Spay and neuter procedures have revolutionised animal management programmes worldwide, and majorly benefited us all in the long run, but is it time for another infertility option?
The world’s bustling cat and dog populations, both feral and pet, are a problem. This fact isn’t earth-shattering news—it’s the reason spay and neuter techniques are endorsed by veterinarians, wildlife charities, and of course, Bob Barker.
But while these sterilisation methods come with lots of perks, there are downsides to both practices. Spay surgeries are invasive and require a few days’ recovery time. Neutering males is far easier in comparison, but still relies on general anaesthetic and a skilled operating team—often working at cost. These factors make procedures almost inevitably pricey (despite being unbelievably valuable), discouraging owners and making wide-scale implementation in feral colonies incredibly tough. Some also argue there are ethical complications associated with the operations, not to mention the whole affair is often very stressful for patients, especially if they’re coming in from the wild.
Bruce Hay heads up a lab at the famous California Institute of Technology, aka Caltech, trying to come up with a way to bypass spay and neuter drawbacks by developing a shot to essentially vaccinate against fertility. By housing DNA that stimulates the production of antibodies that neutralise the sex hormone GnRH, or Gonadotropin-releasing hormone, in an inactive virus capsule and injecting it into the muscle of mice, the team was able to halt sperm and egg production in their subjects.
‘GnRH is the upstream driver of sexual development in the gonads—a tiny 10 amino acid string identical in almost all mammals,’ says Hay. ‘Eliminating this signal is the equivalent of a spay or neuter with a shot.’
Photo by Henk Vrieselaar
Other ways of stimulating the immune system to induce infertility have been tested before, but in most instances individual responses proved too varied. But the wide scale mammalian use of GnRH, and its fundamental role in sexual development, could make it the right candidate. In fact, human GnRH trials in the US go back to 1994.
‘Basically we’re using a form of gene therapy,’ says Hay. ‘Our tagline of sorts is that if the general technology is good enough for use in humans, it should be suitable for animal use too.’
GnRH may be the right mark, but it’s really muscles cells that are the champion of this story, recognising the shot-introduced DNA and mounting an antibody defence to bind to the GnRH. And because muscle cells typically live a long time—usually only replaced when they die or are damaged—the defence will stay functional for a long time, possibly the lifetime of the animal.
Hay says they’re planning a pilot trial with the the Cincinnati Zoo—testing the shot out on their domestic cat colony, kept to study cat reproductive biology for the aid of the Zoo’s bigger feline inhabitants. Then the team will have to figure out how to alter dosages for different body sizes and species. He thinks their technique could be a breakthrough in animal population management, with a lot of outside help, money, and time. They’ve started a small biotech company to help handle some of the rollout details, like clinical trials. He says right now the magic manufacturing number to bring the price per shot down to 20-50 USD is around 1 million.