Fungal Blastomycosis in Dogs: Symptoms, Treatment & Recovery Guide
Learn about fungal blastomycosis in dogs: early symptoms, diagnosis costs, antifungal treatment options, prognosis by stage, and when to see the vet immediately.
What Is Blastomycosis in Dogs?
Blastomycosis is a systemic fungal infection caused by Blastomyces dermatitidis (and the related species Blastomyces gilchristii), a soil-dwelling organism found primarily in moist, acidic soil near waterways. Dogs inhale fungal spores (conidia) from disturbed earth — often while digging, hiking, or playing along riverbanks — and the infection establishes first in the lungs before potentially spreading to skin, eyes, bones, lymph nodes, and the central nervous system.
According to the Merck Veterinary Manual, dogs are significantly more susceptible to blastomycosis than humans — estimated at 10 times the infection rate — likely because they spend more time with their noses close to the ground. The disease is endemic to the Mississippi, Missouri, and Ohio River valleys, the Mid-Atlantic states, and areas around the Great Lakes, though cases have expanded into new regions including parts of the Pacific Northwest and southern Canada.
Blastomycosis is not considered contagious between dogs or from dogs to humans under normal circumstances. However, the AVMA notes that rare transmission through bite wounds or needlestick injuries has been documented. Approximately 75% of infected dogs develop clinical illness, and without treatment, the infection is progressive and often fatal.
Recognizing Blastomycosis: Symptoms by Severity
Blastomycosis symptoms typically appear 3 to 15 weeks after exposure, with most dogs showing signs around 4 to 6 weeks post-inhalation. The insidious onset makes early recognition critical — many owners initially attribute symptoms to a lingering kennel cough or seasonal allergies.
| Severity Level | Symptoms | What to Watch For |
|---|---|---|
| Early / Mild (Lung-limited infection) |
|
Often mistaken for kennel cough or bronchitis. If your dog has recently been in endemic areas and these symptoms persist beyond 7–10 days without improvement, blastomycosis should be on the differential list. |
| Moderate / Progressive (Disseminating infection) |
|
Skin lesions in blastomycosis are distinctive — they often appear as verrucous (wart-like) masses with purulent discharge. Multiple lesions suggest systemic spread. Approximately 30–50% of infected dogs develop cutaneous involvement. |
| Advanced / Severe (Multi-organ involvement) |
|
CNS involvement occurs in approximately 5–10% of cases and carries the poorest prognosis. Ocular involvement affects roughly 40% of dogs with disseminated disease — approximately 20% of those with eye involvement become permanently blind in affected eyes. |
Risk Factors: Which Dogs Are Most Vulnerable?
Key Risk Factors for Canine Blastomycosis
Geographic Location: Dogs living in or visiting endemic regions — particularly states bordering the Mississippi, Ohio, and Missouri rivers, the Great Lakes region (Wisconsin, Minnesota, Michigan), and the Mid-Atlantic corridor — face the highest exposure risk. Wisconsin and Minnesota report some of the highest incidence rates in the country.
Breed Predisposition: While any breed can contract blastomycosis, sporting and working breeds that spend significant time outdoors in endemic areas show higher incidence. Breeds commonly overrepresented in clinical studies include:
- Golden Retrievers
- Labrador Retrievers
- Doberman Pinschers
- Weimaraners
- Pointer breeds
This likely reflects environmental exposure patterns (hunting dogs, field trial dogs) rather than strict genetic susceptibility, though some research suggests a possible genetic component in immune response to fungal pathogens.
Age: Young adult dogs between 2 and 4 years old are most frequently diagnosed, correlating with peak outdoor activity levels and exploratory behavior. However, dogs of any age can be affected.
Sex: Male dogs are diagnosed approximately 2 to 3 times more often than females, again likely reflecting behavioral differences (males roam more widely and dig more frequently).
Lifestyle & Environment: Dogs with access to wooded areas, riverbanks, lakeshores, construction sites, or freshly excavated soil face elevated risk. Hunting dogs, search-and-rescue dogs, and dogs that accompany owners on trail hikes in endemic zones are particularly at risk. Living within 400 meters of a waterway has been identified as a significant risk factor in epidemiological studies.
