Sarcoptic mange is a non-seasonal, intensely itchy and highly contagious parasitic skin disease caused by a tiny, spider-like mite called Sarcoptes scabiei. The layman's term for this condition is "mange". Another name for sarcoptic mange is "scabies." Parasitic sarcoptic mites burrow into the dog's skin and cause extreme itchiness, which in medical terms is called "pruritis." This in turn leads to scratching, biting and chewing, and subsequent skin inflammation, redness and hair loss, in the affected areas. Secondary bacterial infections are also common.
Adult Sarcoptes scabiei mites are between 0.3 and 0.5 millimeters in size, which is very small. They are roughly circular in shape, with no distinctive head. These mites have 4 pairs of legs, which are uniformly short. Female sarcoptes mites are about twice as large as males. The female mites are responsible for most of the symptoms suffered by infected dogs.
Sarcoptic mange is a zoonotic disease, which means that it can be transmitted by and between people and animals. Dogs affected with Sarcoptes scabiei can pass the parasitic infection to people, and people infected with the parasites can transmit them to dogs.
Causes of Sarcoptic Mange
Sarcoptic mange is caused by the tiny parasitic mite, Sarcoptes scabiei. The clinical signs of infestation by these mites are caused when the mites burrow through the outer layers of the dog's skin and cause intense itchiness (pruritis) from mechanical irritation and from the release of irritating, allergenic substances. Infection by Sarcoptes scabiei mites is extremely contagious. Close direct contact by an unaffected dog with an infected dog, especially in animal shelters, boarding kennels, dog parks, grooming facilities or veterinary clinics, almost always causes the development of symptoms within 2 to 6 weeks after exposure. The mites also can be transmitted indirectly on "fomites," which are inanimate objects such as bedding, grooming equipment, pooper scoopers, food or water bowls, shoes, collars and feces.
The female mites tunnel into areas a few millimeters under the dog's skin and lay their eggs there. The eggs usually hatch within 3 to 10 days. The immature mites develop into adults and begin to lay eggs of their own within only two to three weeks. Then, the process repeats itself. The entire life cycle of these parasites is only about 17 to 21 days and is spent entirely on the dog. All aspects of the life cycle of sarcoptic mites cause extreme itchiness in the host animal.
Prevention of Sarcoptic Mange
The only way to prevent a dog from becoming infected with Sarcoptes scabiei mites is to keep that dog away from dogs or people that are infested with this highly contagious external parasite.
Sarcoptic mange is zoonotic, which means that it can be transferred from dogs to people and from people to dogs. People who are in close contact with a dog that has sarcoptic mange may develop a very itchy, red rash on their arms, chest or abdomen. This rash commonly develops around the belt-line on the waist. These mites usually do not live on humans for more than three weeks.
How Sarcoptic Mange Affects Dogs
Infestation with the mites that cause sarcoptic mange leads to an intense and sudden onset of extreme skin itchiness, which is called "pruritis." Affected dogs will scratch, bite and chew at affected areas in an attempt to relieve the discomfort caused by these bothersome parasites. There is probably no other skin disease that will cause a dog to scratch and bite at her skin as much as sarcoptic mange. The itchiness is caused by the female mites burrowing several millimeters under the dog's skin to lay their eggs.
Symptoms of Sarcoptic Mange
Most dogs with sarcoptic mange are intensely itchy. They tend to exacerbate their condition by self-trauma - from scratching, biting and/or chewing at affected areas of their skin. The sores caused by this condition are typically most obvious on the ventral (lower) abdomen and on the inside of the dog's thighs. Elbows, hocks and ears are also very commonly affected by these mites. Owners of affected dogs may notice one or more of the following signs:
Scratching at areas of the skin, especially the ears, elbows, hocks, inner thighs, underside of the belly and face
Biting at these areas of the skin
Chewing at these areas of the skin
Visible raw sores on the skin, especially on the underside of the abdomen, chest, inner thighs, elbows, hocks and ears
Thickened, dark crusty ear flaps
Patchy hair loss (alopecia)
Crusty sores on affected areas; crusty ear tips are characteristic of sarcoptic mange
Dogs at Increased Risk
Dogs that are in close contact with strays, or those that are kept in close quarters with other dogs in animal shelters, boarding kennels, grooming facilities or elsewhere, have an increased risk of contracting sarcoptic mange. Collies, Australian Shepherds and other herding breeds often are highly sensitive to ivermectin, which is one of the drugs that is used to treat sarcoptic mange. When these dogs develop an adverse reaction to ivermectin, they display neurological signs, including hypersalivation, disorientation, dilated pupils (mydriasis), lack of coordination (ataxia), collapse, coma, and unfortunately sometimes even death.
