Skin and Ear Bacterial and Yeast Infections on Dogs & Cats

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Skin and Ear Bacterial and Yeast Infections on Dogs & Cats


Just because your dog doesn’t smell like a bag of corn chips; he still could have a yeast infection. And, if your dog does smell like a bag of corn chips, he more than likely has a yeast infection.

Yeast (fungi) and bacteria are commonly found on all bodies. In fact, they are usually no big deal.

However, when the body’s metabolism is imbalanced or the immune system is compromised, yeast can grow rapidly and overwhelm the dog (or other species). The worst of it is that a fungal infection can predispose to a bacterial infection and vice versa. While we can treat these microbial infections, they are simply secondary or a symptom
of another condition. The challenge is to identify the base condition(s) causing them to flare up.

Common Fungal and Bacterial Infections

So, we know that this dog is scratching or his ears have an inordinate amount of smelly wax build up. What is the microbial overproduction?  

  • Malassezia pachydermatitis – fungus/yeast; found on the skin and mucosal surface areas like the ears of dogs and cats. While it is fairly common for them to harbor some of this fungus, an overgrowth can cause dermatitis (inflammation of the skin).
  • Candida – yeast/fungus; present on the skin and mucosal areas like the ears, vagina and vulva, and between the foot pads and toes. Candida is a relatively common vaginal yeast infection in women. It can colonize in the gastrointestinal area as well.
  • Ringworm (dermatophytosis) – fungus; ringworm can present in typical symptoms such as dandruff, itchiness, hair loss, but can be distinctive by its raised, rounded, nodular lesions known (granulomatous lesions; boils) or lesions that ooze.
  • Pyoderma – bacteria; pyoderma is a general term that encompasses various strains of bacteria such as Staphylococci (i.e. Staph infection) or Streptococci. These bacterial infections typically cause pus-filled lesions of varying sizes. A good example is interdigital furuncles (often referred to as cysts) which are lesions located in the interdigital webs of dogs.  

Short-Term Treatment Protocols

Once the veterinarian figures out the type of infection affecting his patient, he can prescribe a variety of shampoos, fungicides, anti-inflammatories, corticosteroids or antibiotics.  However, I do not like long-term use of these treatment options. But, occasionally, you need to use them to help the dog get ahead of the bacterial or fungal infection.

My colleague, Dr. Karen Becker, offers excellent more natural, over-the-counter and inexpensive tips in her article, “Itchy, smelly dog? Yeast Infection May Be the Problem”.

However, what is the point of these medications that may adversely affect a companion pet’s immune system, or the management tips if we are not addressing the primary underlying disease/disorder for providing long-term care?

Underlying Disease

Typically, a veterinarian should first look for breed type dispositions as a starting point. Certain breeds are more susceptible to fungal or bacterial infections because of genetic predisposition, family history or their physical structure. Basset Hounds often have an excess of Malassezia pachydermatitis on their skin. Dogs with prominent skin folds like the Chinese Shar-Pei develop infections faster because of the moist, warm conditions in their skin crevices. Regarding outer ear infections, Cocker Spaniels, long-eared dogs and Labrador Retrievers are more likely to develop them. Again, these are simply symptoms and a proper diagnosis needs to be explored.

Food Sensitivity
Most veterinarians and veterinary dermatologists agree that food sensitivities are the number one or a primary cause of ear infections and skin conditions. In fact, 80% of food sensitive dogs have otitis externa (outer ear infection). Cats can often develop feline miliary dermatitis, a skin condition that most commonly results from an allergic reaction. 

What should we change the food to? We know that yeast fermentation products have been shown to be severely inflammatory. So, eliminating grains or just glutens from the diet is a good way to start. But, this can be the tip of the iceberg. Even if your pet is eating a grain-free, species appropriate diet, and does not smell like a bag of corn chips, he can still have fungal or bacterial infections due to an underlying food sensitivity.

Several veterinarians might put your dog on a food trial. Unfortunately, food trials do not work because they only last 8-12 weeks and each week or two the food is typically rotated. So, if a pet stops scratching in week 2 or 3 of the trial, you will not know what food or foods stopped the reaction or if the medication given is suppressing the infection.

On top of that, a team of European researchers studied 12 limited-ingredient commercial foods intended for use in food elimination trials for dogs with adverse food reactions. Ten of the 12 foods studied contained ingredients of animal and fish origin that were not listed on the label.

