One Brand of Flea Collars Linked to Over 1,600 Pet Deaths According to 7News Boston's WHDH, one brand of flea collar is linked to over 1,600 pet deaths. The news station is reporting that the Seresto flea collars for dogs and cats have killed nearly 1,700 pets since being introduced into the market in 2012. Since then, according to WHDH, the Environmental Protection Agency has recorded 1,698 pet-related deaths and fielded around 75,000 complaints related to the collars. Nearly 1,000 of the complaints related to the collars involve injuries to or illness in humans, according to the story. According to USA Today, the Food and Drug Administration has yet to issue a warning about the collars.