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Preventing unwanted kitty litters

By Amy Ettinger

potential vaccines offer low-cost sterilization

Every year, more than 100 million feral cats are born in this country, and many must be euthanized because there are no homes for them. Sterilizing feral cats drastically reduces the number of unwanted kittens born each year, but surgery is an expensive, complicated method of contraception. Now, researchers have discovered that a single-shot vaccine could help prevent feline pregnancy for up to five years.

With Morris Animal Foundation funding, researchers at the University of Florida studied a contraceptive vaccine that can be administered just once to aid in population control. Cats can be trapped, given the shot and quickly released back into their environment.

Researchers vaccinated 15 cats with an immunocontraceptive, and after 30 months, 73 percent were still infertile. At 35 months, the vaccine was still 60 percent effective. The shot is most effective during the first two-year period.

No other low-cost, nonsurgical technologies have shown such a high efficacy in cats with only a single treatment, says Dr. Julie Levy, lead researcher. The vaccine was still effective in 27 percent of cats after five years, and researchers are now trying to up that percentage.

“It is very challenging to achieve long-term effects with a single dose of any vaccine,” says Dr. Levy, who has received multiple Foundation grants to study this issue. “We know this is a high priority because it is unlikely that feral animals can be reliably trapped for follow-up treatments.”

In another MAF-funded study, researchers at the Cincinnati Zoo are testing another vaccine, containing a slightly different protein, for immunocontraception in cats. After studying 10 felines, the researchers learned that a single dose provided contraception for six to eight months in most of the cats, and a two-dose vaccine worked for a year. The method should work for both males and females, says Dr. William Swanson, researcher at the Cincinnati Zoo.

Ana Cristina Carranza Martin, a student at Catholic University of Cordoba, Argentina, is studying the effects of melatonin on contraception. During her MAF-funded study, she was able to postpone estrus in cats by 48 days, which indicates that melatonin could reversibly and safely suppress feline estrous cycles during the breeding season.

These studies will likely lead to more cost-effective, efficient ways of sterilizing cats and reducing the feline overpopulation problem around the world.