Warm, cuddly, soft, adorkable, and overall lovable especially when they purr and act all cute. To me, as a cat mum and a cat lover at least, cats are those. But, these fluffy critters have a major problem which needs addressing: overpopulation.

In total, there are approximately 600 million domestic cats on this planet. Out of that number, 80% are stray or feral. Generally, domestic cats “breed like rabbits” and that’s why sterilization is important, especially for females.

However, I know for a fact that spaying cats, in particular, is quite the task. And, looking from a humane point of view, it’s traumatizing to some cats; mine will not be calmed down without anesthesia even during vet home-visits and will be aggressively defensive over sterile-smelling items because of her bad memory with the procedure. 

Well, thankfully, scientists have found a potential and promising new method of cat birth control. It takes the form of contraceptive injections that prevent ovulation, making it long lasting just like regular spaying. The research of this discovery was published in the journal Nature Communications.

According to corresponding and co-senior author of the study Dr Bill Swanson said that the study wanted to address the overpopulation problem of cats and dogs, and consequently euthanasia issue of these animals in shelters. “The best way to avoid euthanasia is not to have all these animals that don’t have homes,” Swanson said.

It all started from hormone experiment

This new feline contraceptive development started from a discovery in Dr David Pépin’s laboratory. 

Pépin and his colleagues were studying a hormone present in ovarian follicles, the layer of cells around a mammalian egg cell that nurtures its growth.

As a part of an experiment to learn more about the hormone’s function, Pépin’s team injected female mice with the gene that produces it. In essence, the team was giving the mice an extra dose of the naturally occurring hormone.

“Much to our surprise, it essentially shut down most ovarian activity in rodents and made them completely infertile. We thought, well, this is a very interesting tool, but what can we use it for?” Pépin said.

Then, Pépin and his colleagues learned about the Los Angeles-based nonprofit Michelson Found Animals Foundation; an organization which supports the development of nonsurgical contraceptives for cats and dogs.

They thought that they made a discovery which they’d known to be working in rodents. “It was just a matter of applying this to a new species. That’s what led us to start collaborating with Bill (Swanson),” said Pépin, who is also a co-senior and corresponding author on the new study. 

 

 

Testing on “lab cats”

For the testing, the new study tested on cats at the Cincinnati Zoo. It is home to the widest array of wild cats in North America, including lions, tigers and tiny sand cats. But not only wild cats, it’s also a research home for about 45 domestic cats.

Swanson said, “Most of them are animals that we’re using for either this study or related studies with the Michelson Found Animals Foundation. We also do a fair amount of research into cat welfare. We’re working with shelters and trying to figure out the best way to manage cats to get them to be less stressed and more healthy and more adoptable.”

The scientists in this study worked with 9 female cats. Three were in a control group while six received injections of the gene of the hormone, which were hitched to a mild virus. Then, the virus makes its way to the muscle cells, which are extremely long-lived.

According to Swanson, the DNA would basically float around. Since muscle cells last so long without being replaced, the gene would stick around as well. 

There would be no changes in the cats’ genomes when they’re given this gene. “We’re basically introducing the blueprint to make a protein, and it’s not incorporated into the animal’s DNA,” Pépin said.

 

 

Preventing ovulation

What the gene does is causing the cats’ bodies to make the hormone that prevents ovarian follicle development. When the cells around the egg don’t mature, the cats don’t ovulate and thus can’t get pregnant, as mentioned previously.

To make sure that the “gene therapy” works well on the cats, the researchers monitored hormone levels in the cats’ urine and feces three times a week for two years. They found elevated levels of the hormone more than two years after the injection. Furthermore, they brought in two male cats.

The three control-group cats all became pregnant, the six cats in the experimental group were all kitten-free.

Swanson noted that these early findings show the potential of the hormone injection as a new means of cat contraception. However, it’s too early to utilize it fully, as it may take several years for the procedure to gain the necessary approvals to widely manufacture it or make it available in veterinary offices.

“We are very optimistic that this is going to be a useful product and we’ll eventually have it approved and available, but it’s not going to happen in the next year or two,” Swanson said.

Potentially making cats future more positive

With the new potential cat birth control, more believe that domestic cats’ future will be brighter. Dr Pierre Comizzoli, in particular, is hopeful about the study’s results, mostly because of the relatively noninvasive nature of the procedure and more limited side effects. 

Comizzoli is a senior program officer for science and research biologist at the Smithsonian’s National Zoo and Conservation Biology Institute. He wasn’t involved with the study but is confident with the potential of it.

“It’s highly significant. It’s also highly innovative. Of course, the number of cats they used for the study is still limited, but those are very encouraging results,” Comizzoli said.

 

 

The need to stop overpopulation

Despite their cuteness, we must remember that cats (particularly the outdoor, feral, or stray ones) are skilled hunters. In large numbers, they’re posing great risks to wild animals such as small mammals, birds, and reptiles; it doesn’t matter if the hunted animals are under threat or not.

To protect wild animals and prevent the overpopulation problem from getting worse, people from different parts of the world have tried curbing their population by spaying and neutering. In friendlier terms, such activity is called TNR (trap, neuter, release).

In extreme cases like in Australia, due to the massive disparity between the population of feral cats and the increasingly diminishing native animals, they’re considered as pests and regularly “controlled.”

Let’s also not forget about the danger of transmitting diseases to humans, like the dreadful rabies. In risky parts of the world, more populations of cats or dogs than humans can also pose a threat, especially if the inhabitants of areas are low in education.

And, like the experts said above, while mostly done as a last resort, euthanasia in animal shelters is an issue. 

Doing it can take a toll on the vets and technicians, and it is sad to see how some of the loveliest cats and dogs must leave this world because there’s just not enough space in the shelters.

Moreover, foster homes and non-kill shelters can only do so much to contain all the cats and dogs. And even then, not everyone can adopt them.

To echo Dr Comizzoli’s words, I do hope that there will be further development of this contraception so that there will be a quicker and more humane way to curb cat overpopulation.

 

Sources

https://edition.cnn.com/2023/06/06/world/cat-contraceptives-scn/index.html 

https://ycspca.org/news-events/blog.html/article/2022/06/30/a-solution-to-cat-overpopulation-tnr