If you are of a certain age, you’ll remember commercials that ran on television proclaiming that people “don’t have time for a yeast infection.” Humans certainly don’t, but did you know that dogs commonly get yeast infections, too? It may be even more surprising, if not shocking, to learn that the microorganism responsible for things like fungal ear infections are living happily on your dog right now!
There is no immediate cause for panic; this fungus also makes a home on your body as well. The single-celled creature we speak of is a yeast called Malassezia pachydermatis. Like the Demodex canis mites that can cause mange in dogs, yeast is a commensal organism. This means that, under normal circumstances, it lives and thrives on the outside of a dog’s body, but does the host neither benefit nor harm.
When conditions are auspicious, however, something upsets the typical balance, and the fungus seizes the chance to reproduce unchecked. This population explosion leads harmless microorganisms to become opportunistic pathogens, which then leads to canine yeast infections. Let’s take a closer look!
The Malassezia pachydermatis fungus is just one among many microorganisms that call your dog home, so what keeps them from running riot? A healthy dog’s immune system is quite good at regulating all of its microflora. Beginning with antibodies drawn from the mother during nursing, strengthened by vaccinations, and bolstered by regular interactions with their environment, the body welcomes and begins adjusting to all manner of tiny creatures from the moment a puppy is born.
This unicellular yeast is like any other fungus, which means it needs the right conditions to live and reproduce. What are these conditions? It’s actually very simple: fungi need heat. The proper temperature for Malassezia pachydermatis is in the range of 86 to 99 degrees F on-site. For this reason, the yeast tends to reside in the warmer corners and crevices of your dog’s body, around the ear canal, and between the toes.
Because of their need of heat, yeast infections tend to arise from late spring through summer and early fall, periods of high humidity. The temperature, outdoors or in, makes a difference, but it is not the only cause of uncontrolled yeast growth. Any agent that prevents proper ventilation of the skin or ears — even the ears themselves — can bring about a canine fungal infection. These agents include:
We’re really only looking here at how these infections get going in typically healthy dogs. Immuno-compromised dogs or puppies are at greater risk, as are dogs suffering from other bacterial illnesses. Additional circumstances that may allow yeast to flourish are allergies to food or fleas, as well as long-term use of certain steroid medications, like prednisone.
Fungal infections happen when mundane microbes take advantage of circumstances, turning into opportunistic pathogens that cause health problems. Opportunities can arise anywhere and anytime the fungi are present; in other words, tiny, short-haired dogs who live in Alaska might be a bit safer from yeast infections than long-haired, floppy eared dogs in Florida, but not much.
The primary focus here is a condition known as otitis externa, or what, in humans, we call “swimmer’s ear.” Symptoms of canine otitis include dogs holding their heads at awkward or unusual angles, or pawing insistently at one ear. As the condition advances and the yeast reproduces, you’ll start smelling a strange odor and seeing crust forming around the outer ear canal, accompanied by discolored ooze and, later, even blood.
Malassezia pachydermatis can also cause skin infections in dogs, a condition known as yeast dermatitis. The first sign you may notice include flaky, dry skin. Look for a dog scratching at a specific site, under their arms, for instance, or rubbing at a certain spot on the nose. They may be chewing or biting at skin that has become darker or redder. The most blatant symptom, “elephant skin,” will appear in more advanced cases. Left untreated, this fungal skin infection can lead to secondary bacterial infections.
The earlier a veterinarian diagnoses a canine fungal infection — skin or ear — the simpler the process of treatment will be. If it is caught soon enough, topical antifungal salves, such as miconazole, can be applied after any excess hair at the site of infection is trimmed and the area is properly cleaned. If the problem is advanced, or if the infection has penetrated further, the vet might prescribe a more intense antifungal medicine, fluconazole, administered in tablet form.
As a fungal ear infection worsens and otitis externa gives way to otitis media, or even otitis interna — the latter being all the way down the ear canal — fluids begin to gather inside the ear canal, whose exit point can swell shut. Worst-case scenario, or at least worst-case excepting deafness, is a surgical procedure called total ear canal ablation, or TECA.
For external issues like yeast dermatitis, special antifungal shampoo can be used to relieve your dog’s symptoms. How long and how often the dog will need bathing depends on the yeast infection. Prevention is always the simplest route to take.
If your dog is at higher risk — one with floppy ears or with hair sprouting from inside the ear — the easiest things to do are to dry them thoroughly after water adventures or baths and keep excess hair trimmed. A dog’s immune system should be strong enough to restore balance with native microbes, but a little help on your end never hurts.