8 Fungal Infections in Dogs You Should Know About
When you hear that your dog has an infection, you’re most likely thinking of a bacterial or viral infection. However, viruses and bacteria aren’t the only pathogens that can affect our pets. Dogs can also contract fungal infections.
While most fungal infections in dogs are restricted to the skin or ears and are easily treated, some fungal infections affect the dog systemically and can be life-threatening. Learn about fungal infections in dogs and how they’re treated.
How Do Dogs Get Fungal Infections?
Dog fungal infections are caused by fungi, which are living organisms that spread in the environment by producing spores. Most commonly, fungi live in the soil. The spores that infect dogs are microscopic.
Fungal infections on the skin, like ringworm, usually pass directly through skin contact or contaminated surfaces. Most of the fungi that infect internal organs are inhaled, but they can also be ingested or enter the dog’s system through an open wound.
Dogs who spend more time outside, like hunting dogs, may be at an increased risk of contracting a systemic fungal infection. Most of the systemic fungal infections, like histoplasmosis and blastomycosis, are not contagious between dogs.
Some canine fungal infections are more prevalent in specific geographic locations. For example, histoplasmosis and blastomycosis are more common in the Midwest United States while coccidioidomycosis is more prevalent in the Southwest United States.
Dog Fungal Infection Symptoms
The symptoms of a dog fungal infection depend on the type of fungus and which part of the dog is affected.
For example, skin infections like dermatophytosis (ringworm) might cause scaly pink lesions on the skin and hair loss. A Malassezia infection of the ear might cause dark brown discharge, itchiness, and a foul odor from the ear. Blastomycosis in the lungs might cause coughing, while histoplasmosis in the gastrointestinal tract might cause diarrhea.
Symptoms of a fungal infection in dogs can include:
- Fur loss
- Scaly lesions on the skin
- Coughing
- Loss of appetite
- Itchiness
- Difficulty breathing or coughing
- Vomiting
- Diarrhea
- Fever
- Nasal discharge
- Dark debris in the ear
8 Types of Fungal Infections in Dogs
Dogs can contract a variety of fungal infections. Here, we’ll cover eight important canine fungal infections.
Dermatophytosis (Ringworm)
Type: Skin
You may be surprised to hear that ringworm isn’t actually a worm at all — it’s a fungus! Ringworm is a common dog fungal skin infection. The fungus passes directly from animal to animal via physical contact. Infection from contaminated environments, such as an uninfected dog lying in the bed of an infected dog, is also possible.
Dogs with ringworm develop scaly areas of hair loss. The skin may be itchy, though this isn’t always the case.
Your veterinarian should give you instructions on how to clean the environment while your pet is undergoing ringworm treatment. Treatment usually entails both topical therapies and oral medications. Topical therapy can include antifungal baths like lime sulfur dips, shampoos with antifungals, and leave-on creams. The oral antifungal drug of choice for dogs with ringworm is terbinafine.
Ringworm can pass from a pet to a person, so it’s important to regularly wash your hands and decontaminate the environment if your pet has ringworm. If you have a lesion that you suspect is ringworm, it’s best to consult with a medical professional.
Malassezia
Type: Skin
Malassezia dermatitis is caused by overgrowth of Malassezia yeast, which is a normal yeast on the skin. Most commonly, this occurs in dogs who have an abnormal skin barrier, such as dogs with allergic skin disease.
Dogs with a Malassezia infection will usually have very itchy skin with areas of redness, thickened skin, and/or hair loss. The coat may be oily, and the pet parent may notice a yeasty smell.
Malassezia is also responsible for most dog fungal ear infections and dog paw fungal infections. When a dog has a yeasty ear infection, the ear will often be quite itchy, red, and have dark debris inside. On the paws, the nailbeds are commonly affected, and a dark discoloration of the nails may be noted.
Treatment may include topical antifungals like shampoos or creams and systemic oral drugs, like terbinafine. Because most dogs who get yeast skin infections have an underlying skin condition, it’s important to manage any underlying factors to prevent recurrence.
Malassezia is not usually considered zoonotic, or able to pass from animals to people. However, caution should be used if there are immunocompromised individuals in the home.
