Mange Mite Infections in the Dog

text - Jenny King and David Vawer

Mange is a parasitic skin disease caused by microscopic mites. Two different mange mites cause skin disease in dogs. One (the Demodex mite) resides in the hair follicles, while the other (the Sarcoptic mite) lives just under the surface of the skin.

Although both mites share some similar characteristics, there are some important differences. It is important not to confuse the two types of mange because they have different causes, treatments and prognoses.

There are other types of mite which infect dogs, but these are not true mange mites, and not discussed here. They include the fur mite, Cheyletiella ("creeping dandruff"), Otodectes, the ear mite, and the harvest mite Trombicula

Sarcoptic Mange or Scabies

The presence of the sarcoptic mite causes severe itching which often looks like severe eczema. The dog will chew and scratch its skin constantly. This leads to a loss of large amounts of hair. Sarcoptes often starts first on the ears and legs, particularly the elbows and hocks, but can rapidly spread over the the legs, shoulders, ears and under the abdomen, and on to cover the whole body in severe cases. Eventually the skin will become thickened and will darken due to pigmentation, and often look rather elephantine. Affected skin in active areas can seep rancid smelling serum which often becomes secondarily infected with bacteria and fungi.

Sarcoptic mange is highly contagious to other dogs. It is also contagious to humans. The dogs bedding should be discarded or, if this is not possible, it should be washed and then sprayed with a veterinary insecticide. Your veterinary surgeon will advise you and supply the correct one to use. Although the mites are not able to complete their life cycle on people, they will burrow into the skin and cause quite a lot of itching before they finally die.

In the Downland Veterinary Group area a lot of cases are the result of contact with the heavily infected local fox population. Cases are also common in kennel situations, particularly racing greyhound kennels where there is frequent interchange and mixing of dogs from a large number of different backgrounds.

Diagnosis

Diagnosis is not always easy as the disease looks very much like allergic eczema. Skin scrapings are performed and examined under the microscope for mites or mite eggs. However, if only a small number of mites may be present on the dog, skin scrapings may be negative. A presumptive diagnosis is then made because the signs are suspicious. Treatment is then commenced without the confirmation of a skin scraping. Age is not a significant factor in sarcoptic mange, although it seems more common in puppies. It will affect all ages of dogs.

Treatment

Treatment is with a specific mange wash and is normally done at 1-2 weekly intervals. Two treatments may be all that is required, although sometimes treatment will continue for several months. There are a number of products available, some of which are of dubious value. Always discuss the treatment with your veterinary surgeon to ascertain the best and safest product to use in your situation.

Should bathing not prove effective, injections with a preparation called ivermectin may be successful. This product is not licensed for use in dogs and the implications of this must be discussed with your veterinary surgeon prior to its use. It cannot be used in Border Collies or similar breeds. If bacterial infection is also present, antibiotics will be prescribed. A spray for the house and bedding will also be needed and your veterinary surgeon will provide you with this.

Inn cases where there is secondary infection, antibiotics and other ancillary treatments may be required.

If any member of the family develops an itching skin rash, it will usually clear once the dogs are treated. If you are at all concerned, it would be wise to see your doctor. In people, the mite cannot complete its life cycle so it will die in a few days. Reinfestation from the dog or premises can result in continued itching.

