Demodectic Mange (Demodicosis)

Summary

Demodectic mange infection (demodicosis) is a very common canine condition in which normally occurring mange mites overwhelm the animal's immunological defenses and thrive on the surface of the skin or within it. Though still considered relatively uncommon in cats, it's now presumed to be more widespread than previously believed. Nonetheless, most details of this article will treat the canine form as its genetic nature is better understood.

Demodicosis (also referred to as "demodex" or, more colloquially, as "red mange") can be classified as either juvenile-onset or adult-onset demodicosis depending upon maturity level at the time of the disease's manifestation. Though the origin of this disease is much argued, the juvenile-onset version is usually associated with genetics, poor nutrition and stress (among other factors) while the adult-onset version (encountered less often) is associated with immunological factors brought on by underlying diseases. This latter form will not be treated in this discussion.

Demodicosis is also categorized by how widespread the infection appears on the patient's body.

In the localized form, dogs are affected in one or more small areas only. The disease is considered generalized once the feet, an entire region of the body and/or several significantly-sized sites are affected. Should the infection appear to spread or should it persist for more than six months, it's also classified as generalized.

Symptoms and Identification

The main signs of demodicosis include hair loss (alopecia), scaling, crusting, pustule formation, and redness, among other skin lesions. Itchiness may or may not be a problem. Sometimes, the presence of itchiness can depend on the exact variety of demodex mite living on the dog's skin.

To diagnose the condition, skin scrapings and/or hair pluckings will be evaluated via microscopy. Demodectic mange mites will often be present in these samples but it's not unusual for mites to evade detection with these basic techniques. Because of this frustrating feature of the disease, some cases are eventually diagnosed based on response to treatment.

Affected Breeds

Any breed of dog can develop juvenile-onset demodicosis. Those most affected are said to include:

• Chinese Shar-Pei

• Collie

• Afghan Hound

• Beagle

• Old English Sheepdog

• Boston Terrier

• Boxer

• Bull Terrier

• Chihuahua

• Dachshund

• Dalmatian

• Doberman Pinscher

• English Bulldog

• Pointer

• German Shepherd

• Great Dane

• Pit Bull

• Pug

• Rottweiler

• Staffordshire Terrier

Even so, its prevalence among these breeds is hotly disputed.

Treatment

Luckily, dogs affected by the localized form of juvenile-onset demodicosis normally recover with or without miticidal treatment in a few weeks to months. In other words, dogs with mildly unsightly, non-spreading patches where demodectic mange mites have been identified do not require mite-killing treatment, according to most dermatologists.

Treatment in these cases is aimed at the secondary skin infection and any discomfort or itchiness that may be present. In the case of generalized demodicosis, however, mite-specific treatment is typically initiated once the disease has been granted this more severe designation. This may include oral and/or topical mite-killing medications in addition to basic oral and topical antimicrobial medications.

Care is always taken in these cases to inform pet owners of the highly frustrating, long-term nature of generalized demodicosis treatment. A year or more may be required before the disease is resolved.

While in some cases the disease may spontaneously resolve on its own, with or without treatment, the converse--a devastating lack of remission--is also possible.

Veterinary Cost

The expense of long-term treatment of generalized demodicosis can easily run into the high hundreds, if not thousands, of dollars. The variability in pricing typically depends on how aggressive the treatment is undertaken and whether veterinary dermatologists are employed in the process.

Prevention

The ideal mode of prevention is based on counseling owners of all affected dogs, whether or not the demodicosis is generalized or localized, to spay and neuter their animals to prevent hereditary transmission. Currently, however, the most typical recommendation only addresses this need in cases of generalized demodicosis.

References

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Hillier A, Desch CE. Large-bodied Demodex mite infestation in 4 dogs. J Am Vet Med Assoc 2002;220(5):623-627.

Chesney CJ. Short form of Demodex species mite in the dog: occurrence and measurements. J Small Anim Pract 1999;40(2):58-61.

Tamura Y, Kawamura Y, Inoue I, et al. Scanning electron microscopy description of a new species of Demodex canis spp. Vet Dermatol 2001;12(5):275-278.

Robson DC, Burton GG, Bassett R, et al. Eight cases of demodicosis caused by a long-bodied Demodex species (1997-2002). Aust Vet Pract 2003;33(2):64-72.

Saridomichelakis MN, Koutinas AF, Farmaki R, et al. Relative sensitivity of hair pluckings and exudate microscopy for the diagnosis of canine demodicosis. Vet Dermatol 2007;18(2):138-141.

Gortel K. Update on canine demodicosis. Vet Clin North Am Small Anim Pract 2006;36(1):229-241.

Scott DW, Miller WH, Griffin CE. Dermatologic therapy. In: Mueller and Kirk's small animal dermatology. 6th ed. Philadelphia, Pa: WB Saunders, 2001;207-273.