CANINE/FELINE DEMODICOSIS (aka: Demodectic Mange in dogs and cats)
This is a really interesting disease, not least because the Demodex canis mange mites causing the problem have to be present in large numbers in the hair follicles of the skin before the disease symptoms exhibit themselves. Another interesting phenomenon is that a low-level Demodex mite infestation does not create a great itch/scratch display. Generally, one assumes that if there is a foreign body (e.g., mites) in any part of the skin, the dog or cat would scratch a lot. Biology/nature is indeed strange.

Q: Does the dog/cat have to be sick with some other disease for the Demodex mite to take a strong hold of the dog or cat?
A: The research literature does seem to be of the view that canine Demodicosis is more prevalent in weak pups and young dogs. Felines infected with the cat mite (Demodex gatoi) can pick up the disease at any age, and even when they are strong and in good health.
Q: Do short-haired dogs get infected more with these mites?
A: I seem to think so, and scientific research tends to support my empirical observation. In fact, I have a theory that dogs, when they are young, actually experience a deficiency in their immune system (at least temporarily). This deficiency tends to disappear as the animals get older; consequently, adult and older dogs do not usually succumb so easily to Demodicosis. Of course, if the adult dog has been bombarded with immune suppressive medication, the pet will more easily be affected with Demodex mites. It follows therefore that if the pet dog is well cared for and healthy, the Demodex mite will not overpower the animal so easily.
The situation in cats is quite different. Sick or healthy, they can be relatively easily infected with the cat-specific demodectic mite.
Q: Can one detect/diagnose Demodectic Mange by just looking at a dog?
A: One should never be too self-reliant and pretend to be all-knowing. However, experienced vets can pretty much detect a Demodex infection without taking scrapings and without undertaking extensive laboratory tests.
Having said that, many (most?) untreated dogs afflicted with the Demodex canis mite will look like the Dobermans in the photo below.
But do not let us get beyond ourselves. Let us have a look at the symptoms of Demodectic Mange.
They are:
(i) Hair loss,
(ii) Some scratching; but not as intense as with a Sarcoptic Mange infection (see last week’s column). Demodex gatoi (demodectic cat mange) does create a lot of scratching in cats.
(iii) Several small, patchy, bald areas emerge at the beginning. Later, if left untreated, these hairless patches tend to merge and look like the dog in photo #2 above.
Q: Once the diagnosis is accurately made, how can the caregiver treat the affected dog/cat?
A: This generation is so lucky. The treatment of skin mites (Demodex and Sarcoptes and any others) has been revolutionised. Nowadays, we have pharmaceutical companies producing medication specifically for dog and cat diseases – and Hurrah!!, they all work well in killing the mites
As part of the total therapeutic intervention, your Veterinarian might actually discontinue any treatment which in his/her opinion would tend to suppress the animal’s innate ability to fight off germs that are getting involved in the mange lesions. Once I am satisfied that the mites have been killed (no live mites seen in monthly scrapings), I tend to be hesitant in introducing antibiotics, etc. Let the animal’s own defense mechanism take over the healing process. Of course, the patient with mange has to return to the clinic as often as is needed.
For me, the cure against mite infestations is only achieved, if there has been no new recurrence during the period of one year after the treatment protocol has been completed.