Causes of Canine Yeast Infection
"Yeast" is an often-used but poorly-understood word. Yeast is a general term for a type of single-celled fungus that reproduces by a process called budding. Budding is a form of genderless reproduction where a portion of the yeast cell body pinches off and becomes a new separate yeast organism. The species of yeast that causes yeast dermatitis or yest skin infections in dogs is Malassezia pachydermatis. These living, one-celled fungi are normal residents of canine skin, especially in the ears. The presence of yeast on a dog’s skin only becomes a problem when the yeast starts to reproduce and bud uncontrollably, causing discomfort and disease in the affected animal.
Why this transformation happens in some dogs and not others is still largely a medical mystery. However, a number of things have been suggested as possible contributors to canine yeast skin infections. These include:
- Prolonged exposure to hot, humid weather
- Allergies to the saliva of fleas, ticks, mites or other external parasites
- Bites from fleas, ticks, mites or other external parasites, which disrupt the normally intact protective skin barrier
- Food allergies
- Hypersensitivity disorders; skin allergies; atopy
- Nutritional deficiencies; poor diet
- Prolonged use of corticosteroids; suppression of normal immune function
- Endocrine disorders (the endocrine system is a group of organs and tissues that secrete regulatory substances, called hormones, directly into the blood; hormones travel in circulation and have a variety of physiological effects on distant target organs, which can be other endocrine glands or non-endocrine tissues; common endocrine disorders in dogs include Cushing’s Disease, Addison’s Disease, hypothyroidism, hyperthyroidism and diabetes mellitus)
- Immunosuppressive illnesses
- Metabolic diseases
- Bacterial skin irritation or infection
Yeast overgrowth causes increased oil production from the dog’s hair follicles. This can lead to severe itchiness (pruritis), which causes frantic licking, chewing, biting, scratching and rubbing in an attempt to relieve the discomfort. Affected animals often develop raw sores from self-trauma, which further weaken the outer skin layers and provide an excellent environment for bacterial and yeast growth.
Preventing Yeast Infections
Fortunately, yeast infections in dogs are somewhat preventable and largely treatable. Dogs with structural or anatomical predispositions to developing skin infections should be kept clean and dry, especially inside their ears, in facial skin folds, under the armpits and between the toes.
Only a veterinarian can properly assess a yeast infection and prescribe appropriately tailored management protocols to eliminate yeast overgrowth, reduce the dog’s discomfort, manage or eliminate secondary bacterial infections and reduce the chances of reinfection. Yeast reportedly have been transmitted from the hands of healthcare workers who own infected dogs to patients they handled in a human intensive care nursery, causing yeast infections in those infants. Yeast infections should be considered zoonotic, which mean that they have the potential to be transmitted from dogs to people. People with compromised immune status, such as the very young, the very old or the very ill, should be especially careful to avoid contact with infective yeast.