Sarcoptic mange (scabies)
Sarcoptic mange is caused by a mite known as Sarcoptes scabiei var cani. There are other varieties of the mite that infest other mammals, and while they can move from one species to another, they don’t typically survive long on different hosts. Other primary hosts include foxes, coyotes and wolves. Transient hosts include cats, horses and other hoofed animals.
The mites live in the outer layer of the skin, where they reproduce and lay eggs. These mites are very contagious, and they are spread by both direct contact between dogs and through contact with contaminated environments such as kennels, grooming facilities, multi-dog households and dog parks.
Older dogs and dogs with other illness or weakened immune systems are more susceptible to becoming infested. Males and females are equally affected, and there are no differences among breeds.
What signs should you watch for in dogs?
Dogs have an intense allergic reaction to both the mite and its feces, which results in extreme itchiness. The areas most commonly affected on dogs are the margins of ears, elbows and hocks (ankles). The skin often becomes red, with crusts and hair loss. In some cases, other parts of the body may also be involved.
In severe cases, dogs may exhibit depression, loss of appetite and weight loss.
Some dogs may temporarily be asymptomatic carriers of the mites.
How is it diagnosed and treated?
Sarcoptic mange needs to be differentiated from other skin diseases that cause itchiness and similar skin changes — including flea allergy dermatitis, atopic dermatitis, food allergy dermatitis, bacterial and fungal infections, demodectic manage, ringworm and autoimmune disease.
In addition to the dog’s history and a physical examination, scabies may be diagnosed through skin scraping samples examined under a microscope. However, in many cases it is not possible to find evidence of the mites. Other skin samples will be examined to look for bacterial and fungal infections. Less commonly, the diagnosis can also be pursued through a blood test that detects antibodies to the mites or via biopsy of the skin.
However, when the mites aren’t found through skin scrapings, the typical next step is a therapeutic trial of a drug known to be effective against scabies, such as:
Selamectin applied topically
Ivermectin administered orally or under the skin
This should not be used in collies and other dogs with the MDR1 gene
Moxidectin applied topically
Isoxazolines: available in topical and oral forms, off-label use
Antibiotics may be necessary if there is a secondary bacterial infection. A short course of corticosteroids (e.g. prednisone) may be used to reduce inflammation and itchiness caused by the dying mites.
All dogs in the household should be treated even if they are not exhibiting clinical signs.
Most dogs show improvement within two weeks, with full resolution taking up to 6-8 weeks.
Treatment is very successful when owners take a multi-step approach — administering medications properly, continuing recommended follow-up examinations and treating all dogs in the household.
Sarcoptic mange is an important disease to consider in all itchy dogs, particularly those that aren’t responding adequately to treatments for other pruritic (itching) conditions. Many of the available flea and tick preventives are effective at killing the mites.
These mites are very contagious to people, who will also become very itchy and exhibit a rash. Infestation is generally self-limiting and resolves when all the dogs in the household are treated. People are encouraged to contact their physicians if they develop clinical signs too.