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Mange

Mange in dogs and cats is caused by a proliferation of mites that burrow in and out of the skin. This burrowing action causes inflammation of the hair follicles and skin that leads to redness, irritation, itchiness, and hairloss. Secondary infection with yeast and bacteria are quite common in cases of canine and feline mange, leading to a cascade of clinical progression that can become very severe and uncomfortable for the pet.

There are two different classes of mange mites that occur in dogs and cats, infectious mange, and non-infectious mange. Infectious mange can be picked up in the environment or can be transmitted from one animal to another. The different kinds of mange all have very similar clinical signs.

Early signs include: hairloss beginning around the eyes and bases of the ears, progressing to hairloss on the front of the legs and tops of feet and front of the torso. As the disease spreads, hairloss becomes more widespread, extending to virtually every part of the body. In addition to hairloss, the skin becomes very reddened, irritated and thickened as secondary bacterial and yeast infections set in. The affected dog or cat will often begin to self traumatize itself, relentlessly licking and chewing affected body parts because of extreme discomfort. This exacerbates the condition causing it to to spiral into widespread severe skin disease.

Types of infectious mange in dogs and cats include sarcoptes (dogs) and notoedres (cats). There is only one type of non-infectious mite that occurs in both dogs and cats, demodex.

Sarcoptic Mange

Sarcoptic mange in dogs is caused by infection with the sarcoptes species mite. Sarcoptic mange is common in unsanitary environments, such as dogs that come from puppy mills, pet stores, less than ideal animal shelters and dog pounds. We also tend to see it more frequently in dogs that spend a great deal of time outside, left to roam countrysides, or dogs utilized for hunting.

Diagnosis of sarcoptic mange can be quite a challenge. When an animal with sarcoptic mange scratches itself, it breaks open the tunnels that the mites have burrowed into and the mites are killed (though the itch persists due to toxins in the skin). The result is that the mites can be very difficult to confirm by skin scraping
tests. (Probably mites are confirmed in 50% or fewer of sarcoptic mange cases).

Since negative test results do not rule out mite infection, a “Maybe Mange” test is frequently performed. This consists simply of treating for sarcoptic mange and observing for resolution of the signs within 2-4 weeks.

Of course, if mite presence is confirmed by skin scraping, then one knows immediately the cause of the itching and need not be concerned about allergy possibilities or other diseases and the condition can be addressed with confidence.

While sarcoptic mange is difficult to diagnose definitively, it is fairly easy to treat and a number of choices are available.

IVERMECTIN – This is one of the most effective treatments against Sarcoptes scabei yet is is off-label as far as the FDA is concerned. There are several protocols due to the very long activity of this drug in the body. Typically an injection is given either weekly or every two weeks in 1-4 doses. In most cases this treatment is safe and effective but some individuals have a mutation which makes ivermectin very toxic at the doses used to kill mites. These individuals are usually of the Collie family: Collies, Shetland Sheepdogs, and Australian Shepherds are classically affected. There is now a test that can determine if any dog has the mutation that makes ivermectin use dangerous. For more information on ivermectin use click here.

***Ivermectin should be used with caution in breeds known to be potential carriers of the MDR1 gene, a gene that can make carriers highly sensitive to ivermectin toxicity. Collies and other herding breeds are rare but known carriers of this gene, making ivermectin derivatives such as selamectin a better alternative for herding breeds in general. There is now a test that can determine if any herding carries the gene mutation that makes ivermectin use dangerous.

SELAMECTIN (REVOLUTION®) – Selamectin is an ivermectin derivative recently marketed for the control of fleas, roundworms, hookworms, ticks, ear mites and sarcoptic mange mites. Normal monthly use of this product should prevent a sarcoptic mange problem but to clear an actual infection studies show an extra dose is usually needed after 2 weeks for reliable results. This product is probably the best choice for Collie or other herding breeds.

DIPPING – Paramite dip (an organophosphate), Mitaban dip (Amitraz), and Lime-Sulfur dips given weekly are often effective. Disease typically resolves within 6-8 weeks. However, with the effectiveness and safety of ivermectin or related compounds so well established, dips have lost favor with most veterinarians, since they tend to be toxic and unpleasant smelling. These dips as a result have become increasingly difficult to obtain.

