Demodex canis: Follicle mite

General Description: The follicle mite is about 0.25mm long, with a cigar-shaped body and 8 stubby legs.

Life Cycle: The life cycle is not well known, but appears to occur continuously within the hair follicles and sebaceous glands of the dog. The mite undergoes incomplete metamorphosis, and the life cycle probably is completed in about 3 weeks.

Location: Within the hair follicles and sebaceous glands.

Geographical Distribution: Widespread, but exact distribution is unknown.

Significance: The follicle mite is irritating, but is of unknown prevalence. Demodex occurs most frequently in young dogs or those already in poor condition. Demodectic mange is generally the most common type of mange in dogs, after sarcoptic mange. The generalised form of demodectic mange is prevalent in some purebred dogs and is usually fatal.

Effect on Host: Irritation from the follicle mites causes hair loss and thickened, wrinkled skin. Large abscesses usually develop in infested dogs from bacterial invasion of the enlarged follicles. Itching may cause further damage and loss of appetite. The mange lesions may coalesce and involve the entire body. Such generalised infections are often fatal. Infested dogs will scratch and rub.

Diagnostic Information: The mites may be seen in microscopic examination of skin scrapings.

Control: Demodex is very difficult to eliminate. Heavily infested animals should be on a good diet and dipped repeatedly in miticides. If a pregnant bitch is heavily infested, it may be advisable to remove her newborn pups and place them on a foster mother or on a hand-feeding regimen. Compounds with systemic activity, such as ivermectin, are usually most effective against this mite. One theory holds that all dogs are infested with Demodex canis but the infestation becomes pathogenic only under certain circumstances, such as stress, immunosuppression of malnutrition.

Demodex – adults		Demodectic mange showing thickened skin on muzzle		Demodex in skin section