Demodicosis

Demodicosis, also called demodectic mange, follicular mange or red mange, is an allergic reaction to Demodex mites, microscopic parasites that live on the dog's skin without causing any problems. However, some breeds of dogs cannot tolerate them and develop allergic reaction. In this case, mites can cause hair loss and redness on the face, around the eyes, or at the corner of the mouth. Sometimes demodicosis affects the whole body. Generalized demodicosis may be associated with the development of a severe secondary folliculitis and furunculosis, which may further suppress the immune system, allowing further mite proliferation. Pododermatitis is also common, often complicating quick recovery because of persistent mite infestation and resulting fibrosis. The condition is more common in purebred dogs and is thought to be heritable. Breeds at risk include the American Staffordshire Terrier, Afghan Hound, Boston Terrier, Boxer, Chihuahua, Shar-Pei, Collie, Dalmatian, Doberman Pinscher, German Shepherd Dog, Great Dane, Beagle, and Old English Sheepdog. Young puppies or older dogs with a suppressed immune system are most susceptible.

Demodex mites are tiny, "cigar-shaped" mites that live in the hair follicles and sebaceous glands of mammals. There are more than 100 species of Demodex mites, many of which are obligatory parasites of cats, dogs, sheep, cattle, pigs, goats, deer, bats, hamsters, rats, and mice. Among them, Demodex canis, which is found ubiquitously in dogs, is the most documented and investigated species.1 The mites are transferred directly from the mother to the puppies within the first week of life. Older dogs who have a depressed immune system can acquire the disease. Affected animals have cracked skin that has a scaly appearance and oozes a clear fluid. There is redness on the face, around the eyes, or at the corner of the mouth. Many dogs become restless, have fever, lose their appetite; however, not all of these signs may be present.



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Diagnosis of demodicosis is normally based on skin scrapings or hair plucks (trichograms) from affected areas. Scrapings from 4 to 5 sites on the body are normally taken. Prognosis is based on the ratios of eggs and larval forms to adults, as well as the number of live to dead mites. Generally, the larger the number of juvenile forms, the worse the prognosis. As treatment progresses, increased numbers of dead mites and decreased numbers of juvenile stages would indicate a favorable prognosis. Scrapings, hair plucks, or both are normally performed periodically during therapy.2 Treatment usually consists of applying insecticides and insecticidal shampoos with benzoyl peroxide. Amitraz is the only molecule approved by the Food and Drug Administration for the treatment of canine demodicosis. Whole-body rinses to topical treatment of localized lesions, at different concentrations and intervals are used. Several side effects, such as lethargy, depression, anorexia, vomiting, diarrhoea, hypothermia, ataxia, pruritus, bradycardia, hyperglycemia) were reported in some breeds, and, more rarely, in owners handling the drug. Alternatively avermectins and milbemycines are also used as pour-on, oral, or injectable formulations to treat generalized demodicosis.3

References

  1. Under the lash
  2. Jan A. Hall and Natalie Keirstead. Diagnostic dermatology. Demodicosis
  3. Efficacy of Amitraz plus Metaflumizone for the treatment of canine demodicosis associated with Malassezia pachydermatis



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