Is Single Injection Sterilization of Male and Female Animals in Our near Future?

There is currently a vaccine that causes the animal’s immune system to produce antibodies that block gonadotropin-releasing hormone (GnRH). This hormone is required for egg and sperm development. By blocking both egg and sperm development the vaccine is effective for male and female animals. Unfortunately, like other vaccines, the immune response will decrease over time and revaccination may be required.

Scientists at the California Institute of Technology have created an injection that causes mouse muscles to produce hormone-blocking antibodies. If the same injection works for cats and dogs then it could be used on pets and feral animals to assist population control. Current sterilization procedures are often limited to surgical procedures. The cost and invasiveness of surgery can often prevent pets and stray animals from being sterilized. In 2014, nearly 2.7 million dogs and cats were euthanized in America's shelters. An easier method of animal sterilization will help save lives.

The researchers created a piece of DNA and put it inside inactive virus shells. When injected into mice the muscles begin producing anti-GnRH antibodies. Muscle tissue is long lasting and could produce antibodies for more than ten years and would therefore not require revaccination in certain animals. This injection takes two months for efficacy to be reached. Biologist Bruce Hay said, “That 2-month delay is because of how long it takes the muscle to start producing enough antibody. Going forward, one goal is certainly to try other systems that wouldn’t have that time lag.”

Using a similar approach (injecting modified DNA) the eggs of female mice can become impenetrable by sperm. The benefit of this approach is that the hormone levels and males and females will remain the same which can be behaviourally beneficial. Hay said, “There might be some instances in wild animals where you just want to inhibit fertility but not disrupt an animal’s behavior.” Researcher, Dr. Robert McCarthy performed a study that suggested that feral cat population control is likely to be much more effective if reproductive hormones remain intact.

Cincinnati Zoo and Botanical Garden Director of Animal Research, William Swanson said, “This looks incredibly promising. We’re all very excited about this approach; that it’s going to be the one that really works.” Swanson will be testing the DNA injection approach in cats. Swanson said, “The challenge is always moving between species.” If the injection works it could change the way we control feral cat populations. “We have to figure out how to control these populations without being harmful to individual cats. And this kind of lifelong contraception might be a safe, effective way to do that,” said Swanson.

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