Canine and feline demodicosis


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.
Aug 01, 2008

Illustration by Paul Chason
Demodicosis 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 identified. These newly observed species of Demodex mites have led to the identification of additional patterns of clinical disease. Conventional and newer miticidal therapies are available to veterinarians to treat this frustrating skin disease.


Figure 1. An adult Demodex canis mite (40X).
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 eight-legged nymph, and an eight-legged adult (Figure 1). Demodex canis is part of the normal cutaneous flora in dogs. Mite numbers are kept low by a dog's immune system.

Figure 2. An adult Demodex injai mite (40X).
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

Figure 3. An adult Demodex cornei mite (modified Wright's stain; 50X).
A newly identified short-bodied Demodex species mite has tentatively been named Demodex cornei. Unlike the other canine Demodex species mites, D. cornei can reside in the most superficial 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.