One of the most common reasons that a
pet is brought in to the veterinary hospital is because of itching. Allergies (environmental, flea, contact,
bacteria/yeast, and food allergies) are probably the most common underlying
problem in the majority of cases; however, this is not always the
case.
In addition to ear mites (which most people have heard of), there are two other types of mites that affect the skin of dogs and cats: Demodex and Sarcoptes. The lifecycles of these mites are very different, but the end result is often very similar: A very itchy pet!
Zionsville Animal Hospital has seen a definite increase in mites over the last several months, particularly in dogs diagnosed with Sarcoptic mange. We have diagnosed it in 4 dogs and have had several other cases respond very favorably to the treatment without actual confirmation. We think that this prevalence has to do, at least in part, to the increased number of foxes residing in Zionsville over the past year or so. Foxes are a known reservoir of Sarcoptes scabei mites.
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| http://en.wikipedia.org/wiki/Dog_scabies |
Interestingly, the sarcoptic mites usually spend their entire life on a dog. The female mite burrows into the skin and lays eggs several times as she continues burrowing—this act is what is thought to incite the itch sensation.
These mites “prefer” to live on the dog (or fox), but will live for several days off of the host in the environment.Because of the mite's ability to survive off of the host, dogs can become infected without ever coming into direct contact with an infected animal.Trees, decks, and other inanimate objects where foxes and coyotes may scratch themselves or have casual contact are thought to be the sources of infection for our unsuspecting pets.
The symptoms of canine scabies usually include hair loss and severe itching especially on the elbows, ears, armpits, hocks, chest, and belly. The mites prefer to live on areas of the skin that have less hair. As the infection worsens it can spread over the entire body. Because of the severe itching and self-trauma to the skin, bacterial and yeast infection are common. Trying to make a diagnosis of canine scabies can be very frustrating. The standard method is to perform a skin scraping and then identify the mite under the microscope. Unfortunately, on average, only ~20% of the infected dogs will show Sarcoptes mites on any given scraping. Therefore, if a dog has a positive skin scraping, the diagnosis is confirmed but a negative scraping DOES NOT rule out sarcoptic mange. Therefore, most diagnoses are made based on history and response to treatment for scabies.
The preferred treatment for scabies is with Revolution, a topical heartworm and flea preventative. The active ingredient is called Selamectin (a derivative of Ivermectin). The key is to apply the Revolution every 2 weeks for at least 6 weeks, and usually 12 weeks is recommended with confirmed cases. I like to give a dose of injectable Ivermectin on Day 1 of a confirmed case of scabies to “get the ball rolling” and start killing these little buggers ASAP. Because of the damage to the skin in sarcoptic mange, many dogs also have bacterial and or yeast infections and these obviously need to be treated as well. Skin cultures are preferred, especially in severe cases, to make sure that the correct antibiotic or antibiotics are given.
Because your dog does not have to come into direct contact with an infected dog to contract scabies, it is difficult to completely protect him. Places where large numbers of dogs congregate are obviously more likely to harbor the mange mite. Since foxes and the environment in which foxes may spend a large amount of time can transmit the mite to dogs, keep dogs away from fox and these areas.
Is Sarcoptic mange contagious to me or my other pets? Yes, although when humans get Sarcoptes scabei from animals, the disease is generally self-limiting, causing only temporary itching. There is a human species of Sarcoptes, which is transmitted from person to person. This human species of sarcoptic mite causes a rash on the wrists, elbows, or between the fingers. In infants, the rash may appear on the head, neck, or body. Other dogs in the house need not be isolated from each other, but because the treatment of scabies is relatively straightforward, it is recommended, however, to treat all pets in the household when there is a confirmed case.
Demodectic Mange:
Demodectic mange, also called demodicosis or “Red Mange,” is caused by a microscopic mite of the Demodex genus. These mites are transmitted by mothers to their young through cuddling and nursing during the first few days of life. Most live in harmony with their mites, never suffering any consequences from being parasitized. However, if conditions change to upset the natural equilibrium, such as some kind of suppression of the dog's immune system (stress or long term/chronic use of steroids), the Demodex mites may gain the upper hand. The mites proliferate and can cause serious skin disease. The mites burrow into the actual hair follicles, causing itching and hair loss, as well as secondary bacterial/yeast infections.
http://en.wikipedia.org/wiki/Dog_demodex
Demodectic mange is NOT considered a contagious disease (to people nor to other dogs or cats) and isolation of affected dogs is generally not considered necessary. While there are still assorted theories about dog to dog transmission of Demodex mites, there is no question that mites cannot be transmitted to humans or to cats.
Demodicosis has Three (3) Forms: Localized, Generalized, and on the Feet (Demodectic Pododermatitis):
1) Localized demodicosis occurs as isolated scaly bald patches, usually on the dog's face, creating a polka-dot appearance. Localized demodicosis is considered a common puppyhood ailment and approximately 90% of cases resolve with no treatment of any kind.
2) Generalized demodicosis the entire dog is affected with patchy fur, skin infections, and bald, scaly skin. The entire body is typically affected, and the secondary bacterial infections make this an itchy and often smelly skin disease. Treatment is needed to facilitate recovery.
3) Demodectic Pododermatitis is confined to the paws. Bacterial infectious usually accompany this condition. Often as generalized demodicosis is treated, the foot is the last stronghold of the mite. Old English Sheepdogs and the Shar Pei tend to get severe forms of this condition. The infection can be so deep that biopsy is needed to find the mites and make the diagnosis. It is one of the most resistant forms of demodicosis.
Treatment: Ivermectin (Ivomec 1%) is a broad spectrum anti-parasite medication with a number of uses, including killing demodex mites. Ivermectin is inexpensive and involves no labor-intensive bathing. It DOES, however, taste terrible if given orally. It requires daily treatment in most cases and should be continued for a minimum of 3 months, or 2 negative skin scrapes 1 month apart. There is, unfortunately, an important occasional problem that keeps other treatment options listed: drug sensitivity. Some individual dogs are sensitive to ivermectin and can die if subjected to a typical therapeutic dose for demodicosis. Benzoyl Peroxide Shampoos (e.g., Pyoben) are great to use with affected animals because it penetrates and flushes out the hair follicles, deep where these mites live on the animal’s skin. Amitraz dips on a weekly basis are effective, but labor-intensive, and are usually reserved for dogs that don’t tolerate the oral Ivermectin.
Relapse?
When relapse occurs it is often because the dog appeared to be normal and the owner did not return for the appropriate re-scrapings. Relapse is always a possibility with generalized demodicosis as there is no easy way to confirm that every mite has been killed, but most dogs that relapse do so within a 6 to 12 month period from the time they appear to have achieved cure.
Sources:
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