Doing surgery in a tent on a tropical island is harder work than you’d think. It gets so hot that the sweat trickles from your surgical cap into your eyes, and when it rains on the tarp roof you can’t hear what your anesthetist is saying. I know this because I’ve worked on spay and neuter projects in the South Pacific, where I’ve gone with teams of veterinarians and volunteers to sterilize as many dogs as fast as we can.

Then, on my way to the airport to go home I’d see all the dogs we hadn’t caught, too many of them pregnant or about to be. With some quick mental math I realized that all our efforts would be negated in a year—litters of fertile pups would quickly replace the dogs we’d worked so hard to remove from the reproductive pool.

That’s when I realized the science wasn’t there—we really didn’t know how to solve the problem. Surgery takes too long and requires too much training. There ought to be a better way: after all, we’d invented contraceptive vaccines for deer, wild horses and elephants. But the study of reproductive physiology of companion animals has long been little more than an eddy in the backwater of science. Veterinary schools place far more emphasis on reproduction of farm animals and horses, and the few doing research on dogs and cats are being financially wedged out.

This is changing, not in a small way due to an organization called ACC&D (Alliance for Contraception in Cats and Dogs.) Started in 2001, ACC&D’s sole purpose has been to promote research into nonsurgical sterilization of companion animals. At first, chairman of the board Linda Rhodes said, "People didn’t take it seriously; they’d say, that’s a dream." But now ACC&D has been joined by Found Animals, the organization behind the Michelson Prize: $75 million in prizes and grants for the invention of the perfect, single dose, permanent, cheap, drug or vaccine that sterilizes both male and female dogs and cats.

Large, unregulated populations of street dogs (or feral dogs) are a global problem. For me, as a veterinarian, the issue is welfare: I hate to see starving dogs, abused dogs, dogs living precariously from one litter to the next. The issue goes beyond welfare, though; dogs impact public health as well. Dogs remain the main transmitter of rabies to people, a uniformly fatal disease. Rabies has been largely eliminated from developed nations, but it still kills 70,000 people a year in developing nations and millions more are exposed and must undergo expensive and risky post exposure treatments. Dogs are also the reservoirs for other debilitating diseases like echinococcosis, leptospirosis, leishmaniasis and visceral larval migrans.

While the Michelson Prize focuses its attention on an ideal solution, Rhodes prefers to imagine a toolbox as the goal. "A whole range of solutions might just be pretty ideal," she says, and goes on to describe several ‘tools’ that are being tested right now around the world.

First she mentions an implant, Suprelorin. Suprelorin is approved for use in New Zealand and Australia to sterilize male dogs temporarily—it suppresses GnRH, the brain hormone that sets the reproductive system into motion. Although only approved for use in males right now, it should (and reportedly does) work in females, too. Its only drawback is that the implant lasts a year at the longest. Still, said Rhodes, "A year could still have a huge impact in places like Africa." The World Society for Protection of Animals captures and vaccinates dogs for rabies every year, in part to protect wild animals from dog-transmitted rabies.

A more permanent treatment is Esterisol, a simple chemical (zinc gluconate) that, when injected into testicles, permanently destroys sperm producing cells. Since it only works on male dogs, some suspect its effectiveness will be limited, as one untreated male dog can impregnate many females. Brian Corbett, president of Ark Sciences that makes Esterisol, questions that theory. "The Esterisol treated dog doesn’t know he’s sterile," says Corbett, "and dogs are both more territorial and more monogamous than we’d thought." That boy dogs remain macho recommends Esterisol to many dog owners, many in Latin America where owners often have cultural and personal prejudices against castration.

The Michelson prize has had impact. According to Rhodes, "Since its inception (when?), scientists who’ve never thought about this area are taking a look at it." Suddenly some cutting edge solutions are being tried, like gene-silencing small, interfering RNA’s, or new vaccines based on manufactured "viruslike–particles".

But these solutions are at best 15 years away. Andrew Rowan, president of Humane Society International is not waiting—he advocates sticking to surgery, but applying it differently. "What that means is persuading local communities to pay to sterilize dogs." HSI partners with willing governments, training native veterinarians in learn rapid techniques. In Bhutan they employed 35 recent veterinary school graduates, paying them to do nothing but spays and neuters for 6 months at a time. "In 18 months we sterilized 15,000 dogs." A number that, I have to say, impressed me.

While admiring HSI’s local approach and efficiency, I still hold out hope for an ideal solution. I still believe a treatment that can be done by non-veterinarians, something cheap and easy, offers more hope for dogs worldwide. And with what I’m hearing, I think it just might be a dream that comes true.

Image credits: photos of dogs in Bora Bora and Rarotonga by Cynthia Mills.

About the Author: Cynthia Mills is a veterinarian and science writer; her work for humane canine contraception has carried her from Rarotonga to Idaho. Besides treating dogs, she has tracked and researched raccoons in Virginia, deer mice in Oregon and pandemic flu in virtual space. Her writings have been featured in Discover and Conservation and selected for the Best American Science and Nature Writing. She blogs about her travels, science and training herding dogs at An Itinerant Dog Doctor.


The views expressed are those of the author and are not necessarily those of Scientific American.