Immune Status: Dogs on immunosuppressive medications (cyclosporine, long-term corticosteroids) or with underlying immune compromise may develop more severe or rapidly progressive disease.
How Veterinarians Diagnose Blastomycosis
Diagnosing blastomycosis requires a combination of clinical suspicion, imaging, and laboratory confirmation. Because symptoms overlap with bacterial pneumonia, fungal pneumonia from other organisms (histoplasmosis, coccidioidomycosis), and even cancer, a definitive diagnosis is essential before starting months of antifungal therapy.
Typical Diagnostic Workup
Step 1: Clinical History & Physical Exam ($65–$120)
Your vet will ask about recent travel, outdoor activities, and symptom timeline. Physical examination may reveal fever, lymphadenopathy, respiratory abnormalities, skin lesions, or ocular changes. Mention any time spent in known endemic areas — this is critical diagnostic information.
Step 2: Thoracic Radiographs ($150–$350)
Chest X-rays typically show a diffuse interstitial to alveolar pattern, often described as a "snowstorm" appearance. Tracheobronchial lymphadenopathy is common. Radiographs help assess the severity of pulmonary involvement and establish a baseline for monitoring treatment response.
Step 3: Complete Blood Count & Chemistry Panel ($120–$250)
Common findings include leukocytosis (elevated white blood cells), mild anemia, hypercalcemia (in approximately 10–30% of cases due to granulomatous inflammation), and elevated liver enzymes. These results are supportive but not diagnostic on their own.
Step 4: Urine Antigen Test — MiraVista® Blastomyces EIA ($100–$175)
This is often the fastest and most practical confirmatory test. The Merck Veterinary Manual cites urine antigen testing as having sensitivity of approximately 85–93% in dogs with disseminated blastomycosis. Results typically return within 1–3 business days. False positives can occur with histoplasmosis cross-reactivity, so your vet may order additional tests if the clinical picture is ambiguous.
Step 5: Cytology or Biopsy ($80–$400 depending on site)
Fine-needle aspirate of affected lymph nodes, skin lesions, or lung tissue can reveal the characteristic broad-based budding yeast forms (8–15 μm diameter, thick refractile wall). This is considered definitive diagnosis. Biopsy of skin lesions is often the easiest and least invasive way to obtain a cytological sample.
Step 6: Ophthalmic Examination ($80–$200)
A thorough eye exam is recommended for all dogs diagnosed with blastomycosis, even without obvious ocular symptoms. Subclinical uveitis or chorioretinitis is common and requires specific treatment to prevent permanent vision loss.
Total diagnostic cost range: Most owners should budget between $500 and $1,200 for a complete diagnostic workup, depending on which tests are needed and regional pricing variation. Emergency or after-hours diagnostics will be significantly higher.
Treatment Options for Blastomycosis in Dogs
Blastomycosis is treatable, and the majority of dogs with mild to moderate disease respond well to antifungal therapy. Treatment typically extends over a minimum of 60 to 90 days, and many dogs require 4 to 6 months of continuous medication. Stopping treatment prematurely is the most common cause of relapse.
