Skin problems are a common reason for taking a pet to the vet. One study estimated that about one in five small animal consultations in general veterinary practice involved animals that had a dermatological problem.
A common cause of skin problems in dogs is having ‘mange’. The term ‘mangy’ is associated with things that look shabby or worn, perhaps an old carpet with threadbare patches. What does it mean for a dog to have mange?
Mange is a skin disease caused by mites and there are two different types of mange mite which cause skin disease in dogs: Demodex and Sarcoptes. Sarcoptic mange tends to be more itchy and uncomfortable for the dog than demodectic mange. Both types of mange present differently and have different treatments.
WHAT IS A MANGE MITE?
Adult mange mites have eight legs and are distant relatives of ticks, spiders and scorpions. They are not insects, and do not have the wings, antennae or segmented bodies typical of an insect. Mange mites are very small (less than half a millimetre in length) and live in the skin.
Demodex canis is the name of a small mite which lives down hair follicles, near the base of the hairs. Demodex mites move from the mother to the puppy, during the first few days of the puppy’s life. The majority of dogs spend all of their lives in harmony with the low numbers of demodex mites which live in their skin and do not have any skin problems.
In a small proportion of dogs, the demodex mites increase in numbers and leads to inflammation of the hair follicles, and subsequent hair loss. Dogs develop bald patches of varying sizes, hence the ‘mangy’ description. The face and feet are the commonest areas of the body to be affected, but patches of alopecia can occur at any location. Demodectic mange can occur in dogs of any age but is mostly seen at less than one year of age, or over five years of age.
Young dogs with small patches of demodectic mange will often recover spontaneously without the need for treatment. The temporary increase in numbers of demodex mites in young dogs may be due to immaturity of the immune system, or to a transient immune imbalance. Young dogs with large areas of demodectic mange are likely to need treatment to reduce the mite population, but usually do well. Once the disease is under control they do not usually need ongoing treatment.
Older dogs with demodectic mange are of more concern. These dogs have lived in balance with low numbers of demodex mites in their skin for many years. What has changed to allow the demodex mites to grow in numbers now? In half of dogs investigated no underlying cause is found for the adult-onset disease. Investigation of the other 50% of affected dogs reveals an underlying disease, which is suppressing the ability of the immune system to function in a normal way. Hormonal imbalances, or certain types of cancer, would be typical underlying diseases. Affected dogs need treatment to reduce the numbers of demodex mites, but also need diagnosis and treatment of any underlying disease.
What does demodectic mange look like?
Most dogs have patchy hair loss but are not itchy. The skin may become red and inflamed, or may turn a grey/black colour after being inflamed for some time. The skin often looks normal, but loses the overlying hair coat in well-defined areas.
Can people catch Demodex canis mites?
You cannot catch Demodex canis mites from your dog. Most species of mammal have their own type(s) of demodex mite. For example, people often have Demodex folliculorum in the hair follicles of the eyelashes, and Demodex brevis in the sebaceous glands.
Can my other dog catch demodectic mange?
Demodectic mange is not contagious, as it depends on the state of the individual immune system, not just on the presence of the mites. However, your other dog probably already has its own demodex mites which it acquired as a young puppy from contact with its mother, and which are not causing any kind of skin disease.
How can my vet make a diagnosis of demodectic mange?
Your vet can pluck out a tuft of hairs, or scrape the skin surface with a scalpel blade. These samples can be examined under the microscope for the presence of the small mites. Your vet may look at the samples with their own microscope, or may send the samples away to a diagnostic laboratory.
How is demodectic mange treated?
A variety of treatment options are available, and treatment is best tailored by your vet to the individual dog. Some dogs get a secondary bacterial skin infection in addition to the demodectic mange, so this may also need treatment. Older dogs, with adult-onset demodectic mange, need investigation and treatment for any underlying cause that may have been discovered. The numbers of demodex mites are monitored during treatment, until they have been successfully reduced to the normal low levels.
The second type of skin mite which causes mange in dogs is called Sarcoptes scabeii. The disease is called sarcoptic mange, or canine scabies. Sarcoptes mites can affect dogs of any age. They can also affect ferrets and foxes, and rarely cats. It is possible to get sarcoptic mange at any time of year.
What does sarcoptic mange look like?
The disease causes a lot of skin irritation. Dogs will scratch, rub and bite at the skin to get some relief from the itchiness. The itch associated with sarcoptic mange is generally severe and relentless, causing dogs to scratch when out for a walk, or during the night. These are times when dogs with other itchy skin diseases may be distracted from their itch, or are able to sleep.
The thinly haired skin of the ear flaps, hocks, elbows and abdomen are the commonest places to be affected, but any part of the body can be involved. Scratching leads to patchy hair loss, and dogs can traumatise their skin to the point of bleeding. The skin is often hot and red. Cases which have been going on for a while have thickened, dark coloured skin with overlying crust and scale.
Can people catch Sarcoptes scabeii?
Yes. Although the dog Sarcoptes mite is adapted to live on dogs, it can transfer to people and cause an itchy skin rash. However, it does not complete its lifecycle on people so the mites will die out and the condition is transient and self-limiting on people. People also have their own type of Sarcoptes mite (var. hominis) which is adapted to live on humans.
Can my other dog catch Sarcoptes scabeii?
Yes, the Sarcoptes mite is easily spread by direct contact, and it can live briefly away from the skin. It is common for all of the incontact dogs to be affected. The absence of itchiness and sore skin in another dog in the household does not exclude the possibility of sarcoptic mange, as sometimes just one dog is affected.
How can my vet make a diagnosis of sarcoptic mange?
Your vet can collect skin samples by scraping the skin surface with a scalpel blade, and then look under the microscope for Sarcoptes mites. Sarcoptes mites are not usually numerous, so may not be found on skin scraping. Your vet can also take a blood sample to measure the level of antibodies made against Sarcoptes. This test is useful if no mites are found on skin scraping, and your dog has had the disease for some time. However, the blood test may not be positive if your dog has only just acquired the Sarcoptes mites, as there has not been enough time for the body to make a significant antibody response.
How is sarcoptic mange treated?
There are a variety of effective treatments for sarcoptic mange, and your vet can provide you with an appropriate one for your dog. Some dogs become increasingly itchy for a short time after treatment for the mites, and this does not mean that the treatment is ineffective. It is important to assess all of the dogs which are in contact with the affected dog, and to pay attention to the hygiene of bedding, grooming tools, coats, harnesses, etc. As well as killing the parasites, dogs will need short term treatment to give relief from the itchiness. They may also need treatment for a secondary bacterial infection.
What should you do if you think your dog looks ‘mangy’?
Mange mites, whether Demodex or Sarcoptes, are common causes of patchy hair loss in dogs. Your local vet can help with the diagnosis and effective treatment of mange, and other skin conditions. However, sometimes skin conditions can be complex and frustrating to diagnose and treat and your local vet may decide to refer the case to a veterinary dermatologist for further assessment and a second opinion.
J. Coatesworth MA VetMB CertVD MRCVS – RCVS Advanced Veterinary Practitioner in Veterinary Dermatology, Head of Dermatology, Animal Health Trust