I treated for scabies 3 days ago. Since then I have new bites on me. Does this mean I still have it?

The 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. These tunnels can actually reach the length of several centimeters. After she deposits the eggs, the female mite dies. In 3-8 days, the eggs hatch into larvae which have 6 legs. The larvae mature into nymphs which have 8 legs. The nymph then molts into an adult while it is still in the burrow. The adults mate, and the process continues. The entire life cycle requires 2-3 weeks.

The mites prefer to live on the dog, but will live for several days off of the host in the environment. In cool moist environments, they can live for up to 22 days. At normal room temperature in a home, they will live from 2 to 6 days. Because of the mite's ability to survive off the host, dogs can become infected without ever coming into direct contact with an infected animal.

What are the symptoms of canine scabies?

The symptoms of canine scabies are varied, but usually include hair loss and severe itching especially on the elbows, ears, armpits, hocks, chest, and ventral abdomen (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. Small red pustules often develop along with yellow crusts on the skin. Because of the severe itching and resultant scratching, the skin soon becomes traumatized and a variety of sores and infections can develop as a result. The itching seems to be much worse in warm conditions such as indoors or near a stove or heat vent. If the infection goes untreated or is mistakenly treated as an allergy, the skin may darken due to the constant irritation, and the surrounding lymph nodes may become enlarged.

Sarcoptic mange is a somewhat common infection and many cases have often been misdiagnosed as severe atopy (inhalant allergy). Any time we see a dog who does not have a prior history of allergies and develops severe itching, or if the itching is not seasonal but year-round, we have to suspect canine scabies.

The intense itching caused by the sarcoptic mite is actually thought to be caused from a severe allergic reaction to the mite. When dogs are initially infected with Sarcoptes they do not develop itching for several weeks. If the animals are treated and then reinfected at a later time, severe itching starts almost immediately, which indicates the itching may be due to an allergic reaction. However, the standard treatments for allergies generally will not decrease the symptoms of scabies, and will do nothing to cure the disease.

How is canine scabies diagnosed?

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 twenty percent 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.

How is scabies treated?

There are several ways to treat scabies. In the past, the most effective treatment had been to clip the dog if he had long hair, bathe him with a benzoyl peroxide shampoo to cleanse the skin, and then apply an organophosphate dip (Paramite). Amitraz dips and Mitaban (also organophosphates), and lime sulfur dips (Lymdip) have also been used effectively. The dogs are usually dipped once every two weeks for two to three times. While effective, these dips are very unpleasant to apply for both the owner and the dog. Because the dip must come in contact with the mites and many mites live on the face and ears of dogs, great care must be exercised when applying these dips to these sensitive areas. The dips can be toxic to humans and are not suitable for very young, old, or debilitated animals. In addition, there are some reported cases of resistance to these dips in some cases of sarcoptic mange.

Fortunately, there are several other products that have been extremely effective, safe, and convenient in treating sarcoptic mange. Selamectin (Revolution) is a topical solution that is applied once a month and also provides heartworm prevention, flea control, some tick protection and protection against Sarcoptic mange. Frontline Plus, Frontline Top Spot, and Frontline Spray are also labelled for use as aids in controlling sarcoptic mange. Liquid ivermectin is an off label alternative that is sometimes used. It is used at much higher concentrations than are found in heartworm preventives (e.g., Heartgard). Ivermectin should not be used in Collies or Shetland sheep dogs and should be used with caution in the herding breeds. In dogs that are sensitive to ivermectin, some veterinarians have been having success using milbemycin oxime (Interceptor) at an off-label dose. All of these products should only be used under direct veterinary supervision and care.

In addition to treating the dog, the environment such as the dog's bedding can be treated with a residual insecticide. Since Sarcoptes scabiei is easily transmitted between animals, all dogs in contact with an infected animal should also be treated. Because of the length of the life cycle and ability of the mite to live off of the animal, treatment must continue for a minimum of 4 weeks.

Because of the damage to the skin in sarcoptic mange, many dogs also have bacterial and or yeast infections. These need to be treated as well.

How is canine scabies prevented?

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 fox and the environment in which fox may spend a large amount of time can transmit the mite to dogs, keep dogs away from fox and these areas.

