symptom-respiratory 8 min read

Could My Dog Have a Fungal Respiratory Infection (Valley Fever and More)?

Breed: All Dogs | Published: July 7, 2026 | Source: allpets.ai

Fungal respiratory infections in dogs—like Valley fever, blastomycosis, histoplasmosis, aspergillosis—can cause cough, nasal discharge, lethargy and weight loss. Early vet diagnosis and long-term antifungal therapy are often needed.

Could My Dog Have a Fungal Respiratory Infection (Valley Fever and More)?

Fungal respiratory infections in dogs range from nasal-only disease to serious, body-wide (disseminated) illness. Some — like coccidioidomycosis (Valley fever), blastomycosis, and histoplasmosis — are regional and linked to environmental exposures; others (aspergillosis, cryptococcosis) occur in specific breeds or after chronic nasal disease. This guide helps you recognize symptoms, understand how veterinarians diagnose and treat these infections, and decide whether your dog needs emergency care now.

Sources referenced include the Merck Veterinary Manual and public health resources on coccidioidomycosis (Valley fever) (Merck Veterinary Manual; CDC).

When to See a Vet Immediately

Bring your dog to a veterinarian or emergency clinic right away if you notice any of the following:

Severe or rapidly worsening difficulty breathing (open-mouthed breathing, very fast or very shallow breaths)
Blue, very pale, or gray gums or tongue (signs of low oxygen)
Collapse, seizures, or inability to stand
Severe, ongoing bleeding from the nose
Sudden extreme lethargy, refusal to eat or drink, or continuous vomiting

These signs indicate an urgent, life-threatening problem that needs immediate veterinary evaluation and supportive care.

Common Symptoms of Fungal Respiratory Infection in Dogs

Symptoms vary by fungus, where the infection is located (nose, lungs, or disseminated), and how advanced it is. Typical signs include:

Persistent cough (dry or productive)
Nasal discharge — clear, cloudy, mucoid, or sometimes bloody
Sneezing or reverse sneezing
Nasal ulceration, swelling, or deformity of the nose
Lethargy, low energy, poor appetite, weight loss
Fever (not always present)
Labored breathing or rapid breathing
Lameness or bone swelling if the infection has spread
Eye problems or neurologic signs if there is extension to the eyes or brain

Onset may be gradual over weeks to months for many fungal diseases. With some organisms (e.g., Coccidioides), initial signs may follow a few weeks after exposure.

Most Likely Causes (Differential Diagnosis — ranked for a dog presenting with chronic respiratory signs)

Note: local geography and exposure history dramatically change these probabilities.

Bacterial pneumonia or chronic bronchitis — very common causes of cough (common)

Viral respiratory disease (e.g., canine influenza) or secondary bacterial infection (common)

Parasitic lung disease (angiostrongylosis, lungworms) — depending on region (possible)

Fungal infections (see below: Valley fever/coccidioidomycosis, blastomycosis, histoplasmosis, aspergillosis, cryptococcosis) — more likely in dogs with travel or residence in endemic areas or with breed predispositions (possible to likely, depending on geography)

Nasal or pulmonary neoplasia (cancer) — more common in older dogs (possible)

Heart disease with pulmonary edema or pulmonary thromboembolism — may mimic respiratory disease (less common)

Fungal-specific likelihoods (geography dependent):

Coccidioidomycosis (Valley fever): high likelihood in dogs living in or that have traveled to the American Southwest (AZ, CA Central Valley, NM, TX, UT) (Merck Veterinary Manual; CDC).
Blastomycosis: higher likelihood in dogs in the Mississippi, Ohio River valleys and Great Lakes region.
Histoplasmosis: associated with soils rich in bird or bat droppings in similar river valley regions.
Aspergillosis: often causes chronic nasal disease in long-nosed breeds and can disseminate in German Shepherds.
Cryptococcosis: seen with nasal disease and potential CNS involvement; associated with pigeon droppings or decaying trees in some areas.

How Vets Diagnose Fungal Respiratory Disease

Your vet will combine history (travel, outdoor activity, breed), physical exam, and tests. Common diagnostics include:

Bloodwork (CBC, biochemistry) to evaluate overall health and look for inflammation or organ involvement
Thoracic radiographs (chest X-rays) to assess lungs and detect nodules, consolidation, or pleural effusion
Chest CT for more detailed imaging when available
Nasal imaging (rhinoscopy/CT) for chronic nasal disease
Cytology or culture from nasal swabs, aspirates, bronchoalveolar lavage (BAL), or fine-needle aspirates of affected lymph nodes or masses
Fungal serology or antigen tests (e.g., Coccidioides serology, urine antigen for Blastomyces/Histoplasma)
PCR testing or tissue biopsy when needed for definitive diagnosis

Diagnosis often requires multiple tests. Culture or histopathology confirms the organism but can take time; serology and antigen tests are helpful and can be monitored during treatment (Merck Veterinary Manual).

Treatment Overview

Only a veterinarian can prescribe and monitor antifungal therapy. Treatment depends on the fungus, extent of disease, and the dog's overall health.

