Pet Vet: Pug’s missing hair, itchy skin could be mange from mites

February 15, 2016

Hadley is a 6-month-old pug dog with a skin problem. His caretakers, Forest and Sherry, have had him since he was 8 weeks old and noticed recently that he is developing patches of missing hair on his body, some of which show reddened skin. Hadley seems otherwise unaffected although Sherry reports he does seem itchy. He has been treated with a flea preventative and, according to Forest and Sherry, he has no fleas.

The absence of visible fleas does not rule out a skin problem due to fleas. They can be very difficult to spot and, in dogs with flea sensitivities, there may not be any fleas on the dog, as they have chewed them all off. That said, I do not think Hadley has fleas.

Young dogs such as Hadley can take time to develop a fully competent immune system and, as a result, they can be more susceptible to certain diseases. These diseases would not affect a normal adult dog, but in a case in which the immune system has not matured, they can manifest. I suspect that is what is happening with Hadley, that he has a case of mange.

Mange is a collective term representing a skin disease caused by different types of mites. Mites are in the arthropod group of organisms and there are many different species that can cause "mange" depending on the species of animal. In dogs, we see predominately two types of mites associated with mange — Sarcoptes scabeii and Demodex sp.

In Hadley’s case, I suspect he has a case of mange caused by Demodex mites. These mites live in the hair follicles of an infected dog and, as they increase, the hair shafts fall from the follicles, creating patches of hair loss as described in Hadley. This invasive process causes an inflammatory response leading to reddening of the skin. As one might imagine, these dogs can be itchy. To definitively diagnose Demodex, Hadley needs to be taken to a veterinarian.

To diagnose Demodex, we use a simple diagnostic test called a skin scrape. This is accomplished by scraping a pinched ridge of skin in several affected areas of the patient and examining the skin scrapings under a microscope. It is important to scrape relatively aggressively as these mites can be burrowed fairly deeply into the hair follicles. Under the microscope the Demodex mites appear very distinctive. They are cigar shaped with three pair of stubby legs in the forward third to half of their body. In a heavy case of Demodex there will be large numbers of mites wiggling under the microscope.

If I am correct in my diagnosis and Hadley has Demodex, he will need to be treated. Sometimes Demodex can manifest as a single lesion somewhere on the body and can simply be treated topically in that one location or, in some cases, not treated at all. In Hadley’s case, the process sounds more generalized. For him, it is best to treat his entire body. In the past this would involve a topical therapy usually done in the veterinary hospital and repeated multiple times until rechecked skin scrapings are negative for the mite. Recently, a new flea product Bravecto has shown great promise in treating dogs with Demodex. It is an oral medication given once every three months for flea prevention. In the cases with which I have been involved using it against Demodex, it took only one treatment to cure the patient.

One last point about Demodex is that it occurs on many dogs. However, the mite population is kept in check by the dog’s immune system. Patients with decreased or immature immune systems, as in Hadley’s case, can break with Demodex-associated mange. Adult dogs rarely get this disease unless they are immune compromised.




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