Demodectic Mange

Demodectic mange is sometimes just called Demodex. It is caused by the Demodex mange mite, a parasite which lives in the hair follicles of affected dogs. Under the microscope, this mite appears shaped like an alligator with eight legs. All dogs (and many humans) have a few of these mites on their skin. As long as the body's immune system is functioning, these mites cause no harm. Demodectic mange most often occurs when the dog has an immature immune system, allowing the mites to grow rapidly. Therefore, this disease occurs primarily in dogs aged less than 18 months. In most cases as the dog matures, the immune system also matures. Adult dogs that have the disease usually have defective immune systems. Since the mite is found on virtually all dogs, exposure of a normal healthy dog to one with demodectic mange is not dangerous. Development of the immune system is under genetic control. Thus, an affected dog usually comes from a litter containing other affected puppies. Owners of littermates should be put on alert to watch for it. If the disease is widespread over the body it may be due to a genetic defect and affected dogs should not be used for breeding. Also, parents of the affected dogs should not be bred from again. Although any breed can be affected the Bull Terrier breeds seem to make up a large proportion of the dogs which are seen with clinical Demodex. Sometimes the disease can occur as a result of treatment of the dog with immunosuppressant drugs including corticosteroids.

Signs of the disease

Surprisingly, a dog with demodectic mange does not itch severely, even though it looses hair in patches. Areas of bare skin will be seen. The hair loss usually begins on the face, especially around the eyes. When there are only a few patches of hair loss, it is termed localised demodectic mange. If the disease spreads to many areas of the skin, it becomes generalised demodectic mange. It may become itchy if the skin becomes infected with bacteria or yeasts. We can check for these if necessary.

Diagnosis

The presenting signs will usually arouse your veterinary surgeon's suspicions. Diagnosis is made in most cases by the laboratory examination of skin scrapings as is Sarcoptes. As the mite can get 2-3mm below the skin surface in the follicles, deep scrapings are necessary. Sometimes it may be necessary to take a skin biopsy to confirm infection.

Treatment

The localised form is usually treated with topical medication and clears easily. The generalised form may require more intensive treatment.

Shampooing with a follicular flusher to open the hair follicles (roots). An example of these shampoos is Etiderm or Paxcutol. The dog is thoroughly dried afterwards.

Wash with an anti-Demodex shampoo. We prefer Aludex solution. It is important that the solution is diluted according to instructions on the bottle and scrubbed into all of the skin. It is essential for you to wear gloves while applying the solution. The wash contains the insecticide Amitraz. The product can have side effects on the dog and you if not used properly. Most dogs will appear sleepy for a few hours after the bath.

These two treatments are repeated every 5-7 days until the mites are eliminated. This can take anywhere from weeks to several months. We will keep a regular check on you and your dog and advise you when to stop. After the treatment it will be necessary to examine your dog for the presence of live mites or eggs.

Vitamin E can be taken as tablets or capsules and helps stimulate the immune system.

Antibiotics. For dogs with generalised demodectic mange, secondary skin infections may represent a complicating factor requiring antibiotic therapy. Dogs with skin infections have very red, inflamed itchy skin. This is the source of the term "red mange".

As Sarcoptic infections, your veterinary surgeon may suggest the use of ivomectin in the treatment of severe or intractable cases. We must again emphasise that this is not a drug licensed for use in the dog and should only be used after full discussion with your vet. It is, however, sometimes necessary to use products such as these since the risk surrounding their use is less than the risk of untreated demodectic mange.

Prognosis

Treatment of the localised form is generally successful. Treatment of the generalised form is also usually successful, but takes time and perseverance. However if the immune system is defective, neither the mites or the skin infection may respond to treatment.

Because the immune system does not mature until 12-18 months of age, a dog with demodectic mange may have relapses until that age. It is important for treatment to begin promptly to minimise the possibility of developing uncontrollable problems. demodectic mange may also occur in very old dogs because function of the immune system often declines with age. Dogs who have immune suppression due to illness or medication are also candidates for the development of demodectic mange.

and Finally

Demodectic mange can be one of the most frustrating conditions to treat in the dog. In young animals it can keep returning until the immune system is mature enough to keep the mites in check. It is important that you and your veterinary surgeon work together to help keep it under control and ultimately to cure it. We as a profession only want the best in treatment for your dog, and are fully aware that the time involved in the treatment of mange can be frustrating for all involved (including the dog!!). To this end, please keep your appointments and follow up treatments as requested, and if you are frustrated let us know!