Vaccine Could Help Control Feral Cat Population

UF researchers test a long-acting contraceptive on feral cats.

A study performed by University of Florida researchers could aid in the management of feral cat populations.

The researchers found that a single dose of the immunocontraceptive vaccine GonaCon controls fertility over multiple years in adult female cats.

“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,” said Julie Levy, DVM, Ph.D., lead researcher and director of the Maddie’s Shelter Medicine Program at UF.

Non-profit veterinary research organization Morris Animal Foundation funded the five-year study, which was published online in August in the scientific journal Theriogenology.

The UF researchers administered single dose vaccinations to 15 female cats and placebos to another five cats. The cats were then allowed access to a breeding male cat. All five placebo females became pregnant within seven to 28 days.

Among the cats treated with GonaCon, 93 percent remained infertile for the first year, 73 percent remained infertile in year two, 53 percent in year three, 40 percent in year four, and 27 percent in year five. Levy said researchers expected the decrease in the vaccine’s efficacy as the cats’ antibodies to the vaccine decreased.

“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,” said Joyce Briggs, president of the Alliance for Contraception in Cats and Dogs, an advocacy group for nonsurgical birth control methods in animals.

Feral cats have recently come under attack as contributors to the spread of rabies. Many wild bird advocates consider feral cats a threat to bird populations, and consider more drastic measures than feral cat sterilization necessary.

Researchers at the USDA Animal and Plant Health Inspection Service National Wildlife Research Center developed GonaCon, and the UF researchers do not have any licensing agreements with the USDA or any commercial interests in the vaccine. The vaccine is registered by the U.S. Environmental Protection Agency for use on female white-tailed deer, and it been effective with other mammal species including feral horses, bison, elk, prairie dogs and ground squirrels.

The 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 the animal’s ability to stimulate the release of these sex hormones. All sexual activity is inhibited, and the animals remain in a non-reproductive state as long as a sufficient level of antibody activity is present.

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