Sarcoptic Mange

(ALSO CALLED "SCABIES")

THE ORGANISM AND HOW IT LIVES

Sarcoptes

SARCOPTES SCABEI

Sarcoptic mange is the name for the skin disease caused by infection with the Sarcoptes scabei mite. Mites are not insects; instead they are more closely related to spiders. They are microscopic and cannot be seen with the naked eye.

Adult Sarcoptes scabei mites live 3-4 weeks in the host’s skin. After mating, the female burrows into the skin depositing 3-4 eggs in the tunnel behind her. The eggs hatch in 3-10 days producing a larvae which, in turn, move about on the skin surface eventually molting into a "nymphal" stage and finally into an adult. The adults move on the surface of the skin where they mate and the cycle begins again with the female burrowing and laying eggs.

sarcoptic2

Female sarcoptes mite burrowing in the skin and
leaving a trail of eggs behind her. Her presence
generates an inflamatory response in the skin
similar to an allergic response.

 

 

 

 

 

APPEARANCE OF THE DISEASE

The motion of the mite in and on the skin is extremely itchy. Further, the presence of burrowed mites and their eggs generates a massive inflammatory response in the skin which creates yet more itchiness.

sarcoptic3

Dog with dematitis problem typical of sacrcoptic mange.

Note: Many dogs do not develop the classical ear margin crusts until later in the disease.

Mites prefer hairless skin thus leaving the ear flaps, elbows and abdomen at highest risk for the red, scaly itchy skin that characterizes sarcoptic mange. It should be noted that this pattern of itching is similar to that found with airborne allergies (atopy) as well as with food allergies. Frequently, before attempting to sort out allergies, a veterinarian will simply treat a patient for sarcoptic mange as a precaution. It is very easy to be led down the wrong path (pursuing allergy aggressively) if one considers sarcoptic mange too unusual or unlikely.

As the infection progresses, eventually most of the dog's body will be involved. Classically, though, the picture begins on the ears (especially the ear margins), the elbows, and abdomen.

The term "Scabies" refers to mite infestations by either Sarcoptes scabei or other mite species closely related to Sarcoptes scabei. While Sarcoptes scabei can infect humans and cats, it tends not to persist on these hosts. When people (including some veterinarians) refer to "sarcoptic mange" or "scabies" in the cat, they are usually referring to infection by Notoedres cati, a mite closely related to Sarcoptes scabei. In these feline cases, it would be more correct to refer to "notoedric mange," though the treatment for both mites is the same. Notoedric mange, in cats, generally produces facial itching and scabbing.

For more information on notoedric mange, click here.

HOW THE INFECTION IS SPREAD

Sarcoptic mange mites are usually spread by direct contact from host to host. While mites can live off of a host for days to weeks depending on their life stage, they are only infective for 36 hours which means that environmental decontamination is generally not necessary.

Mite infections on humans are self-limiting (i.e., they go away on their own) as the mite is not able to complete its life cycle on the "wrong" host. The condition is extremely itchy, though, while it lasts. The mites are most active where skin is warm (in bed and where clothing is snug).

IF A SARCOPTIC MANGE ANIMAL IS PRESENT IN THE HOME,
IT IS A GOOD IDEA TO WASH ANY BEDDING IN
THE WASHING MACHINE (OR REPLACE WITH NEW BEDDING),
AND WASH ANY COLLARS OR HARNESSES.

DIAGNOSIS

SKIN SCRAPING – Classically, mite infection is diagnosed by scraping the skin surface with a scalpel blade and examining the skin debris under a microscope for the presence of mites. If the mite’s presence is confirmed by skin scraping, then one knows immediately the cause of the itching and other conditions need not be pursued.

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).

MEDICATION TRIAL - 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. Treatment is very simple and highly successful in most cases so it is fairly easy to rule out sarcoptic mange with a trial course of medication. See below for treatment options.

BIOPSY - Mange mites are rarely seen on a skin biopsy sample, though, if the sample is read out by a pathologist who specializes in reading skin samples, the type of inflammation seen in the sample can be highly suggestive of sarcoptic mange. As a general rule, if skin is biopsied, it is best for the veterinarian to request that a dermatohistopathologist read the sample.

TREATMENT

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

REMEMBER, ALL DOGS IN A HOUSEHOLD WHERE
SARCOPTIC MANGE HAS BEEN DIAGNOSED
SHOULD BE TREATED.

IVERMECTIN - This is one of the most effective treatments against Sarcoptes scabei yet 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. An additional cautions comes from an interaction with the relatively new flea control product Comfortis® (spinosad). Relatively high doses of ivermectin are needed to treat sarcoptic mange and if Comfortis® is used concurrently, ivermectin side effects are more likely to occur. While ivermectin is a prototype compound upon which most other sarcoptic mange treatments are based, it may be worth using a product that has actually been approved for the treatment of sarcoptic mange.

For more information on ivermectin use click here.

revolution small dogsSELAMECTIN (REVOLUTION®) - Selamectin is an ivermectin derivative recently marketed in the dog for the control of fleas, ticks, heartworm, 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 Australian shepherd breeds.

Click here for more information from the manufacturer on Revolution.

advantage multi dogMOXIDECTIN (ADVANTAGE MULTI®) – Moxidectin is yet another ivermectin derivative. In Advantage Multi, it is combined with imidocloprid, a flea killing topical, to create a product used against heartworm, hookworm, roundworm, whipworm, and fleas. In the U.S. this product is not FDA labeled for sarcoptic mange but it is in other countries and should still be effective even though technically it is off-label.

Click here for more information from the manufacturer on Advantage Multi.

MILBEMYCIN OXIME (INTERCEPTOR®, SENTINEL®, OR TRIFEXIS®) - Milbemycin oxime is approved for heartworm prevention as a monthly oral treatment (as either Interceptor®, Sentinel®). Happily, it also has activity against sarcoptic mange and several protocols have been recommended by
different dermatologists. This is another medication that one might find recommended.

Interceptor green

 

Sentinel yellow small

Trifexis

For more information from the manufacturer, visit their page for Interceptor:

www.interceptor.novartis.us/

or their page for Sentinel:

www.sentinelpet.com

For information from the manufacturer of Trifexis, visit their page at:

www.trifexis.com

DIPPING - Anti-bacterial or anti-itch shampoos precede one of several anti-mite dips. Mitaban dip (Amitraz), or Lime-Sulfur dips given weekly are usually effective. Disease typically resolves within one month.  Dipping is labor intensive and rarely done any more as the other products are easier and more rapidly effective. We mention dipping since it has been a standard mange treatment for decades prior to the introduction of ivermectin.

Mitaban

 

LymDyp

IN THE MEANTIME

During the time it takes to control the mite infection, the pet will be very itchy. Control of secondary bacterial infections with antibiotics is important. Also, since the body's reaction to the mite is one of hypersensitivity (essentially an allergic reaction), a cortisone-derivative is worthwhile to quell the itchiest symptoms. Ask your vet about whether either such prescription is appropriate for your pet. As for anti-itch shampoos, rinses, and other forms of itch relief, please visit out Relief of Itch page for further suggestions.

 

Page last updated: 4/4/2012