February 10, 2010 at 4:42 pm #458
By Carol S. Foil, DVM, MS, Diplomate A.C.V.D.
Board-certified specialist through the American College of Veterinary Dermatology
Sarcoptic mange is a very itchy disease caused by a small mite not visible to the naked eye. Areas where the mites tend to burrow under the skin include the tips of the ears, elbows, hocks, chest and belly. However, in a severe infestation, mites can cause problems on the animal’s entire body.
Diagnosis is made by performing several skin scrapings and examining the debris under a microscope. Unfortunately, in many dogs that have sarcoptic mange, no mites can be seen on skin scrapings. If sarcoptic mange is suspected, treatment may be the only way to diagnose and cure your dog.
This disease is highly contagious and can spread from pet to pet or from pet to human. Other dogs in the household should be treated whether or not they have symptoms. If any members of the family have red itchy bumps on their skin, they should consult their physician. Mites can only survive a short time off the dog; however, to ensure that there is no reinfection, your dog’s living quarters should be thoroughly cleaned and bedding washed or thrown away.
No matter which treatment is chosen, your dog may remain contagious for the next 2 to 4 weeks. Please keep him/her confined and away from other dogs and unexposed persons until you re-check appointment.
Treatment sometimes includes clipping your dog’s hair coat. This will depend upon length of the hair coat and severity of the disease. If a dip is used, a good shampoo to remove all the scales and crust before dipping is recommended.
Several medicines can be used to kill the mites. These are in the form of dips, oral/injectable medications, or spot-on products.
The Organism, and how it Lives
Sarcoptic mange is the name for the skin disease caused by infection with the Sarcoptes scabiei 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 scabiei mites live 3 to 4 weeks in the host’s skin. After mating, the female burrows into the skin depositing three or four eggs in the tunnel behind her. The eggs hatch in 3 to 10 days and produce larvae that move about on the skin surface. It eventually molts into a nymphal stage and finally into an adult. The adults move on the skin surface where they mate and the cycle begins again when the female burrows and lays eggs.
Appearance of the Disease The motion of the mite in and on the skin is extremely itchy. Furthermore, burrowed mites and their eggs generate a massive allergic response in the skin that is even itchier.
Mites prefer hairless skin and thus the ear flaps, elbows and abdomen are at highest risk for the red, scaly itchy skin that characterizes sarcoptic mange. 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 easy to be led down the wrong path and pursue 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), elbows, and abdomen.
The term Scabies refers to mite infestations by either Sarcoptes scabiei or other mite species that are closely related to Sarcoptes scabiei. While Sarcoptes scabiei 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 a cat, they are usually referring to infection by Notoedres cati, a mite closely related to Sarcoptes scabiei. 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.
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. However, the condition is extremely itchy while it lasts. The mites are most active where skin is warm, such as in bed and where clothing is snug.
If a pet affected by sarcoptic mange is 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.
Skin Scraping – Classically, mite infection is diagnosed by scraping the skin surface with a scalpel blade and examining the skin debris for mites under a microscope. If skin scraping confirms mites, then one knows immediately the cause of the itching and need not be concerned about allergy possibilities or other diseases; the condition can be addressed with confidence.
When an animal with sarcoptic mange scratches itself, it breaks open the tunnels that the mites have burrowed into and the mites are killed; the itch persists due to toxins in the skin. The result is that the mites can be 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 to 4 weeks. Treatment is simple and highly successful in most cases so it is fairly easy to rule out sarcoptic mange with a trial course of medication.
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.
Date Published: 1/1/2001
Date Reviewed/Revised: 04/10/2009
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