Malassezia pachydermatis is a common yeast which is a normal part of the flora (microenvironment) of the superficial layers on both human and animal skin.
The organism usually lives on the skin, ear canals, oral cavity and body orifices (vagina and anus) in low numbers where it usually causes no harm. In some cases a proliferation occurs and causes disease. There are several types of Malassezia yeast, but disease in cats is usually caused by Malassezia pachydermatis, of which there are several sub-strains. The yeast metabolises fats on the surface of the skin (lipophilic).
There are a number of contributing factors to this, essentially when normal immunological or physical mechanisms break down, yeast overgrowth can occur. As well as barriers keeping the yeast in check, environmental conditions may play a role. Most yeasts and funguses thrive in moist, humid conditions.
- Immunosuppression - There are a number of reasons your cat's immune system may be suppressed including feline immunodeficiency virus, feline leukemia and certain cancers. When the immune system isn't working as it should, normal bacteria and yeasts which are usually kept in check can over grow, causing disease.
- Long term antibiotic use - These can affect the normal bacterial which are also a part of the microenvironment, giving the Malassezia a chance to proliferate.
- Allergies (atopic dermatitis, food allergy, flea allergy dermatitis) - Food, flea allergies, inhaled (dust mites, pollens) or contact allergies can contribute to the excess growth of Malassezia as cats tend to express allergy symptoms through their skin. This can result in itching, scratching and eventually damage to the surface of the skin, this may provide an idea environment for the yeast to flourish.
- Long-term use of systemic corticosteroids - Which can dampen the immune system.
- Endocrine disorders - Including Cushing's disease and hypothyroidism (which is rare in cats).
- Seborrhea - A skin disorder caused by an over-production of sebum, an oily substance which lubricate and protect the skin. Excess sebum can create an ideal environment for Malassezia to grow.
- Certain tumours including thyomas (a tumour originating from the epithilial cells of the thymus), pancreatic or liver carcinoma.
There is no gender or age predilection, however Devon Rexes and Himalayan cats appear to be over-represented. The condition is extremely common in dogs, but quite rare in cats.
What are the symptoms of Malassezia in cats?
Commonly affected areas include the face and facial skin folds, chin, neck, ear canals (Malassezia otitis media), outer ear (Malassezia otitis externa), armpits, between the toes and claw folds. Lesions may be localised or generalised (covering a large area of the body). Symptoms include:
- Multiple areas of alopecia (hair loss)
- The skin may appear thickened (hyperkeratosis)
- Inflamed or crusted areas
- Greasy yellow/brown coloured lesions
- Unpleasant odour
- Facial fold dermatitis
- Chin acne, with swelling
- Claws and nail folds, redness, hair loss, brown greasy exudate
- Ears, redness, pain, waxy build up.
As well as symptoms of Malassezia, your cat may also have additional symptoms relating to the underlying disease which has caused Malassezia.
The yeast may also be responsible for non-responsive cases of feline acne.
How is Malassezia diagnosed?
As Malassezia is commonly associated with a serious underlying disease, it is important to seek veterinary treatment.
- Complete blood count, biochemical profile and urinalysis to evaluate the overall health of your cat and look for signs of allergy or infection (such as increased white blood cells).
- Skin cytology from greasy areas using direct impression smears onto glass slides, cotton swabs, skin scrapings or sticky tape on dry patches of skin or exudate, these samples are stained with Diff-Quik and examined under a microscope. Low numbers of malassazia may not indicate disease as it is normal for cats to naturally have this yeast on their skin, but if large numbers are present in samples, this can be suggestive of an over growth.
- Culture may also be carried out, particularly if a concurrent bacterial skin infection is suspected. This involves taking a sample from the skin and growing it on a special medium.
In addition to the above, additional tests may be required to determine underlying disease. This may include radiographs or ultrasound, food trials (to determine if your cat has a food allergy), skin allergy tests, FIV and FeLV tests.
How is Malassezia treated?
Treatment of Malassezia is twofold. Find and treat the underlying cause as well as reduce numbers of yeast on the skin. Most anti-fungal medications contain one of the following, miconazole, clotrimazole, thiabendazole, ketoconazole and chlorhexidine. There is concern about a growing resistance of Malassezia to azole containing medications.
This is accomplished by the following methods:
- Anti-fungal shampoos, sprays, mousse or wipes may be prescribed for mild or localised infections affecting the skin. Treatment is usually required one to two times a week for 4-6 weeks. Some products may also treat both yeast and bacterial growth concurrently.
- For Malassezia in the ears, anti-fungal ear drops will be prescribed. The ear will need to be thoroughly cleaned to remove exudate before anti-fungal medication is applied. Some ear cleaning products already contain anti-fungal treatments.
- For more severe cases of Malassezia, oral Itraconazole or fluconazole will be prescribed. This may be given alone or used in conjunction with anti-fungal shampoos. Some side effects may occur in cats treated with azole anti-fungals including nausea, vomiting and anorexia (loss of appetite). Cats on long term azoles may also experience elevated liver enzymes, so follow up appointments with your cat's veterinarian and testing may be necessary.
- Oral antibiotics may also be prescribed for concurrent bacterial infection.
If the cat is only treated with the above, and the underlying cause is not addressed, Malassezia is highly likely to come back.
Is Malassezia contagious to other cats or humans?
No, it is not contagious.