Mange in Dogs
by: Laura McLain Madsen DVM
What is mange in dogs?
Mange in dogs refers to several types of skin parasites that can cause itching and skin inflammation in dogs. It’s important to have a veterinarian diagnose the exact type of parasite for successful treatment.
What causes mange?
The primary mange mites are Demodex (demodectic mange, demodicosis, “red mange” or “black mange”) and Sarcoptes (sarcoptic mange or “red mange”). Both cause itching and skin irritation, but the two kinds of mites are very different in their treatment and their contagious potential.
• Demodex canis is a microscopic mite that is shaped like a cigar with tiny legs. All dogs have Demodex mites naturally. In normal dogs, the mites live in the hair follicles, surviving on skin oils and debris and not causing any symptoms whatsoever. However, in certain dogs, there is a defect of the immune system which allows Demodex mites to overpopulate, getting out of control and causing symptoms. The immune system defect can be worsened by immaturity (in puppies), hypothyroidism, Cushing’s disease (hyperadrenocorticism), cancer, or severe primary infections. The immune system defect is genetic.
• Sarcoptes scabei is another microscopic mite, sort of crab-shaped. Unlike Demodex, Sarcoptes is not normally found on dog skin. The mite burrows into the skin and is highly contagious, spread from one animal to another through contact.
• Another skin mite of dogs is called Cheyletiella, but it isn’t called “mange.” It’s commonly called “walking dandruff.”
Is mange in dogs contagious?
Yes and no. Since Demodex mites are found on the skin of every dog, they are not contagious. But Sarcoptes is contagious to other dogs (and cats, rabbits and humans) through contact, such as by animals playing together or sharing a bed.
What are the symptoms of mange?
Demodectic mange causes hair loss, itchiness, and leaves the dog susceptible to secondary bacterial infections (i.e., a bacterial infection on top of the parasitic infection). Bacterial skin infections also cause itchiness, along with redness, pain, and oozing.
Demodex infections can either be localized or generalized. In localized infections, typically just one or two small spots of hair loss will be apparent (particularly on the head, and usually in puppies and young dogs). The spots sometimes have a grey flaky appearance.
In generalized Demodex infections, large areas of the body are affected. There will be extensive patches of skin that are thickened, hairless and itchy, and may appear either red (due to inflammation and bacterial infection) or black (due to pigmentation from chronic inflammation).
Generalized demodectic mange is much more serious than localized cases because it indicates that there is a primary disorder which has suppressed the immune system so that the body can no longer keep the mites in check. Without treatment, generalized demodectic mange can be fatal.
Sarcoptic mange usually causes a profound itchiness. The mites particularly live in the areas of the body that are thinly furred, such as the ears, belly, elbows, and ankles, but the infection can quickly spread across the whole body. Besides being itchy, dogs with sarcoptic mange will have hair loss, reddened skin and crusty scabs. Infected pets might scratch themselves raw, with large bleeding sores.
How is mange diagnosed?
Both demodectic and sarcoptic mange in dogs are diagnosed by a skin scraping. Using a sterile scalpel blade, your veterinarian will scrape off the top layers of skin in an inflamed spot, and mix the skin cells with mineral oil. Then she will look at the sample under a microscope; live parasites can be seen swimming in the oil.
If an adult dog develops Demodex infection, your veterinarian will likely recommend additional testing to look for underlying disorders, including blood and urine panels, adrenal gland testing, and x-rays or ultrasound.
Sarcoptes can sometimes be difficult to diagnose as the mites can be hard to find. Even if the skin scrape is negative (no mites seen), your vet may still recommend treatment against Sarcoptes if the case is suspicious.
What is the treatment for mange in dogs?
Treatment varies depending on the type of mange, and may be complicated.
Localized demodectic mange in dogs will often spontaneously resolve within a month or two. Some veterinarians will recommend various topical medications to be applied to the lesions, including chlorhexidine, Pyoben Gel® (benzoyl peroxide), Tresaderm® (thiabendazole, an anti-parasitic and anti-fungal drug, plus neomycin, an antibiotic, plus dexamethasone, a cortisone-type anti-inflammatory), and Goodwinol® (rotenone).
If there is a secondary bacterial infection (typically Staph bacteria), antibiotics such as cephalexin (Keflex®) or amoxicillin/ clavulanic acid (Clavamox®) will also be prescribed.
The treatment of generalized demodectic mange is much more intensive; it may take up to a year to clear the infection and the necessary medications can be expensive. Possible treatments include:
• Mitaban® (amitraz) dips have historically been used to treat generalized demodectic mange, but the chemical is potentially toxic. Many veterinarians no longer use Mitaban® dips because it can cause health problems for humans who handle it (staff members of the veterinary hospital or pet owners at home).
Side effects in dogs include sedation, vomiting, diarrhea, low heart rate, low body temperature, seizures, skin irritation, wobbliness and weakness. Side effects in people exposed to the dip include asthma-like attacks, contact dermatitis, and severe headaches. Amitraz was also marketed as a spot-on (Promeris®) but it has been pulled from the market due to side effects. Amitraz is also formulated as a tick collar (Preventic®) but the collar form is not effective against Demodex.
• Ivermectin (Ivomec®) can be used off-label (meaning, not FDA-approved) for treating demodectic mange. Collies, Shelties, Aussies and related herding breeds can have severe neurologic side effects from ivermectin. (There is a blood test for a mutation called MDR1 that will determine whether a Collie-type dog can tolerate ivermectin.)
Even in non-Collie-type breeds, most veterinarians recommend starting at a very low dose and gradually increasing over a week or so to make sure the dog will tolerate the drug. Ivermectin is typically given by injection but for Demodex infections, the injectable form can be given by mouth. It is given daily until the infection is cured (at least 2-3 months). Side effects include lethargy, wobbliness, seizures and blindness.
• Milbemycin (Interceptor®) can also be used off-label to treat demodectic mange. Interceptor® is primarily a monthly heartworm preventative but if used daily is effective against Demodex. The main downside to this approach is the cost of daily treatment.
• Advantage Multi® (imidacloprid plus moxidectin) may also be effective against Demodex but is not well-studied. Its use is also off-label.
Severe secondary bacterial infections will be treated with long-term, broad-spectrum antibiotics, such as Clavamox® (amoxicillin/ clavulanic acid), cephalexin, Baytril® (enrofloxacin), or Zeniquin (marbofloxacin®). Skin scrapes should be repeated monthly to evaluate the response to treatment, and medications should be continued for a full month after no more mites are seen on the scrape.
Sarcoptic mange is easier to eliminate than demodectic mange. The mites can be killed with ivermectin or, more conveniently, Revolution® (selamectin). Revolution® is applied topically on the back of the shoulders but absorbs into the bloodstream to circulate systemically. It is effective against many internal and external parasites. All pets in the household should be treated, even if some do not show symptoms. Anti-inflammatory corticosteroids (prednisone) can be used for the short-term to relieve intense itching.
What is the prognosis?
The prognosis for young dogs with just a few localized Demodex spots is good. Usually the spots will resolve within two months, and no further problems will occur. However, dogs with generalized Demodex, or older dogs with Demodex, have a worse prognosis. With adequate treatment, the cure rate for generalized demodectic mange is 90%, but if treatment is stopped too soon the disease will reoccur.
For any case of Demodex, the dog should be spayed or neutered and not bred, as the immune system defect that allows the mites to proliferate is genetic. Littermates of affected dogs should also not be bred.
The prognosis for sarcoptic mange in dogs is good, as long as all in-contact animals are treated. However, a dog who has recovered from sarcoptic mange can become re-infected in the future.
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