Mange in Dogs: Sarcoptic vs. Demodectic and How Each Is Treated
Two Very Different Diseases with the Same Name
"Mange" is a catch-all term for mite infestations of the skin in dogs, but it covers two entirely distinct conditions with different causative mites, different transmission, different presentations, and different implications for the dog's health and household. Understanding the difference is important because the treatment and prognosis of sarcoptic and demodectic mange are quite different.
Sarcoptic Mange (Scabies)
Caused by Sarcoptes scabiei, a microscopic mite that burrows into the outer layers of skin and causes an intensely itchy, contagious infestation. Sarcoptic mange is highly contagious between dogs and is also zoonotic — it can temporarily infect humans, causing itchy red bumps on skin that contacts an infected dog (though it doesn't establish a permanent human infestation).
Transmission: Direct contact with an infected animal. Commonly acquired from wildlife (foxes are a reservoir) or other infected dogs. Can survive briefly in the environment.
Signs: Intense itching (often more severe than the visible skin changes suggest), hair loss, red and crusty skin particularly on the ear margins, elbows, belly, and chest. The intense itch is caused by allergic sensitization to the mites and their byproducts.
Diagnosis: Skin scraping (looking for mites under a microscope). However, mites are difficult to find even with careful scraping; "you can't rule out sarcoptes by a negative scraping" is a clinical maxim. Response to treatment is often used as confirmatory evidence.
Treatment: Highly effective treatments exist, including isoxazoline antiparasiticides (Bravecto, Simparica, NexGard) which kill the mites quickly. All in-contact dogs should be treated. Bedding should be washed in hot water. The prognosis is excellent — sarcoptic mange resolves completely with treatment.
Demodectic Mange (Demodicosis)
Caused by Demodex canis, a different mite that normally lives in small numbers in the hair follicles of all dogs. In healthy dogs with competent immune systems, the immune response keeps Demodex populations at subclinical levels. Demodectic mange occurs when the immune system fails to control Demodex populations, allowing them to proliferate to the point of causing disease.
Transmission: Demodex is transferred from mother to puppy during nursing and is not contagious between adult dogs under normal circumstances. It is not zoonotic.
Signs: Focal (localized) or generalized hair loss. Itching is less prominent than in sarcoptic mange unless secondary bacterial skin infection develops. In puppies, localized patches around the face and forelimbs are common (localized juvenile demodicosis) and often self-resolving. Generalized demodicosis — widespread disease, particularly in adult dogs — requires investigation for underlying immune suppression (endocrine disease, cancer, immunosuppressive drugs).
Diagnosis: Deep skin scraping or hair plucking to demonstrate large numbers of mites.
Treatment: Localized juvenile demodicosis often resolves without treatment. Generalized demodicosis requires long-term treatment (isoxazolines, historically amitraz dips) and investigation of underlying immune causes in adult dogs. Prognosis varies significantly by case — localized juvenile cases do very well; generalized adult-onset cases require careful management.