The End of Rats?

As much as my friends love to hunt rats, the world would be a much better place if rats were eradicated from our cities and farms.

The good news is that this day may soon be at hand. As The Guardian notes, the work of remarkable American researcher Loretta Mayer, who went back to school at age 46.

Solving the rat problem by putting them on the pill sounds ridiculous. Until recently no pharmaceutical product existed that could make rats infertile, and even if it had, there was still the question of how it could be administered. But if such a thing were to work, the impact could be historic. Rats would die off without the need for poison, radar or coyotes.

SenesTech, which is based in Flagstaff, Arizona, claims to have created a liquid that will do exactly that. In tests conducted in Indonesian rice fields, South Carolina pig farms, the suburbs of Boston and the New York City subway, the product, called ContraPest, caused a drop in rat populations of roughly 40% in 12 weeks. This autumn, for the first time, the company is making ContraPest available to commercial markets in the US and Europe. The team at SenesTech believes it could be the first meaningful advance in the fight against rats in a hundred years, and the first viable alternative to poison. Mayer was blunt about the implications: “This will change the world.”

The article goes on to note that the The Pill for Rats was an almost accidental outcome that came out of working on a better solution for studying the effect of heart disease on women. It seems Mayer was working on a way to push rats and mice into early-onset menopause when she was contacted by a colleague.

Three years into her efforts, Mayer was contacted by Patricia Hoyer, a colleague in Phoenix, who said that she had stumbled across a chemical that seemed to make mice infertile, without having any other effects. Together, Mayer and Hoyer synthesised a new compound, which they called Mouseopause.

Shortly after Mayer and Hoyer published their work on Mouseopause in 2005, Mayer received a telephone call from a veterinarian in Gallup, New Mexico, who had read about her research. The Navajo reservation where he worked was overrun by wild dogs. There were too many to spay and neuter, so he was euthanising almost 500 a month. “If you could do for a dog what you can do for a mouse, I could stop killing dogs out here,” he told her.

Mayer describes herself as “extremely connected to animals, dogs in particular”. When she arrived in Gallup and saw the piled corpses, she agreed to test Mouseopause on an initial group of 18 reservation dogs. “I held up that first puppy, who I called Patient Zero,” she told me, “and I said, ‘I don’t know what this is gonna do to you, but you will live on a satin pillow the rest of your days.” The injection made the dogs infertile, but left them otherwise happy and healthy. (Mayer brought home all 18 dogs and built a kennel in her yard to house them until she could find homes for them with families she knew personally. Patient Zero, renamed Cheetah, lived with her until she died of old age – though the pillow was fleece.)

So the chemical that makes mice and rats sterile can work on dogs too? Fantastic! But how about if you are not injecting the drug, and simply feeding it to female rats? It turn out that when delivered in food, it was not as effective on a larger animal. But then something remarkable happened.

Eventually, out of a mix of curiosity and desperation, she fed it to both males and females. The result was dramatic. It turns out that the triptolide destroyed sperm – the males became sterile almost immediately after ingesting the formula. This was a total surprise: no one had ever tested triptolide on male rats before. It was “stunning”, Dyer told me. “Totally unpredictable.” Test after test: no pups. She sighed. “Man, you should have seen the No Pup party.” After three years of research and development, they had a product that worked and did not harm other animals. (The active ingredients are metabolised by the rat’s body in 10 minutes, which means that any predator that eats it is not affected, and the compound quickly breaks down into inactive ingredients when it hits soil or water.)

ContraPest, the finished product, is viscous and sweet. Electric pink and opaque, it tastes like nine packets of saccharine blended into two tablespoons of kitchen oil. “Rats love it,” Dyer said. “Love it.” Mayer, who taste-tested every version during the development process, could not say the same for herself.

In 2013, New York’s Metropolitan Transit Authority (MTA) reached out to Mayer after hearing about SenesTech’s early trials to ask whether the company would test ContraPest in New York’s subways as part of a citywide effort to find new, more successful alternatives to poison.

...Mayer dispatched two of SenesTech’s youngest scientists, women in their 20s, to New York in order to test whether the formula was appealing enough. Would New York rats prefer ContraPest to water or pizza? Wearing their best approximation of hazmat suits to protect themselves from the filth, the scientists patrolled the subway’s trash storage rooms under Grand Central Station. They planted bait boxes filled with feed stations of ContraPest and then stood nearby, counting the rats that came in and out with clickers in order to track how many rats were taking the bait. For six months, they baited and counted, washing their suits at the end of each day in bleach.

The two young women went home to Arizona with good news: not only did the New York rats drink ContraPest, the drink actually worked on them. The test confirmed the highest hopes of the company – there was an alternative to poison that would work, even in New York City, and they had found it.

So is this the end of rats? Not yet. This stuff will have to get EPA FDA approval sold, distributed, and used widely, but it's pretty clear that this stuff is a game changer, and maybe not just for rats, but in a different dosage, perhaps for feral dogs too. Could it work on feral cats? How about deer in areas where they are overcrowded? How about feral pigs and horses? How about people?

The mind reels at the wonderful possibilities. Even Stephen Hawking is impressed.