. This is the same way that vaccines work to protect us from diseases like the flu. We call this the porcine zona pellucida—or pZP—vaccine.

HSI continues to lead development of this technology, which offers a humane and safe means of controlling wild mammal populations.