By Stephanie Russo The Arizona Republic
A Flagstaff, Ariz., scientist may have discovered a nonsurgical way to sterilize dogs — an advance that would revolutionize animal-shelter medicine and address many states’ canine-overpopulation problem in the process, according to one veterinary expert.
Dr. Loretta Mayer was looking for a way to artificially induce menopause in mice so they could be used to study human diseases when she and another scientist developed a drug that they realized also could be used to sterilize female dogs, removing the need for painful and expensive surgery.
Although the drug is years away from being approved by the Food and Drug Administration, Mayer will soon return to India, where she has been working to eradicate the spread of rabies in stray dogs there.
Dr. Nancy Bradley, director of medical services with the Arizona Humane Society, said previous nonsurgical sterilization products have had mixed success. But, she said, if one proved to be safe and successful, she would use it in a heartbeat.
Mayer’s path to contributing to a scientific breakthrough was not a direct one.
Mayer worked with Dr. Patricia Hoyer, an ovarian toxicologist, studying diseases common in aging women but faced an obstacle in the lab when experimenting on mice.
Mice, unlike women, never lose their reproductive capabilities. Hoyer and Mayer developed a drug they dubbed “mouseopause” that induced menopause in female lab mice by eliminating eggs in the ovaries without surgery.
By 2007, Mayer began testing ContraPest, SenesTech’s version of “mouseopause,” on rat populations that devastate rice fields in Indonesia. The drug provides an alternative to poison, which many Southeast Asian farmers use to deal with rats.
“I would really like to see us do things that improve our environment and are compassionate to other beings,” Mayer said. “My passion, without question, is to stop killing animals, however we might do that.”
Applying to dogs(AT)
Mayer, a dog lover, then developed Chemspay, a contraceptive drug for female dogs that can be administered orally or by injection. Mayer and SenesTech tested the contraceptive from 2004 to 2008 on dogs . The trials proved that Chemspay reduced the number of eggs in the tested dogs significantly, making them sterile.
Last year, SenesTech became involved in a project with the nonprofit group Humanitarian Efforts Reaching Out. The project combines rabies vaccinations with fertility control for the feral-dog population in parts of India. Mayer will return to India this December to resume her work with the group.
“This technology, if successful, will really have a huge impact on unwanted dog populations,” Mayer said. “The biggest impact will be where dogs are reservoirs for human diseases, like in India.”
Mayer is not the first scientist to develop nonsurgical sterilizing drugs for animals, and shelters will have more options once the technologies are determined to be effective and safe.
Neutersol, a sterilizing injection for male dogs, was approved by the FDA and tested in trials at the Arizona Humane Society a few years ago. It was taken off the market in 2005 because of a manufacturing disagreement and is now being marketed under another name. It is not currently available in the U.S.
GonaCon is another animal contraceptive being used on deer populations. According to the Alliance for Contraceptives in Dogs and Cats’ website, studies are determining whether the drug will work on cats and dogs.
However, Bradley, of the Arizona Humane Society, is not optimistic that any chemical sterilization, including Mayer’s Chemspay, will be deemed completely safe and 100 percent effective for at least a decade.
“There is a very long timeline in this project,” Mayer said. “Each and every one of our products takes years to develop.”
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