FAQs About Blastomycosis In Dogs

Four Minutes
Feb 03, 2023

Is your pooch wheezing or short of breath? They may have been infected by a fungal organism! Blastomycosis in dogs occurs when Blastomyces dermatitidis infiltrates their body. It may sound scary, but it can be treated. Keep reading for answers to your most pressing blastomycosis questions.   

What Is Blastomycosis in Dogs?

Blastomycosis is a disease caused by an infectious organism. The fungus Blastomyces dermatitidis reproduces by emitting microscopic spores. When inhaled, the spores enter the respiratory system and the fungus takes root. Over time it begins to reproduce and spreads internally, extending the infection to other organisms. Pulmonary disease is the most common result, but blastomycosis has also been known to cause other issues throughout the body.

How Common Is Blastomycosis in Dogs?

The Centers for Disease Control have identified Blastomyces dermatitidis throughout the midwestern and southern states, particularly in the:1

  • Ohio River Valley: Pennsylvania, Ohio, West Virginia, Kentucky, Indiana, Illinois
  • Mississippi River Valley: Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, Louisiana
  • Great Lakes Area: Michigan, Wisconsin, Minnesota, Illinois, Indiana, Ohio, Pennsylvania, New York

The fungal spores of Blastomyces dermatitidis are capable of infecting multiple species, including humans and cats. However, dogs seem to be particularly vulnerable to the invasive organism. According to VCA Animal Hospital, dogs are 100 times more likely to contract blastomycosis than cats.2 The reason for this is unclear, although it may have to do with common dog behavior.

The fungus can live in damp soil and decaying wood. What dog doesn’t enjoy chewing on a stick or sniffing through the underbrush? These activities may expose your pup to the fungal spores.

Blastomycosis in humans

Humans are just as capable of becoming infected as cats and dogs. Does that mean you need to worry about the fungal organism jumping from your pup to you? The answer is usually no. Once Blastomyces dermatitidis enters a host, it transitions to a different stage in its lifecycle. It appears to no longer be infectious. Your household is more likely to be at risk of infection from the same fungal source that your dog encountered.2  If the family dog is diagnosed with blastomycosis, it’s a good idea to let your physician know, too.

What Are Some Blastomycosis Symptoms in Dogs?

Because the fungal spores tend to enter the body via the respiratory tract, the most common signs of infection are pulmonary. That includes shortness of breath, wheezing, and frequent coughing. However, your pup may develop other symptoms if the infection spreads. Here are some signs to watch out for:1

  • Skin lesions: These open sores can develop as a result of blastomycosis. Fluids drained from the lesions are not likely to be infectious, but should still be handled hygienically.
  • Swollen lymph nodes: In dogs, lymph nodes are located beneath the jaw, above the shoulders (in the “chest” area), and behind the knees. Inflammation of the lymph nodes is a common response to infection, so watch out for swelling along with other symptoms listed here.
  • Blindness: If the Blastomyces dermatitidis infection spreads to the eyes it can cause sudden blindness.
  • Weight loss
  • Fatigue
  • Fever
  • Depression/lack of activity
  • Seizures
  • Loss of limb functionality

Any one of these symptoms can be reason enough to take your dog to the vet as soon as possible. If your pup is suffering from more than one, it could indicate blastomycosis. Either way, it’s time to get a diagnosis.

How Do Vets Diagnose Blastomycosis in Dogs?

There are a few methods your vet may use to diagnose blastomycosis. One or all may be required before a conclusive diagnosis is given.


The only method that can provide a definitive answer is cytology — the microscopic examination of cells. If your dog has blastomycosis symptoms, your vet will likely want to take a sample of fluid from skin lesions or the lymph nodes to look for Blastomyces dermatitidis cells. If no fluid is available, your vet may perform a biopsy instead.

Enzyme immunoassay

This test looks for antigens, or toxic substances, in your dog’s urine or blood. It can be done quickly and, in the case of a urine test, is noninvasive. This test detects Blastomyces dermatitidis by looking for its interaction with enzymes produced by the immune system, called antibodies. However, an immunoassay may not be as reliable as cytology. Of those infected, 30% of dogs with blastomycosis don’t have enough antibodies in their system to produce a positive result on the test.1  

Agar-gel immunodiffusion

This test — AGID for short — looks for antibodies in your dog’s blood serum. As with the enzyme immunoassay, there is the possibility that an infected dog doesn’t have enough antibodies to be detected. Even if your pooch gives a positive AGID result, that may only indicate that they’ve been exposed to Blastomyces dermatitidis. AGID may be considered the first step in diagnosis.

