Symptoms of Demodectic Mange (Demodex) in Dogs

1 Demodectic Mange in Dogs: Symptoms and Forms

The mite that causes disease in dogs is called Demodex canis. These mites live in hair follicles and sebaceous glands, feeding on cell debris. Once off the dog, they do not survive long, about an hour. The entire Demodex life cycle is 25 to 30 days, completed on the host. The process has four stages: spindle-shaped eggs, six-legged larvae, eight-legged nymphs, and eight-legged adults. The pathogenesis of mite overgrowth is not fully understood. Most animals have very few mites. In infected animals, the mites multiply heavily within the follicles.

Symptoms of canine demodicosis. Skin signs that suggest demodicosis include red spots, papules, pustules, patches of hair loss, blackheads, dandruff, and excessive skin pigmentation. Itching may or may not be present.

Some dogs with demodicosis do not lose hair but show itching. So these dogs are easily misdiagnosed with allergy. Demodectic lesions concentrate mainly on the face and feet.

Main clinical forms fall into two distinct types: juvenile-onset (under 2 years) and adult-onset (over 2 years).

Juvenile-onset demodicosis. The juvenile type is further divided into localized and generalized demodicosis. Prognosis and treatment vary by individual. Some breeds have higher incidence, including Afghan Hounds, Boston Terriers, Boxers, Dalmatians, Chihuahuas, English Bulldogs, Doberman Pinschers, American Bulldogs, German Shepherds, Old English Sheepdogs, Shar-Pei, American Staffordshire Terriers, and Great Danes.

Localized demodicosis. In this case, only one body area is affected, based on skin scraping results. This type is usually benign and self-resolving, and may include one to several localized red, scaly bald spots. Affected areas concentrate on the face and feet. In addition, bacterial infection may be present, causing pustule outbreaks.

Localized demodicosis usually has a good prognosis, because over 90% of affected dogs resolve on their own within 3 to 8 weeks.

Generalized demodicosis. In this type, lesions exist in multiple body areas. Dogs with pododemodex (foot mites) are classified as generalized. This type has breed predisposition. Affected breeds include Pit Bulls, Bulldogs, Boston Terriers, Beagles, Collie Sheepdogs, Dobermans, Boxers, Dachshunds, Dalmatians, Shar-Pei, Poodles, and Lhasa Apsos.

Generalized is a more severe form than localized, and affected dogs have a genetic predisposition to the disease.

Relapse is common, but the prognosis is still favorable. However, if secondary bacterial infection is effectively managed, because bacteria can be immunosuppressive, up to 50% of these cases may still recover on their own without antiparasitic treatment.

Even if the disease resolves without treatment, both male and female dogs should be neutered.

Adult-onset demodicosis. Demodicosis usually occurs secondary to another disease or as a side effect of immunosuppressive treatment. Diseases often associated with adult-onset demodicosis include endocrine diseases (such as hypothyroidism and Cushing’s syndrome), metabolic diseases, and cancers (such as lymphoma).

Demodicosis can also be triggered by long-term steroid treatment. This is the most common cause of adult-onset demodicosis.

The prognosis of adult-onset demodicosis depends on the nature of the disease. In some cases (up to 50%), diagnosis may find no underlying disease, because demodicosis may be the first sign of an immunosuppressive problem.