Demodex

 

Demodex (Demodex parasite in the hair follical Demodectic mange):

Demodex is caused by an external parasite that is present on healthy animals. Demodectic mange is the most common, form of mange in dogs. It is caused by the demodectic mange mite, a parasite which lives in the hair follicles of affected dogs.
As long as the body's immune system is functioning, these mites cause no harm. Demodectic mange most often occurs when a dog has an immature immune system, allowing the mites to grow rapidly. Therefore, this disease occurs primarily in dogs younger than 12 to 18 months of age. In most cases, as a dog matures, the immune system also matures. Adult dogs which have the disease, usually have defective immune systems.