Demodectic Mange in Dogs
Demodectic mange (Demodecosis) is caused by an external parasite that is also present in low numbers on healthy animals, including people. Whether or not a pet shows symptoms of this disease depends primarily on their immune status. Since there is no easy test to determine immune status, it is impossible to predict which pets will get this disease, or how well a pet will heal if it shows symptoms of demodex.
It is important to note that the diagnosis of this skin condition, like most skin conditions, cannot be made just by looking at a pet. Diagnostic tests are mandatory to arrive at a correct diagnosis and achieve a satisfactory outcome to therapy. Stating that an animal looks "mangey" is not the same thing as making a positive diagnosis of mange. Pets that have Ringworm or Sarcoptic mange can look like they have demodex.
Demodectic mange is caused by a mite, a microscopic ectoparasite that infects the hair follicles. Most pups pick up these mites from their mother when they are nursing, and do not normally cause any problems. It is those pets that have an inadequate immune system that develop this disease.
The parasite is cigar shaped and has several pairs of legs. It is only visible under a microscope. This is a picture of one that is laying on its back, its legs are towards the right, and its mouth is at the far right.
There are underlying causes that can weaken the immune system and make a pet more susceptible to this disease. These include the chronic use of cortisone, Cushing's disease, heartworm, cancer, and hypothyroidism.
Adult dogs that have demodex take longer to treat than young dogs.
One of the most common symptoms of this disease is small patches of hair loss (alopecia), towards the front of the body initially, with the ability to affect the whole body. When it is present in adult dogs it commonly affects the feet.
If a pet has only a few small patches of alopecia the disease is classified as localized. If it has spread throughout the body it is classified as generalized. Most pets that have demodectic mange are young, which is a big aid in the diagnostic process.
The patch of hair missing on this pups face is caused by Demodex, and is an example of the localized classification.
This is an example of generalized demodecosis on the chest and front legs. This is a serious condition and carries a guarded prognosis.
The primary way to diagnose demodectic mange is to do a skin scraping where the patches of alopecia occur. The fortunate thing about demodex is the ease of diagnosis in most dogs (Shar Pei's can be an exception). In most cases the mites are easy to find under the microscope, and if your pet is diagnosed as having this disease, one of our staff members will show them to you. A positive skin scraping of large numbers of demodex mites, along with alopecia (remember demodex is naturally found in the skin also), is verification of demodectic mange and necessitates treatment.
We are fortunate to have several medications at our disposal to treat demodecosis. Unfortunately, one of the most common medications called Mitaban, is no longer available. These medications have proven to be highly effective, and have saved many pets from suffering, and even euthanasia. Sometimes the most we can hope for is to control the problem, not cure it. Treatment duration needs to based on skin scrapings, not just the appearance of the skin. a skin that looks like it is healed can still harbor demodex mites. This is especially true for adult dogs with feet lesions.
Unfortunately, due to the fact that the immune system is paramount in whether or not your pet gets this disease, no guarantee can be made that these medications will work. No matter which form of demodex is treated, several ancillary issues need to be addressed. Your pet needs to be on optimum nutrition, stay current on vaccines, and be free of internal parasites (worms). Like any disease process, the psychological needs of your pet need to be met, which includes plenty of exercise, TLC, and access to fresh water at all times. Other skin conditions like allergies can occur simultaneously, and need to be treated also.
1. Localized Treatment
Bathing with an antibacterial shampoo is the first step in therapy. This loosens up scales, removes oily discharges, and decreases the secondary bacterial infection that is usually present.
Localized demodex can be treated with a medication called Goodwinol. It is a creme that is rubbed into the areas of alopecia once daily. This rubbing initially causes more hair to fall out, but within 1-3 weeks the problem usually goes away. If more areas of alopecia appear during this time they should be treated with Goodwinol and brought to the attention of one of our doctors during recheck exams.
Another treatment for localized demodex involves the use of Mitaban mixed into olive oil. This mixture is applied on the areas of hair loss daily. It is possible for localized demodex to progress to generalized demodex even if it is treated. Localized demodex might even resolve without any treatment.
2. Generalized Treatment
Generalized demodex is treated with a combination of medications and modalities. It is important to understand that treatment may take 2-3 months to be effective. The hair is usually clipped to allow the topical medication easy access to the skin, which makes it substantially more effective. Secondary pyoderma (skin infection) is usually present also, so your pet is put on oral antibiotics for several weeks to months.
The main drug used to treat generalized demodex is called Mitaban. Unfortunately, Upjohn no longer makes it, so we have to use substitutes. Mitaban has to be used precisely by label instructions. Since it is difficult for people to do this properly in their homes, we treat most pets in our hospital. Pets are dipped once per week, in between these dips your pet should not be bathed. We continue dipping until successive skin scrapings are negative for the mites.
If Mitaban does not work there are other medications that are used with varying success to cure the problem. These include oral Ivermectin and Milbemycin (Interceptor). Side effects like excess salivation, incoordination, even coma and death are possible, so they must be used judisciously. They should not be given to Collies, Shelties, australian shepherds, or dogs that are positive for heartworm. There can be no guarantee that they will work, especially in a disease that is so closely associated with the immune system. Spaying infected females is helpful.