Two Types of Mange — Two Very Different Diseases
The word "mange" is often used loosely to describe any severe, generalised skin condition in dogs, but it refers specifically to infestation with one of two distinct mite species: Sarcoptes scabiei or Demodex canis. These two conditions look superficially similar — both cause hair loss, skin changes, and intense discomfort — but they differ fundamentally in their cause, contagion, typical presentation, and implications for the dog's overall health. Confusing them leads to incorrect treatment and missed diagnoses.
Sarcoptic Mange: The Highly Contagious Itch Mite
Sarcoptic mange is caused by Sarcoptes scabiei var. canis, a burrowing mite that tunnels into the superficial layers of the skin. The female mite lays eggs within these burrows, and the subsequent immune response to the mites, their eggs, and their faeces produces the intense pruritus — itching — that characterises this condition.
Sarcoptic mange is extremely contagious. It spreads rapidly between dogs through direct contact and can survive off the host for several days in bedding, grooming equipment, and the environment. A dog that has been in kennels, attended a training class, or visited a dog park with an infected dog is at risk. It can also be transmitted from dogs to humans, causing a self-limiting but very uncomfortable rash typically on the arms, torso, and legs — the human immune response generally clears it without treatment once the source is removed.
Clinical Signs of Sarcoptic Mange
The hallmark of sarcoptic mange is the intensity of the itch — it is frequently described as relentless and disproportionate to the visible skin changes, particularly early in the disease. Preferred sites include the ear margins, elbows, hocks, and ventral abdomen, though the condition can generalise rapidly. The ear pinnae sign — a pedal-auricular reflex where the dog scratches at its ear when the margin is rubbed — is a useful clinical indicator but is not diagnostic on its own.
- Intense, often severe pruritus — frequently rated as one of the most pruritic conditions in veterinary dermatology
- Hair loss, particularly at ear margins, elbows, and ventral surfaces
- Crusty, thickened skin that may develop yellow-grey crusts
- Secondary bacterial infection and excoriation from self-trauma
- Rapid spread to other dogs in the household
Diagnosis of Sarcoptic Mange
Diagnosis of sarcoptic mange can be frustrating because mites are notoriously difficult to find on skin scrapes — the sensitivity of multiple deep skin scrapes is estimated at only 20 to 50%. A negative scrape does not rule out the diagnosis. Many experienced dermatologists will treat presumptively for sarcoptic mange in a dog with classic clinical signs and a compatible history, using response to treatment as a diagnostic indicator.
Serological testing (measuring IgG antibodies to Sarcoptes) is available and offers better sensitivity, though false negatives can occur early in infection before the immune response has developed. In practice, a classic presentation combined with a history of contact with other dogs or wildlife — foxes are a common source — is often sufficient to justify treatment.
Demodectic Mange: Not Contagious, but Potentially Serious
Demodectic mange is caused by Demodex canis, a cigar-shaped mite that lives within the hair follicles of all healthy dogs in small numbers. This is a normal commensal relationship — the mites are present in virtually every dog and cause no problems under normal circumstances. Disease occurs when the mite population proliferates abnormally, which happens when the immune system loses its ability to maintain normal mite numbers.
This immune insufficiency is the central factor in demodectic mange, and it distinguishes the disease fundamentally from sarcoptic mange. Demodex is not contagious between adult dogs in normal circumstances, and healthy dogs sharing a household with a Demodex-affected dog are at essentially no risk. Puppies acquire their normal commensal Demodex population from their dam during the first few days of life through close contact.
Localised vs Generalised Demodicosis
Demodectic mange presents in two forms with quite different implications. Localised demodicosis typically affects puppies between three and twelve months of age, producing focal patches of hair loss, usually on the face, around the eyes, and on the forelimbs. It is self-limiting in the majority of cases, with 80 to 90% of affected puppies resolving spontaneously without treatment as their immune system matures.
Generalised demodicosis is far more serious. It involves widespread hair loss, skin thickening, secondary bacterial folliculitis, and significant discomfort. It can affect young dogs with an inherited immune defect or older dogs in which immunosuppression has developed from an underlying condition such as hyperadrenocorticism, hypothyroidism, malignancy, or immunosuppressive drug therapy.
- Localised: focal, self-limiting in most puppies, minimal treatment usually required
- Generalised: widespread, requires sustained treatment, underlying cause must be investigated in adult-onset cases
- Secondary pyoderma is common and requires concurrent antibiotic treatment
- Pruritus is less intense than in sarcoptic mange — Demodex itself causes follicular distension and furunculosis more than direct itch
Treatment: Different Mites, Different Approaches
Treatment for sarcoptic and demodectic mange has evolved substantially with the advent of isoxazoline parasiticides — the same class of drugs used in many monthly flea treatments, including afoxolaner (Nexgard), fluralaner (Bravecto), and sarolaner (Simparica). These products are highly effective against both Sarcoptes and Demodex and have largely replaced older treatments such as amitraz and selamectin spot-on in many practices, though all remain licensed options.
For sarcoptic mange, a course of two to four treatments with an isoxazoline at appropriate intervals is typically curative. All in-contact dogs should be treated simultaneously, and bedding and the environment should be cleaned thoroughly. The intense pruritus usually begins to resolve within a week or two of starting treatment.
Generalised demodicosis requires a longer treatment course — typically monthly isoxazoline treatment continued for at least one month beyond two consecutive negative skin scrapes, which may mean several months of treatment in severe cases. Adult-onset generalised demodicosis requires a thorough investigation for underlying disease, and simply treating the mites without addressing the root cause of immunosuppression will likely result in recurrence.
Prognosis
The prognosis for sarcoptic mange is excellent — with appropriate treatment, full recovery is expected in the vast majority of cases. Recurrence is possible if the dog is re-exposed to infected animals without ongoing preventative treatment.
The prognosis for demodectic mange is more variable. Localised juvenile cases carry an excellent prognosis. Generalised juvenile cases have a good prognosis with sustained treatment, though breeding from affected dogs is discouraged due to the likely hereditary component of the immune defect. Adult-onset generalised demodicosis has a prognosis that depends heavily on the underlying cause — if a treatable condition is identified and managed, control of the mite population often follows. Where the underlying cause is advanced malignancy or severe immunosuppression, the outlook is more guarded.
When presented with a dog that has significant hair loss and skin changes, the distinction between sarcoptic and demodectic mange is not academic — it determines the approach to treatment, the advice given about household contacts, and the depth of investigation warranted. Getting the diagnosis right from the outset makes everything that follows more straightforward.