The demodex canis, a hair follicle mite, is one of the most feared of its kind, since it causes a very serious skin disease primarily in the dog’s hair follicles. These mites or ectoparasites are very tiny and invisible to the naked eye.

Demodex has been becoming more prevalent in recent years among Shar-Pei dogs. The big question is whether this is because the breeding and rearing conditions are bad, or is it because unqualified breeders are mating pairs who then pass on genetic disorders? In any case, all those concerned, but especially breeders, breeding inspectors, and canine associations should certainly be alarmed when whole litters of puppies suffer from generalized demodex. Or does enlightenment come otherwise?

There are two known forms of demodex – general and local. Since this information is based on my own experiences, I would like to concentrate here on generalized demodex as it affects Shar-Pei dogs.

In relevance to ear infections in Shar-Pei, I will inform you on another page about demodectic otitis externa, in which mites infect the outer ear’s cerumen (ear wax). 

General congenital demodex (demodex canis)
The dog is considered to have generalized demodex, if the disease occurs frequently without any signs of external agents having weakening its immune system.

Scientists and vets are of the opinion that generalized demodex likely involves a congenital, autosomally recessive immunodeficiency, probably a general T-lymphocyte disorder against demodex mites or a secondary inducing agent. The immune system weakness is not believed to be the result of external agents such as cortisone treatments, tumors, etc., but the outcome of varying degrees of cell-mediated immunosuppression.

Important: The Shar-Pei breed is predisposed to congenital demodex!

The dog’s immune system is weak, making it prone to all kinds of illnesses, including generalized demodex. This disease appears in young dogs aged three months to about two years. Often, all the puppies in a litter are infected, but some may not display any symptoms at all. An infected dam can transmit the follicle mite to the pups through its milk only during the first three days.

Demodex canis is considered a normal member of the household, and small numbers of this mite are found in a healthy dog’s skin and ear canals. In cases where demodex is clinically observed, however, the mites multiply rapidly. An interesting and scientifically proven fact is that C-section puppies raised without their mother tend to be free of demodex canis.

Generalized demodex is a serious matter, especially if the dog simultaneously has a staphylococci or streptococci bacterial skin infection. How demodex progresses depends mainly on the degree of immunodeficiency. At the same time, the presence and extent of a secondary bacterial infection is also critical when that further suppresses the animal’s immune response.

Symptoms of demodex begin to appear after the pups are weaned from the mother. The newborn pup’s skin first starts to change in areas that were in closest contact with its mother – the head, flews, eyelids, and front legs. The paws, in particular, may be severely infected. The disease then spreads across the neck, breast, stomach, and thigh folds. One does not always see measurable hair loss with simultaneous build-up of dandruff and redness of the skin. But then hairless, dandruff-like masses tend to flow together, and the skin around the eyes begins to look like a pair of glasses. The infected skin serves as the ideal climate for the demodex mites, which then multiply even faster.

Demodex soon reaches the generalized stage!

Consequential bacterial infections become very common, and these are accompanied by itchiness and pain. Secondary bacterial infections lead to large patches of suppurating eczema, the skin darkens, and turns crusty. At times, this can develop into generalized lymphadenopathy, a swelling of the body’s lymph nodes, and into general disorders and fever. Bacterial toxins and inflammation mediators also damage other organs, and blood poisoning can even kill the sick dog.

Generalized demodex involves a cell-mediated immunoresponse disorder in the dog. In order to type the immune system’s status properly, one must demonstrate T-cell suppression as defined by comparative values. Furthermore, before commencing systematic treatment, I believe it is important to screen the dog for an MDR1 mutation or multidrug resistance.

To diagnose demodex, the vet needs to take several deep skin scrapings, using a spatula or sharp-edged spoon. As mentioned earlier, the head, flews, eyelids, and front legs are mostly infected, since these parts of a newborn puppy come in closest contact with the mother. The scrapings are mixed in 1-2 drops of glycerin or a 10% solution of potassium hydroxide, placed on a specimen slide and covered. At a magnification of 100, one can view the mites and establish their level of vitality. These mites are longish with eight legs on the frontal part of the body.

It may be necessary to take a skin biopsy from some dogs and in particular Shar-Pei dogs who have deep-lying hair follicles or if their paws are infected. This procedure for surgically removing several small pieces skin for lab histology is done under local or general anesthesia.

Demodex is often difficult to treat, but the infected animal and especially its mother in whom the symptoms could be very subtle, must be treated.

Be extremely patient and set aside at least 4 to 6 months for curing demodex canis, and don’t be surprised at high bills. Professionals say that about 70% of the cases are treatable. Success, however, is dependent largely on you sticking strictly to the prescribed treatment and regular examinations at the vet. Many times, supposedly hard to treat cases turn out to be ones where the treatment was either not pursued long enough or not intensively enough.

Cortisones are highly contraindicated, because they negatively impact the animal’s immune system. If your dog is undergoing any cortisone therapy, stop it immediately.

Even after successfully treating generalized demodex, do not re-administer cortisones – without first having the dog reexamined carefully by the vet and weighing all attendant risks and benefits. It is also critical for the vet (dermatologist) to do everything necessary to strengthen the dog’s constitution. Hence, deworming is just as important as improving your Shar-Pei’s living conditions and care. A bit of extra vitamin E can also help matters. 

Mites are killed through an intensive and systematic localized therapy, which means baths with anti-parasitic solutions and shampoos. In Germany, Amitraz is the approved medication sold under the name Ectodex (Bayer). Two alternatives are Interceptor tablets from Ciba Geigy, and Ivomec from MSD given orally.

My comment at the beginning of this article about demodex being one of the most feared mite diseases is supported by the instructions in the Ectodex pack.

Amitraz is an acaricide that inhibits the enzyme MAO, monoamine oxidase, and thus paralyzes and kills demodex and other mites. Unfortunately, Amitraz has very severe side-effects that can be fatal at times. Some of these are really scary, so:

•    Do not administer Amitraz to diabetic dogs, because it affects the glucose metabolism; 
•    Do not apply Amitraz washing solution to large wounds;
•    Do not treat pregnant or nursing bitches, or pups;
•    Do wear safety gloves and goggles when washing your dog, and
•    Do continue the treatment and veterinary examinations for several months.

Take your dog for a thorough check-up to the vet every two to three weeks, for scrapings to monitor progress and clinical symptoms. The aim here is to do before and after comparisons in terms of the total count for mites, ratio of living to dead mites, and the ratio of adult to young mites.

Once two concurrent negative scrapings are obtained, continue treatment for at least another four weeks. Only after that can you be sure that your dog is healthy again. Remember, interrupting the treatment prematurely risks a relapse.

Breeding ban
Dogs are predisposed to generalized demodex, which is passed on to their offspring.

Although one has yet to conclusively demonstrate the hereditary nature of demodex, ethical and medical grounds demand that dogs with this disease and their parents should never be bred. Bitches with demodex should be spayed, especially since this disease can worsen under the influence of coming into heat, false pregnancy, pregnancy, and breastfeeding.

Information on reference values for immune typing of a dog: 

Leucocyte antigens    Base range
T-cells    CD3    67 - 88
Helper T-cells    CD4    31 - 44
Cytotoxic T-cells    CD8    15 - 31
Ratio: Helper T-cells / cytotoxic T-cells    Ratio CD4 / CD8    1.13 / 2.31
B-cells    B-cell antigen    6 - 19
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