Don't panic if your vet says your dog has a few demodex mites -- the bodies of most canines host a small population of them. According to the Companion Animal Parasite Council, they're considered "normal mammalian fauna." That means your dog not only survives demodex mites, he probably thrives with a normal amount of them. Older dogs developing demodetic mange probably suffer from an underlying disease.
Demodex canis, the demodetic dog mange mite, is species specific. This minute, eight-legged, cigar-shaped creature lives its entire life cycle on the dog's hair follicles, from egg to adult. Mother dogs usually pass the mites on to their puppies, but the mites are otherwise seldom contagious. You can't see a demodex mite without the aid of a microscope, so your vet must determine their presence on a dog via skin scrapings.
Demodicosis, or demodetic mange, occasionally occurs in dogs with compromised or immature immune systems. In the latter case, localized demodicosis develops in puppies younger than 6 months and usually resolves itself without treatment within a few months. Symptoms include hair loss on the legs or head. Your puppy might look like he's got polka dots on his face, according to the California-based Mar Vista Animal Medical Center. Localized demodicosis involves no more than four bald spots on a dog.
Generalized demodicosis, or red mange, usually involves an underlying illness impairing a dog's immune response, such as cancer or a serious infection. Immunosuppressive drugs, such as steroids, can trigger demodicosis. Besides hair loss spreading over the entire body, the affected dog's lymph nodes likely are swollen. Crusty, infected lesions can form. If your dog develops demodicosis after the age of 18 months, suspect a serious illness. In some dogs, demodicosis is hereditary -- these dogs should not be bred.
Your vet will conduct various tests to determine the underlying cause of the demodicosis -- that will be treated separately. To clear up the demodicosis, your vet might prescribe daily dosing of ivermectin, the same medication used in many monthly heartworm preventives. However, collies and some other herding breeds might be sensitive to the drug. For these dogs, treatment consists of regular dipping with a prescription miticide. Your vet prescribes antibiotics for dogs suffering from infected sores.