The Fungal Disease That Doesn't Care Where You Live
- 7 hours ago
- 10 min read
Post one in this series:Â Most Ohio Dog Owners Have Never Heard of It. That's the Problem.
Post two in this series:Â Histoplasmosis in Dogs: The Fungal Disease Ohio Dog Owners Need to Know About
We've spent the last two posts in this series talking about Blastomycosis and Histoplasmosis — two serious fungal infections that share a regional fingerprint. Both are endemic to the Ohio River Valley. Both disproportionately affect sporting and hunting breeds. Both are contracted primarily outdoors, near water, in disturbed soil.
Aspergillosis plays by different rules.
It's not a regional disease. It's not a sporting dog disease. The fungus that causes it — Aspergillus — is one of the most common molds in the world, present in soil, compost, hay, dust, decaying organic matter, and even the air we breathe. Its microscopic spores are found both outdoors and indoors, which means healthy dogs encounter them regularly throughout their lives. Most never become sick because a normal immune system clears the spores before they can establish an infection.
Aspergillosis develops when those natural defenses fail — or when the fungus finds an opportunity to gain a foothold.
That distinction is important. Exposure is common. Disease is not.
When Aspergillosis does take hold, however, it takes hold hard — and the form it takes determines almost everything about what happens next.
This one is worth understanding on its own terms.
Two Diseases in One Name
Aspergillosis in dogs comes in two distinct forms, and they are so different in their presentation, their risk factors, and their prognosis that understanding which form you're dealing with is the first and most critical piece of information.
Sinonasal Aspergillosis is the more common form. It is a localized infection of the nasal cavity and sinuses, caused primarily by Aspergillus fumigatus. It is painful, destructive to nasal tissue and bone, and often treatable — particularly when caught before it extends beyond the nasal passages.
Disseminated Aspergillosis is the form that keeps veterinarians up at night. It is far less common but dramatically more serious — a systemic infection that spreads beyond its original site to the spine, kidneys, bones, eyes, and other organs. By the time most dogs show clear symptoms of the disseminated form, the disease is often already advanced. The prognosis is poor.
These two forms are caused by different Aspergillus species, follow different disease courses, and are not a progression from one to the other.
Sinonasal aspergillosis does not become disseminated aspergillosis. They are separate diseases that happen to share a name.
Which Dogs Are at Risk — and Why It's Different This Time
This is where Aspergillosis diverges meaningfully from Blastomycosis and Histoplasmosis.
Sinonasal Aspergillosis tends to affect dogs with long nasal passages —dolichocephalic breeds like Collies, German Shepherds, Greyhounds, and similar long-nosed dogs. The anatomy of these longer nasal passages appears to create a more favorable environment for fungal spores to settle and establish an infection.
Disseminated Aspergillosis shows a striking pattern: it is reported most often in middle-aged female German Shepherds. Researchers suspect these dogs may have an inherited immune system defect that makes them less able to eliminate the fungus before it spreads, although the exact mechanism hasn't been fully identified.
Dogs with weakened immune systems — whether from illness, cancer, long-term corticosteroid use, chemotherapy, or other immune-suppressing conditions — also face increased risk.
Critically, unlike Blastomycosis and Histoplasmosis, Aspergillosis is considered an opportunistic infection. Most healthy, immunocompetent dogs inhale Aspergillus spores without consequence. This is not a disease that usually strikes simply because a dog walked through the wrong patch of woods. It tends to find a foothold where something has already compromised the dog's defenses — or where anatomy gives it an advantage.
That said, it can occur in otherwise healthy dogs. The absence of a known immune problem doesn't rule it out.
Symptoms by Form
Sinonasal Aspergillosis
The signs of sinonasal aspergillosis tend to stay localized to the nose and sinuses—but they're persistent, unusual, and often frustratingly resistant to standard treatments like antibiotics. That lack of response to routine therapy is frequently the first clue that something fungal may be at work.
Watch for:
Chronic nasal discharge, often with a strong odor — may involve only one nostril initially
Thick discharge that may be yellow, green, bloody, or a combination
Frequent sneezing
Nosebleeds (epistaxis)
Ulceration, depigmentation, or raw tissue around the nostrils
Facial pain or discomfort
Pawing at the face
In advanced cases, neurological signs if the infection extends through the cribriform plate into the brain
The one-sided presentation is a particularly useful clue. While many nasal conditions affect both nostrils, sinonasal aspergillosis often begins on only one side.
That doesn't mean a one-sided nasal discharge automatically points to Aspergillosis. Nasal tumors, grass awns and other foreign bodies, severe dental disease, and chronic bacterial infections can all look similar. But discharge that persists for weeks, smells notably foul, and fails to improve with antibiotics deserves a more thorough investigation — including fungal disease as part of the differential diagnosis.
Disseminated Aspergillosis
The disseminated form usually has no characteristic nasal symptoms at all. Instead, the signs reflect whichever organs the fungus has invaded, and they often develop slowly over weeks or even months.
