Sarcoptic mange, aka “Scabies,” is a parasitic skin disease caused by mites living on and burrowed within the skin of the host animal. Although these mites exhibit a host preference, they have zoonotic potential for causing skin problems in humans. Sarcoptic mange may be the cause of severe itch in dogs but may be cured with effective treatment.
Understanding Scabies
Scabies (sarcoptic mange) causes a non-seasonal intensely pruritic (itchy) skin disease in dogs and is caused by the mite Sarcoptes scabiei var. canis. Although scabies mites are extremely small, they can cause severe itching and skin irritation that will decrease a dog’s quality of life significantly. Scabies is highly contagious and is primarily transmitted by direct contact with an infested animal. Transmission to humans or other animals via fomites such as bedding or grooming equipment can occur. Cats may be reservoirs for these mites, but do not usually need to be treated. Scabies mites can also transiently infest humans, resulting in itchy red bumps on the skin that typically resolve on their own within a few weeks but can remain for longer periods of time with repeated or continued contact with an affected animal.
The body sites typically affected in the dog include the ear flaps, elbows, ankles, and underside. Lesions and itchiness can become widespread, but the top of the back is usually spared. Early lesions are characterized by erythematous papular eruptions (red bumps) that develop thick yellowish crusts (scabs). With time, self-trauma results in patchy to widespread alopecia (hair loss), and generalized redness, pimples, and crusts. Hyperpigmentation (darkening of the skin) and lichenification (thickening of the skin) are common with chronicity. Some dogs are intensely itchy but have few lesions other than mild redness and occasional scabs. Others may have only mild itchiness yet have an abundance of mites. Some dogs will be asymptomatic carriers, meaning they will harbor the mites on their skin with no associated clinical signs. It is not uncommon for dogs with scabies to be diagnosed.
Diagnosing Scabies
The diagnosis of scabies is based upon 1) a history of rapid onset of intense itching and progressive skin lesions, 2) having a likely source of infestation from visits to training or boarding facilities, dog shows, dog parks, grooming parlors, etc., 3) recognizing a potential exposure of the dog to other species known to harbor the mite, e.g., coyote or fox, and/or 4) having another in contact animal or human develop itching and rashes. The absence of itch among in-contact animals or their humans does not rule out scabies. To make a definitive diagnosis, one must demonstrate the presence of a life stage of the mite on the skin. This is typically achieved via superficial skin scrapings from multiple areas of the skin, which are then reviewed under a microscope. Unfortunately, scabies mites can be very difficult to find. Therefore, failure to find scabies does not rule out scabies, and trial treatment is often used if the degree of suspicion is high enough to justify empirical treatment.
Treating Scabies
Several products are effective for treatment of sarcoptic mange. Most recently, flea and tick preventatives in the isoxazoline class of drugs (including Nexgard®, Bravecto®, Credelio™, and Simparica ®) have successfully been utilized off-label for the treatment of scabies in dogs. These medications have revolutionized treatment of scabies by providing a much easier and safer treatment option than were available in the past. A veterinarian should be consulted about the most appropriate treatment plan for each individual pet.
People with suspicious lesions should consult a medical dermatologist for evaluation and treatment. All dogs in contact with the affected animal should be treated. Affected and in-contact animals should not socialize with other dogs. If a therapeutic trial does not result in the reduction and subsequent resolution of clinical signs within three to four weeks, the animal should be reassessed by a veterinarian for other causes of itch.
