Gene therapy could curb stray cat problem

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An adult female cat participating in a study of a new non-surgical contraceptive based on viral vector delivery of a substance called feline anti-Mullerian hormone that interferes with the development of follicles within the ovaries. Cincinnati Zoo & Botanical Gardens (via New York)

For all cats who share our homes as companion animals, there exists a vast shadow world of feral cats—a vast and rapidly breeding herd.

Their lives are plagued by the threat of infectious diseases, predators and fast-moving vehicles. And they are major predators themselves, hunting millions of birds and small mammals each year.

In the United States, volunteers are particularly active in capturing cats, taking them to clinics, sterilizing them, and returning them to colonies.

However, controlling feral cat populations is costly and logistically cumbersome. Many communities, particularly in the United States and countries outside Europe, lack the veterinary and financial resources to coordinate such efforts.

“Creating an alternative to surgery has been the goal of many for decades, but no other method has proven effective,” said William Swanson, director of animal research at the Cincinnati Zoo and Botanical Gardens. ‘ said. park.

Such a method may finally come true.In a recent study published in the journal Nature CommunicationsOne shot of gene therapy prevented pregnancies in cats for at least two years. The study was very small, comparing 6 female cats that received gene therapy with 3 female cats that did not.

By limiting the study to a few cats, Swanson said, the researchers were able to extensively track each individual cat, showing estrogen and progesterone levels in 15,220 freeze-dried poop samples. They analyzed levels and examined 1,200 hours of video of mating behavior.

Birth control pills introduce genes into muscle cells that allow them to release a substance called anti-Müllerian hormone (AMH), which prevents the development of follicles in the ovary.

The researchers cautioned that more studies would be needed to validate their preliminary findings. And if large-scale studies confirm that this treatment (the first gene therapy developed specifically for animals) is safe and effective for the life of cats, it could be used to control cat populations. A veterinarian’s surgical expertise will no longer be needed, Swanson said.

David Pepin, a reproductive biologist at Massachusetts General Hospital in Boston, was initially studying AMH as a potential treatment for ovarian cancer, but decided to look at its effects on the ovaries. When he injected the hormone into mice, their ovaries shrank to neonatal size, suggesting that AMH may have a contraceptive effect.

Dr. Pepin is investigating the possibility of using AMH in people as pills or injections that need to be taken continuously, rather than as gene therapy. Most current contraceptives block ovulation, but AMH works to hasten ovulation and prevent follicular maturation.

He believes it may be useful for women who cannot take progesterone- or estrogen-containing oral contraceptives for medical reasons, or it could help women maintain fertility during cancer treatment.

“This is a hormone that we haven’t been able to work with before, and it has a lot of potential applications in women’s health,” she said.

AMH is unlikely to be used in humans as a permanent gene therapy. “But really, it’s the perfect tool for controlling cat overpopulation,” he says.

Four of the cats in the study showed no behavior indicating mating readiness, and two were allowed to mate with male cats but did not ovulate.

Dr. Pepin and feline reproductive expert Mr. Swanson, who is on the scientific advisory board of the Michelson Animal Foundation, which funded the study, said a large-scale study that could support an application to the Food and Drug Administration for approval consideration. I am planning a study. The treatment will be marketed for use in cats.

They are also testing the treatment in kittens, which can be treated from eight weeks of age, and in dogs, which have a large feral population, especially overseas.

“This is really exciting and I hope it goes well,” said Julie Levy, a veterinarian at the University of Florida School of Veterinary Medicine in Gainesville, Florida. He was not involved in this research. “Wouldn’t it be great if we could send a technician to the site to inject the cat and release it?”

The study is an example of the Michelson Foundation’s practice of “throwing a lot of money into this problem” to find non-surgical birth control methods for feral cats and dogs, according to the study, which is conducting cat research in outdoor colonies and shelters in the United States. said Professor Levy. In-state and internationally.

But she cautioned that there is still much to be learned from larger studies, including how long injections last, are they as safe as they look, and what percentage of cats can actually be saved from pregnancy. Not 100%. ”

Some point out that it may not be that easy. Autumn Davidson, a veterinarian at the University of California, Davis School of Veterinary Medicine, said the vaccine could be very valuable if it were effective, long lasting, and cheaper than spaying and neutering. rice field.

But the animals must be captured to receive the injections, and the queen bee, which is good at evading human traps, may still make population control difficult.

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