The U.S. Environmental Protection Agency (EPA) is calling for an array of changes in the way spot-on pet flea and tick prevention products are tested, labeled and monitored, following a 10-month evaluation of health problems, including deaths, associated with use of the products.

In a 90-minute Webcast Wednesday that was open to the public, agency officials acknowledged that the numbers and types of “adverse incidents” reported by pet owners in recent years warrant action by the government. The EPA published its proposals in today's Federal Register and will take public comment for 60 days. Officials could not predict when labeling and other product changes might take effect.

“The bottom line is that the (EPA’s) Office of Pesticide Programs believes it is necessary to make significant changes in how we regulate pet spot-on products,” said Lois Rossi, director of EPA’s pesticide registration division.

The flea and tick killers are known as “spot-on” products because they come as liquids that are dabbed onto the skin of a pet’s back, usually between the shoulders. The products typically are applied once a month during flea and tick season to prevent infestations.

Most spot-ons, which as a class were introduced more than a decade ago, are considered highly effective in controlling parasites that can transmit disease as well as cause discomfort to pets.

However, the EPA, which regards the products as pesticides, became concerned about safety when the number of “adverse incidents” reported shot up 53 percent between 2007 and 2008.

In 2008, 44,000 incidents were reported. That equaled one incident for every 6,136 doses sold (a total of 270 million doses were sold that year).

The majority of incidents were classified as minor — along the lines of skin irritations that resolved quickly — but all products were associated with deaths and other major incidents, as well, said Dr. Kit Farwell, a veterinarian and toxicologist in the EPA’s Health Effects Division.

The organ systems affected were dermal, gastrointestinal, neurological, ocular and respiratory — the last two only rarely, Farwell said.

The EPA’s analysis, conducted with input from the U.S. Food and Drug Administration’s Center for Veterinary Medicine (FDA CVM) and Canada’s Pest Management Regulatory Authority, looked at 21 different products registered by Bayer, Fort Dodge (now Pfizer), Hartz, Merial, Pet Logic, Sargeants, Summit VetPharm and Wellmark. Reports on each are posted on the EPA's Web site.

The evaluation did not identify particular ingredients nor specific product lines as the problem. “I don’t believe there’s necessarily one group of products that’s safer than another,” said Farwell, who led the scientific review.

Rather, problems apparently were shared among the whole class of spot-ons. Among the issues the agency identified:

Products designed for cats and products designed for dogs need to be better differentiated from one another. In particular, cats being exposed to dog products is “a big problem, and label warnings are not effective,” Farwell said.

The problem is twofold, he said: “Not only are cats getting a larger dose (due to their typically smaller size), but cats are more sensitive to a lot more chemicals.”

In some cases, cats were treated directly with products made for dogs; in other cases, cats were exposed to dogs that had been treated. Officials advised keeping cats away from dogs for a period immediately following treatment.

For the future, the EPA is proposing a prohibition on using the same brand names on cat and dog products. That would apply even to formulations that are safe to use on cats and dogs alike, said Kimberly Nesci, an EPA Registration Division official.

"What we want to do is put out to the public a message that dog products should never be used on cats,” Nesci said. “We want that message to be universal.”

Dosages may be assigned to too broad a range of weights, the EPA stated. Consumers typically choose a spot-on treatment based on the species and weight of their pet. As an example, the product Frontline Plus for Dogs comes in four dosage sizes: for dogs 22 pounds and less; dogs between 23 and 44 pounds; dogs between 45 and 88 pounds; and dogs between 89 and 132 pounds.

Farwell said that in some cases, animals at the low or high end of their weight range may be receiving too much or not enough of a dose. Nesci said the agency is considering labeling and/or packaging changes that would result in narrower weight ranges.

Spot-on treatments are not monitored by the government once their registration has been approved. Unlike drugs approved by the FDA, the officials said, flea and tick treatments do not undergo post-market surveillance. The EPA said it would like to grant conditional registrations for new products, which would give the agency an opportunity to monitor the safety of products after they go to market.

Safety testing required before products are registered may be inadequate. Specifically, Farwell said the beagle is the standard laboratory animal used for companion-animal safety studies, but that breed is not sensitive to spot-on products. “The beagle is not the appropriate animal,” he said. He did not say what changes, if any, the agency would propose on testing protocol.

The EPA said it also will pursue whether inert ingredients may be contributing to adverse reactions.

Meanwhile, pet owners are advised to continue using flea and tick treatments as needed and to follow existing label instructions.

Information and updates on the EPA’s ongoing evaluation of spot-on products is posted at http://www.epa.gov/pesticides/health/petproductseval.html.

EPA officials involved with the evaluation can be reached by e-mail at pets@epa.gov