Common approaches:

Azole antifungals: itraconazole is commonly used for many systemic and nasal mycoses; fluconazole may be chosen for certain infections (e.g., cryptococcosis). These are oral medications given for months.
Amphotericin B: used for severe or life-threatening disease or when azoles fail; given intravenously under hospital care because of potential kidney toxicity.
Local therapy: for nasal aspergillosis, topical antifungal irrigation or instillation (performed under anesthesia) may be curative in many cases.
Supportive care: oxygen, IV fluids, pain management, anti-nausea medication, nutritional support, and treatment of secondary bacterial infections.

Treatment courses are long — often 3–12 months or longer — and veterinarians will monitor liver and kidney function during therapy. Stopping treatment early can lead to relapse. Never give human antifungal medications or over-the-counter remedies without veterinary guidance.

Home Care and Monitoring (What You Can Safely Do)

Follow all medication instructions from your veterinarian exactly, including dosage and duration.
Keep your dog calm and avoid strenuous exercise while breathing is compromised.
Provide a clean, low-dust environment; avoid dusty runs or digging in soil in endemic areas during treatment.
Monitor and record appetite, energy level, breathing rate at rest (normal resting respiratory rate for most dogs is 15–30 breaths per minute), coughing frequency, nasal discharge, and any new signs such as limping or eye changes.
Attend all recheck appointments and bloodwork to monitor drug side effects and response.

Never attempt to treat a fungal infection at home with herbal remedies, unprescribed antifungals, or inhaled household agents. These can delay proper treatment and harm your dog.

Red Flags — Seek Emergency Care

Seek immediate emergency veterinary care if your dog shows any of the following:

Marked respiratory distress (open-mouth breathing, gasping)
Collapse or inability to rise
Seizures or sudden neurologic signs (circling, head tilt, blindness)
Continuous, heavy nosebleed or blood in vomit
Rapid deterioration despite starting therapy

If your dog is already diagnosed and on antifungal drugs, call your veterinarian promptly for new problems such as vomiting, yellowing of gums/eyes, severe diarrhea, or marked change in drinking (possible drug toxicity).

Prognosis

Prognosis varies by organism, how early treatment starts, and whether the infection has spread beyond the lungs or nose. Many dogs improve with appropriate therapy, but some fungal infections are protracted, require long-term treatment, and can relapse. Disseminated disease or severe lung involvement carries a more guarded prognosis.

Preventing Future Infections

Avoid high-risk outdoor activities in known endemic areas when possible (dusty environments, digging in soil, locations with bird/bat droppings).
Reduce exposure to large accumulations of bird or bat guano (histoplasmosis associations).
There is no vaccine for most fungal respiratory diseases in dogs; prevention focuses on exposure reduction and prompt veterinary care for suspicious signs.

Key Takeaways

Fungal respiratory infections in dogs include Valley fever (coccidioidomycosis), blastomycosis, histoplasmosis, aspergillosis, and cryptococcosis. Geography and exposure history strongly influence which fungus is likely.
Symptoms are variable and can be mild or progress to severe respiratory distress or systemic illness.
Diagnosis requires veterinary testing (imaging, cytology/culture, serology/antigen testing); treatment is with prescription antifungal medications, often for months.
Seek veterinary care immediately for severe breathing problems, collapse, seizures, severe bleeding, or rapid deterioration.
Never attempt to diagnose or treat serious infections at home. Follow veterinary instructions closely and attend rechecks and monitoring.

If you suspect your dog has a fungal respiratory infection, contact your primary veterinarian promptly. If your dog is in respiratory distress, go to an emergency clinic right away.

References:

Merck Veterinary Manual: Fungal respiratory diseases in dogs and cats (Merck Veterinary Manual).
Centers for Disease Control and Prevention (CDC): Coccidioidomycosis (Valley fever) information.

Frequently Asked Questions

Can I catch Valley fever from my dog?

Most fungal respiratory diseases are acquired from the environment (soil, dust, droppings). Direct transmission from an infected dog to a person is rare for coccidioidomycosis; people are usually infected from environmental spores. Standard hygiene (hand washing) and avoiding dusty exposures are sensible precautions.

How long does treatment usually take?

Treatment commonly lasts months (often 3–12 months) and sometimes longer for severe or disseminated disease. Your veterinarian will guide duration based on clinical response and follow-up testing.

Are certain breeds more at risk?

Yes. German Shepherds are predisposed to disseminated aspergillosis and some systemic fungal infections. Long-nosed breeds (dolichocephalic) are more likely to develop nasal aspergillosis. Exposure and geography are often more important than breed, however.

Will my dog need hospitalization?

Hospitalization is sometimes necessary, especially for dogs with severe respiratory distress, those needing IV antifungal therapy (e.g., amphotericin B), oxygen therapy, or intensive monitoring.

References & Citations

Parts of this article reference data from Merck Veterinary Manual.

Tags: fungal infectionrespiratorydogsValley feverdog health