Seresto Flea Collars Linked to Dog and Cat Deaths Have Scientists Livid with the EPA

“What diagnosis and follow-up care is normally prescribed for a dead dog?”

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A Seresto pet collar
A Seresto pet collar
Photo: Scott Olson (Getty Images)

Scientists with the Environmental Protection Agency have called the handling of pet deaths linked to a popular flea and tick collar a “travesty” and have bemoaned how the agency is trying to “cover [its] ass for doing nothing” about tens of thousands of customer complaints, according to emails released last week. The emails were obtained by the Center for Biological Diversity, which filed a lawsuit against the EPA to obtain the documents and also has filed a legal petition to ban Seresto, a collar that uses pesticides to kill fleas and ticks on dogs and cats.

“I’ve read hundreds of FOIAs, and I’ve never read documents like this,” Lori Ann Burd, the Environmental Health Program Director at the Center for Biological Diversity, told Earther.

The EPA approved the Seresto collar, originally produced by pharmaceutical giant Bayer, in 2012. Since then, the collar has been the subject of more than 86,000 user complaints filed with the EPA, according to information on the complaint database obtained by the Center for Biological Diversity; 2,340 of those report pet deaths. Internal documents obtained by the Midwest Center for Investigative Reporting last year showed that an EPA scientist in 2018 noted that the agency had been getting reports of between 50 and 100 pet deaths linked to the collar each quarter “for the past couple of years,” and that the trend appeared to be increasing. ​​(Canada’s equivalent of the EPA declined to let Bayer sell Seresto in 2016.) Over the past few years, several investigations, including a bombshell report from USA Today, have raised public concern about the collars.


But the agency still hasn’t issued any public recalls for the collars, nor has it conducted specific investigations into these incidents. (It has, Burd said, updated its website in recent months advising owners to take off the collar if their pet shows specific symptoms.) Instead, it has said that it is “in conversation” with Elanco Animal Health, which bought the brand from Bayer in 2020, “to better characterize the nature and scale of the incident reports.”

Earther reached out to Elanco Animal Health and the EPA for comment on the released emails, and both declined to speak on the record.

The emails show how career scientists within the EPA have internally expressed concern and frustration over the agency’s public handling of the pet deaths and complaints. “I hope this time someone can blow the lid off this travesty,” wrote one staffer in an email last year.

In another 2021 exchange, EPA staff share a concern posed by a staffer at the California Department of Fish and Wildlife using Seresto collars on San Joaquin kit foxes, an endangered (and incredibly cute) fox species living in the Southwestern U.S. and parts of Mexico. One staffer asks who is the best person at the EPA to direct questions about Seresto.


“It depends if you want the real answer or just some talking points to cover our ass for doing nothing,” a scientist responded.

The emails also illustrate the agency’s black box-esque system for reporting adverse incidents—which can be heartbreaking to read. In March of last year, a citizen wrote in describing the death of her 9-year-old Maltese, which had a seizure after two months of wearing the collar and died in her husband’s arms. The staffer in charge of handling complaints responded with a form letter with general information about hotlines for pesticide complaints and veterinary care. “Please be sure to follow up with your veterinarian and provide the same information you provided to us to ensure the best diagnosis and follow-up care,” the letter reads.


“Are you kidding me?” the complainant responded. “What diagnosis and follow-up care is normally prescribed for a dead dog?”

There are no mandates for the agency to follow up or take any sort of action with these complaints, despite the tens of thousands on record. (Burd said that the EPA has estimated approximately five incidents happen in the real world for each pesticide complaint it has on file, so it’s reasonable to extrapolate that more pets wearing Seresto have been hurt or killed.)


“There’s no automatic trigger for any action,” Burd said. “It’s just like, okay, you told us, thank you so much, and that’s it.”

The implications for what’s going on extend beyond just being worried about pet health, Hurd said, and point to a worrying failure on reporting adverse pesticide effects in general.


“Every time there’s an incident, it’s going into a black box,” she said. “That for me has been the most disturbing part.”