Dogs have many parasites, both internal and external. Internal parasites are those which live in the various organs inside the dog’s body. External parasites, such as fleas, ticks, and mites, live on the outside of the body. Itching scratching dogs are frequent visitors to the Animal Clinic at Thorndale. Perhaps one of the itchiest diseases a dog can get is sarcoptic mange.
Mange is a parasitic skin disease caused by microscopic mites. Two different types of mange mites are significant in dogs. One type lives just under the surface of the skin, while the other type resides in the hair follicles. Although both types of mites share some similar characteristics, there are also important differences. It is important not to confuse the two types of mange because they have different causes, treatments, and prognoses.
Contributing Factors
The sarcoptic mange mite is highly contagious between dogs. Exposure to a dog infested with this mite will likely lead to spread of the parasite. Fox carry these mites and they are also contagious to our dogs and often contributors to the spread of this parasite.
Prevalence
Sarcoptic mange is a common parasitic skin disease of dogs. It can be found year round.
Causes/Transmission
Sarcoptic mange is caused by a mite that burrows just beneath the surface of the skin. It may also crawl around on the skin surface. This mite feeds on material in and on the skin. Exposure to mites can be by direct contact with an infected dog, or contact with an environment where a sarcoptic mange infested animal has recently been. The mite does not survive for extended times off its host.
Clinical Signs
The presence of the sarcoptic mite causes severe itching. The dog will chew and scratch its skin constantly. This leads to the loss of large amounts of hair, especially on the legs and belly. It is often an “under sided” skin disease and the ear margins are also often crusty and extremely itchy. Eventually, the skin will become thickened and will darken due to pigmentation. Frequent scratching and rubbing often leads to secondary skin infections.
Diagnosis
Diagnosis is made by a skin scraping that is examined under the microscope. However, only a small number of mites may be present. Multiple scraping may not produce the mites. There is about 30% success in finding them due to the extreme area of skin that becomes itchy with even a few mites present. Because of this, a dog may be strongly suspected of having sarcoptic mange but multiple skin scrapings are negative. A presumptive diagnosis can be made because the signs are quite typical. A positive “pinnal-pedal” reflex is often considered diagnostic. In this case, rubbing the crusty ear margin (pinnal) of the affected dog is so itchy that it starts to thump or scratch with its back foot (pedal). Age is not a significant factor in sarcoptic mange. Although most common in puppies, dogs of all ages are at risk.
Treatment
There are several insecticides that are effective against this mite. Topical spot on treatments, such as Revolution, are effective against sarcoptic mange. These are generally easy to apply and also effective against other parasites. Various dips have been used successfully. Dipping should occur weekly for at least 4 weeks, at which time your dog should be re-examined to determine if further treatment is needed. An oral product, ivermectin, is also effective. This drug is approved for use in preventing heartworms; it is not officially approved for use in treating sarcoptic mange. However, its ease of administration compared to dipping makes it the drug of choice in certain situations, and it may actually be more effective than dipping in some dogs
Many dogs will benefit from antihistamines to help with the extreme itching. Steroids should not be used because they suppress the dog’s immune system and allow the mites to flourish. Antibiotics are often needed to cure the secondary skin infections.
All dogs in the house should be treated for the mites, even if not showing signs.
Prognosis
With appropriate therapy, the prognosis for recovery is excellent. Re-infestation from a contaminated environment or other dogs is possible.
Transmission to Humans
Sarcoptic mange is highly contagious to other dogs; it is also contagious to humans. The dog’s bedding should be washed in hot water with bleach or, preferably, discarded. The mites are not able to complete their life cycle on humans; therefore, they will die in a few days without treatment. However, they do bite us and will cause quite a bit of itching before they finally die.