Veterinary Medicine - November 2007 - (Page L6)

FLEA BITE FACTS Q&A Flea Trax I Efficacy and residual activity of topical products can depend on: • Level of infestation • Hair coat length and density • Where the pet’s weight falls within the unit dosing range • Exposure to water • Active ingredient’s chemistry and formulation. I If the above variables are present, veterinarians often increase the frequency of topical product application or combine different products. efficacy and residual activity during product use by clients. Efficacy and perception of product performance are also affected by challenge rates. Heavier environmental infestations result in higher numbers of fleas challenging the animal and a greater likelihood that fleas will survive the effects of the flea control products. Veterinarians often recommend increasing the frequency of application of topical products if one or more of the above variables might be affecting efficacy and residual activity. Veterinarians and clients should be aware that certain product labels prohibit deviation from the recommended frequency of application. Orally administered products that work via systemic routes are unaffected by wetting and bathing of pets. Dr. Terese DeManuelle: From a clinical perspective, it appears that in heavy flea burdens, the flea treatment needs to be applied more frequently than the label instructions indicate. Usually, I recommend a topical flea medication twice monthly rather than monthly for my patients. In addition, for dogs with severe flea loads, I may also utilize a permethrin flea spray with an insect growth regulator that has a repellent effect (e.g., Knockout—Virbac; dogs only) combined with a similar environmental treatment. Ihrke: In northern California, the Sacramento Valley, and the San Francisco Bay area, we find that monthly topical spot-on products seem to lose their efficacy after the first three weeks of application. Consequently, we commonly use these products in an off-label manner, recommending their reapplication every three weeks. In my experience, all of these spot-on products tend to have diminished efficacy if the dog is bathed or swims. Medicated shampoos are more likely to strip these spot-on products off an animal and diminish efficacy considerably. Griffin: The efficacy of flea products is determined by the product’s ability to kill fleas, which generally happens within 24 hours. The reported efficacy is generally lower the more time passes after application. For heavy infestations, a product with 100% efficacy from Day 1 to 21 following treatment and 97% efficacy at Day 30 allows 3% of fleas to survive for greater than 24 hours at Day 28. If the dog is exposed to 10 fleas on Day 30, that may not be enough to cause a break in flea control or the dog’s clinical signs. But the same dog exposed to 1,000 fleas now has 30 fleas survive for more than 24 hours, potentially biting the dog repeatedly over that time and laying eggs, so a break in the flea control is realized. In addition, for flea allergic dogs, even 100% efficacy at 24 hours may allow too many flea bites if the dogs are exposed to a heavily infested environment. Obviously, it is best to reapply products so that efficacy is still 100% in areas with heavy flea infestations that cannot be avoided. What determines the severity of flea allergy dermatitis in affected patients? Do flea numbers and speed of flea kill affect the severity? 4 Blagburn: The severity of flea allergy dermatitis is affected by the number and frequency of fleas feeding, individual pet responses to flea allergens, other concurrent allergic responses, 6

Table of Contents Feed for the Digital Edition of Veterinary Medicine - November 2007

Veterinary Medicine - November 2007 Contents Leading Off The Veterinary Medicine Interview: Dr. Lila Miller Clinical Exposures Idea Exchange A Challenging Case: Uveitis and Secondary Glaucoma in a Cat Is it Immune-Mediated Neutropenia? Pimobendan Treatment in Dogs with Congestive Heart Failure CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller Special Supplement by Lilly: Flea Bite Facts Q&A

Veterinary Medicine - November 2007

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