Fungal infections in dogs can range from simple skin irritations to serious systemic conditions affecting internal organs. This type of infection can occur when certain types of fungi take hold in a dog’s body, either externally on their skin or internally in their lungs, bones, or other tissues. 

Some dog fungal infections, like ringworm, are superficial and relatively easy to treat. Others, like blastomycosis or histoplasmosis, can be life-threatening if not caught early. 

In this blog, we’re going to talk all about fungal infections in dogs, including the types and symptoms. Next, we’re going to talk about diagnostics, treatment methods, and preventive measures. 

What Are the Common Types of Dog Fungal Infections?

Canine fungal infections differ, which means varying symptoms and different ways of dealing with them. Here’s a quick overview of the common ones. 

Yeast Dermatitis

Yeast dermatitis is a superficial fungal infection caused by the overgrowth of Malassezia pachydermatis, a yeast that naturally resides on a dog’s skin. While typically harmless, this yeast can multiply excessively under certain conditions, such as allergies, humidity, or a weakened immune system. 

The infection often targets areas like the ears, paws, armpits, and skin folds, making it especially common in breeds with floppy ears or wrinkled skin. These breeds include Basset Hounds, Poodles, and Dachshunds. Common symptoms include

• Persistent itching and scratching

• Red, inflamed, or irritated skin

• Oily or greasy patches are often accompanied by scaling or flaking

• Discoloration of the skin, with a darker appearance in chronic cases

• A distinct odor emanating from the affected areas

• Recurring ear infections, with redness, discharge, or head shaking

Ringworm

Despite its name, ringworm isn’t caused by a worm but by dermatophytes such as Microsporum canis. This superficial fungal infection affects a dog’s skin, hair, and nails. It’s highly contagious and can easily spread through physical contact with infected animals and contaminated objects.

Puppies, seniors, and dogs with impacted immune systems tend to be more susceptible to this disease. Ringworm is also zoonotic, meaning it can be transmitted to humans. Some of the common symptoms of ringworm in dogs include: 

• Circular patches of hair loss

• Redness or inflammation in the affected areas

• Brittle or damaged nails if the fungus infects the claws

• Mild to severe itching accompanied by discomfort

• Scaly or crusty skin, with dryness and irritation present

Blastomycosis

Blastomycosis is a systemic fungal infection in dogs caused by Blastomyces dermatitis, a fungus found in moist soil, decaying wood, and areas near water. Dogs typically contract the infection by inhaling fungal spores.

These spores then travel to the lungs and may spread to other parts of the body, such as the skin, bones, brain, and lymph nodes. This infection is more common in areas where water is present. Signs include: 

• Respiratory problems, such as coughing and breathing problems

• Fever and urinary issues

• Weight loss and decreased appetite

• Enlarged lymph nodes

• Skin lesions or sores that may ooze or crust over

• Lameness or swelling

Histoplasmosis

Histoplasmosis is caused by Histoplasma capsulatum. Dogs can contract the fungus by inhaling or ingesting them through soil enriched with bird or bat droppings. Because of this, histoplasmosis primarily affects the respiratory system. 

Dogs under the age of 4 are usually the most common victims of this disease. In some cases, the infection can spread to the gastrointestinal system, liver, spleen, or other organs. Common signs of this disease include: 

• Chronic coughing or difficulty breathing

• Fever and general lethargy

• Weight loss and poor appetite

• Diarrhea and vomiting

• Enlarged lymph nodes

Coccidioidomycosis

Coccidioidomycosis, also known as Valley Fever, is a systemic dog fungal infection caused by the Coccidioides fungi. These fungi thrive in dry, dusty environments.

Dogs typically contract the infection by inhaling fungal spores from soil, especially after digging or being exposed to windblown dust. The infection primarily affects the respiratory system but can spread to bones, joints, or the nervous system in severe cases. Some of the symptoms are:

• Persistent coughing or wheezing

• Fever and lack of energy

• Weight loss and poor appetite

• Lameness or swollen joints if the fungus spreads to the bones

• Neurological symptoms, such as seizures, may occur in rare advanced cases

Cryptococcosis

Cryptococcosis is another fungal infection in dogs caused by Cryptococcus neoformans or Cryptococcus gattii. These fungi are commonly found in soil contaminated with bird droppings, especially from pigeons. 

Dogs can contract the fungal infection by inhaling fungal spores, which primarily affect the respiratory system. In severe cases, the infection can worsen and spread to the central nervous system, eyes, or skin. Here are the common symptoms:

• Sneezing and nasal discharge, often with blood or mucus

• Coughing, sneezing, and breathing problems

• Neurological symptoms, such as head tilt, seizures, or difficulty walking

• Eye abnormalities, including cloudiness or blindness

• Lethargy, fever, and weight loss

Aspergillosis

Aspergillosis is a dog fungal infection caused by species of the Aspergillus fungi commonly found in soil, decaying vegetation, and dust. Dogs typically contract the infection by inhaling fungal spores, which primarily affect the nasal passages or, in rare cases, spread to other body parts.

Certain breeds, such as German Shepherds, are more prone to the disseminated form due to a genetic predisposition. Common signs of nasal aspergillosis include: 

• Nasal discharge with a strong odor

• Sneezing and frequent nose rubbing

• Swelling or pain around the nose or face

• Nasal sores or ulcers

For disseminated aspergillosis, these are the signs:

• Fever and overall weakness

• Lameness and lack of coordination

• Weight loss and poor appetite

• Neurological symptoms in severe cases