Mange

There are two different types of mange which can be distinguished with a skin scrape. When performing a skin scrape, a veterinarian runs a dull scalpel blade across the skin to collect a sample of mites (generally along with hair and skin cells) and examines the sample under the microscope. The two mites look very different microscopically. It is important to use isolation protocols on all dogs with suspected mange who have not yet had a skin scrape, since that is the only way to know whether or not the mange is contagious.

Demodectic Mange

Demodectic mange (Demodicosis) is caused by the demodex mite. Demodex mites live inside hair follicles. They are naturally present on all dogs and not usually problematic. An overgrowth of mites, due to a weakened immune system, causes mange. Since puppies have weaker immune systems than adult dogs, demodectic mange is most common in puppies. Demodectic mange is not contagious to other dogs, cats, or humans.
File:Demodex mite 1.JPG
Photograph by Joel Mills under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Symptoms

  • Hair loss
    • Thin hair or complete baldness across the entire body (generalized demodicosis)
    • Patchy hair loss in one or two spots (localized demodicosis) or in many spots around the body (generalized demodicosis)
  • Scaly skin
  • Skin infections (which often cause the skin to smell)
  • Pruritus (Itchy skin)

Treatment

Since the overgrowth of mites is usually due to a weakened immune system, an important component of treatment is dealing with the underlying cause of this weakness. Healthy puppies who have localized demodicosis may "grow out of it" as their immune system matures without needing treatment. Parvo weakens the immune system, making the dogs more susceptible to demodicosis. Additionally, many of the dogs we see have weakened immune systems because they been strays without adequate nutrition, shelter, or veterinary care.

Dogs with generalized demodicosis and dogs with weakened immune systems are typically treated. Ivermectin, commonly used in heartworm prevention, is the most common treatment for demodectic mange. It is generally given orally for several weeks or months until symptoms have resolved.  Ivermectin can sometimes cause GI upset, so treatment is usually not started until dogs are discharged from the Parvo ICU.

Many dogs with demodectic mange have secondary skin infections. These are treated with antibiotics, which may or may not be the same as those used to treat parvo. They may also receive topical or oral medications for itch relief.

Sarcoptic Mange

Sarcoptic Mange is caused by the Sarcoptes scabiei mite. After mating, female scabies mites burrows into the dog's skin to deposit their eggs. The eggs hatch, crawl back up to the surface of the skin, and live there until they mate and restart the cycle 3-4 weeks later. The burrowing mites generate an allergic inflammatory response from the skin, which is extremely itchy and uncomfortable. The movement of the mites on top of the skin is itchy for the dog as well.
File:Canine scabies mite.JPG

Symptoms

Scabies mites prefer hairless skin, so mange often begins on the ears, elbows, and belly but will spread to the entire body if not treated.

  • Hair loss
  • Severe pruritus
  • Self trauma (due to pruritus)
  • Scaly, thickened skin 
  • Secondary skin infections
 File:Street dog-Gianyar Bali-2009.jpeg
Photograph by Jack Merridew under public domain.

Isolation Protocols

Sarcoptic mange is contagious to other dogs through direct contact and through contact with infected surfaces, including cages, clothing, and bedding. Scabies mites can also infect humans, cats and wildlife, although these are not the mite's preferred hosts and the infection is usually milder and self-limiting. There is a different mite that prefers humans as its host.
  • Wear a gown over your scrubs- you can transmit the mite on your clothing
  • Wear gloves while handling the dog or its bedding
  • Wash your hands and arms thoroughly with soap and water
  • Disinfect the runs and cages of dogs with sarcoptic mange using Dleach. Trifectant will not kill the mites. 
  • You do not need to cover the cage of a dog with mange.

Treatment

There are several options for treating mange. Revolution can be used to kill the mites, and Benadryl for itch relief in parvo patients.
  • Revolution (selamectin)- two doses of Revolution given topically two weeks apart 
  • Diphenhydramine (Benadryl) can be given orally or SQ 
  • Advantage Multi (moxidectin) to kill mites
  • Dips -  Mitaban or Lyme-sulfur dips. Dogs are dipped weekly for one month. This is an older, more labor-intensive treatment and is less common now that other treatments are available.
  • Antibiotics that penetrate the skin for secondary skin infections
  • Corticosteroids at an antiinflammatory dose for severe pruritus (not used in parvo patients due to immune suppression) 
  • Topical shampoos and creams can also reduce itching
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