A birth control shot for cats?

Stray cats Amman, Jordan. (Credit: Alexey Komarov, Wikimedia Commons)

Stray cats Amman, Jordan. (Credit: Alexey Komarov, Wikimedia Commons)

Birth control for cats and dogs might sound like the setup for a joke, but it’s no laughing matter. There are more than 1.5 billion homeless dogs and cats in the world, suffering on the streets, being killed to stop the spread of rabies or protect wildlife, or getting euthanized in overcrowded shelters. Spay/neuter surgery can help keep pet numbers down–indeed it has made a massive impact on shelter euthanasia since the 1970s–but it’s too slow and too expensive to put a dent in the global overpopulation crisis.

That’s why scientists have been trying to come up with an alternative to the surgery for more than 20 years. They’ve been hoping to develop something like a shot or a pill–a one-time, permanent contraceptive that’s cheap and easy to administer. I wrote about these efforts in 2009, but nothing has worked–until now.

In a new study, researchers report a gene therapy approach that appears to contracept female cats for at least two years, and perhaps much longer.  The strategy delivers a gene for antimüllerian hormone, which is produced by follicles in the ovary that give rise to eggs. Cats that received the shot overproduced the hormone, which seems to disrupt the formation of their ovarian follicles, preventing ovulation. No cats given the shot became pregnant, despite spending lots of time with a willing male.

The study is small–there were only six treated cats and three controls–but experts say it’s by far the most promising progress they’ve seen towards the “holy grail” of pet contraception. If the approach proves safe and long-lasting (ideally permanent)–and if it works in dogs–it could truly revolutionize birth control for dogs and cats. No joking.

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