Fungal Infection (Malassezia pachydermatis) of the Skin in Dogs

Malassezia pachydermatis is a fungus that is frequently found on the skin and in the mucosa, and ear canals and of dogs. In small numbers, it is asymptomatic, but the fungus can take advantage of a weakened immune system or another disease to multiply and cause an opportunistic infection. This is called malassezia or yeast dermatitis. Most dogs with this infection have patches of itchy, flaky or crusted skin. The fungus flourishes in conditions of humidity, so symptoms will develop around moist areas such as the eyes or groin, or in between the claws. Malassezia can also cause ear infections, usually otitis externa. Yeast dermatitis often develops due to excess oil in the skin and is more common in dogs with folding or pouched skin. A fungal infection may be caused by allergies that make the skin oily, or it can be a sign of more serious disease such a staph infection or an endocrine imbalance. Dogs taking immunosuppressant drugs are particularly at risk. Most cases will clear up with antifungal treatment, but dogs with recurrent symptoms may need continuous treatment. This type of fungal infection is not contagious so it will not spread to other dogs.

Malassezia pachydermatis is a fungus that is found naturally in small numbers on most dogs. It can multiply and cause skin infection in dogs that weak or unhealthy, or have oily skin from allergies. This is called malassezia dermatitis or yeast dermatitis. It usually clears up with antifungal treatment.

Take your dog to see a veterinarian if you notice any of the following symptoms.

• Thickened skin
• Hyperpigmentation (areas of darkened skin)
• Red areas
• Dry flaky skin (seborrhea sicca)
• Oily skin (seborrhea oleosa)
• Crusted skin
• Itching
• Musky odor
• Chronic or recurrent ear infection (otitis externa)

Types

A malassezia infection can take several forms.

• Localized – small patches of infected areas
• Generalized – infection that covers the entire body
• Otitis – ear infection, usually otitis externa, but occasionally otitis media (middle ear infection) in very severe cases

Fungal skin infections are frequently associated with excess oil in the skin as well as a weakened immune system. These conditions can put your dog at risk.

• Allergies
• Seborrhea oleosa from another condition
• Weakened immune system
• Endocrine disease (Cushing’s disease or hypothyroidism)
• Immunosuppressive drugs
• Pyoderma infection of staphylococcus bacteria
• Breeds that tend to be predisposed are West Highland White Terrier, Basset Hound, Cocker Spaniel, Springer Spaniel, Silky Terrier, Australian Terrier, Maltese Terrier, Chihuahua, Poodle, Shetland Sheepdog, Lhasa Apso, Dachshund, Chinese Shar Pei

The veterinarian will examine your dog’s symptoms. The fungus is diagnosed by taking a sample from the skin and examining it under a microscope. A stain may be added to make the malassezia fungi more visible. Several fungi cells are normal, but high numbers suggest an infection. Some dogs respond more drastically to a lower concentration of fungi, so diagnosis will also be based on symptoms. The veterinarian will need to check for the presence of staphylococcus bacteria as well, since the two are frequently found together and can cause similar skin infections.

The veterinarian will also diagnose the underlying condition that is causing the fungus to proliferate. This could include testing for allergies, hormone imbalance, or other skin parasites such as scabies. Bloodwork and urine tests will be done to evaluate the overall state of your dog’s health. Other medications your dogs is taking, particularly immunosuppressant drugs, are also relevant.

Treatment will depend on the severity of the condition. Shampoos containing selenium sulfide or benzoyl peroxide will help to remove excess oil from the skin and treat generalized infection in cases that are mild. Antifungal creams containing miconazole, ketoconazole, or clotrimazole can be applied locally. Dogs with otitis externa will need their ears cleaned, preferably with an antifungal cleaner, and antifungal drops or cream will need to be applied in the ear also. Any topical treatment will need to be repeated several times a week for at least two weeks and possibly as long as three months.

Cases that are more severe will require oral antifungal treatment as well. Daily medication containing ketoconazole, itraconazole, or fluconazole will be prescribed for 2-3 weeks. You will need to return for a check-up so the veterinarian can retest your dog to see if the medication is working. Topical treatment will be necessary at the same time. Oral antifungal medications can cause side-effects, so these drugs will only be prescribed for severe symptoms, or cases that do not respond to topical treatment. The oral dose will be discontinued as soon as possible.

Other treatments will focus on the cause of the problem. Dogs with allergies may be put on a special diet. Endocrine imbalance will be treated with medication. Antibiotics may be given for simultaneous staph infection. If scabies are present, medication will be given to kill this parasite.

The chances of your dog making a full recovery from yeast dermatitis is good. Most infections clear up with antifungal treatment. Recurrence will depend on identifying and treating the underlying cause that has weakened your dog’s health. Long term medication could be needed to rectify an endocrine imbalance, but most bacteria and parasite infections will clear up with treatment. Life-long diet modification might be necessary to reduce allergic reactions.

If your dog has an unidentifiable allergy, or is very sensitive to the presence of a few malassezia fungi, continuous topical treatment might be necessary to manage the problem. This could also be true for dogs with a suppressed immune system from chemotherapy, or from treatment for an autoimmune disorder. Regular bathing with an antifungal shampoo and frequent application of creams or ear-drops can usually keep symptoms under control. Very severe cases might need oral medication administered intermittently.