Demodectic mange is one of three kinds of skin disease in dogs caused by mites. Demodectic mange is not considered contagious, as are the other two types, Cheyletiella mange ("walking dandruff") and Sarcoptic mange (scabies). Demodectic mange is transferred from mother to puppy, and the younger the dog at the onset of the infestation, the more likely it is to recover completely. Some cases of demodectic mange can be controlled, but never eradicated.
Demodectic mange is diagnosed with skin scrapings to identify the microscopic mite that causes it. There are three species of Demodex mites in dogs. Most dogs that contract demodectic mange coexist with the mites without visible signs of the infestation. Those dogs that suffer from the parasite develop thinning hair around the eyelids and the mouth, and sometimes on the body, the legs, and the feet. Hair thinning caused by demodectic mange progresses to patches of hair loss. The dog's skin can appear red, infected or scaly. A proliferation of demodex mites can lead to serious skin disease.
Female dogs with Demodex mites transfer them to their newborn puppies within the first few days of life through physical contact. Puppies that are over a week old generally will not be infected because their immune system has started to mature. Some species of demodex mites are more contagious and can affect puppies from three to 12 months old. Demodex mites are present in the pores of almost all puppies' skin, and generally do not cause symptoms. It has been hypothesised that mites cause mange in puppies with weak immune systems, and that a dog with a healthy level of resistance to disease will not provide an environment that allows the mites to multiply.
There are three types of Demodectic mange: localised, generalised and pododermatitis. Localised demodicosis infects a dog in small isolated patches, usually on the face. Localised demodicosis usually involves no more than four spots at any one outbreak, and no more than two areas of the body. It is considered a disease of puppies, and resolves in about 90% of cases.
With generalised demodicosis, a dog's entire body is affected with bald patches of fur, scaly skin and infection. Secondary bacterial infections are common with generalised demodicosis, with accompanying severe itch and foul odour. The third type of Demodectic mange is confined to a dog's paws. Bacterial infections usually accompany this type of mange as well. This type, called pododermatitis, is the most difficult to treat.
Females that have demodectic mange should be spayed as soon as the infestation is under control. It is not advisable to breed infested dogs, and the predisposition to demodectic mange is hereditary. Care should be taken to minimise stress for a dog with demodectic mange. Heat, pregnancy, and travel are stress-inducing situations. A high quality diet, current vaccinations and flea control will also help a dog's system resist mite infestation. About 80% of dogs with demodectic mange will outgrow it and recover completely. The balance of dogs with demodicosis will usually respond to medical treatment.
Medication that controls other parasites do no work on demodex mites. Ivermectin in daily doses is generally the preferred prescription. Amitraz or Mitaban dips are an alternative treatment for Ivermectin-sensitive dogs. A veterinarian should be consulted for diagnosis of mites, treatment and follow-up.
Dogs of the herding breeds, but especially Collies, Shetland sheepdogs, Australian Shepherds and Old English Sheepdogs should not be treated with Ivermectin. The typical therapeutic dose for demodectic mange can be fatal for these breeds.
Interceptor, which is marketed as a monthly heartworm preventive, may be effective as a treatment for generalised demodicosis. This treatment is expensive however, because Interceptor is sold in 6-dose packages and demodectic mange may require several months worth of daily doses. A veterinarian may be able to provide short-dated product at a discounted price.
Demodectic mange may cause related health problems. Small patches of skin might be affected by alopecia, or hair loss. Secondary bacterial infections may also occur.