WHY SUSPECT YEAST?
Yeast infections are especially itchy, crusty, and smelly. Often a dog starts with a rash or with simple itching but the skin thickens to an "elephant" skin appearance. The itch is extreme and the
odour can be especially troublesome. Parts of the body or the entire body can be affected. Mostly dogs are affected but cats can get yeast infections as well. Yeasts are the spore-like forms of fungi; Malessezia dermatitis is a fungal infection of the skin.
WHERE WOULD A DOG GET A YEAST INFECTION?
Yeast happily live on most normal skin and in ears and anal glands. To get a yeast infection, conditions on the skin surface have to change to
favour the proliferation of the yeasts. The yeasts in small normal numbers are harmless but when the yeasts are present in large numbers, disease results.
So what conditions lead to a yeast proliferation? An increase in skin oils (which often occurs in an allergic flare up) would be the most common situation. Sometimes there is an immune deficiency which allows the yeast proliferation. Some animals are battling
seborrhoea (excessive oil production of the skin) and thus are naturally predisposed to the yeast proliferation. Some animals are actually allergic to the yeasts themselves. The most important thing to realize is that yeast infections are not contagious but they tend to recur unless the underlying allergy,
seborrhoea, or whatever problem is controlled.
The following breeds are predisposed genetically to yeast infections: the West Highland White Terrier, Basset
Hound, Cocker Spaniel, Silky Terrier, Australian Terrier, Maltese, Chihuahua, Poodle, Shetland
Sheepdog, Lhasa Apso, and the Dachshund.
HOW IS THIS CONFIRMED?
There are several testing methods to confirm the overgrowth of yeasts:
Impression smear (pressing a microscope slide on the skin to collect yeast organisms)
Scotch tape sampling (pressing a piece of clear tape to the skin to collect yeast organisms)
Skin scraping with a blade (scraping the skin with a blade to collect yeast organisms)
Cotton swab (rubbing a moistened Q-tip on the skin to collect yeast organisms)
Skin Biopsy (removing a small plug of skin with a biopsy punch with a local anesthetic. This is the most invasive choice but provides substantially more diagnostic information)
Very few yeasts need to be seen under the microscope to confirm yeast infection.
HOW DO WE GET RID OF IT?
Treatment can be topical, oral, or both. Topical treatment alone is not usually adequate but, since oral medications are expensive, often topical management alone is attempted first, especially if the pet is small enough for convenient frequent bathing or if only a small body area is involved.
Shampoos: While degreasing shampoos such as the benzoyl peroxide (oxydex®, pyoben®) and
sulfur/salicylate (sebolyte®, sebolux®) shampoos will help remove the skin oils feeding the yeast, there are shampoos that are specifically anti-yeast. We prefer the 4% Chlorhexidine shampoo called Chlorhexiderm Max as it both strips skin oil and kills yeast; however, other anti-yeast products include Selsun Blue, Miconazole shampoo, Nizoral shampoo, and more. The pet must be bathed twice a week to start and the shampoo requires a 15 minute contact time (meaning do not rinse the lather for 15 minutes).
If only a small area is involved, it is probably not necessary to bathe the entire animal. Special acetic acid wipes can be used to cleanse the affected area. Mixtures of vinegar and water can be used but the pet will develop a distinct vinegar
Oral therapy: Ketoconazole (Nizoral®) rules when it comes to oral therapy. Typically a several week treatment is needed and there are numerous protocols involving different dosing schedules. Higher doses tend to be needed if recurrence is a problem. The extreme itch usually resolves within one week. This medication is expensive, especially in larger dogs, but often there is no way around its use.
Treatment of the Underlying cause: It is important to realize that yeast overgrowth occurs in response to a primary problem be it allergy,
seborrhoea or something else. If the underlying problem is not controlled, yeast dermatitis is likely to periodically recur.
What is Malassezia dermatitis?
