Fungal infections in dogs are generally caused by an overgrowth of fungal yeasts. Although fungal yeasts are naturally present in and on the body, certain circumstances can promote overgrowth of these organisms which can disrupt the natural functioning of the body.

Overgrowths of normally benign fungal yeasts can cause disruptions to the natural functioning of the body in the area of the overgrowth.

The symptoms of a yeast infection will vary depending on where the overgrowth is located. 

Candida yeasts are opportunistic pathogens that tend to be concentrated in the digestive system, mouth, rectum and genital areas. A thick whitish coating of Candida fungi in the mouth and tongue area is commonly identified as Thrush, and Candida overgrowth in the genital area is often referred to simply as a “yeast infection”. The Candida yeast can also infect the lower intestine and the urinary tract system.

Malassezia pachydermatis is a fungal yeast that takes up residence in the ear canal and the folds of the ear, in folds of skin, and in between the toes. It is the most common cause of yeast infections in these areas and can cause scaly or smelly build-up on the skin, hair loss and excessive itching in the affected areas.

The yeasts that cause these infections are part of the normal flora in the body of the dog as well as on its skin. Many circumstances can promote overgrowth in these organisms which can cause disruptions in the proper functioning of the colonized system. Conditions that may contribute the overgrowth of fungal yeasts can include, but are not limited to:

In order to make a diagnosis your veterinarian will first ask for a full history of the animal, as well as a general physical exam, taking particular note of any abdominal swelling or pain, as well as any unusual odors or skin abnormalities. A scraping may be taken of the skin if any abnormalities are present and any unusual discharges will be tested. Viewing the samples under a microscope may show evidence of the yeast infection, as well as revealing other possible irritants such as bacteria, viruses, and even mites. A complete blood count, biochemistry profile, and urinalysis would be ordered and cultures may be requested on any samples that were collected. Yeast infections in dogs commonly have an underlying cause, and your veterinarian may also be able to use the information from these tests to determine if that is the case. Depending on where the infection is located and the severity of the symptoms a treatment plan may be put into place even before culture results have been returned.

The treatments for yeast infections in canines can vary widely depending on the placement and severity of the infection, the type of yeast involved, and what underlying causes may be contributing to the overgrowth. Treatment or management of any underlying triggers (such as dietary factors or the use a catheter) will be initiated as soon as feasible, often before the results from the culture have been made available. In some situations, treating the underlying cause is enough to resolve the problem but in many cases, additional steps will need to take place. In the case of fungal infection of the skin, a topical anti-fungal/anti-yeast medication is usually the first recommendation to treat the infestation. Topical medications usually require an application to the area several times a week, if not several times a day. Instructions for topical medications should be read thoroughly and followed carefully to ensure safety and effectiveness. If the yeast infection is in an internal system or if it does not respond to topical antifungal treatments, oral antifungal medications are often prescribed. Both Candida and Malassezia pachydermatis are known to respond to antifungal medications in the azole family, and it is not uncommon for a full course of antifungal treatments to take four to seven weeks to complete.

During the recovery period, it is best to have a comfortable and quiet space available for your companion to recuperate with plenty of access to food and water if they need it. Your pet may be asymptomatic during all or part of their treatment, and do not need to have their activity restricted unless instructed by your veterinarian or other signs of distress are noted. Infections by both varieties of fungus are zoonotic and can be transmitted to humans. The very young, the very old and those with compromised immune responses should avoid contact with the infective yeast to prevent transmission.  Both topical and oral antifungal treatments can take several weeks to completely clear up an infection and your veterinarian may request that you bring your pet in for further cultures and testing, both during treatment and after. Although some dogs may require lifelong treatments to manage outbreaks, the overall prognosis is favorable.