| Medication | Typical Dosage | Duration | Monthly Cost (50 lb dog) | Key Considerations |
|---|---|---|---|---|
| Itraconazole (First-line treatment) |
5 mg/kg every 12–24 hours, given with food (fatty meal improves absorption) | 60–90 days minimum; continue 30 days past clinical resolution and negative urine antigen | $150–$400 (compounded vs. brand name Sporanox®) |
Most commonly prescribed. Monitor liver enzymes every 2–4 weeks. Hepatotoxicity occurs in ~10% of dogs. Anorexia may indicate liver involvement — report immediately. Compounded itraconazole capsules from reputable pharmacies show comparable bioavailability to brand-name. |
| Fluconazole (Alternative / CNS cases) |
5–10 mg/kg every 12–24 hours | Same as itraconazole; often preferred for CNS or ocular involvement due to better tissue penetration | $80–$250 | Better penetration into the eye and CNS. Lower hepatotoxicity risk than itraconazole. May be less effective for severe pulmonary disease as a sole agent. Often used in combination with itraconazole for CNS cases. |
| Amphotericin B (Lipid complex — Abelcet® or AmBisome®) |
1–2 mg/kg IV, 2–3 times per week | 12–16 total doses, then transition to oral azole | $300–$800 per treatment course (hospital-administered) | Reserved for severe, life-threatening cases or dogs not responding to oral azoles. Requires IV administration and hospitalization. Significant nephrotoxicity risk — kidney values (BUN, creatinine, SDMA) monitored before each dose. Lipid formulations reduce but don't eliminate kidney risk. |
| Combination: Amphotericin B + Itraconazole | Standard doses of each agent | Amphotericin B course followed by extended azole therapy | $500–$1,200+ total | Gold standard for severe disseminated disease. Studies show faster clinical improvement compared to azole monotherapy. The combination allows shorter amphotericin B courses while maintaining efficacy. |
Supportive and Adjunctive Care
Beyond antifungal medications, treatment often includes:
- Anti-inflammatory corticosteroids (short course): In dogs with severe pulmonary inflammation, a brief 3–5 day course of prednisone at anti-inflammatory doses (0.5 mg/kg/day) can reduce life-threatening lung inflammation during the first week of antifungal treatment. This is a clinical judgment call your veterinarian will make.
- NSAIDs or pain management: For dogs with bone involvement or painful skin lesions. Carprofen (2 mg/kg every 12 hours) or gabapentin (5–10 mg/kg every 8–12 hours) may be prescribed.
- Oxygen therapy: Dogs with severe respiratory compromise may require hospitalization with supplemental oxygen (flow-by or oxygen cage) during the first 24–72 hours of treatment.
- Ophthalmic treatment: Topical corticosteroids, atropine, and systemic anti-inflammatories for dogs with uveitis. Uncontrolled ocular inflammation can lead to glaucoma and permanent blindness.
- Nutritional support: Highly palatable, calorie-dense food for anorexic dogs. In severe cases, assisted feeding via syringe or temporary feeding tube may be necessary.
Surgical Intervention
Surgery is rarely the primary treatment for blastomycosis, but it may be indicated in specific situations: removal of large, abscessed skin lesions that don't respond to medical therapy; enucleation (eye removal) in cases of severe, uncontrolled ocular blastomycosis causing intractable pain; or debridement of isolated bone lesions. Your veterinarian will determine if surgical intervention is warranted on a case-by-case basis.
Prognosis and Survival Rates by Stage
Prognosis for blastomycosis depends heavily on the severity of disease at diagnosis and the organs involved. With appropriate treatment, the overall survival rate for dogs with mild to moderate blastomycosis is approximately 70–75%. Dogs with only pulmonary involvement and no dissemination have the best outcomes.
| Disease Stage | Approximate Survival Rate | Recovery Timeline | Key Prognostic Factors |
|---|---|---|---|
| Mild (Pulmonary Only) | 75–90% | Clinical improvement within 1–2 weeks; full course 60–90 days | Excellent prognosis with prompt treatment. Most dogs return to full activity. Recurrence rate approximately 10–20%. |
| Moderate (Disseminated — Skin/Lymph Nodes) | 60–75% | Improvement in 2–4 weeks; full course 90–180 days | Good prognosis with aggressive treatment. Skin lesions may take 4–6 weeks to resolve. Monitor for relapse for 6 months post-treatment. |
| Severe (Bone, Eye, or Multi-Organ) | 40–60% | Improvement may take 4–8 weeks; full course 4–6+ months | Bone involvement (osteomyelitis) responds slowly. Ocular involvement may result in permanent vision loss even with successful systemic treatment. Lameness may persist. |
| Critical (CNS Involvement or Severe Respiratory Failure) | 20–30% or lower | Guarded; may require intensive care hospitalization | CNS blastomycosis carries the worst prognosis. Severe respiratory distress at presentation (hypoxemia requiring oxygen support) is associated with higher mortality, particularly in the first 3–5 days of treatment when fungal die-off can temporarily worsen inflammation. |
Relapse: Approximately 10–20% of treated dogs experience relapse, typically within 3–6 months of completing therapy. Relapse is more common in dogs with severe initial disease, those treated for fewer than 90 days, or dogs whose urine antigen test remained positive at treatment cessation. Relapsed cases generally respond to a second course of antifungal therapy, though the prognosis is slightly more guarded.
