Ectoparasites: Sarcoptic and Demodectic Mange Mites

Companion Animals May 29, 2011|Print

Mange is a skin condition caused by mange mites - arachnids that live in the skin and cause irritation for our companion animals. There are two types of mange that affect companion animals - sarcoptic mange and demodectic mange. Regardless of the type, mange tends to more frequently affect dogs than cats; therefore, this article addresses the condition in dogs.


Sarcoptic mange

Sarcoptic mange, also occasionally referred to as scabies, is a highly contagious skin disease caused by mites that burrow into the skin. The scientific name of the mite is Sarcoptes scabiei; these arachnids infest a wide range of mammalian hosts, including dogs and other canids.

Dogs with sarcoptic mange will suffer from intense itchiness and lesions, and in advanced stages can undergo hair loss and severe debilitation. Because the lesions can become extremely itchy, they are often the cause of self-mutilation; if left untreated, they can become bloody and infected. The areas most commonly affected are the margins of the ears, the knees (stifle joints), and feet, although lesions may also be observed on the flanks and stomach.

Since the mites burrow into the dog’s skin, sarcoptic mange is diagnosed by microscopically examining skin scrapings; both mites and eggs will be clearly visible at low-power microscopy, although several samples may be required for definitive diagnosis. The incubation is variable and can depend on level of exposure, body size, and number of mites transmitted. Sarcoptic mange is treated by isolating the animal, clipping hair from the affected area, and applying an appropriate dip or ointment; the animal will also undergo antibiotic treatment to prevent secondary bacterial infection. Ivermectin and selamectin are considered effective for treatment, as well as for prevention. Be sure to discuss the best treatment option with your veterinarian.

There are several convenient topical products available that protect our dogs from sarcoptic mange. These products are applied to the skin at the base of the neck and have residual action; the active ingredients get absorbed into the hair shaft and then get slowly released over time throughout the skin. Because sarcoptic mange is highly contagious (it is readily transmitted between dogs by direct contact), precautions should always be taken when allowing your dog to interact with other animals. Be advised that sarcoptic mange is also zoonotic, meaning that it is possible to transfer the mites between animals and humans.


Demodectic mange

Demodectic mange, or demodicosis, is a noncontagious form of mange, although neonates may acquire mites from their dam due to close contact during nursing, usually within the first 72 hours after birth. Most demodex mite species are considered normal residents of the skin and can live on the skin of many dogs without ever causing a problem. It is not clear why some dogs become affected while others do not, but many cases appear to be related with another underlying condition that compromises the immune system. Also, some breeds (e.g., American Staffordshire terriers, Boston terriers, boxers) seem to have a higher incidence of the condition. Other factors that are known to predispose the dog include systemic disease, estrus, and heartworm infection.

In affected dogs, the mites may be associated with irregular patches of hair loss (alopecia) or mild to severe redness and skin lesions, including pustules and crusting. The condition may be localized or generalized. Localized demodicosis commonly develops on the head or limbs, whereas generalized demodicosis can develop anywhere on the body. Both forms may present in either juvenile or adult dogs, although the localized form usually develops in puppies under 6 months of age.

The condition is diagnosed through microscopic examination of deep skin scrapes from affected areas. Most localized cases will resolve spontaneously without treatment, but generalized cases often require more aggressive and extended therapy with a miticide (e.g., amitraz), as well as antibiotic therapy to treat secondary bacterial infections. Regular skin scrapings after treatment should be performed to make sure the condition has resolved. Evaluation for underlying disorders that may be affecting the immune system should also be performed. Spaying female dogs will prevent recurrence during subsequent estrous cycles. Although the hereditary nature of demodectic mange is not completely understood, breeding affected animals is highly discouraged.

Amy Fischer, Ph.D. - University of Illinois

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