Mange
Mange is a generic term used to identify a group of skin diseases characterized by patches of hair loss that at times cause itching. Mange can be classified into 2 causes; demodectic mange and sarcoptic mange. Fleas are another type of skin parasite that can resemble mange but fleas remain on top of the skin whereas demodectic and sarcoptic mange are secondary to burrowing mites.
Demodectic mange (also known as red mange or demodicosis) is caused by a mite of the Demodex species, the most common being Demodex canis. Demodex mites typically affect dogs but can affect cats as well, although far less frequently. The mite is often transmitted to puppies through direct contact with the mother during the first several days of life through nursing. Demodex is not typically considered a contagious type of mange and in routine cases, no extra home care is needed during treatment of these animals. Once inhabiting a dog, the mites cannot be transmitted to people or cats.
In a healthy animal, Demodex resides in the skin in small numbers and does not cause clinical disease. The body's immune system keep the population under control, but if the immune system is stressed, clinical disease may result. If a dog becomes symptomatic, demodectic mange will cause areas of hair loss of varying sizes and shapes. They may be singular or multiple depending on the type of infestation, and may or may not cause itching. Common places to see infections are around the eyes or muzzle.
Infections can be localized (one given spot on the body) or generalized (over the entire body or several areas of the body). Occasionally, localized disease will progress to generalized demodicosis. There are 2 distinct syndromes known as juvenile onset and adult onset. Juvenile onset usually occurs in dogs less than 1-2 years of age. Many of these dogs have immune systems that are not fully developed and can be sensitive to developing the disease. A large portion of juvenile onset demodicosis will spontaneously recover on their own, but all dogs are treated to speed the recovery from disease.
Adult onset disease is often associated with animals having a suppressed immune system from infections, cancer or systemic metabolic disease such as Cushing’s disease, liver disease or kidney issues. If an adult dog gets Demodex, a full examination as well as bloodwork and radiographs should be considered to evaluate for underlying diseases. Occasionally, pets on systemic steroids will have an infection due to the suppression of the immune system by steroids.
Demodex is diagnosed by a skin scrape and associated clinical signs. A skin scrape involves using a blade to scrape the skin to remove cells. Demodex requires a deep skin scrape, so many times the dogs will have a small area of redness after the scraping. This will heal on its own very quickly. If a diagnosis cannot be made based upon a scraping, a biopsy may be needed.
Treatment for Demodex depends on the form of disease and possible underlying circumstances. Any underlying disease should be treated appropriately. In most circumstances, treatment involves using a medication called ivermectin, although small isolated lesions can sometimes be treated with topical medications. Ivermectin is an anti-parasitic medication and will kill the mites over a period of time. It is very important to use this medication with caution in several of the herding breeds such as Collies, Shelties, Australian Shepherds and others. These breeds are more sensitive to the medication and often a very gradual introduction to the medication is needed. Also, a test can be performed through Washington State University’s Veterinary School to see if a pet will be sensitive. The primary signs seen with toxicity are primarily neurologic such as stumbling, seizures, weakness and lethargy. Consultation with a veterinarian is needed prior to starting treatment and if any of these signs are seen, contact a veterinarian immediately. Treatment continues until 2 negative skin scrapes are obtained 1 month apart. Many pets are on ivermectin daily for 2-6 months with monthly rechecks until cleared.
Sarcoptic mange (otherwise known as Scabies) is caused by a superficial burrowing skin mite called Sarcoptes scabiei. The mites secrete an allergic substance that produces very intense itching. The disease is often characterized by excessive itching that can occur year round and does not respond to steroids.
Scabies is easily transmitted between dogs, most often in a kennel, at boarding or in other areas of close containment. It can also be transmitted to humans and cats. Clinically the dogs will be itchy primarily around areas of decreased hair such as elbows, hocks and ear tips. Many times the skin will be red, crusted or have pustules. Scabies is diagnosed through clinical signs, history, skin scrapings and treatment. The pinna-pedal reflex, which involves rubbing the ear tip to see if a scratch reflex or motion is produced, can be helpful, however if positive, this is suggestive of Scabies but not a definitive diagnosis. Scabies can be difficult to find with skin scrapings, therefore a negative scrape does not rule out the disease.
Treatment is most commonly performed with the use of selamectin (Revolution) at 2 week intervals. Many times, if skin scrapes are negative, but a veterinarian is highly suspicious of the disease, a treatment trial will be performed. Occasionally, selamectin may not work and at times ivermectin is needed. Many dogs get secondary bacterial infections and oral antibiotics may be required.
With scabies, environmental care is very important to prevent re-infestation as well as transmission to other animals and humans. Bedding should be disposed of and the home thoroughly vacuumed. Prognosis is good if medical and environmental care are performed.
There are several diseases that can causes patches of hair loss, so a thorough examination by a veterinarian is always recommended to determine the underlying cause. Any time a new pet is brought into the home, a cursory exam by owner is ideal to evaluate for hair loss and if noted, a veterinary visit is recommended.