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A recent report from a government watchdog could stir up new questions for pet owners about the safety of Seresto flea and tick collars for dogs and cats.

A years-long controversy over Seresto flea and tick collars for pets is flaring anew, kindled by a government watchdog report that criticizes how the collars have been regulated.

The Feb. 29 report says the U.S. Environmental Protection Agency, which regulates pesticides, including over-the-counter parasite control products for pets, has failed to determine whether the collars pose an unreasonable risk to pet health. It also enumerates a list of shortcomings in standards and procedures at the agency that need to be fixed to improve its regulation of pet pesticide products more generally.

The review was conducted by the Office of the Inspector General of the EPA. Offices of the inspector general, often shortened to OIG, are independent entities within government agencies charged with evaluating decisions and detecting waste, fraud and abuse.

The EPA rebutted the OIG top-line conclusion. In a response to an earlier draft of the OIG report, which is included in the final report, EPA said it has determined Seresto collars meet the standards of no unreasonable adverse effects when used as directed based on an extensive multi-year re-evaluation released in July. On the report's broader points, the agency said in a statement provided to the VIN News Service that it "appreciates the OIG's explicit recognition that the agency lacks the infrastructure, including proper staffing, technical expertise, and funding to better regulate these types of pet products."

The EPA itself has highlighted these deficiencies in recent years and has proposed solutions in coordination with the U.S. Food and Drug Administration, which regulates oral pet parasiticides as well as certain topical forms.

In February 2023, the agencies jointly proposed that the FDA take over the responsibility for regulating topically administered pet pesticide products for which it is better staffed and equipped. Such a handover would require legislative action and likely would take years.

Seresto collars, which are manufactured by Elanco Animal Health, release a small amount of the insecticides flumethrin and imidacloprid onto the animal's fur over months. The EPA originally granted Seresto collars a 15-year registration in 2012, which allowed the collars to be sold in the United States.

Report follows three years of controversy

If the latest report causes phone calls to veterinary clinics from clients expressing worries over Seresto collars, it wouldn't be the first time.

A USA Today article in 2020 linking the collars to hundreds of pet deaths and tens of thousands of injured animals, based on adverse incident reports submitted to the EPA, released a wave of anxiety that practitioners said translated into queries from pet owners. Environmental activists and pet owners criticized the EPA, saying it had not done enough to protect cats and dogs.

The article spawned a petition demanding the collars be pulled from the market, a class action suit against Elanco, a congressional hearing examining the regulator's actions and the EPA re-examination of Seresto's registration and the adverse incident reports.

The OIG evaluation of EPA conduct overlapped with the agency's review of Seresto.

Gaida Mahgoub, a health scientist with the EPA OIG, described the aims of the evaluation in a podcast posted to the department's website. She said that in addition to determining whether the EPA's response to complaints had provided assurance of the collars' safety, the OIG wanted to evaluate whether the EPA followed pesticide registration requirements, particularly relating to toxicological data, in its approval of the collars.

To this question, the report answered, "Not completely." While the EPA Office of Pet Pesticides adhered to some toxicological data requirements, it did not conduct "domestic animal risk assessments" for either flumethrin or imidacloprid despite having committed to doing so.

The report continued: "Furthermore, according to a long-tenured EPA scientist we interviewed, the EPA's 1998 Guideline 870.7200 for companion animal safety studies is inadequate."

The report builds on that assessment, saying the EPA was following out-of-date guidelines, relying on an adverse-event reporting system that wasn't collecting data essential for making informed assessments, and lacking standard operating procedures and measurable standards for determining whether the products could impact pet health.

The OIG recommended eight corrective actions. Four relate to a need for updated standards on pesticide registration and reviews, three are intended to improve pesticide incident reporting and one is aimed at adherence to law and regulations related to the Seresto registration process.

For the last item, the OIG wants the agency to issue amended proposed interim registration review decisions for flumethrin and imidacloprid that include domestic animal assessments among other determinations and explanations, and make them available for public review.

In its response to the OIG draft report, Michal Freedhoff, assistant administrator for the EPA's Office of Chemical Safety and Pollution Prevention, said the agency "partially agrees with OIG's conclusions and recommendations." It accepted or offered alternative fixes to all but one of the recommendations, and referred repeatedly to the proposal to transfer oversight to the FDA.

However, Freedhoff defended the EPA's assessment that the collars are safe. He said the agency's "comprehensive scientific review of Seresto pet collars" released in July was the equivalent of the "domestic animal risk assessment" called for by the OIG.

As a result of that review, the EPA decided that Seresto collars could continue to be sold with several mitigation requirements for collar-maker Elanco, including improving how it reports adverse incidents, adding new warnings to product labels such as instructions to remove the collar if adverse effects occur, and expanding outreach to veterinarians. The registration was also limited to five years, rather than the normal 15, during which the EPA will continue to evaluate incidents.

The OIG is not convinced by the EPA's contention that its review last year fulfills the OIG recommendation to demonstrate the collars pose no unreasonable risk to pet health. In a memo included in the final report, Inspector General Sean W. O'Donnell described the matter as "unresolved." He said the EPA has 60 days from Feb. 29 to provide specific actions or alternative corrective actions to address the recommendation.

Seresto critic, Elanco weigh in

Critics of the collars take the OIG's findings as vindication.

"This report exposes in disturbing detail what many of us have known all along, that the EPA's oversight of Seresto is absolutely abysmal," said Nathan Donley, environmental health science director at the Center for Biological Diversity, a nonprofit environmental organization that has been driving the effort to get the collars pulled from the market. "We urge the agency to quickly implement all the recommendations from the Inspector General's Office and finally begin to protect the public instead of neglecting its duties."

Elanco Animal Health said the report doesn't impugn the collars.

"The OIG review is a procedural assessment of EPA's process and not a substantive assessment of Seresto's safety," the company said in a statement provided to VIN News.

"EPA continues to stand by its conclusion that Seresto meets all of EPA's standards that ensure that, when used as instructed, pesticides will not cause unreasonable risk of harm. Most of the OIG findings identify recommendations to strengthen the agency's review across the pet parasiticide industry, similar to the enhanced stewardship actions Elanco has already implemented for Seresto."

Seresto collars were developed by Bayer Animal Health, which Elanco bought in 2020. The company said 41 million collars have been sold in the U.S. since 2013.

Through the controversy, most veterinarians have not voiced alarm about the collars.

Two veterinary toxicologists who spoke to VIN News when the USA Today story was published said that consumer reports, as described in the article, didn't present a consistent or coherent picture of heightened risk for a collar that is effective at protecting pets against fleas and ticks, exposure to which pose health risks of their own.

An online poll in June 2022, which garnered nearly 2,500 responses from members of the Veterinary Information Network, found that among veterinarians with patients using Seresto collars, the majority saw no adverse reactions. Of those who did see reactions, mild skin pathology was by far the most common. One respondent reported a death associated with the collar. VIN is an online community for the profession and parent of VIN News.

The American Veterinary Medical Association in 2022 opposed canceling Seresto's registration. The AVMA did not respond to a VIN News request for comment on the OIG report.