Spot-On Flea and Tick Preventives Can Harm Pets

Pet Owners Should be Aware of Dosage and Labeling Issues

Mar 18, 2010
Holly Anderson

Read Product Labels Carefully To Protect Your Pets - Benjamin Earwicker

Preventive medications applied to the neck or back of pets are effective pest control methods. However, new studies confirm that improper use has caused health problems.

The U.S. Environmental Protection Agency (EPA) is responsible for registering and monitoring the labeling and use of pesticides. "Spot-on" flea and tick preventive medications applied to the back or neck of pets are considered pesticides and come under EPA's jurisdiction.

Following review of 2008 data on illness and mortality incidents associated with the products, EPA required additional, more detailed data from all companies with current spot-on medication pesticide registrations. A team of veterinarians and toxicologists from EPA's Office of Pesticide Programs, together with members of the Health Canada Pest Management Regulatory Authority and the Food and Drug Administration Center for Veterinary Medicine, reviewed the data. Their findings confirmed labeling and dosage issues with almost all of the available products.

Summary of Findings and Conclusions From the EPA Report

The spot-on incident review report was released on March 12, 2010. The findings and conclusions are summarized as follows:

Most incidents were classified as minor, but all products were associated with at least some major incidents and some deaths.
Clinical signs included vomiting, diarrhea, excess salivation, itching, hair loss, skin ulcerations, lethargy, nervousness, ataxia, tremors, and seizures. Organ systems affected were dermal, gastrointestinal, and nervous system.
Small breed dogs were affected most often and were affected most by products containing cyphenothrin and permethrin.
Chihuahuas, Pomeranians, Shih Tzus, Dachshunds, and Bichon Frise were breeds most commonly affected.
The dose range may be too wide for some products.
Misuse or inadvertent exposure from dog products on cats is an important issue.
Label warnings against use of dog products on cats are not adequate.
The companion animal safety studies conducted for these products did not predict the toxicity reflected in the incident reports.

Understanding EPA's Findings and Concerns

EPA is not recommending that any currently-registered products be withdrawn from shelves or that manufacturing should be discontinued. EPA is also not recommending that consumers should discontinue use of any of these products.

EPA has initiated a detailed review of all registered spot-on products, current dosing guildelines, and their package labelling. The agency believes that problems revealed during the incident report review can be addressed through proper dosing and better labelling.

The scientists who reviewed the data carefully compared incident results against breed popularity statistics as reported by the American Kennel Club in order to remove any bias in the statistics created by breed popularity. Therefore, the higher incidence of illness in small breed dogs weighing between 10 and 20 pounds can be considered accurate and not affected by breed popularity. This indicates that dosing is a critical concern.

Most spot-on products currently contain wide weight ranges. In one particular product referenced in the EPA report, the lowest dose range was for dogs weighing less than 33 pounds. The next product range was for dogs weighing 33 to 66 pounds. For comparison purposes, if a 33-pound dog received the lower dose product, it would receive 1/6 the dose of a dog weighing 5 pounds receiving the same product. If the 33-pound dog received the higher-range dose product, it would receive twice the dosage of a dog weighing 66 pounds. EPA's review found that most incidents were in dogs falling in the lower half of a product's weight range. As a result, EPA is considering requiring more narrow weight-ranges associated with product dosing.

Many of the reported incidents in cats were due to intentional or inadvertent use of products designed for dogs. EPA found that packaging for dog and cat products was almost exactly the same and that warnings against using dog products on cats did not stand out from other information on the product labels. EPA also found that some dog and cat products had exactly the same name. Problems occur because cats are more sensitive to chemicals than dogs and have a decreased ability to detoxify chemicals in their bodies. As a result, EPA is considering requiring changes to these labels.

EPA is also reviewing the current standards for companion animal testing. The guidelines are intended to demostrate a margin of safety if the product is misused or overused and to serve as the basis for product labelling. Beagles were used for the initial spot-on studies and have been found to be less sensitive to pesticide toxicity than other breeds. As a result, the testing did not predict the problems that have been identified in the incident reports. EPA is currently reviewing testing standards and protocols for possible modifications.

Actions Recommended for Consumers

There are precautions that consumers should take to insure that pets are protected when using spot-on treatments:

Specifically discuss the use of spot-on treatments carefully with your vet, including verifying the proper dosage for individual pets.
Insure that dog products are not used on cats.
Use extra care with weak, aged, medicated, sick, pregnant or nursing pets.
Keep all used product packagings for reference in case of future incidents.
Monitor pet health closely and report any health incidents to your vet and to the product registrant according to the product package instructions. Encourage your vet to report any incidents through the National Pesticide Information Center's Veterinary Pesticide Adverse Effects Reporting System.

Spot-on treatments can be used safely in most pets. Increased diligence by pet owners and upcoming changes in product dosings, packaging, and labelling should insure that health incidents are reduced.