Can I get Sarcoptes from my pet?

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.



References and Further Reading
Ackerman, L. Skin and Haircoat Problems in Dogs. Alpine Publications. Loveland, CO; 1994.

Fourie, LJ; Kok, DJ; Rugg, D; du Plessis, A. Efficacy of a novel formulation of metaflumizone plus amitraz (PromerisTM) for the treatment of demodectic and sarcoptic mange in dogs. Presented at the 32nd Annual World Small Animal Veterinary Association, Sydney, Australia; Aug 23-27, 2007.

Griffin, C; Kwochka, K; Macdonald, J. Current Veterinary Dermatology. Mosby Publications. Linn, MO; 1993.

Newbury, S; Moriello, KA. Skin diseases of animals in shelters: triage strategy and treatment recommendations for common diseases. In Campbell, KL (ed.) The Veterinary Clinics of North America Small Animal Practice: Updates in Dermatology. W.B. Saunders Co. Philadelphia, PA; 2006:78.

Scott, D; Miller, W; Griffin, C. Muller and Kirk's Small Animal Dermatology. W.B. Saunders Co. Philadelphia, PA; 2001.

School settings typically do not provide the level of prolonged personal contact necessary for transmission of the mites.

Can you catch scabies from a dog or cat?

Dogs and cats are infected by different types of mites than those which infect humans. Animals are not a source of spread of human scabies. Scabies on dogs is called mange. When canine or feline mites land on human skin, they fail to thrive and produce only a mild itch that goes away on its own. This is unlike human scabies which gets worse and worse unless the condition is treated.

What are risk factors for scabies?

Scabies can infest any human who comes in contact with the mites. The only known risk factor is direct skin contact with someone who is infested. The contact one experiences in social or school settings is not likely to be sufficient to transmit the mites. Sexual or other close contact (such as hugging) is required to spread the condition. The condition does appear in clusters, so outbreaks may occur within a given community.

What does scabies rash look like? What are scabies symptoms and signs?

Scabies produces a skin rash composed of small red bumps and blisters and affects specific areas of the body. Scabies may involve the webs between the fingers, the wrists and the backs of the elbows, the knees, around the waist and umbilicus, the axillary folds, the areas around the nipples, the sides and backs of the feet, the genital area, and the buttocks. The bumps (medically termed papules) may contain blood crusts. It is helpful to know that not every bump is a bug. In most cases of scabies affecting otherwise healthy adults, there are no more than 10-15 live mites even if there are hundreds of bumps and pimples on the skin.

The scabies rash is often apparent on the head, face, neck, palms, and soles of the feet in infants and very young children but usually not in adults and older children.

Textbook descriptions of scabies always mention "burrows" or "tunnels." These are tiny threadlike projections, ranging from 2 mm-15 mm long, which appear as thin gray, brown, or red lines in affected areas. The burrows can be very difficult to see. Often mistaken for burrows are linear scratch marks that are large and dramatic and appear in people with any itchy skin condition. Scratching actually destroys burrows.

What does scabies feel like?

It is important to note that symptoms may not appear for up to two months after being infested with the scabies mite. Even though symptoms do not occur, the infested person is still able to spread scabies during this time. When symptoms develop, itching is the most common symptom of scabies. The itch of scabies is insidious and relentless and often worsens over a period of weeks. The itch is typically worse at night. For the first weeks, the itch is subtle. It then gradually becomes more intense until, after a month or two, sleep becomes almost impossible.

What makes the itch of scabies distinctive is its relentless quality, at least after several weeks. Other itchy skin conditions -- eczema, hives, and so forth -- tend to produce symptoms that wax and wane. These types of itch may keep people from falling asleep at night for a little while, but they rarely prevent sleep or awaken the sufferer in the middle of the night.

How is a scabies infestation diagnosed?

Scabies is suggested by the presence of the typical rash and symptoms of unrelenting and worsening itch, particularly at night. Ultimately, the definitive diagnosis is made when evidence of mites is found from a skin scraping test. By scraping the skin (covered with a drop of mineral oil) sideways with a scalpel blade over an area of a burrow and examining the scrapings microscopically, it is possible to identify mites, eggs, or pellets. This process can be difficult, however, since burrows can be hard to identify. Sometimes scratch marks are mistaken for burrows, and even the examination of scrapings from 15 or more burrows may only reveal one or two mites or eggs. If the characteristic physical findings are present, scabies can often be treated without performing the skin scrapings necessary to identify the mites.

