Pesticides in Pet Products: Why Your Dog or Cat May Be at Risk

Last June Diane Bromenschenkel applied a flea-and-tick product to her English pointer, Wings, so the dog wouldn't get ticks while hunting pheasant in the tall grasslands of western Idaho. Wings, a healthy five-year-old with a sleek white coat and a chocolate brown mask, enjoyed long walks in the woods, bacon treats, and burying things in the yard. But three months after the pesticide was applied, the animal was dead.

It was just hours following the use of the product that Bromenschenkel knew something was wrong. She noticed her dog walking around in a daze. Wings was unresponsive. On the advice of her veterinarian, Bromenschenkel tried to wash off the treatment —Bio Spot Spot On Flea and Tick Control for Dogs -- but the next day Wings was still suffering.

The dog stopped eating and drinking despite the application of appetite increasers, said Patricia Pence, the veterinarian and owner of South Wind Veterinary Hospital in Nampa, Idaho, where Wings was treated. "The anorexia is a direct result of the Bio Spot," Pence said. She believes the insecticide in Bio Spot damaged the portion of Wings' brain responsible for hunger and thirst. So she inserted a feeding tube into the dog's neck and for the next three months Bromenschenkel and Wings were in and out of the veterinary hospital.

During this period, Bromenschenkel woke up every two hours at night to give Wings an injection of liquid nutrient through the neck. She spent thousands of dollars on vet bills. Despite the best efforts of Bromenschenkel and Pence, however, the damage was done. In September, Wings' kidneys failed and Bromenschenkel made the difficult decision to put her dog to sleep. In days Wings had gone from a healthy dog, running alongside horses in the Owyhee Mountains, to an emaciated wreck, chasing phantom birds in the kitchen. "What's so terrible about it is that if you had known, you would never have used it," said Bromenschenkel of the Bio Spot.

The Debate Over Pyrethroids

Wings died three months after being treated with Bio Spot flea and tick drops; her vet thinks the product damaged the part of Wings' brain responsible for hunger and thirst. Credit: Diane Bromenschenkel. Bio Spot contains a 45 percent solution of the active ingredient permethrin, a synthetic neurotoxin belonging to the pyrethroid family of chemicals. Bio Spot is one of several over-the-counter spot on (meaning squeezed on to a particular spot) anti-flea-and-tick products that consumers apply to cats and dogs between the shoulder blades and sometimes at the base of the tail. The animal's natural oils spread the insecticide over its body, making its skin and fur inhospitable to parasites. These pyrethroid-based flea and tick treatments -- from Hartz, Sergeant's, Farnam, and Bayer -- are approved for sale by the Environmental Protection Agency (EPA), and they are readily available at grocery stores, specialty pet retailers, and hardware stores. But they are also linked to thousands of reported pet poisonings, and they have stirred the ire of pet owners, the concern of veterinarians, and the attention of regulatory agencies.

Manufacturers and distributors of over-the-counter spot on treatments say the products are generally safe and effective when used properly, but they concede there are cats and dogs that either have a preexisting condition or an acute sensitivity to these treatments that leads to an illness.

The industry position, however, may dismiss safety concerns too casually. At least 1,600 pet deaths related to spot on treatments with pyrethroids were reported to the EPA over the last five years, according to an analysis of EPA pesticide incident exposure data by the Center for Public Integrity. That is about double the number of reported fatalities tied to similar treatments without pyrethroids, such as Frontline and Advantage -- although these products also have critics.