How Sarcoptic Mange is Diagnosed
Dogs infested with sarcoptic mites will present to the veterinarian with a history of the sudden onset of intense itchiness (pruritis), and probably also with red, raw skin sores and thick crusted areas caused by self-trauma from the dog's effort to alleviate the itchiness. The most common method of diagnosing Sarcoptes scabiei infection is by treating the dog with a topical medication that specifically targets and kills these mites. It is called a "scabicidal" medication, and this process is called "diagnosis by treatment" or "trial therapy." Other tests can be conducted to identify the mites, but those tests are uncommonly done in routine veterinary practices. The physical signs that the dog presents with, together with the results of treating the dog with scabicidal medications, are the best way to definitively diagnose and to treat this disorder.
Skin scrapings and examination of fecal samples can also be useful in the diagnosis of sarcoptic mange, although they are not particularly reliable. They certainly are not as helpful as the response to scabicidal treatment. In Europe, there is an enzyme-linked immunosorbent assay (ELISA) available to test for sarcoptic mite antigen. It is not yet widely available in North America. Another way that sarcoptes mange can be diagnosed is by rubbing the edge of the dog's ear and watching for a reflex scratching action in one of its hind legs. This is an extremely common reaction in dogs with sarcoptic mange. Occasionally, the mites or their eggs can be identified in a fecal sample through a fairly simple procedure called a fecal floatation.
Once sarcoptic mange is diagnosed and treatment is begun, it can take up to two weeks to see any significant reduction in the itchiness suffered by the affected animal. It may take 3 months or more for a complete resolution of the condition to occur.
The primary therapeutic goal of treating a dog with sarcoptic mange is to get rid of the nasty infective mites. Because infestation by these mites is highly contagious, all nearby dogs should be assessed and treated, even if they do not show signs of discomfort or distress. Treatment almost always should be done under strict veterinary supervision.
Dogs with sarcoptic mange will be washed with a specialized shampoo, probably a benzoyl peroxide product, to loosen the hair pores. Then, they will be treated with a scabicidal dip, which means a dip that will kill the mites. The obviously affected areas should be clipped to facilitate the penetration and effectiveness of the topical medication. The entire dog must be treated; simply applying the dip only to the obviously affected areas of the dog will not achieve the desired results. The face and ears must be treated in almost all cases.
There are a number of different medications that can be applied topically to kill these mites. Unfortunately, scabies mites have developed resistance to many of the traditional treatments. Still, the common dips include ivermectin, selamectin (Revolution), milbemycin (Interceptor), lime-sulfur (LymDyp), doramectin and amitraz (Mitaban), among others. The dog's veterinarian can recommend the best treatment protocol. Many authorities suggest that the dog be dipped weekly or every other week for at least six consecutive weeks or until its symptoms resolve, under the supervision of its veterinarian. Many veterinarians recommend treating for two weeks after the signs of infection have gone away. Oral medications may also be part of the treatment protocol. Amitraz dips reportedly should not be used on Chihuahuas, pregnant or nursing bitches or puppies under 4 months of age.
All dogs that have had contact with an infected dog should also be treated. The physical environment should be disinfected to eliminate the mites that may affect dogs and their owners.
Sarcoptes mites usually die fairly quickly when they are exposed to the outer environment. However, it may take up to one or two months for them to be eliminated, and it can take several more weeks for the itchiness (pruritis) to resolve on affected dogs. Most veterinarians recommend clipping the areas where the mites have been active before treating, which can help to enhance the effectiveness of applying the topical drugs.
Traditional antihistamines and steroid medications (corticosteroids) may or may not relieve the itchiness that is always associated with sarcoptic mange. Broad spectrum antibiotics may be useful to resolve secondary infections that can develop as a result of these parasitic infestations. Topical and oral antibiotics will also help to relieve infected skin sores caused by these mites.
The prognosis for most dogs suffering from sarcoptic mange is quite good. With treatment, the itchiness usually goes away and the dog usually returns to a normal, full and good quality of life. Sometimes, dogs develop increased itchiness during the first few days of treatment. This is probably caused by their immune system's response to the dying mites.
Oral ivermectin, while quite effective against scabies, has produced central nervous system abnormalities and even deaths in Old English Sheepdogs, Australian Shepherds, Collies, Shetland Sheepdogs and other herding breeds and crosses of those breeds. Dogs should always be tested for heartworms before being treated with ivermectin.