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The “Pill” for Strays: Nonsurgical Sterilzation

Vet Gwen Davis, who is also founder of the Puerto Rico Animal Welfare Society, used Neutersol on more than 300 stray male dogs. She found that about one in every 100 reacted with a bad inflammation at the injection site — a figure that she says might be acceptable in strays, but not in owned animals.

Then there’s the fertility-control product, ContraPest™, which was developed by the biotech company SenesTech to humanely control rodent infestations in rice-producing countries in Southeast Asia. As ChemSpay™, this product is being expanded for use in other species; ultimately, it will be used to address overpopulation of dogs and cats. The active ingredient, which is based on an industrial chemical, has been shown to cause permanent sterility in female rodents by depleting egg follicles in the ovaries without adverse effects to either the animal or the environment.

A dose of ChemSpay in the form of dog biscuits doled out over 15 days was given to 18 dogs by its co-developer and SenesTech’s chief scientific officer, Loretta P. Mayer, PhD. The dogs, who had been rescued from the Navajo reservation and subsequently adopted, were then spayed by traditional surgical procedures to analyze their ovarian egg-count levels. Each dog showed 73 percent depletion, which results in sterility in other species. However, Mayer is quick to point out that this sample does not provide conclusive proof. To get that, the dogs would have to have been artificially inseminated and then tested for subsequent pregnancies. In mice and rats, the dosing number has been reduced to three days, which is promising for other species as well.

“This isn’t a pill sitting on my desk: this is a technology based on scientific fact that we believe can be developed,” says Mayer. “We believe that anything that decreases eggs in the ovary of one mammal can also deplete them in another mammal, but that is an academic argument that hasn’t been tested yet.”

Mayer would dearly love to do that testing. In particular, she wants to see the technology further developed to be effective as a single exposure — injection, implant or biscuit. But finding the funding necessary to continue development and then get the product through the many U.S. regulatory hurdles is challenging. SenesTech has allied itself with the nonprofit rescue group 600 Million Stray Dogs Need You to bring attention to the issue and appeal to potential donors.

Wide-Angle Impact
In U.S. markets, an FDA-approved nonsurgical sterilant would likely have the most impact in shelter medicine, where it could address the still-shameful statistic of four million dogs and cats euthanized every year.

“We know from surveys that the reason some people in this country still don’t sterilize their pets is primarily cost, but also convenience, such as transportation to and from the clinic,” says Zawistowski. “We also know that even people who intend to get their pets sterilized can end up with what we call the ‘oops’ litter.” That’s “oops” as in, “Who knew a four-month-old kitten could get pregnant?” In the United States, this accounts for about threequarters of kitten births and about half the puppies.

Zawistowski envisions a return to the days when families slogged over to the local armory to stand in line for their polio-vaccine sugar cubes. Or perhaps teams of vet techs could fan out into rural areas, going door to door, offering health exams and services to companion animals. A permanent sterilant would be just one of many tools in their portable health kit. Of course, it’s in the international arena where the impact of a nonsurgical sterilant is the most critical. It has the potential to do for animal welfare what Facebook did for social interaction. That’s an idea that makes a rescuer’spulse start racing. For years, major cities around the world have resorted to mass poisonings, shootings and worse in their efforts to reduce the number of dogs on the streets. Not only are these methods barbaric, they are also ineffective.

“The field is so exciting because if an affordable, easy-to-administer product is developed, it will reach all corners of the earth and improve animal welfare in a way that we have never seen before — and really never thought would be possible,” says Levy.

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