The mites that cause disease in dogs are called Demodex canis. These mites live in hair follicles and sebaceous glands and feed on cellular debris. Once the mites leave the dog, they don’t live long—about an hour. The entire life cycle of Demodex mites is 25-30 days and is completed in the host. The process can be roughly divided into four stages, including: spindle-shaped eggs, six-legged larvae, eight-legged nymphs, and eight-legged adults. The pathogenesis of diseases associated with the proliferation of Demodex mites is not fully understood. Most animals have low numbers of mites. In infected animals, the mites multiply within the hair follicles.
Symptoms of demodicosis in dogs
Skin symptoms suggestive of demodicosis include: red spots, papules, pus Blisters, hair loss patches, blackheads, dandruff and excessive skin pigmentation. Itching may or may not be present.
Some dogs with demodicosis do not experience hair loss, but rather itching. So these dogs can easily be misdiagnosed with allergies. The lesions of worm disease are mainly concentrated on the face and feet.
The main clinical manifestations can be divided into two distinct types: juvenile-onset (less than 2 years old) and adult-onset (over 2 years of age).
Juvenile-onset Demodex
The juvenile-onset type can be further divided into localized Demodex disease and systemic helminthiasis. Prognosis and treatment vary from individual to individual. Some dog breeds have a higher incidence, including: Afghan Hound, Boston Terrier, Boxer, Dalmatian, Chihuahua, English Bulldog, Doberman Pinscher, American Bulldog, German Shepherd, Old English Sheepdog, Shar Pei, American Staffordshire Terrier, and Great Dane.
Localized helminthiasis. In this case, only one body area will be affected, which is based on the results of a skin scratch test. This type of demodicosis is usually benign and self-healing and may include one to several localized erythema, scaly alopecia, etc. The affected areas are mainly concentrated on the face and feet. In addition, bacterial infection may be present, which can lead to the eruption of pustules.
The prognosis for localized helminthiasis is generally good, as more than 90% of affected dogs resolve spontaneously within 3-8 weeks.
Systemic helminthiasis. Lesions under this type will be present in multiple areas of the body. Dogs with toe mite disease are classified as generalized. There is a varietal tendency for this type of mite disease. Susceptible breeds include: Pitbull, Bulldog, Boston Terrier, Beagle, Collie, Doberman, Boxer, Dachshund, Dalmatian, Shar-Pei, Poodle, and Lhasa Apso .
The generalized form is a more severe form than the localized form, and affected dogs have a genetic predisposition to the disease.
Recurrence is common, but prognosis is still assured. However, up to 50% of these cases recover spontaneously without the use of antiparasitic treatment if secondary bacterial infections are managed effectively, as the bacteria may be immunosuppressive.
Even if the disease goes away on its own without treatment, both male and female dogs should be spayed.
Adult-onset demodicosis
Demodicosis is usually secondary to another disease or a side effect of immunosuppressive therapy. Disorders commonly associated with adult-onset demodicosis include: endocrine disorders (eg, hypothyroidism and Cushing’s syndrome), metabolic disorders, and cancers (eg, lymphoma).
Demodicosis can also be triggered by long-term treatment with steroids. 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%), the diagnosis may not reveal the underlying disease because demodicosis may be the first sign of an immunosuppressive problem.