Life expectancy after recovery: Dogs that fully recover from blastomycosis and do not experience relapse generally have a normal life expectancy. Permanent sequelae — such as vision loss, mild exercise intolerance from lung scarring, or chronic lameness from bone involvement — may require ongoing management but do not typically shorten lifespan significantly.
Home Care, Monitoring & Lifestyle Adjustments
The majority of blastomycosis treatment happens at home. Here is what daily management looks like during the treatment period:
Medication Administration
Itraconazole must be given with a full meal — ideally one containing fat (such as canned food or a meal mixed with a teaspoon of olive oil or peanut butter) — to ensure adequate absorption. The capsule form has variable absorption when compounded; the oral solution formulation (Sporanox® solution) has more reliable bioavailability but is more expensive. Never skip doses. Set phone alarms if needed — consistency is critical for antifungal efficacy.
Activity Restriction
During the first 2–4 weeks of treatment, limit exercise to short leash walks only. Dogs with significant pulmonary involvement should avoid strenuous activity until follow-up radiographs show improvement. Gradual return to normal activity is typically possible by weeks 4–8, guided by your veterinarian's assessment.
Monitoring at Home
- Respiratory rate at rest: Count breaths per minute while your dog is sleeping. Normal is 15–30 breaths/minute. Consistently above 40 breaths/minute at rest warrants a call to your vet.
- Appetite tracking: Log daily food intake. Sudden anorexia during treatment can indicate hepatotoxicity from itraconazole — contact your vet the same day.
- Body weight: Weigh weekly on a home scale. Ongoing weight loss despite treatment suggests the infection is not responding adequately.
- Skin lesion documentation: Photograph lesions weekly with consistent lighting and distance to track healing progress. Share these images with your vet at recheck appointments.
- Temperature monitoring: If your vet recommends home temperature checks, use a rectal digital thermometer. Normal canine temperature is 101–102.5°F (38.3–39.2°C). Persistent fever above 103°F (39.4°C) after the first week of treatment warrants re-evaluation.
Follow-Up Schedule
Expect recheck appointments at approximately:
- Week 2: Physical exam, liver enzymes (if on itraconazole), assessment of clinical response
- Week 4: Repeat chest radiographs, blood work, urine antigen test to assess treatment response
- Week 8–12: Repeat urine antigen — treatment should continue until antigen is negative and clinical signs have resolved for at least 30 days
- 3 and 6 months post-treatment: Urine antigen monitoring to detect early relapse
Treatment Costs: What to Budget For
Blastomycosis treatment is a significant financial commitment. Here is a realistic breakdown for a 50 lb (23 kg) dog:
| Cost Category | Mild Case | Moderate Case | Severe Case |
|---|---|---|---|
| Initial diagnostics (exam, X-rays, blood work, urine antigen) | $500–$800 | $700–$1,200 | $1,000–$1,800 |
| Antifungal medication (full course) | $300–$600 | $500–$1,200 | $800–$2,500 |
| Recheck exams & monitoring (2–4 visits) | $200–$500 | $400–$800 | $600–$1,500 |
| Hospitalization (if required) | $0 | $0–$1,500 | $2,000–$6,000+ |
| Amphotericin B (if needed) | $0 | $0–$500 | $800–$2,000 |
| Estimated Total | $1,000–$1,900 | $1,600–$5,200 | $5,200–$13,800+ |
Pet insurance can significantly offset these costs if you have an active policy before diagnosis. Most major pet insurance providers (Trupanion, Healthy Paws, Nationwide) cover blastomycosis treatment under illness plans, though pre-existing condition exclusions apply. If cost is a concern, ask your veterinarian about compounded itraconazole from a PCAB-accredited compounding pharmacy, which can reduce medication costs by 40–60% compared to brand-name Sporanox®.
Prevention Strategies for At-Risk Dogs
There is currently no commercially available vaccine for blastomycosis in dogs. Prevention relies on environmental management and exposure reduction:
- Avoid high-risk environments: In endemic areas, keep dogs away from marshy areas, riverbanks with exposed soil, and construction or excavation sites. Stick to paved or well-maintained trails rather than letting dogs dig in wooded areas.
