The Center for Biological Diversity filed a legal petition Thursday morning asking the U.S. Environmental Protection Agency to ban a popular flea and tick collar that has been linked to thousands of incident reports about pet and human harm. 

Seresto, a popular flea and tick collar developed by Bayer and now sold by Elanco, has faced increased scrutiny, including a Congressional inquiry and class action lawsuits, following a March story by the Midwest Center for Investigative Reporting and USA TODAY. The story found more than 75,000 incident reports of harm linked to the collar, including at least 1,698 pet deaths and almost 1,000 people harmed. The Center for Biological Diversity, a national nonprofit conservation organization that acts as a watchdog of the EPA as part of its mission to protect endangered species, obtained those documents showing the widespread harm and shared them with the news outlets.

The group’s petition, to which the EPA is required to respond, argues that the agency needs to take action to protect pets and people. Seresto has been the subject of more adverse incident reports than any other product in EPA history, according to EPA documents, yet the agency has not taken any action to inform the public of risks associated with the pesticide-based collar. The petition outlines how the EPA’s registration decisions regarding the pesticides failed to protect pets and humans.

“Every day this is on the market, someone else might get poisoned,” said Lori Ann Burd, environmental health program director for the Center for Biological Diversity.

The U.S. Environmental Protection Agency, which under federal law must decide whether the use of pesticides causes unreasonable adverse effects, did not immediately respond to a request for comment about the petition.

Burd said petitions have been filed over controversial pesticides in the past, including chlorpyrifos, a pesticide linked to brain damage in children, and tetrachlorvinphos, another pesticide often used in pet collars. The National Resource Defence Council originally petitioned to ban it in 2009. Neither pesticide has been banned, despite years of legal action.

Burd said the agency frequently ignores petitions, but organizations have a six-year statute of limitations to sue the agency to get them to respond.

The Biden administration has pledged to follow science in its decision-making and has raised concerns about Trump administration decisions that valued politics over science. 

“If this administration wants to show it’s different, this is the chance,” Burd said.

Elanco Animal Health spokeswoman Keri McGrath said in a statement the company stands by the safety of Seresto collars, and there is no medical or scientific basis to cancel the registration of the collar.

The company is “disappointed this is causing confusion and unfounded fear for pet owners trying to protect their pets from fleas and ticks,” she said.

McGrath said more than 80 countries have rigorously reviewed and approved the product, and that incident report numbers are “raw data” that cannot be used to draw conclusions on what caused adverse incident reports.

“Thorough investigation of available data has shown no established link between exposure to the active ingredients in Seresto and pet deaths,” she said.

Elanco Animal Health, a former subsidiary of Eli Lilly and Co., purchased German pharmaceutical giant Bayer’s animal health division in 2019 for $7.6 billion. In its 2019 annual report, German agribusiness and pharmaceutical company Bayer reported revenue of more than $300 million on Seresto alone. In previous interviews, Elanco has said that it has reviewed the 1,698 incident reports related to pet deaths and found no link between the collars and the deaths.

Problems with EPA approval of pesticides

The U.S. Environmental Protection Agency is in charge of regulating products containing pesticides, and conducts registration review of chemicals every 15 years. 

Seresto collars, which are supposed to work for eight months by frequently expelling a pesticide onto a pet’s fur, contain two active ingredients: flumethrin and imidacloprid. 

Imidacloprid is a member of the neonicotinoid class of insecticides, which are the most widely used in agriculture. Much of the registration focused on agricultural uses, though imidacloprid is frequently used in pet flea and tick treatments. Imidacloprid and most neonicotinoids are banned in the European Union because of their links to massive die-offs of non-target insects such as bees.

Flumethrin is a pyrethroid insecticide that is only used in one product: Seresto.

Both pesticides are in the final stages of re-approval. Many of the studies the EPA approval is based on are conducted by the company that sells the product.

The petition argues that the EPA underestimated the danger of the collar in its approval of both pesticides.

For example: 

  • Epidemiological studies of both pesticides found that when pregnant women are exposed to the chemicals, their children have an elevated risk of autism spectrum disorder. 
  • Despite a Bayer study emphasizing the two chemicals “synergy,” or the toxic effects caused by the mixing of the pesticides, the agency only looked at each chemical individually when approving Seresto.
  • In a 2017 risk assessment for imidacloprid, the agency relied on toxicity studies on rats to determine that the chemical is safe for dogs, despite studies showing that dogs are more sensitive than rats at one-seventh the dose. 
  • In a 2017 risk assessment, the EPA determined that children exposed to imidacloprid in pet collars could be at risk. However, after the assessment, Bayer Animal Health submitted two new studies that lowered the likelihood that children would be exposed. One of these studies was conducted on rats using an agricultural seed treatment, rather than a pet collar.

The petition also includes copies of a handful of complaints filed by pet owners and veterinarians about Seresto with the National Pesticide Information Center and Food and Drug Administration. 

Company maintains collar has low incident rates

Under federal pesticide laws, companies must submit incident reports associated with products to the EPA. Often, the company receives the complaint via customer service and then later forwards the complaint numbers to the EPA.

The Center for Biological Diversity argues that this leads to an underreporting of incidents, but Elanco and associated veterinarians argue it could inflate the number of adverse incident reports because the reports show correlation, not causation.

In a recent interview, Renee Schmid, a senior veterinary toxicologist at the Pet Poison Helpline and SafetyCall International, said she is “very comfortable with the safety profile with both of these ingredients.” 

Schmid said the Pet Poison Helpline has received 400 calls about Seresto in the past five years and about 9 out of 10 involve a pet ingesting the collar. Most of those pets were vomiting or had diarrhea.

Elanco recommended that the Midwest Center and USA TODAY speak with Schmid. Elanco frequently hires SafetyCall International to assess the safety of Seresto, as well as other products.

Schmid said one of her colleagues did a review of incidents related to Seresto and found that it was unlikely Seresto caused the 1,698 deaths.

“We feel the likelihood of a true fatality being due to the ingredients in a Seresto collar would be very, very low,” Schmid said.

With more than 25 million collars sold, the overall incident review rate is also low, Schmid said. In a press release, Elanco said it has an incident rate of 0.3%, meaning one-in-300 dogs has a reported issue. Most of those are hair loss, the company has said.

This story has been updated with comments from Elanco Animal Health.

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