But did you know that yeast is one of the most common culprits when it comes to causing infections in all kinds of pets, including dogs, cats, rabbits, guinea pigs, and birds?
Yeast – Little Buggers, Big Problems
Yeast are a spore-like form of fungus. They happily hang out on most normal skin surfaces, especially between your pet’s toes, inside his ears, under his tail and armpits, and on his face and abdomen. Yeast can also be found in the mouth, nose, and gastrointestinal tract. Most of the time the body maintains a normal population of both yeast and bacteria, and neither cause a problem because they are kept in check by the immune system. But sometimes changes in the body can cause yeast to overgrow, leading to opportunistic infection.
These changes usually happen due to an increase in skin oils (which occurs during allergic flare-ups, or with the skin disease seborrhea), hormone imbalances, a deficiency in the body’s immune system, or if the pet already has a bacterial infection.
Pets with lots of skin folds, such as Pugs, Bulldogs, Shar-peis, and Persian cats are at an increased risk of developing yeast infections of the skin, while some cats and dogs can develop an overgrowth of yeast in the mouth and throat, commonly known as “thrush”.
Yeast infections can cause intensely itchy, inflamed, thickened, crusty skin with a bad odor. They can also cause body-wide systemic infections that can be very serious for pets with compromised immune systems (such as cats with FeLV or FIV).
The Culprits – 2 Different Types of Yeast
There are two major types of yeast that cause infections in our pets:
Malassezia pachydermatis live on the skin’s surface. Overgrowths happen when the skin becomes damaged, or if the body’s immune system becomes weakened. This can occur in pets with the following conditions:
- Allergies (either to fleas, certain types of food, or inhalants like pollen or mold)
- Endocrine disorders (such as Cushing’s disease or hyperthyroidism)
- Autoimmune skin diseases, where the body’s immune system attacks its own skin by mistake
- Pets who are on long-term use of steroids, which suppress the immune system
Malassezia thrives in a warm, moist, humid environment, so it can cause nasty ear infections in dogs with long, floppy ears that don’t allow sufficient airflow through the ear canal. It can also infect the ears of cats who are already suffering from an infestation of ear mites. Dogs and cats with yeast infections in the ear usually have a black, brown, or yellowish waxy, bad-smelling discharge. They may shake or tilt their heads, and scratch constantly at their ears.
Ear infections must be treated promptly, since they can cause the eardrum to rupture. They can also progress to the inner ear and cause loss of balance, paralysis of the muscles in the face, walking in circles, or permanent head tilting.
Skin infections caused by Malassezia are not contagious, either to humans or to other pets.
Candida albicans is a sugar-digesting yeast normally found in a pet’s mouth, digestive system, ears, and nose. Candida infection can occur in one specific part of the body (localized), or it can spread throughout the entire body (systemic). Either types of infection can cause extreme discomfort.
Pets at risk for developing candida infection include:
- Cats with compromised immune systems, such as those with Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV).
- Dogs with allergies, skin trauma, burns, or parvovirus.
- Any pet with diabetes, due to fluctuating blood sugar levels.
- Rabbits and Guinea pigs who are stressed or have other bacterial infections.
- Birds (especially cockatiels) who are malnourished, or have experienced stress or smoke inhalation.
- Any pet who has to have a urinary catheter in place for any length of time.
Symptoms of candida infection will depend on what part of the body is affected. Candida overgrowth in the mouth and throat causes drooling, while candida in the bladder can cause cystitis (inflammation of the bladder). Candida can also infect the ear, causing the same symptoms as Malassezia.
Diagnosing Yeast Infection
If your veterinarian suspects a Malassezia infection, he or she can perform any one of the following tests:
- Skin scraping: a scalpel blade is used to scrape the skin to collect yeast organisms.
- Impression smear: a microscope slide is pressed directly against the skin, and any yeast present will stick to the slide.
- Cotton swab sample: a moistened cotton swab is rubbed on the skin or in the ear canal to collect yeast.
- Acetate tape preparation: a piece of clear tape is applied to the skin; yeast will stick to the tape.
- Skin biopsy: a small piece of skin is obtained using a tool called a biopsy punch. This is the most invasive test, but will indicate if the yeast has penetrated the surrounding tissues.
Samples are then viewed under a microscope to determine if yeast is present.
If your veterinarian suspects a Candida infection, he or she can:
- Take a urine sample, and examine the urine under a microscope for the presence of yeast clumps.
- Use a sterile swab to collect a sample, and send the swab to the lab for a fungal culture. The swab is then smeared across a small round plate containing a nutrient-rich gel. Any yeast present will begin to grow and can easily be seen on the surface of the plate.
- Perform a skin biopsy (see above).
Treating Yeast Infections
Yeast infections are treated topically, orally, or by using a combination of both.
1. Topical Treatments
For skin infections, medicated shampoos containing benzoyl peroxide, chlorhexidine, and the antifungal medications miconazole or ketoconazole are very effective. These shampoos need to be left on the skin for at least 10 minutes before they are rinsed off. Treatments must be done every 3-5 days for a period of two to twelve weeks.
For small individual lesions, some veterinarians recommend using a mixture of acetic acid (white vinegar) and water applied directly to the affected spots. A topical antifungal ointment may also be prescribed. Antifungal medications are also available in lotion, spray, and wipe forms.
For yeast infections in the ears, one of the most commonly prescribed medications is Tresaderm®. This medication combines thiabendazole (a drug that controls fungus, parasites, and bacteria), neomycin (an antibiotic to kill bacteria), and dexamethasone (a steroid to help reduce itching and inflammation). Other antifungal ear medications such as miconazole or clotrimazole may also be used.
2. Oral Treatments
For severe or recurring cases of yeast infections of the skin, veterinarians usually prescribe oral antifungal medications such as ketoconazole, itraconazole, or fluconazole. These medications are very effective, but they often need to be given for several months to clear the infection. They can also be somewhat hard on the liver, so additional blood tests may be needed to make sure the liver is functioning normally during treatment.
Pets with yeast dermatitis often have a simultaneous bacterial infection, so oral antibiotics are also given for about 4-12 weeks to kill the bacteria. Benadryl may also be used to help with severe itching.
If a veterinarian suspects the yeast infection was caused by a food allergy, the recommendation may be to change the pet to a hypoallergenic diet.
Are Some Breeds of Dogs More at Risk?
Certain dog breeds are thought to be genetically predisposed to developing yeast infections. These include:
- Australian terrier
- Basset hound
- Cocker spaniel
- Lhasa apso
- Shetland sheepdog
- Silky terrier
- West Highland White terrier
However, any dog can develop a yeast infection.
Yeast, Yeast Go Away
Yeast infections can be quite aggravating. Tricky to diagnose, they’re easily confused with other types of skin conditions. They’re also difficult to treat, as treatment needs to be continued for long periods of time and there’s no guarantee that the infection won’t come back.
Regardless, yeast infections need to be treated immediately to get them under control. Without treatment, yeast will continue to spread, causing intense discomfort and sometimes permanent damage to skin, ears, or other organs.
It’s not unusual for some dogs with severe allergies to have yeast and/or bacterial infections several times a year. If this happens to your dog, your veterinarian can work with you to develop a treatment plan to help you best manage his condition.
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Have you ever treated a pet for a yeast infection? Please tell us about it in the comments below!