Sarcoptic mange in a dog

Meegan Larsen

Animal Health Laboratory, University of Guelph, Guelph, ON. 

AHL Newsletter 2024;28(3):24.

A three-year-old Labrador retriever crossbred dog presented in early autumn for erythema and pruritus that was unresponsive to courses of antibiotics and steroids. There was severe erythema of the legs, ventrum and groin with a few dried pustules on the ventral abdomen (Fig. 1). Skin cytology showed neutrophils and rare macrophages with no bacteria or acantholytic cells. Four skin biopsies were taken from the affected ventral abdominal skin, fixed in formalin and sent to the AHL for histopathology. Microscopically there was chronic hyperplastic superficial perivascular dermatitis with hyperkeratosis, intracorneal pustules and intralesional Sarcoptes scabiei mites (Fig. 2). The severe erythema and pruritus were therefore attributed to sarcoptic mange.

Canine sarcoptic mange is an intensely pruritic contagious skin disease caused by Sarcoptes scabiei, a burrowing epidermal mite. Transmission occurs by contact with an infected dog or a contaminated object or environment. Wild canids such as red foxes and coyotes can be infected, and can also serve as a source of infection through direct contact or contact with contaminated dens. Sarcoptes scabiei is relatively host specific; however, transmission can occur to non-host adapted species such as cats or humans, generally resulting in a self-limiting pruritus that appears as a rash in human skin. Pruritus is the main clinical feature of canine sarcoptic mange. Erythema, crusts, papules and alopecia are also seen, sometimes with excoriations secondary to self-trauma. In longstanding cases there may be widespread alopecia with lichenification and hyperpigmentation. The margins of the pinnae are often the first site involved; ventral trunk (both abdomen and chest), lateral elbow and face are other commonly-affected sites. Secondary lymphadenopathy, pyoderma and Malassezia dermatitis may be present. Clinical differential diagnoses include flea allergy dermatitis and superficial pyoderma. Diagnosis may be achieved by skin scraping or fecal flotation (to detect ingested mites and eggs). Mites can be difficult to find in skin scrapings, so if the clinical suspicion is high and these tests are negative, then empirical treatment or skin biopsy are useful for diagnosis.   AHL

Figure 1. Sarcoptic mange. Erythema with crusts and multifocal dried pustules on the ventral abdomen.

Figure 2. Histologic section of the skin. Embedded in the stratum corneum of the epidermis are several Sarcoptes scabiei mites (arrows). H&E stain.