Risk Factors For Demodex

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Based on Pet Health Data

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Which Breeds are More Susceptible to Skin Disease?
Demodicosis is one of the most common skin diseases in dogs, especially puppies. It is an inflammatory parasitic skin disease in which the affected pet is burdened with larger than normal numbers of Demodex mites.
Dogs are often classified as having either localized or generalized disease. Those with generalized disease are further subdivided into juvenile-onset and adult-onset categories. Classification into one of these three groups helps veterinarians formulate a prognosis and treatment plan.
This article covers which breeds are at risk, other factors associated with an increased risk of being diagnosed and clinical signs.
High Risk Dog Breeds
A retrospective case-control study examining the electronic medical records of 1,189,906 dogs examined at Banfield Pet Hospitals® in 2006 identified risk factors associated with a diagnosis of juvenile-onset generalized demodicosis (JOGD).
The following breeds have the greatest risk of developing JOGD.
  • The American Staffordshire Terrier
  • Staffordshire Bull Terrier
  • Chinese Shar Pei
Other susceptible breeds include
  • The French Bulldog
  • Pit Bull
  • English Bulldog
  • Mixed breeds
  • American Bulldog
  • Boxer
  • Great Dane
  • Boston Terrier
  • Miniature Pinscher
  • Jack Russell Terrier
  • The Pug, whose puppies are also susceptible to skin diseases.
Other Factors That Increase Risk of JOGD
In addition to breed risk, a bacterial skin inflammation marked by pyoderma (skin infection), coccidiosis (parasitic infection), hookworm infestation, short-hair coat and the lack of regular check-ups were also factors associated with an increased risk of being diagnosed with JOGD.
Clinical Signs of Skin Disease in Dogs
  1. Localized demodicosis typically involves fewer than five lesions that are usually found on the face, forelimbs and feet. It often spontaneously resolves over a period of several weeks to months. The affected pet may have no clinical signs other than well-defined, localized patches of alopecia (hair loss). The pet may also display red and scaly lesions that cause itching.
  2. Generalized demodicosis (GD) is characterized by many lesions, often more than 12, across the body. Dogs that present with six to 12 lesions need to be evaluated individually. GD often begins with skin discoloration and round areas of hair loss that can progress to folliculitis (inflammation of the hair follicle). Edema (an accumulation of an excessive amount of fluid in body tissue) is also typical. Secondary patches of hair loss can form later and can become severe with edema and plaque formation as well as hyperpigmentation (dark spots on the skin).
  3. Juvenile-onset generalized demodicosis (JOGD) is the classification when young dogs (younger than 18 months) have numerous lesions, two or more feet involved or large areas of affected skin. Pruritus (itching) varies from mild to severe. Common lesions include alopecia, folliculocentric erythema (small rough bumps or “goose bumps”) and comedones (plugged hair follicles). Dogs may develop papules (pimples), pustules (pus-filled lesions), crusts, edema and furunculosis (boils of the hair follicle), especially when complicated by secondary bacterial folliculitis. Regional lymphadenopathy (enlargement of the lymph nodes), pain and malaise are common in severely affected dogs.
  4. Adult-onset generalized demodicosis (AOGD) can develop in dogs 2 to 4 years old, but most of these dogs had undiagnosed demodicosis as puppies. True AOGD occurs in dogs that first experience the disease at 4 years old or older. The clinical signs of AOGD are indistinguishable from JOGD, except for those attributable to underlying causes, the most common being Cushing’s disease. In most cases, these are dogs that have been receiving chronic glucocorticoids to control atopic dermatitis. Additional causes of immunosuppression that may lead to AOGD include hyperadrenocorticism (excessive cortisol), hypothyroidism (underactive thyroid), neoplasia (abnormal growth of cells) and systemic infectious diseases.
There is a genetic predisposition to JOGD, so affected dogs should not be used for breeding. Although it is not known whether there is a genetic component to AOGD, it would be wise not to breed from these pets either.
Have Questions?
If you have further questions about skin infections including clinical symptoms and treatment, please contact your neighborhood veterinarian or refer to our Skin Infections Handout for additional information.
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