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Flagstaff company's rat contraceptive gets EPA approval

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EPA Approval

Loretta Mayer, CEO of Flagstaff-based SenesTech, holds up a test cup of the company's rat contraceptive formula, which recently received final approval from the Environmental Protection Agency. That approval means that after more than a decade of work, the company is clear to release the product commercially. 

Loretta Mayer cracked a broad smile as she took a sip of milky white formula in Flagstaff-based SenesTech’s small lab room last week.

After more than a decade of work, Mayer, the CEO of SenesTech, has a pretty good reason to be grinning.

That's because the Flagstaff biotech company has, at long last, received Environmental Protection Agency approval for the formula Mayer was holding, which acts as a highly effective contraceptive for rats.

The federal approval clears the way for the company to make its product commercially available to customers, ranging from municipalities to subway systems to restaurants.

Already, SenesTech has gained major attention for presenting a more humane, safe and environmentally friendly alternative to traps and rat poisons.

“It’s a totally different paradigm in pest management,” said Ali Applin, SenesTech’s vice president of business development.

The sweet liquid bait induces egg loss in female rats and impairs sperm development in males, reducing reproduction capacity in both genders to zero.

If females drink the bait for long enough, they’ll become sterilized for life, Mayer said, and tests show it takes as little as two weeks for the formula to start causing declines in rat litter size.

Past trials have shown that use of the bait reduced rat population numbers by up to 40 percent, Mayer said. But the population never goes to zero because, although certain rats become sterilized, others may not take up the bait as effectively and will continue to reproduce to some extent, while new animals also continuously join the population.

And that’s a good thing, Mayer said.

“Whenever you have animal and human interactions you never want to eradicate or kill, you want to balance populations and that’s what this does without poisoning our environment or poisoning other species,” she said.

Making the perfect formula

SenesTech's bait has two active ingredients: a chemical compound used in manufacturing rubber tires, polyesters and plastics; and a plant-derived ingredient used in traditional Chinese medicine. The sweet, fatty formula is a special recipe made to be extra tasty to the rodents, while the liquid delivery makes it even more appealing because rats need to drink 10 percent of their body weight in water each day, Applin said.

Creating a formula that the rats would prefer above all else was the company's first challenge, she said. But SenesTech knew it had a winning mixture after a palatability trial in New York City where the bait was set in the subway system’s large trash repositories.

Even with a constantly replenished buffet of garbage “the rats ate the bait like crazy,” Applin said.

Several aspects about the formula and the way it’s delivered make it a much safer option than rodenticides or trapping. The dosage is specific to rats, so it won’t affect larger animals that may eat the rodents or to humans or animals that unknowingly or mistakenly ingest the bait. A 165-pound person would have to ingest 2 gallons of the product every day for 15 days to reach a dose that would cause infertility in rats, according to the company’s website.

Additionally, the half-life of the bait’s active ingredients is less than 15 minutes when it enters a rat’s blood stream and they also degrade rapidly when they come into contact with water or soil. The liquid doesn't cause any observable side effects to the animals, according to the company’s website.

As an added layer of protection, the bait is dispensed in a tamper proof, weather proof, pet proof and child proof station that has entry holes just large enough for rats to enter.

Mice, wild hogs and more

The company is already testing how its formula might work on other animals, Applin said. A version of the bait formulated specifically for mice will go into trials next week, she said, adding that the company also is exploring how the formula could be used for dogs, cats and wild hogs.

In the weeks and months ahead, the company will work on getting state environmental registrations, which Applin said is usually a much faster process.

The EPA approval means production will soon ramp up at SenesTech’s east Flagstaff facility as the company eyes expansion into both national and international markets. SenesTech is already adding employees for the product launch, Applin said.

Emery Cowan can be reached at (928) 556-2250 or

“It’s a totally different paradigm in pest management.”

--Ali Applin, SenesTech vice president of business development


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Environment, Health and Science Reporter

Emery Cowan writes about science, health and the environment for the Arizona Daily Sun, covering everything from forest restoration to endangered species recovery efforts.

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