These are just some of the reasons we suggest testing with NutriScan Food Sensitivity & Intolerance Test that the team at Hemopet and I developed. Instead of guesswork elimination trials, eliminate reactive foods with scientific proof. 

Seasonal, environmental sensitivities
These sensitivities are best diagnosed with a blood test that measures the antibody level of IgE (testing antibody levels of IgG and IgD is also available). This test should always be done at a veterinary clinic. Over-the-counter, inexpensive environmental tests that use hair or cheek swab samples do not have scientific published documentation of their efficacy.

If a pet is sensitive to something that is indoors, it is relatively easy to fix by getting rid of the offending object(s), cordoning the area off, or covering it with a blanket.

The outdoors is more problematic since it is difficult to control Mother Nature. Dogs definitely need to be walked and let outside for exercise. However, preventative measures exist such as removable booties, washing your dog’s paws, or wearing cones to prevent licking and spreading of the bacteria or fungus. The goal in this instance is to manage these symptoms and be ahead of them. Prescription medication should be used as the last resort. Again, please refer to Dr. Becker’s tips, mentioned above to avoid these medications.

Cushing’s Disease
This disease occurs when the adrenal glands produce too much cortisol. Since the pituitary gland helps to regulate the adrenals, we have two types of Cushing’s disease: adrenal-dependent (more rare) and pituitary-dependent. 

The connection between excessive cortisol release and infections is well documented. Skin-related symptoms are thinning skin, and atrophy of hair follicles and sebaceous glands. So, based on these symptoms and possibly weight gain around the belly, the veterinarian will need to do extensive testing to find out what gland is over-performing. First, veterinarians will order an ACTH (adrenocorticotropic hormone) Stimulation test. This test is usually able to determine if Cushing’s disease is present or not. We now need to identify the type of Cushing’s. The next test is called the Dexamethasone Suppression test (usually Low-Dose; i.e. LDDS); endogenous ACTH concentrations can also be measured. Alternatively, an abdominal ultrasound can be performed to assess the size of the dog’s adrenal glands.  If Cushing’s disease is confirmed, several medications are available to treat it.

On a side note, corticosteroids can produce Cushing’s-like symptoms because they can be over-supplementing the body with cortisol. Once reduced or stopped, the body should be able to repair the secondary infections or other side effects like increased appetite, excessive drinking and urination.

The thyroid hormone is involved in basically all metabolic functions including hair growth and wound healing. When the thyroid gland is not producing enough thyroid hormone or is dysfunctional, wounds do not heal normally or fast enough, so the body is more susceptible to infection. 

Testing for hypothyroidism is a simple blood draw. The trick of course is what to measure. On a weekly basis, I hear from concerned pet parents that their pet’s symptoms are not going away. It is eventually revealed that their veterinarian only measured one or two thyroid analytes and failed to test for thyroid autoantibodies, the latter being a major cause of thyroid dysfunction in people and pets. Dogs need to have their T4, FT4, T3, FT3, and TGAA antibodies tested for an accurate diagnosis. Hypothyroidism is extremely rare in cats but they commonly have the opposite condition, hyperthyroidism, in older age. Their thyroid testing should include T4, FT4, T3, FT3, and TSH. Thyroid tests can be run at either Hemopet’s Hemolife Diagnostics or Michigan State University.

Let’s suppose that the complete thyroid profile was done and it was determined that the dog is truly hypothyroid. However, the infections are not going away. First thing, we need to make sure that the thyroid medication is given at the right dosage and that it is being administered properly. Thyroid medication should be given twice per day, 1 hour before OR 3 hours after feeding, and without foods or treats containing calcium or soy as these interfere with absorption. If these steps do not work, it is possible that another concurrent condition is causing the infections.  

Compromised Immunity
The immune system keeps parasites such as mites in check. When it is underdeveloped or compromised, mites can in turn promote fungal and bacterial infections. Another cause are the autoimmune disorders such as sebaceous adenitis. Sebaceous adenitis is quite rare and mostly affects Standard Poodles and Akitas.  

Final Words

We want to have a one test diagnosis instead of several. We want one condition instead of several conditions. We want simplicity. Don’t become upset if the infections do not disappear or only get slightly better. More than one disease can be contributing to the infections. As I always say, “Medical diagnosis is just as much about ruling out as it is ruling in.” So, bear this in mind.

W. Jean Dodds, DVM
Hemopet / NutriScan
11561 Salinaz Avenue
Garden Grove, CA 92843

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