CHAPTER 19 DEMODICOSIS (CANINE AND FELINE) 297
Demodex cornei: short-bodiedDemodexmite; not considered a separate species: rep-
resents a morphologic variant ofD. canis;often more found more superficially
(Figure 19.2).Demodex injai: large-bodiedDemodexsp; resides in the sebaceous glands; often asso-
ciated with a seborrheic dermatitis along the dorsal midline; most often identified in
West Highland white terriers and wire-haired fox terriers (Figure 19.3).Cats
Demodex cati: similar in appearance toD. canis; resides in the hair follicles and seba-
ceous glands (Figure 19.4).
Demodex gatoi: resides in the stratum corneum layer of the epidermis; considered
potentially contagious; may cause a hypersensitivity reaction; frequency of occur-
rence differs by geographic location (Figure 19.5).Demodex felis(unnamed in some publications): presumed to reside in the hair follicle
(undetermined).
SIGNALMENT/HISTORY
Dogs and rarely cats.
Increased incidence in purebred dogs: American Staffordshire and Staffordshire bull
terriers, Chinese shar-pei, Boston terrier, West Highland white terrier, and French and
English bulldogs.Reported increased incidence in Siamese and Burmese cat breeds.
Categorized as:
Juvenile onset
Adult onset
Localized
Generalized.
Juvenile onset less than 18 months of age.
Localized: usually in young dogs; median age 3–6 months.
Generalized: both young and old animals; defined as involving the feet, an entire body
region, or several remote sites; persistent or progressing.
Dogs
Exact immunopathologic mechanism unknown.
Studies indicate that dogs with generalized demodicosis have a subnormal percentage
of IL-2 receptors on their lymphocytes and subnormal IL-2 production.
Serum insulin-like growth factor 2 (IGF-2) is elevated in dogs with generalized
demodicosis; IGF-2 is associated with regulatory functions of B and T cells.
Genetic factors, immunosuppression, and/or metabolic diseases may predispose
to disease development, including endocrinopathy, lymphoma, and autoimmune