Signs may include:
Back pain that progresses to weakness or partial paralysis
Lameness affecting one or more limbs
Swollen joints or bones
Weight loss and muscle wasting
Poor appetite
Lethargy
Vomiting
Blood in the urine or urinary accidents
Enlarged lymph nodes
Eye abnormalities, including inflammation or vision changes
The spinal involvement — back pain progressing toward weakness or paralysis — is one of the more distinctive features of disseminated aspergillosis and warrants urgent veterinary evaluation.
The slow, creeping progression across multiple body systems is what makes this form especially dangerous. By the time all of the puzzle pieces fit together, the disease has often had significant time to spread.
Diagnosis
Aspergillosis is genuinely difficult to diagnose, and misdiagnosis isn't uncommon.
The sinonasal form can resemble nasal tumors, chronic rhinitis, bacterial infections, or even a foreign object lodged in the nose. Disseminated aspergillosis can mimic spinal disease, autoimmune disorders, orthopedic conditions, or certain cancers.
Unfortunately, there isn't a single definitive test that provides an easy answer. Diagnosis usually requires combining several pieces of evidence — including history, physical examination, imaging, laboratory testing, and tissue samples —to build the complete picture.
For sinonasal aspergillosis:
Rhinoscopy — direct visualization of the nasal passages using a small camera. Characteristic fungal plaques may be visible.
CT or MRI imaging — to evaluate destruction of the nasal turbinates and surrounding bone.
Fungal culture from nasal tissue or discharge.
Biopsy of affected tissue to identify fungal organisms microscopically.
Serology — blood tests looking for antibodies against Aspergillus.
For disseminated aspergillosis:
Blood work and urinalysis to identify evidence of systemic disease or kidney involvement.
Advanced imaging of the spine, bones, or affected organs.
Urine or tissue fungal culture.
Biopsy of affected tissue, lymph nodes, bone, or other involved organs.
Ophthalmologic examination if eye involvement is suspected.
Unlike Blastomycosis and Histoplasmosis, there is no widely used urine antigen test for Aspergillosis in dogs. Diagnosis relies much more heavily on imaging, cultures, and biopsy findings than on a single screening test.
If your dog has chronic, unusual nasal discharge — particularly if it's one-sided, foul-smelling, or hasn't responded to antibiotics — don't be afraid to ask your veterinarian whether fungal disease has been ruled out.
Sometimes the most important question isn't "What is it?" but "What haven't we considered yet?"
Treatment
Sinonasal Aspergillosis
The most effective treatment for sinonasal aspergillosis is usually performed under general anesthesia. First, your veterinarian (or a veterinary specialist) removes as much of the fungal plaque as possible through a procedure called rhinoscopy. This debridement physically removes large colonies of fungus that cling to the damaged tissue inside the nasal passages.
Once those plaques have been removed, a topical antifungal medication — most commonly clotrimazole — is infused directly into the nasal cavity and sinuses. Delivering the medication directly to the infection exposes the fungus to concentrations that simply can't be achieved safely with oral medications alone, making this approach significantly more effective.
Oral antifungal therapy by itself is generally considered less successful for the sinonasal form, although it may be used alongside topical treatment or when topical infusion isn't possible.
Some dogs require a second treatment if small areas of fungal infection remain or if the disease recurs. Fortunately, when diagnosed before extensive bone destruction or spread beyond the nasal cavity, the prognosis for sinonasal aspergillosis is generally good. Many dogs recover completely.
Disseminated Aspergillosis
Treating disseminated aspergillosis is an entirely different challenge.
Because the fungus has spread throughout the body, treatment relies on long-term systemic antifungal medications such as itraconazole, voriconazole, posaconazole, or other antifungal drugs selected by the treating veterinarian. Therapy often continues for many months — and sometimes longer than a year.
Even with aggressive treatment, success is far less predictable than with the sinonasal form. Once multiple organs, bones, or the spine are involved, eliminating the infection becomes extremely difficult.
The prognosis is guarded to poor, and despite everyone's best efforts, disseminated aspergillosis is frequently fatal.
That's the difficult reality of this disease.
Early detection — which is admittedly challenging because the symptoms develop so gradually — offers the best opportunity for successful treatment.
Any dog showing progressive back pain, unexplained lameness affecting multiple limbs, or signs of illness involving several body systems deserves a thorough diagnostic workup that includes fungal disease on the list of possibilities, especially if that dog is a German Shepherd.
Can My Dog Give Aspergillosis to My Other Pets — or to Me?
This is one of the first questions many owners ask.
Fortunately, the answer is no.
Aspergillosis is not considered contagious between dogs, from dogs to cats, or from dogs to people. Your dog didn't "catch" Aspergillosis from another sick animal, and they aren't likely to spread it to anyone else in the household.
The infection develops after inhaling fungal spores from the environment. Since those spores are already widespread in the world around us, isolation isn't necessary. The focus should be on diagnosing and treating the affected dog —not worrying about contagion.
Prevention
Unlike some infectious diseases, there's no vaccine for Aspergillosis and no practical way to eliminate exposure.