- Yard management: If you live in an endemic zone, remove decaying organic matter, wood piles, and areas of moist, acidic soil from your yard. Improve drainage in low-lying areas. Consider replacing areas of bare soil with mulch or gravel.
- Supervise outdoor activity: Discourage digging and nose-burying in soil, especially near waterways. Use a long-line leash in wooded areas to maintain control.
- Know the season: Blastomycosis cases peak in late summer and early fall (August–October in most endemic regions) when soil conditions favor spore dispersal, though infections can occur year-round.
- Early detection: For dogs that regularly hunt, compete in field trials, or spend extensive time outdoors in endemic areas, discuss baseline health screening with your veterinarian. Knowing your dog's normal values makes it easier to detect early changes.
🚨 When to See the Vet Immediately
Seek emergency veterinary care if your dog exhibits any of the following:
- Open-mouth breathing or severe respiratory distress — this is a life-threatening emergency
- Sudden blindness or dramatic eye changes (cloudiness, bulging, blood in the eye)
- Seizures, disorientation, or collapse
- Temperature above 104°F (40°C) that doesn't respond to cooling measures
- Complete refusal to eat or drink for more than 24 hours
- Coughing up significant amounts of blood
- If your dog is on itraconazole and develops jaundice (yellow gums, eyes), vomiting, or sudden anorexia — these may indicate hepatotoxicity requiring immediate medication adjustment
For mild symptoms (persistent cough, mild lethargy, small skin lesions) in a dog with potential endemic area exposure, schedule a regular veterinary appointment within 48–72 hours. Mention blastomycosis risk factors when booking so your vet can prioritize appropriately.
Frequently Asked Questions
Can I catch blastomycosis from my dog?
Direct transmission from dogs to humans is extremely rare and has only been documented through needlestick injuries or direct contact with infected tissue through broken skin. You and your dog were likely exposed to the same environmental source. If your dog is diagnosed, family members who share the same outdoor exposure should mention this to their physician, especially if they develop respiratory symptoms or skin lesions. The CDC provides guidance on blastomycosis in humans.
How long does it take for a dog to recover from blastomycosis?
Most dogs show noticeable clinical improvement within 7–14 days of starting antifungal treatment. However, the complete treatment course typically lasts 60–90 days for mild cases and 4–6 months for moderate to severe cases. Treatment should continue for at least 30 days beyond complete resolution of clinical signs and a negative urine antigen test. Full recovery — including return to pre-illness stamina — may take 3–6 months after treatment ends.
Will my dog relapse after treatment?
Approximately 10–20% of dogs experience relapse, most commonly within 3–6 months of completing treatment. Relapse risk is higher in dogs with severe initial disease, those treated for fewer than 90 days, or dogs whose urine antigen test was not rechecked. Most relapsed cases respond to a second course of antifungal therapy. Your vet will typically recommend urine antigen monitoring at 3 and 6 months post-treatment to catch relapse early.
Should I test my other dogs if one is diagnosed?
Since blastomycosis is acquired from the environment rather than transmitted between dogs, testing asymptomatic housemates is generally not necessary. However, if other dogs share the same outdoor exposure history, monitor them closely for symptoms over the following 3–6 months. If any housemate develops persistent cough, skin lesions, or lethargy, have them evaluated promptly.
Can a dog with blastomycosis go to daycare or the dog park?
During active treatment, keep your dog away from group settings. While dog-to-dog transmission is not a significant concern, your dog's immune system is compromised, and they are vulnerable to secondary infections. Additionally, exercise restriction is an important part of recovery. Resume normal social activities only after your veterinarian confirms clinical resolution.
Is there a blastomycosis vaccine for dogs?
As of 2026, there is no commercially available blastomycosis vaccine for dogs. Research into vaccine development has been conducted at the University of Wisconsin–Madison, but no product has reached the market. Prevention relies entirely on environmental awareness and exposure reduction.
Aaron Whyte
All our authors care for dogs every day — read more of their work on the authors page.