Notoedric Mange

Notoedric mange in cats presents very much like sarcoptic mange in dogs, with a clinical progression very similar to that of sarcoptic mage in dogs. Diagnosis is by skin scraping just like in sarcoptic mange in dogs, however, the vet tends to have a greater likelihood of seeing the notoedris mange mite on microscopic analysis than the sarcoptic mange mite. Still, however, lack of visualizing a mite on microscopic analysis is does not rule out disease. Therefore, like sarcoptic mange in dogs, sometimes a test treatment must be done to truly diagnoses the disease.

Treatment for notoedric mange in cats is pretty much the same as for sarcoptic mange in dogs. However, I tend to avoid dipping in cats, as they tend to be especially sensitive to their toxic chemicals than dogs.

Demodectic Mange

Demodectic mange is primarily a problem of dogs, but is occasionally reported in cats. However, given the rarity of demodectic mange in cats, this discussion will focus on the diease in dogs.

The demodex mite is a normal inhabitant of the canine and feline skin. It lives within the hair follicle, and exists in a balance with the immune system in numbers that do not cause any problems for the normal patient. When the numbers of demodex mites proliferate beyond the balance, clinical disease sets in. What truly sets the proliferation of demodex mites off is not truly known, but it is believed that it is from an age related or genetically flawed immune system that does not keep the numbers in check.

There are two presentations of demodectic mange in dogs, juvenile onset (age birth to 18 months of age), and adult onset (4 years or older). Juvenile onset carries a fair to good prognosis, since the flawed immune system is usually age related, and clinical disease will often abate with age. Adult onset demodectic mange, however, carries a guarded to poor prognosis, since the immune system flaw is likely genetic. It is not uncommon for dogs affected with adult onset demodectic mange to have to eventually be euthanized.

Diagnosis of demodectic mange in dogs, like the other two types of mange previously described, is by skin scraping and follow up microscopic analysis. However, of all the different types of mange, this one is the most elusive when trying to view as skin scraping microscopically. Therefore, when we are suspicious of canine demodectic mange, we are often left test treating for 2 – 4 weeks and confirm with treatment success. Both presentations, adult onset and juvenile onset demodectic mange, are treated the same, often for long term, usually for life in adult onset canine patients.

Ivermectin is a broad spectrum anti-parasite medication generally used for food animals and horses. It is licensed for use in dogs and cats as a heartworm preventive and as a topical ear mite therapy at this time thus the use of this medication to treat demodicosis is not approved by the FDA. When ivermectin was a new drug it was hoped that it could be used against demodectic mange mites. At first it was found ineffective but later it was determined that daily doses are needed to control demodectic mange effectively. Administered this way, ivermectin is higly effective in management of demodectic mange, and considered by most vets to be the treatment of choice. Ivermectin is inexpensive relative to milbemycin (see below) and involves no labor intensive bathing. It does, however, taste bitter if given orally (it may be necessary for the owner to learn how to give ivermectin as an injectable treatment.)

***Again, Ivermectin should be used with caution in breeds known to be potential carriers of the MDR1 gene, a gene that can make carriers highly sensitive to ivermectin toxicity. Collies and other herding breeds are rare, but known carriers of this gene, making ivermectin derivatives such as selamectin a better alternative for herding breeds in general. There is now a test that can determine if any herding carries mutation that makes ivermectin use dangerous.

For breeds determined to be sensitive to ivermectin, an alternative to daily oral treatment with an ivermectin derivative, Milbemycin, is also acceptable. This treatment usually requires once weekly to every other week orally. Milbemycin seems to be a bit less effective than treatment with ivermectin, sometimes requiring the concurrent use of dipping.

DIPPING – Paramite dip (an organophosphate), Mitaban dip (Amitraz), and Lime-Sulfur dips given weekly can be helpful, but often fall short in effectively managing demodectic mange. As a result of the effectiveness and safety of ivermectin or related compounds is so well established, dips have lost favor with most veterinarians, since they tend to be toxic and unpleasant smelling. In MDR1 ivermectin sensitive collies and other herding breeds where treatment with ivermectin is not advisable, dips are sometimes needed to augment daily treatment with oral milbemycin for maximum effect. Since demodectic mange patients tend to be juvenile and/or immune suppressed, it is generally advisable to avoid potentially toxic dips if possible.

 

By: Roger L. Welton, DVM
Founder, Web-DVM
President, Maybeck Animal Hospital
Author Canine and Feline 101