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Demodex in dogs

If your dog begins to lose hair in patches, it means that something has happened in the hair follicles. One cause can be hair follicle mites – a skin disease called demodicosis or demodex. Here we have gathered information about the different forms of demodex and how they are treated.

To diagnose demodex, several, rather deep, scraping samples are taken, as the mites cannot be seen with the naked eye. This means that the vet uses a scalpel to scrape up small abrasions in various places on the dog's skin. Under a microscope, the vet can then see the parasites as small cigar-shaped insects.

Demodex mites and the immune system

Demodex mites are normally found in all dogs, but when sampling a healthy dog, it is next to impossible to find the mites through a scratch test. The immune system of a healthy dog ​​fights the mite and keeps the mite in good condition. 

In dogs that are sick with another disease or have a weakened immune system, the mites can cause problems. The immune system does not have the ability to prevent the mites from thriving and multiplying. Demodex is hereditary and more common in certain breeds.

Demodex and hairless spots

The fur in the areas falls out in whole or in part, causing the characteristic hairless patches that demodex implies. The mites cause the hair follicles, and the areas around them, to become irritated and inflamed, which can lead to troublesome bacterial infections and itching.

Different forms of demodex

Demodex comes in different forms and is often divided into when in life the dog is affected (juvenile or adult) and how affected the dog is (local or general). For example, a dog that suffers from major problems at a young age is considered juvenile (due to age) and general (due to the extent of affected skin).

When in life does a dog get demodex?

Juvenile demodex

Juvenile demodicosis appears before the age of one and a half years. Most commonly, the first symptoms appear between six and nine months of age.

Adult demodex

Adult demodicosis affects dogs in adulthood. There is often an illness or medication behind it. If a dog is affected by demodex in adulthood, it is important not only to treat the demodex itself, but also to find the underlying cause.

How does demodex affect dogs?

Local demodex

If a dog has small hairless spots, it is usually called local demodex. It is the mildest form of demodex and can often heal by itself. Most of the time it doesn't cause any major problems in the affected dog.

General demodex

The general form is more difficult to treat and often requires a longer treatment. Dogs with general demodex not only lose hair, but can also suffer from itching, rashes, thickening of the skin and dandruff. If a dog's paws are affected, it is always considered general.

Treating demodex in dogs

There are different types of treatment depending on which form the dog is affected by. Most commonly, a dog will have a spot-on form or tablets that kill the parasites. Treatment is followed up with scraping samples and ends when mites cannot be detected at 2 samplings one month apart.

In parallel with treatment of demodex, it should also be investigated if there is an underlying disease that has negatively affected the immune system. If an underlying disease is identified, that will also need treating.

The vast majority of dogs with demodex can do well by bathing in an antibacterial shampoo as it reduces the risk of secondary skin infections that the disease can otherwise cause. Demodex does not normally spread between dogs.

Frequently asked questions about demodex

About the Author

Kerstin has studied demodex in dogs in a project financed by Agria and the Swedish Kennel Club Research Fund.

More articles from Kerstin Bergvall

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