Histoplasmosis
Type: Generalized/systemic, respiratory, gastrointestinal
Histoplasmosis is a fungal disease that’s more common in young adult dogs, especially sporting (hunting) breeds. The fungus is typically inhaled by a dog nosing around in the soil. Bat and bird feces may contribute to soil contamination. Histoplasmosis can remain isolated to the lungs or gastrointestinal tract, or it can spread throughout the body.
Dogs may have general signs like lethargy, weight loss, and appetite loss. If the lungs are affected, pet parents may notice difficulty breathing and coughing. Dogs who have histoplasmosis affecting their gastrointestinal tract usually have severe diarrhea and weight loss. In some cases, histoplasmosis can affect the eyes and/or brain, causing changes to vision and neurologic signs like seizures or an abnormal gait.
For mild to moderate histoplasmosis that remains in either the lungs or gastrointestinal tract, oral antifungal medications like itraconazole or fluconazole may be used. Treatment with oral medications lasts at least four to six months. Dogs who are very sick may benefit from intravenous amphotericin B. Some dogs, especially those with lung involvement, may benefit from a short course of steroids.
Dogs who have histoplasmosis restricted to their lungs are more likely to have a positive outcome than dogs who have histoplasmosis in their gastrointestinal tract or elsewhere in the body.
Histoplasmosis does not spread from pets to people, but people can become infected with histoplasmosis from soil.
Blastomycosis
Type: Generalized/systemic or respiratory
Blastomycosis is contracted by inhaling fungal spores from soil. Dogs who roam outdoors and live close to water are at an increased risk of contracting blastomycosis.
Symptoms of blastomycosis in dogs include loss of appetite, weight loss, cough, difficulty breathing, exercise intolerance, changes to the eyes and vision, and limping. In some cases, dogs can develop neurologic signs like seizures, drunken gait, and walking in circles. The lymph nodes may be enlarged.
Out of the oral antifungals, itraconazole is the treatment of choice for blastomycosis. Fluconazole is also an option for dogs. In severe cases or cases with neurologic signs, intravenous amphotericin B may be recommended. Steroids may be recommended short-term for dogs with difficulty breathing.
Most dogs will achieve a cure with appropriate treatment, but prognosis is worse if blastomycosis has spread throughout the body. It’s also possible for dogs to experience recurrence of blastomycosis after antifungal therapy is stopped.
The disease is not transmitted from infectious dogs to people through the air. Humans can get blastomycosis from a needle stick injury, but this is more of a risk for veterinary staff than pet parents.
Aspergillosis
Type: Nasal/respiratory or generalized/systemic
Most commonly, aspergillosis is inhaled and causes a nasal infection. In some cases, however, the fungus can disseminate through the bloodstream to other parts of the body.
In dogs who have nasal aspergillosis, signs will include nasal discharge, sneezing, and bleeding from the nose. If aspergillosis has spread systemically, the dog may be lethargic, experience loss of appetite, and potentially spinal pain and weakness in limbs.
For nasal aspergillosis, treatment is to infuse intranasal clotrimazole endoscopically. For systemic aspergillosis, antifungal voriconazole is the antifungal of choice. Treatment may last for months. In some cases, antifungal treatment is lifelong.
Aspergillosis does not spread from dogs to people.
Cryptococcosis
Type: Generalized/systemic
Dogs usually contract cryptococcosis by inhaling the spores. The spores will then disseminate throughout the body in the dog’s bloodstream. Pigeon droppings are known to harbor this fungus.
Although cryptococcosis more commonly causes inflammation in the nose and sinuses (rhinosinusitis) in cats, this fungus tends to affect dogs more systemically.
Symptoms of cryptococcosis in dogs can include changes to their eyes and vision, lethargy, loss of appetite, skin masses and sores, changes to temperament, seizures, and circling. They can develop symptoms associated with the nose, like sneezing and discharge, but this is much less common in dogs than in cats.
Dogs are usually treated long-term with oral antifungals like fluconazole or itraconazole. In some cases, intravenous amphotericin B may be recommended. If large masses are present, surgical removal may be recommended. In dogs with a lot of nervous system signs, steroids may be recommended to reduce inflammation. Treatment may last for months to over a year.
The prognosis is guarded for dogs with systemic disease, especially if they have neurologic signs like seizures, blindness, or a wobbly gait.
Cryptococcosis cannot pass from your dog to you. Humans can get cryptococcosis from inhaling the spores in the air, much like our dogs do.
