I recently received the following question from Wanda, for whom brevity is a forte:

Can mange from a puppy be contagious to a human?

The answer depends upon the type of mange.

In the developing world, the most common type of mange in puppies (so common that it is known colloquially as puppy mange) is caused by an organism called Demodex canis. Puppy mange (also known as demodectic mange) occurs very frequently in dogs less than two years old. It most often causes non-itching hair loss in small patches on the face, trunk, and limbs. The patches of hair loss most frequently resolve on their own without treatment. Rarely, individuals may suffer secondary skin infections or more generalized hair loss that requires treatment.

Demodex canis is a ubiquitous mite. It lives on virtually every dog on earth. The mite causes symptoms in individuals whose immune systems are not able to suppress it. This occurs most frequently in juveniles with immature immune systems — hence the symptoms are most common in puppies.

Demodex canis can theoretically infest humans. However, dog-to-human transmission appears to be very rare. And, humans almost never develop symptoms from infestation with the mite. Be aware that we have our own species of Demodex — folliculorum and brevis. These are much more common causes of symptoms in humans, and they are not spread by dogs.

In my career I have never seen or heard of a case in which a puppy or a dog transmitted symptomatic Demodex to a person.

A second type of mange occurs commonly in dogs in developing countries and occasionally in the developed world. Called sarcoptic mange, it is caused by a different type of mite: Sarcoptes scabiei. Sarcoptic mange, also known as scabies, is highly contagious among dogs, and it can cause severe symptoms. Infested dogs may lose large quantities of hair, especially on their undersides. Severely infested dogs may become completely bald, with thick and inflamed skin. Sarcoptic mange causes severe itching in most individuals.

Humans can contract scabies from dogs and may suffer from rashes and itching as a result. However, the dog variety of the mite generally can infest humans only for a few weeks before it is cleared. Be aware that we have our own variety of scabies, which is not spread by dogs (or cats), and which causes severe and progressive symptoms that require treatment.

In developed countries, it is not common for mange in dogs to cause skin problems in the people who come into contact them. Most of the time, infectious diseases and parasites are relatively species specific. Dogs contract problems from other dogs. Humans contract problems from other people.

However, common sense is in order. If your dog has a skin problem, he should see the vet immediately.

Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column.

(Note that if you have an emergency situation, please see your own vet immediately!)