Veterinary Medicine - November 2008 - (Page PD9)

A PRACTICAL PARASITE PLAN IMAGE: GETTY IMAGES FOR PRURITIC PATIENTS John C. Angus, DVM, DACVD Animal Dermatology Clinic, Pasadena, Calif. Many diseases can cause pruritus; however, a short list of ﬁ ve common conditions cause most clinical cases: atopic dermatitis, adverse food reaction, parasitism, pyoderma, and Malassezia dermatitis. Skin infections with bacteria and Malassezia are usually secondary to atopic dermatitis, adverse food reactions, or parasitism. Therefore, veterinarians have two goals for pruritic patients: manage primary disease and eliminate secondary infections. This article focuses on how parasites and parasite hypersensitivity cause pruritus and provides the busy practitioner with tips to help improve diagnosis, treatment, and client interactions. Perform parasite treatment trials to rule out occult parasitism. Heavy parasite burdens cause direct damage to the skin inducing pruritus, excoriation, and infection. Identifying the causative parasite is not generally difficult in heavily parasitized patients. However, in many patients, clinical signs result from hypersensitivity reactions to small parasite burdens rather than direct damage. Hypersensitivity is most commonly associated with flea, Sarcoptes, Cheyletiella, or Otodectes infestations. Classic distribution patterns for these parasites should trigger recognition; however, because patterns are variable, always consider occult parasitism, even if classic patterns are absent. Make every effort to ﬁnd parasites during the initial evaluation. This provides a deﬁnitive diagnosis, spares discussion of food trials and allergen testing, and improves client acceptance. However, failure to demonstrate parasites does not rule out parasite hypersensitivity. Treatment trials are easy diagnostic tests to eliminate the possibility of parasitism before pursuing more complicated testing for atopy or adverse food reactions. Failure to eliminate occult parasitism results in ongoing clinical disease and frustration. There is minimal risk and potential for maximal gain if parasites are the cause and are appropriately treated. Prescribe safe and eﬀective miticides for parasite treatment trials. For parasite treatment trials, prescribe an effective miticide and reapply during the full life cycle of the parasite to ensure adequate treatment of all life stages. Because subclinical carrier animals can perpetuate low parasite burdens, all animals in the household must receive treatment at the same time as the affected animal, even if these animals show no signs of pruritus or parasitism. Selamectin administered every two weeks for three treatments is a common protocol for Sarcoptes and Otodectes in dogs and cats. Off-label use of ivermectin at 200 to 600 ug/kg once weekly for four weeks is also widely used to treat canine Sarcoptes. Certain breeds commonly carry a gene mutation that increases the risk of neurotoxicity from ivermectin at this dosage. However, any individual dog of any breed can be ivermectinsensitive. Since consequences SPONSORED BY PFIZER ANIMAL HEALTH 9

Table of Contents Feed for the Digital Edition of Veterinary Medicine - November 2008

Veterinary Medicine - November 2008 Contents Leading Off Editors' Guest Just Ask the Expert Letters Practice Makes Perfect Clinical Exposures Practice Matters Idea Exchange Author Guidelines A Challenging Case: Esophageal Leiomyoma in a Dog Osteoarthritis in Cats: What We Now Know About Recognition and Treatment Product Preview CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - November 2008

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