What are treatment options and home remedies for a scabies infestation?

Curing scabies is rather easy with the administration of prescription scabicide drugs. There are no approved over-the-counter preparations that have been proved to be effective in eliminating scabies. The following steps should be included in the treatment of scabies:

Apply a mite-killer like permethrin (Elimite). These creams are applied from the neck down, left on overnight, then washed off. This application is usually repeated in seven days. Permethrin is approved for use in people 2 months of age and older.
An alternative treatment is 1 ounce of a 1% lotion or 30 grams of cream of lindane, applied from the neck down and washed off after approximately eight hours. Since lindane can cause seizures when it is absorbed through the skin, it should not be used if skin is significantly irritated or wet, such as with extensive skin disease, rash, or after a bath. As an additional precaution, lindane should not be used in pregnant or nursing women, the elderly, people with skin sores at the site of the application, children younger than 2 years of age, or people who weigh less than 110 pounds. Lindane is not a first-line treatment and is only recommended if patients cannot tolerate other therapies or if other therapies have not been effective.
Ivermectin, an oral medication, is an antiparasitic medication that has also been shown to be an effective scabicide, although it is not FDA-approved for this use. The CDC recommends taking this drug at a dosage of 200 micrograms per kilogram body weight as a single dose, followed by a repeat dose two weeks later. Although taking a drug by mouth is more convenient than application of the cream, ivermectin has a greater risk of toxic side effects than permethrin and has not been shown to be superior to permethrin in eradicating scabies. It is typically used only when topical medications have failed or when the patient cannot tolerate them.
Crotamiton lotion 10% and cream 10% (Eurax, Crotan) is another drug that has been approved for the treatment of scabies in adults, but it is not approved for use in children. However, treatment failures have been documented with the use of crotamiton.
Sulfur in petrolatum applied as a cream or ointment is one of the earliest known treatments for scabies. It has not been approved by the FDA for this use, and sulfur should only be used when permethrin, lindane, or ivermectin cannot be tolerated. However, sulfur is safe for use in pregnant women and infants.
Antihistamines, such as diphenhydramine (Benadryl), can be useful in helping provide relief from itching. Sometimes, a short course of topical or oral steroids is prescribed to help control the itching.
Wash linens and bedclothes in hot water. Because mites don't live long away from the body, it is not necessary to dry-clean the whole wardrobe, spray furniture and rugs, and so forth.
Treat sexual contacts or relevant family members (who either have either symptoms or have the kind of relationship that makes transmission likely).
Just as the itch of scabies takes a while to reach a crescendo, it takes a few days to subside after treatment. After a week or two, relief is dramatic. If that doesn't happen, the diagnosis of scabies must be questioned.

Are cases of scabies often misdiagnosed?

Scabies is very easy to misdiagnose because early subtle infestation may look like small pimples or mosquito bites. Those affected may believe they have another condition, such as bedbug bites or other kinds of rashes. Over a few weeks, however, mistakes like this become evident as patients feel worse and worse with symptoms they can't ignore.

What are possible complications of scabies?

The intense itching of scabies leads to prolonged and often intense scratching of the skin. When the skin is broken or injured due to scratching, secondary bacterial infections of the skin can develop from bacteria normally present on the skin, such as Staphylococcus aureus or beta-hemolytic streptococci.

Can a scabies infestation be prevented?

Scabies can be prevented by avoiding close personal contact with infested people. Sexual contacts and household members of people who develop scabies can be treated as soon as the condition is identified so that they will not develop the signs or symptoms of the condition. The treatment for these exposed people is the same as the treatment of the infested individual.

In what special situations can scabies be more easily spread?

Elderly and weakened people in nursing homes and similar institutional settings may harbor scabies without showing significant itching or visible signs. In such cases, there can be widespread epidemics among patients and health care workers. Such cases are dramatic but, fortunately, uncommon.