Q: My rescue Pitbull mix suffers from chronic demodectic mange, and the only thing that our vet has used to treat it is Ivermectin and some sulfur bath treatments. He is taking more and more Ivermectin with only occasional success (as in the hair loss will subside for a month or two, but then it falls out again and his skin gets so bad that it pusses.) The more Ivermectin he takes the more lethargic he seems. Isn’t there any other treatment?
A: Demodicosis or Demodectic Mange occurs when there are excessive numbers of Demodex canis mites in the hair follicles. The mites are generally obtained shortly after birth from the mother. In most dogs the number of mites is very small and no clinical disease occurs. Demodectic mange is not contagious. Some dogs are genetically or immunologically susceptible to the proliferation of the mites which leads to the clinical signs. Certain breeds such as the pit bull terrier are predisposed to the disease. As the mites accumulate in the hair follicles the skin becomes red with areas of hair loss. Secondary bacterial infections are common and cause more severe lesions such as pustules and draining tracts. Lesions can occur anywhere but the face and the feet are most commonly affected. When the secondary infections are severe and deep the dog may appear systemically sick. Demodicosis is diagnosed by doing skin scrapings. A scalpel blade is used to collect a sample from the skin and the mites can be seen under a microscope. Skin scrapings are also used to monitor the treatment. Juvenile onset demodicosis is when the disease began when the dog is less than eighteen months old. While the disease can still be very severe, most (but not all) of these dogs can be cleared of the disease. Treatment may be needed for 6 months or longer. When older dogs develop demodectic mange there may be an underlying cause which is weakening the dog’s own ability to keep the number of mites low. Anything that weakens the immune system such as chemotherapy, cancer, hyperadrenocorticism, hypothyroidism, steroid therapy, internal parasites,or stress can lead to the development of demodicosis. Therefore it is recommended to do diagnostic testing to see if a cause can be found and treated. Unfortunately a cause can not be found in many cases and long term treatment is often required. It is important to treat the secondary bacterial infections. Long courses of antibiotics may be needed and culture and sensitivity testing are often necessary to choose the correct antibiotic.
Giving oral Ivermectin daily is well tolerated and can be effective in most dogs (80-85%). Certain breeds of dogs such as Collies and other herding breeds do not tolerate the higher doses of ivermectin needed to treat demodectic mange. Dogs can be tested for the genetic mutation which can help predict which dogs can safely take Ivermectin. The dose of Ivermectin has a wide range and difficult cases will often require the higher end of the dose range. Ivermectin is often started at a low dose and the dog is observed for side effects. If there are no serious side effects the dose is increased gradually until an effective dose is attained. Periodic examinations and skin scraping are done to monitor the progress. Treatment is continued until there are no mites found on two skin scrapings one month apart.
Milbemycin is an oral drug in the same class as ivermectin. It is tolerated by most dogs. Unfortunately it is more expensive and currently unavailable
Mitoban dip can be used for dogs that do not tolerate Ivermectin. Mitoban contains amitraz. The dip must be diluted and applied properly in a well ventilated area. Long haired dogs must be clipped prior to dipping. The dips are done every 7-14 days for several months and can have a 60-80% cure rate. I would recommend that you bring your dog to see a veterinary dermatologist since demodectic mange can be a difficult and frustrating disease to treat.