Today's Veterinary Practice

JUL-AUG 2017

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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38 PRACTICAL PARASITOLOGY PEER REVIEWED The extended duration of action makes the product convenient to use but may also increase the likelihood of a client forgetting to replace the collar frequently enough for optimal control. In addition, some patients (notably cats) will not tolerate wearing a collar or may develop dermatitis underneath the collar. Is Water Resistance Likely to Be an Issue? This may not be a relevant question for most cats, but many dogs swim or are bathed frequently. Oral agents (eg, spinosad, afoxolaner, fluralaner, sarolaner) are completely waterproof, as are topical agents that rely on systemic absorption and distribution (selamectin). Many topical agents may be removed by frequent bathing or water immersion or by bathing within 24 to 48 hours of application. 3,4 Agents that are fairly water resistant include indoxacarb, deltamethrin, topical fluralaner, and dinotefuran; fipronil is partially water resistant. 3,5 In my experience, imidacloprid has very poor resistance to water. The exception is the Seresto collar, in which the active ingredient still washes off but is replaced from the collar. Is the Agent Effective on Immature Fleas? Products that can kill or inhibit development of flea eggs or larvae prevent establishment of a self- perpetuating environmental population by fleas not killed by adulticides. Furthermore, the use of multimodal therapy may decrease the likelihood of the development of resistance. Some agents have inherent effects against immature stages, including spinosad (ovicidal), imidacloprid, selamectin, and indoxacarb (larvicidal). 4,6,7 Other products may incorporate insect growth regulators (IGRs), such as lufenuron (found in Sentinel [ sentinelpet.com ]), methoprene (found in Frontline Plus [ frontline.com ]), and pyriproxyfen (found in Advantage II [ bayerdvm.com ] and Vectra [ vectrapet.com ]). Is the Agent Safe to Use On or Around Cats? Pyrethroids (synthetic pyrethrins; examples include permethrin and cyphenothrin) are often incorporated into combination flea control products to provide efficacy against ticks. However, with few exceptions, most pyrethroids are extremely toxic to cats. 8 Exceptions include natural pyrethrin, flumethrin, and etofenprox. A recent retrospective work by Malik et al reported several cats with pyrethroid toxicosis. 9 In some cases, clients accidentally or knowingly treated cats with dog- only formulations. However, a few cases of toxicosis have occurred in cats that came into close contact with treated dogs soon after application. For this reason, it may be prudent to limit pyrethroid use (or use cat-friendly pyrethroids) if possible on dogs that live with cats or when using environmental treatments in homes with cats. Does the Patient Have Known or Suspected Food Allergies? All oral flea treatments available (except for Capstar) have some form of food-based flavoring. Comfortis ( comfortis.com ), Trifexis ( trifexis.com ), Sentinel Flavor Tabs, Bravecto ( us.bravecto.com ), and Simparica ( simparica.com ) contain pork protein; Sentinel Spectrum contains beef; and NexGard ( nexgardfordogs.com ) contains soy. Although individual food-allergic patients may be able to tolerate the small amount of food protein in these products, care should be taken to make sure that no other variables are changed when the product is instituted. It is prudent to avoid the use of any flavored product during a food allergy elimination diet. However, because Bravecto lasts for 3 months, this product can be given at the beginning of an elimination diet; this should provide flea control for the duration of the diet trial. Is Tick Control Also Needed? Some active ingredients are efficacious against ticks (eg, fipronil, pyrethroids, afoxolaner, fluralaner, sarolaner), whereas other products may be formulated to include agents (usually a pyrethroid) that kills ticks (Advantix [ bayerdvm.com ], Vectra 3D, and Activyl Tick Plus [ us.activyl.com ]). Are There Any Relevant Medical Issues or Concomitant Medications? Most flea control products in current use have good margins of safety. However, there are a few conditions under which certain products might be best avoided. Several oral flea control products should be used with caution in animals with preexisting seizure disorders (eg, spinosad, afoxolaner, sarolaner). 6,10,11 Oral fluralaner is normally well tolerated by dogs with seizure disorders, but there is some indication that topical fluralaner may be more problematic in these patients. 5 Concomitant use of spinosad and extralabel doses of ivermectin has been associated with the development of seizures, ataxia, twitching, and other neurologic signs. 6

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