“The agency has known about these incidents for years but has not informed the public of the potential risks associated with this product,” Karen McCormack, a retired employee who worked as both a scientist and communications officer.

U.S. Environmental Protection Agency (EPA) documents show one of the most popular fleas and tick collars have been linked to hundreds of pet deaths, tens of thousands of injured animals and hundreds of harmed humans.

Since the introduction of Seresto flea and tick collars in 2012, the agency has received incident reports of at least 1,698 related pet deaths, explained Johnathan Hettinger,  Midwest Center for Investigative Reporting. 

The EPA is responsible for regulating products that contain pesticides. However, according to Karen McCormack, a retired employee who worked as both a scientist and communications officer. “The agency has known about these incidents for years but has not informed the public of the potential risks associated with this product.”

The findings obtained from federal documents through a public record request from the Center for Biological Diversity, a nonprofit organization that watchdogs the EPA, show that overall, through June 2020, the agency has received more than 75,000 incident reports collars, including nearly 1,000 involving human harm.

Seresto contains the insecticides: imidacloprid (10%) and flumethrin (4.5%), which are released within 24 hours in small quantities into the animal’s skin and fur for months at a time.

The insecticides are supposed to kill fleas, ticks and other pests while remaining safe for cats and dogs. The data used to help Seresto’s registration was collected by the company that manufactured it, Bayer.

The majority of the research focused on each pesticide separately. However, a 2012 Bayer study discovered that they have a “synergistic effect,” suggesting that they are more toxic to fleas when used together, wrote Hettinger.

At the time of publication, Seresto Flea and Tick Collars are still available in Canada and the USA. Read the full story, which was co-published with USA TODAY at Midwest Center for Investigative Reporting.