Demodicosis, commonly referred to as Demodex, is a disease caused by a mite (Demodex spp.) that lives deep in the hair follicles. This mite is transmitted from the dam to offspring during suckling and is found in very small numbers on all dogs. It is believed these mites may initially cause dermatitis in dogs due to an immunologic or genetic disorder.
Types and Causes of Demodicosis in Dogs
This can occur in two “general” ages of dogs. One group is less than 2 years old at onset (juvenile onset) demodicosis. The other age group affected is older dogs (adult onset demodicosis).
In the younger group, the pathogenesis of the immune system disorder is not completely understood. Approximately 50% of the dogs cure relatively easily, often spontaneously, therefore their immune system probably matures and should be considered normal. The other 50% of dogs require treatment.
Adult onset demodicosis, usually develops because of a systemic disorder/disease or recent treatment with corticosteroids. A thorough physical examination, laboratory tests and possible x-rays and abdominal ultrasound are performed initially to assess for any underlying disorders. Diseases that can induce adult onset demodicosis include: liver or kidney disease, heartworm disease, hormonal disorders, chronic corticosteroid use, and neoplasia.
Symptoms of Demodicosis in Dogs
Symptoms of a demodex infection in dogs can vary. Some dogs will loose hair (alopecia) in some areas or develop generalized hair loss and dermatitis. Some dogs will itch, and have scales, crusts and redness.
Dogs with adult onset demodex may also have other signs of underlying disease.
Diagnosis of Demodicosis in Dogs
Diagnosis of demodex in dogs is generally based on a skin scraping. A skin scraping involves pinching the skin to help expose the mites from the hair follicle and then scraping the surface of the skin with a scalpel blade. The hair follicles and materials are then evaluated under a microscope looking for the Demodex spp mite. Occasionally, a skin biopsy may be recommended to diagnose the condition.
In adults, additional tests may be recommended to evaluate for any underlying diseases.
Treatment of Demodicosis in Dogs
Previous recommended therapies included Mitaban dips, milbemycin tablets and ivermectin liquid orally. Treatment now is often administration of one of the oral flea and tick preventatives in the isoxazoline class. These products may include Bravecto, NexGard or Simparica. When administered per the recommended dose and schedule for flea and tick prevention the response is excellent.
Scrapings and mite counts to assess progress of therapy may be performed monthly, and treatment should continue until there have been at least 2 consecutive negative scrapings and all skin lesions have resolved. After stopping therapy, your pet may be periodically monitored for recurrence.
Prognosis for Dogs with Demodicosis
With proper treatment, canine demodicosis can usually resolve within a few months.