Causes of Mange
Mange is a bothersome skin disease caused by tiny parasitic mites. The mites live on or in the dog’s skin, causing varying degrees of discomfort and coat abnormalities. The mites that most commonly cause canine mange are described below.
Sarcoptes scabiei canis mites cause sarcoptic mange, often referred to as “canine scabies.” This is a non-seasonal, highly contagious and intensely itchy skin condition that can affect dogs of all breeds and ages. People can also become infested. Sarcoptes mites have a 17-21 day lifecycle, all of which is spent on the host animal. Females burrow through several skin layers and lay their eggs, releasing a highly irritating substance that causes severe itchiness, scratching, hair loss and self-trauma. Sarcoptic mange is transmitted by direct contact between infested and non-infested animals. Indirect transmission, such as by a clean dog contacting mites in the bedding of an infested animal, is less common but does happen. Common sites of transmission are boarding kennels, animal shelters, dog parks, grooming facilities and other high-density dog-friendly areas.
Cheyletiella yasguri mites cause cheyletiellosis, frequently called “walking dandruff.” Cheyletiellosis is extremely contagious and causes marked skin scaling, which normally is most apparent on the dog’s back but can appear anywhere. It may or may not be accompanied by itchiness. Unlike sarcoptes mites, cheyletiella mites rarely cause deep skin irritation. They spend their entire 21-day lifecycle on top of their host’s skin scuttling through its fur. These are large mites that can easily be seen with a hand-held magnifying glass. People and other animals can become infested by direct or indirect contact. Boarding kennels, animal shelters, dog parks, grooming facilities and other high-density dog-friendly areas are common sites of transmission.
Demodex canis mites cause demodicosis, also called “demodex” or “demodectic mange.” Unlike other forms of mange, dogs with demodex typically are not itchy. Demodex mites are normal inhabitants of canine hair follicles and sebaceous glands. Sebaceous glands secrete sebum, an oily substance that lubricates the skin and coat through ducts that open from the glands into hair follicles. Clinical disease develops when the mite population proliferates beyond what the dog’s immune system can handle. This leads to patchy hair loss and inflammation, which can be localized or widespread. Why demodex mites get out of control is not well understood, although a genetic component is likely. Many authorities suspect that the immune systems of affected dogs are suppressed, permitting the mites to reproduce without restraint.
Otodectes cynotis mites cause otodectic mange in dogs, but even more so in cats. These ear mites burrow deep into the external ear canal, and sometimes into the inner and outer ear flaps, causing varying degrees of irritation, inflammation and itchiness. Otodectic mange is extremely contagious between dogs, but rarely affects people. Dogs become infested by contact with affected strays or other infested animals at shelters, boarding kennels, grooming facilities, dog parks or other high-dog-traffic areas.
Trombiculid mites, also called harvest mites, red bugs or “chiggers,” cause a much less common form of canine mange. Adult mites, which look like tiny spiders, live in decaying vegetation. Dogs become infested with larval mites when the adults are reproducing, usually during late summer into fall, as they romp through fields or forests containing rotting plant material. The larvae attach to the dog’s skin, eat a blood meal and drop off after a few days.
Preventing Canine Mange
The best way to prevent mange is to prevent contact between affected and unaffected animals. Because demodex may have a genetic component, dogs with the generalized form of this disease probably should not be bred.