What is Malassezia?
Malassezia pachydermatis is a common yeast that is a normal part of the flora (microenvironment) of the superficial layers of 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, proliferation occurs and causes disease. There are several types of Malassezia yeast, Malassezia pachydermatis is the most common form to affect cats. The yeast metabolises fats on the surface of the skin (lipophilic).
Causes
There are several contributing factors to this; essentially when; tests 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 several reasons your cat’s immune system may be suppressed including feline immunodeficiency virus, feline leukemia, and certain cancers.
- Long-term antibiotic use – These can affect the normal bacteria which is 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 ideal 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 that lubricates and protect the skin. Excess sebum can create an ideal environment for Malassezia to grow.
- Certain tumours include thyomas (a tumour originating from the epithelial 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.
Symptoms
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 confined to one small spot or cover a large area of the body.
- Overgrooming
- Multiple areas of alopecia (hair loss)
- The skin may appear thickened (hyperkeratosis)
- Itching
- 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.
Diagnosis
As Malassezia is commonly associated with a serious underlying disease, it is important to seek veterinary treatment.
Diagnostic workup:
- Baseline tests: Biochemical profile, complete blood count, 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: Samples from affected areas using direct impression smears, cotton swabs, skin scrapings or sticky tape on dry patches of skin and exudate; these samples are stained with Diff-Quik and examined under a microscope. Low numbers of Malassezia 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 overgrowth.
It is also necessary to determine the underlying cause, tests can include the following:
- X-rays or ultrasound
- Food trials
- Skin allergy test
- FIV and FeLV blood test
Treatment
The goal of treatment is to address the underlying cause as well as reduce the number 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.
- Anti-fungal shampoos, sprays, mousse or wipes may for mild or localised infections. Treat one to two times a week for 4-6 weeks. Some products may also treat both yeast and bacterial growth concurrently.
- Antifungal drops for Malassezia in the ear. Clean the ear of exudate before applying the medication. Some ear cleaning products already contain anti-fungal treatments.
- For more severe cases of Malassezia, oral Itraconazole or fluconazole will be prescribed which can be given alone or used in conjunction with anti-fungal shampoos. Some side effects may occur in cats treated with azole antifungals 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 to treat concurrent bacterial infection.
If the underlying cause is not treated, Malassezia is highly likely to come back.
Is Malassezia contagious to other cats or people?
No, it is not contagious.
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