Coccidioidomycosis
Type: Respiratory or generalized/systemic
Coccidioidomycosis usually develops in dogs who inhale the spores from the environment. Infection may remain within the respiratory tract, or it may spread throughout the body, including to the brain and bones.
Symptoms of this fungal infection in dogs include cough, respiratory distress, loss of appetite, weight loss, lethargy, limping, skin masses, vision loss, seizures, and drunken gait. Some dogs can develop heart failure.
Treatment usually includes oral antifungals like fluconazole, itraconazole, or ketoconazole. In some cases, intravenous amphotericin B may be recommended. Dogs who have the disease limited to their lungs may have a good outcome. Prognosis is poorer for full recovery if the disease has spread to the bones and/or brain.
While there haven’t been reports of coccidioidomycosis spreading from dogs to people, there have been reports of the disease spreading to a person via cat bite.
Sporotrichosis
Type: Skin
Dogs usually get sporotrichosis when the fungus enters through a puncture wound.
In dogs, sporotrichosis is more likely to affect the skin, while cats can also develop a disseminated form that spreads throughout the body. In some cases, it can affect both the skin and lymph nodes.
Symptoms include mass-like or sore-like lesions on the skin with draining tracts. The dog is often lethargic and has a poor appetite. Lymph nodes may be enlarged.
Treatment for sporotrichosis in dogs includes an oral antifungal like itraconazole or fluconazole. Treatment usually lasts for at least 30 days after the signs have resolved.
While cat-to-human transmission is considered possible, dog-to-human transmission is unlikely or rare.
| Type of Fungal Infection | Nasal / Respiratory | Gastrointestinal | Skin | Generalized/Systemic | Zoonotic Risk |
| Dermatophytosis (Ringworm) | X | X | |||
| Malassezia | X | ||||
| Histoplasmosis | X | X | X | ||
| Blastomycosis | X | X | |||
| Aspergillosis | X | X | |||
| Cryptococcosis | X | ||||
| Coccidioidomycosis | X | X | |||
| Sporotrichosis | X | Rare |
How to Treat Fungal Infections in Dogs
The specific treatment for a dog fungal infection depends on the type of fungus.
Generally speaking, most fungal infections in dogs are treated with one or more of the following treatments:
- Topical creams like miconazole
- Antifungal baths
- Antifungal wipes
- Oral antifungal medications like itraconazole or terbinafine
Some fungal infections, particularly ones that are affecting the lungs or parts of the nervous system (like the brain) may require hospitalization. In some cases, intravenous antifungal medications like amphotericin B are recommended.
Many systemic fungal infections require months of treatment. In some cases, treatment is lifelong.
Antifungal Medications for Dogs
Veterinarians have a range of options when it comes to antifungal medications for dogs. These can include oral antifungal medications, topical medications, antifungal shampoos, and more.
Itraconazole: This is an oral antifungal that’s used for a lot of systemic fungal infections, like blastomycosis or histoplasmosis. Use in dogs is off label.
Fluconazole: This oral antifungal is often used off-label for systemic fungal infections.
Terbinafine: This oral antifungal is often used off-label for ringworm and Malassezia infections. It is sometimes used for systemic fungal infections, as well.
Miconazole cream: Miconazole is often applied directly to ringworm lesions.
TrizUltra + Keto Solution: This ear flush contains an antifungal that may be useful for fungal ear infections.
MiconaHex+Triz Shampoo: This shampoo can help with both bacterial and fungal skin infections.
Duoxo S3 Pyo Shampoo: This shampoo is also useful for bacterial and fungal skin infections.
How to Prevent Fungal Infections in Dogs
Pet parents should familiarize themselves with the fungal infections that can affect their dog in their area. Consider restricting your dog’s ability to sniff around in moist soil or near pigeon droppings.
Pet parents can also monitor their dog’s skin by practicing regular grooming. Make sure to check the skin, ears, and nails for any abnormalities when you bathe your pet or trim their nails.
Parasite prevention is important for skin health. Dogs who have skin parasites like fleas may be more likely to develop a yeasty skin infection.
Lastly, keep up on your pet’s health care! Your veterinarian may be able to detect any changes to your pet’s health before you can. They can also help you to manage underlying conditions, like allergic skin disease, that can contribute to fungal skin infections in dogs.
