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Demodectic Mange

The term mange is often over used when describing skin problems in dogs. True mange in dogs is generally due to one of two mites found in the skin: Demodex and Sarcoptes. This article deals with the former.

It important to realise that the Demodex mite is a normal inhabitant of a dog’s hair follicle and therefore lives in harmony with the host. When the mite causes disease it appears to be due to the host failing to regulate the mite numbers rather than the fault of the mite. As the multiplies within the follicle damage occurs and the hair falls out. This will appear as patches of thinning hair or hair loss. In young dogs it is often seen around the eyes and other parts of the face, under the neck and on the front legs.

The causes of juvenile-onset generalised demodex infection is still not well understood. There is certainly a breed disposition and selective breeding has greatly reduced the incidence. Any factor that causes stress is thought to predispose to outbreaks as well. It was once thought that an immune deficiency was involved,  but this theory has lost support in the past few years. It seems now that the mites, when in numbers, can cause immune suppression which will stop the condition from resolving.

Adult-onset Demodex seems to be associated with concurrent systemic diseases. Many studies indicate the dogs hormonal status may have some influence on mite numbers. If we see an adult dog with Demodectic mange that doesn’t respond to treatment we often need to do further tests to look for other problems.

What we do know is that there is still a lot to learn.

As far as treatment goes, we do know is that we have to address the mite if we are to see any clinical resolution of the problem. Besides the mites there is usually secondary skin infections which will require antibiotic therapy and/or medicated shampoo. Certain shampoos are useful to flush the hair follicle to allow better penetration of the mite killing rinses. Each case will be treated differently but often require repeat skin scrapings to assess the response to the particular treatment chosen.

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