Malassezia pachydermatitis is a common yeast organism that is found on normal and abnormal canine skin and ears. On normal healthy skin it causes no problems, but when the environment of the skin is altered for any one of many reasons, Malassezia can cause severe dermatitis or otitis (inflammation of the skin or ears respectively). Some of the factors that can lead to Malassezia dermatitis include moisture (as in dogs with skin folds or floppy ears with narrow ear canals), excessive waxy or scaly build-up (as in seborrhea), and allergic and bacterial skin disease.
Not only is Malassezia a secondary cause of dermatitis in any dog with one of these predisposing conditions, but it may be the primary or initiating cause of skin problems in certain breeds of dogs. This may be related to an alteration in immune response to the yeast.
Malassezia pachydermatitis is also known as Malassezia canis, Pityrosporum pachydermatitis, P.
How is Malassezia dermatitis inherited?
What breeds are affected by Malassezia dermatitis?
Malassezia can be a complicating factor in a dog of any breed with a skin condition, but dogs of the following breeds have a higher risk of Malassezia dermatitis or otitis: American cocker spaniel, basset hound, dachshund, English setter, poodle, Shetland
Sheepdog, Shih Ezu, and many Terrier breeds including the West Highland
White, Australian, Jack Russell, Maltese, and Silky.
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
What does Malassezia dermatitis mean to your dog & you?
Malassezia ear and/or skin infections are extremely itchy. The problem may be confined to certain regions - generally the ears, lips, muzzle, inner thighs, or feet - and your dog may chew its feet or scratch in a frenzied manner at the muzzle or ears with its front paws. With ear infection there is often head shaking, pain if the ear is touched, and a waxy discharge. Dogs with more generalized
Malassezia dermatitis have reddened, itchy, crusty skin, and are often greasy, scaly and smelly.
Malassezia dermatitis often starts in the summer, corresponding to an increase in humidity and to allergy season, and persists over the winter.
How is Malassezia dermatitis diagnosed?
About 50% of dogs with this condition have an underlying problem, especially seborrhea, allergies, or a bacterial skin infection. Dogs with these conditions generally all have greasy, crusty, smelly skin but where there is Malassezia infection, there is also extreme itchiness.
It is essential to sort out whether the Malassezia is the primary problem or is occurring secondary to another condition that can be treated. In either case the yeast infection must be cleared up, and then your veterinarian will look for an underlying cause. If none can be found, and the yeast infection quickly recurs, this suggests that the Malassezia is the primary problem.
For the veterinarian: There are many differential diagnoses for this condition and most of them can also be associated with or can trigger Malassezia infection. This can make diagnosis perplexing. Malassezia-associated dermatitis should be considered in any persistent scaly, seborrheic, pruritic dermatitis where other differentials have been ruled out and there is a lack of response to treatment.
Cytologic examination is a useful and readily available diagnostic tool. Samples are collected by vigorous rubbing of a cotton swab on affected skin, superficial skin scrapings or pressing a slide onto the skin. These samples should be heat-fixed, stained (NMB or Diff-Quik), and examined for numerous round or oval, budding
Skin biopsies may also demonstrate the presence of the yeast. Culture is not a reliable way to identify a Malassezia infection.
How is Malassezia dermatitis treated?
This condition is treated with anti-fungal drugs and medicated shampoos. The itchiness usually subsides within a week, and the skin lesions within a few more weeks. Your dog must continue taking the drug for another week or so beyond that.
Commonly there is recurrence of the yeast infection, although the frequency may be reduced if an underlying cause can be identified and treated or managed. Sometimes maintenance treatment is required to prevent frequent yeast infections. This may involve weekly medicated baths and your dog taking antifungal drugs once or twice a week. Your veterinarian will work with you to determine how your dog's skin condition can best be kept under control.
Although little is known about the inheritance of this condition, it is preferable not to use dogs with severe or recurring yeast infections for breeding.
For more information about this disorder, please see your Vet.