Atlas of livestock parasites
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Demodex canis



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Canine Demodicosis

This skin disease of dogs occurs when large numbers of Demodex canis mites inhabit hair follicles and sebaceous glands. In small numbers, these mites are part of the normal flora of the skin of dogs and cause no clinical disease. The mites are transmitted from dam to puppies during nursing within the first 72 hr after birth. The mites spend their entire life cycle on the host, and the disease is not considered to be contagious. The pathogenesis of demodicosis is complex and not completely understood; evidence of hereditary predisposition for generalized disease is strong. Immunosuppression, natural or iatrogenic, can precipitate the disease in some cases. Secondary bacterial deep folliculitis, furunculosis, or cellulitis may occur, leading to a guarded prognosis.


Two clinical forms (localized and generalized) of the disease exist. Localized demodicosis occurs in dogs <2 yr old, and most of these cases, especially the nummular forms, are thought to resolve spontaneously. Lesions consist of areas of focal alopecia, erythema and/or hyperpigmentation, and comedones. Pruritus is usually absent or weak. A percentage of these cases, especially the diffuse localized forms, progress to the generalized form. Generalized demodicosis is a severe disease with generalized lesions that are usually aggravated by secondary bacterial infections (pyodemodicosis). Accompanying pododermatitis is common. Dogs can have systemic illness with generalized lymphadenopathy, lethargy, and fever when deep pyoderma, furunculosis, or cellulitis is seen. Diagnosis is not difficult, as deep skin scrapings or hair plucking reveal mites, eggs, and larval forms in high numbers. Whenever generalized demodicosis is diagnosed in an adult dog, medical evaluation to identify an underlying systemic disease should be pursued.


Nummular localized demodicosis can be lef


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