Aspergillus spores are simply too common. They're found in soil, compost, mulch, hay, dust, and even normal outdoor and indoor air. Most dogs inhale them every day without becoming ill.
While it's reasonable to keep dogs away from obviously moldy hay, compost piles, or heavily decaying organic material, most cases can't realistically be prevented through environmental management alone.
Instead, prevention looks a little different.
It means recognizing when a problem isn't following the expected course.
A chronic nasal discharge that won't resolve. A dog that's been through multiple rounds of antibiotics without improvement. A German Shepherd with slowly worsening back pain that doesn't quite fit the usual orthopedic diagnoses.
The earlier Aspergillosis is considered, the earlier it can be diagnosed — and the more treatment options may still be available.
A Quick Comparison
Feature | Blastomycosis | Histoplasmosis | Aspergillosis |
Fungus | Blastomyces dermatitidis | Histoplasma capsulatum | Aspergillus spp. |
Where it's found | Moist soil near rivers, lakes, wetlands | Soil contaminated with bird or bat droppings | Decaying vegetation, compost, hay, grain, moldy organic matter |
Highest-risk dogs | Sporting and hunting breeds, young large-breed dogs | Sporting and hunting breeds, young large-breed dogs | German Shepherds (disseminated), dogs with heavy environmental exposure |
How dogs are infected | Inhalation of spores | Inhalation or ingestion of spores | Usually inhalation |
Primary organs affected | Lungs, eyes, skin, bones, lymph nodes | Lungs, GI tract, liver, lymph nodes | Nasal passages or multiple organs (disseminated) |
Hallmark symptoms | Cough, fever, eye disease, lameness | Weight loss, diarrhea, fever, lethargy | Chronic nasal discharge, nosebleeds, facial pain (nasal)Â or vague systemic illness (disseminated) |
Diagnosis | Urine antigen, imaging, cytology | Urine antigen, imaging, biopsy | CT/rhinoscopy, biopsy, fungal culture/PCR |
Treatment | Itraconazole ± amphotericin B | Itraconazole ± amphotericin B | Topical antifungals for nasal disease; systemic antifungals for disseminated disease |
Can it relapse? | Yes | Yes | Yes |
Can it be prevented? | Reduce exposure; no vaccine | Reduce exposure; no vaccine | Reduce exposure; no vaccine |
What This Means for Ohio Dog Owners
Aspergillosis doesn't carry the same regional risk profile as Blastomycosis and Histoplasmosis. Aspergillus lives nearly everywhere, and geography alone doesn't define your dog's risk.
But that's not a reason to dismiss it.
It's a reason to think about it differently.
The questions to ask here aren't:
"Did my dog swim in a river?"
or
"Were we exploring around a bat roost?"
Instead, they're:
Does my dog have a long nose and chronic nasal discharge that won't go away?
Has my veterinarian tried multiple antibiotics without clearing up the problem?
Is my German Shepherd developing slowly progressive back pain, weakness, or unexplained lameness?
Is there anything affecting my dog's immune system?
Aspergillosis won't usually announce itself with a dramatic environmental exposure. More often, it lingers quietly — a nasal problem that never quite gets better or a dog that slowly loses ground over weeks or months.
Knowing the signs — and knowing when to push for more answers — is the work.
Quick Questions
Can indoor dogs get Aspergillosis?
Yes. Because Aspergillus spores are present in both indoor and outdoor air, dogs don't have to spend significant time outdoors to be exposed. Exposure is common. Disease is not.
Is Aspergillosis common?
No. Although exposure is nearly universal, most healthy dogs eliminate the fungus without ever becoming sick.
Can dogs catch Aspergillosis from each other?
No. The disease isn't considered contagious. Infection comes from environmental exposure rather than contact with another infected animal.
Should every dog with a runny nose be tested for Aspergillosis?
Not necessarily. Many cases of nasal discharge are caused by allergies, viral infections, foreign material, dental disease, or bacterial infections. But chronic, foul-smelling, one-sided discharge that doesn't improve with treatment deserves a more comprehensive evaluation that includes fungal disease.
The Full Picture
Three posts.
Three fungal diseases.
Three very different organisms with one important thing in common.
They often begin with symptoms that don't immediately point to a fungal infection. They progress quietly. They can become serious before anyone realizes what's happening. And because they're relatively uncommon, they're often mistaken for something else first.
That's what this series has been about.
Not fear.
Awareness.
Because awareness changes conversations.
It helps owners recognize when something isn't adding up. It helps veterinarians broaden the list of possibilities. And it helps dogs receive the right diagnosis sooner rather than later.
If you missed the earlier posts in this series, I encourage you to read the articles on Blastomycosis and Histoplasmosis as well — especially if your dog spends time outdoors in Ohio or anywhere else in the Ohio River Valley.
Know what's out there.
Know what questions to ask.
Your dog is counting on it.
As always, this post is for informational purposes and is not a substitute for veterinary care. If you have concerns about your dog's health, contact your veterinarian.