One-dose contraceptive for cats

U. FLORIDA (US) — A single dose of a contraceptive vaccine can make most female cats infertile for several years.

“Millions of free-roaming feral cats exist in the United States and in other countries around the world,” says lead researcher Julie Levy, director of Maddie’s Shelter medicine program at the University of Florida. “Unfortunately, their welfare is not always adequate, and they can have a negative impact on public health and the environment.



“We’re hoping this research will lead to a nonlethal method of control for feral cat populations that is less expensive, labor-intensive, and invasive than current methods, such as surgical sterilization.”

For the five-year study, published online in the scientific journal Theriogenology, 15 adult female cats received a single dose of the vaccine called GonaCon and five received a placebo. After the injections, the female cats were allowed access to a breeding male cat.

Cats injected with the vaccine remained infertile from five months to more than five years. All five placebo females became pregnant within seven to 28 days. All of the cats were adopted at the end of the study.

“A total of 93 percent of the cats treated with GonaCon remained infertile for the first year,” Levy says. “In subsequent years, we saw a steady and expected decline in infertility as antibodies to the vaccine decreased.

However, numbers were still quite high, with 73 percent of the cats remaining infertile during the second year, 53 percent in year three, 40 percent in year four, and 27 percent in year five when we ended the study.”

Although permanent sterilization is ideal, the relatively short lifespan of many free-roaming feral cats suggests that a contraceptive that blocks fertility for several years may be successful in reducing the population.

“We are intrigued by this study,” says Joyce Briggs, president of the Alliance for Contraception in Cats & Dogs, a group advocating for nonsurgical birth control methods. “Although a permanent sterilant would be ideal, a long-acting contraceptive could be an effective tool for managing feral cat populations, especially where surgery is unavailable or impractical.”

GonaCon is currently registered by the U.S. Environmental Protection Agency for use on female white-tailed deer; and has also proved successful with several other mammal species including feral horses, bison, elk, prairie dogs, and ground squirrels.

The single-shot, multiyear vaccine stimulates the production of antibodies that bind to GnRH, a hormone in an animal’s body that signals the production of sex hormones, such as estrogen, progesterone, and testosterone. By binding to GnRH, the antibodies reduce its ability to stimulate the release of these sex hormones. All sexual activity is inhibited, and animals remain in a nonreproductive state as long as a sufficient level of antibody activity is present.

The vaccine was developed by researchers at the USDA Animal and Plant Health Inspection Service National Wildlife Research Center. Researchers involved in the testing do not have any licensing agreements with the USDA or any commercial interests in the vaccine.

The study was funded by the Morris Animal Foundation.

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