Who gets sarcoptic mange?

Sarcoptic mange can infect all ages and breeds of dogs. While it prefers to live on dogs this particular mite will also infect cats, humans, and foxes. Cats, foxes and humans all have their own particular species of mite within the Sarcoptes family. Each species of mite prefers one specific kind of host (e.g., dog) but may also infect others. Since all of these species of mites have a similar life cycle and respond to the same treatment we will assume that the vast majority of dog infections are caused by the mite Sarcoptes scabiei and treat accordingly.

What is the life cycle of Sarcoptes scabiei?

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 dog.

What are the symptoms?

The symptoms are varied but usually include hair loss and severe itching on the elbows, ears, armpits, hocks, chest and ventral abdomen (belly). The mites prefer to live on areas of the skin that don't have less hair. As the infection worsens it can spread over the entire body. Small red pustules often develop along with yellow crust on the skin. Because of the severe itching and resultant scratching from the dog, 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 on 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 sarcoptic mange.

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 don't 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 sarcoptic mange diagnosed?

Trying to get a diagnosis for scabies can be very frustrating. The standard method is to perform a skin scraping and then identify the organism 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 it 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 animals 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 mange.

Fortunately there are several newer products on the market that have been extremely effective, safe, and convenient in treating sarcoptic mange. The most widely used is the liquid cattle wormer Ivermectin (Ivomec). This product is available in a 1% liquid formula and is currently only labeled for use in cattle but is widely used by veterinarians to treat Sarcoptic mange. In my practice, it is the first choice for treatment. Most dogs get one oral dose and then another oral dose two weeks later. The success and safety rate is excellent. 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 oxine (Interceptor) at an off-label dose of once a week for three weeks. Both ivermectin and Interceptor should only be used under direct veterinary supervision and care.

Recently a new product containing Selamectin(Revolution) was released on the market. This product is a topical solution that is applied once a month and provides heartworm prevention, flea control, some tick protection and protection against Sarcoptic mange. I expect this product will be widely used in areas where Sarcoptic mange is a problem.

In addition to treating the dog, the environment can be treated with a residual insecticide (e.g., permethrin).

How is sarcoptic mange 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 number 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. In my experience, dogs that are well groomed, eat a good diet, have a healthy skin and coat, and don't spend much time with other dogs or where dogs are brought together, are less likely to contract this disease. With the new product Revolution we have an approved product that will help prevent Sarcoptic mange.

Can I get Sarcoptes from my pet?

Yes, although when humans get Sarcopties scabei from animals, the disease is generally self-limiting, causing only temporary itching. There is a human race of Sarcoptes scabie, which is transmitted from person to person. This human race 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.