Blastomycosis Treatment in Dogs: What to Expect   

Blastomycosis is a treatable disease. If your dog receives a diagnosis, your vet may prescribe an antifungal agent to fight off the infection. Itraconazole is the drug of choice for many vets when dealing with blastomycosis in dogs. Treatment often lasts a minimum of 4 – 6 months. If the infection doesn’t respond to the itraconazole, your vet might suggest a combination of several alternatives, including:

  • Fluconazole: Administered orally, either through tablet or liquid suspension, the side effects of fluconazole may include vomiting, diarrhea, and low appetite.3
  • Ketoconazole: Administered orally with food, via tablet or liquid suspension, the side effects of ketoconazole may include vomiting, diarrhea, and low appetite.4
  • Amphotericin B: This is administered intravenously (IV).5 This can be done by your vet, or they may be able to teach you how to handle IV fluids at home.

What is My Dog’s Prognosis?

Recovery rates for blastomycosis in dogs can fall between 50% and 75%.1 The healthier your dog is in general, the better chance they may have of fighting off the infection and bouncing back. However, there are potential complications to be aware of.

Because Blastomyces dermatitidis tends to concentrate in the lungs, there’s the possibility of a severe inflammatory response to treatment as the fungal organisms begin to die. This could result in respiratory failure. As such, your vet may want to examine your dog’s lungs before deciding on treatment.

Relapses are also possible, especially if the fungus has infected the nervous system, eyes, or testicles. These areas have high natural defenses, which in this case is a double-edged sword. They’re good at keeping potential toxins out, but that may also apply to antifungal drugs. If the infection has moved to the eyes or testicles and is proving resistant to treatment, your vet might recommend removing the infected organs to save your pup’s life.

Can You Prevent Blastomycosis in Dogs?   

Blastomyces dermatitidis can’t be reliably removed from the environment. That means that your furry family may always be at risk of exposure. There is also no existing vaccine. The best way to keep your dog safe is to keep them away from where they’re most likely to get infected:6

  • Avoid moist environments like riverbanks.
  • Keep your dog away from decaying organic matter that’s likely to harbor fungi.
  • Discourage activities like digging or rolling in mud and soil.

While these precautions can help, they’re not foolproof. Despite all your best efforts, infection may still occur. You may want to consider investing in dog insurance for extra security. An insurance plan could help cover some or all of the cost of treatment, including prescriptions and even surgery. That means that, if the worst happens, you will have help getting the treatment your pup needs. Learn more by fetching a free quote from MetLife Pet Insurance. 

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1 “Where Blastomycosis Comes From,” CDC

2 “Blastomycosis in Dogs,” VCA Animal Hospital

3 “Fluconazole,” VCA Animal Hospital

4 “Ketoconazole - Oral,” VCA Animal Hospital

5 “Anti-Fungal Therapy with Amphotericin B and Azoles,” MiraVista Veterinary Diagnostics

6 “Blastomycosis for Dog Owners,” Ontario Animal Health Network [PDF]

Coverage underwritten and issued by Independence American Insurance Company (“IAIC”), a Delaware insurance company, headquartered at 11333 N Scottsdale Rd, Ste 160, Scottsdale, AZ 85254 or Metropolitan General Insurance Company (“MetGen”), a Rhode Island insurance company, headquartered at 700 Quaker Lane, Warwick, RI 02886. Coverage subject to restrictions, exclusions and limitations. Application is subject to underwriting review. See policy or contact MetLife Pet Insurance Solutions LLC for details. MetLife Pet Insurance Solutions LLC is the policy administrator for this coverage. The entity may operate under an alternate, assumed, and/or fictitious name in certain jurisdictions as approved, including MetLife Pet Insurance Services LLC (New York and Minnesota), MetLife Pet Insurance Solutions Agency LLC (Illinois).

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