Veterinary Medicine - August 2008 - (Page 444)

CE PEER-REVIEWED Canine and feline demodicosis You know demodectic mange frequently occurs in dogs. Now it appears to be more common in cats than previously thought, and new species have been discovered. Find out the latest on diagnosing and treating this frustrating skin disease. Kathy C. Tater, DVM, DACVD, and Adam P. Patterson, DVM, DACVD D emodicosis is a common dermatosis in dogs and is now a more recognized problem in cats. Although follicular mites have been well-documented, new mite species residing in the follicular adnexa and on the surface epithelium have recently been identi ed. These newly observed species of Demodex mites have led to the identi cation of additional patterns of clinical disease. Conventional and newer miticidal therapies are available to veterinarians to treat this frustrating skin disease. CANINE DEMODICOSIS: CLASSIFICATION AND DIAGNOSIS Dogs have three recognized species of Demodex mites. Clinically, the most common is Demodex canis. This mite is limited to the hair follicle and, rarely, the sebaceous gland. The D. canis mite develops through four life stages: a fusiform egg, a six-legged larva, an eightlegged nymph, and an eight-legged adult (Figure 1). Demodex canis is part of the normal cutaneous ora in dogs. Mite numbers are kept low by a dog’s immune system. Demodex injai, the large-bodied Demodex species mite, is larger in all life stages than D. canis (Figure 2).1 Histologic examination shows that these mites tend to reside within the sebaceous glands. Cases of D. injai infection are associated primarily with a dorsal seborrheic dermatitis.2,3 A newly identi ed short-bodied Dem- odex species mite has tentatively been named Demodex cornei. Unlike the other canine Demodex species mites, D. cornei can reside in the most super cial layer of the epidermis. It is 50% shorter than the adult form of D. canis (Figure 3).4,5 The clinical signs and treatment of D. cornei so far appear to be similar to those of D. canis. Classiﬁcation and causes Canine demodicosis is separated into two categories according to the patient’s age at the onset of disease. Juvenile-onset demodicosis typically occurs in dogs less than 18 months of age. When a dog is considered an adult may vary based on its breed. Animals that develop demodicosis after the completion of physical growth and development are considered to have adult-onset demodicosis. Juvenile-onset demodicosis is further categorized as localized or generalized according to the extent of the disease. A variety of opinions exist on de ning localized vs. generalized demodicosis. We consider a dog to have generalized demodicosis if the condition involves the feet, an entire body region, or several sites; is spreading; or has persisted for at least six months. The exact pathogenesis of canine demodicosis is unknown but is suspected to be related to an aberration in the immune system. Juvenile-onset demodicosis is associated with genetics, poor nutrition, stress, and various breeds. The breeds considered to be predisposed to juvenile-onset demodicosis vary in different reports. Ultimately, any breed of dog can develop juvenile-onset demodicosis. Adult-onset demodicosis is associated with systemic diseases (e.g. hyperadrenocorticism, hypothyroidism, diabetes mellitus, neoplasia) or with immunosuppressive therapies. Thus, a full physical examination, careful patient history taking, and laboratory testing (complete blood count, serum chemistry pro le, urinalysis, microscopic Kathy C. Tater, DVM, DACVD Angell Animal Medical Center 350 S. Huntington Ave. Boston, MA 02130 Adam P. Patterson, DVM, DACVD Chesapeake Veterinary Dermatology Associates 1209 Cromwell Bridge Road Towson, MD 21286 444 August 2008 VETERINARY MEDICINE Illustration by Paul Chason

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

Veterinary Medicine - August 2008 Contents Editors' Note Leading Off ClinQuiz Idea Exchange Practical Matters Diagnosing and Treating Canine Copper-Associated Hepatopathies Canine and Feline Demodicosis CE Form Advertiser Index Product Preview Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - August 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.