Blastomycosis in Dogs

While we love spending time exploring the great outdoors with our dogs and cats, there are many risks that we need to be familiar with. Some of these risks are better known, like rabies being transmitted by wildlife, local predators, and toxic blue-green algae blooms. In this article, we’re going to look at a danger you may not be familiar with but may be lurking in your favourite parks and getaway spots – Blastomycosis in dogs.

Recently, the Wiancko Veterinary Housecall Services announced the diagnosis of a dog in the Six Mile Lake area (Port Severn, Ontario) with a Blastomycosis infection. As we have previously shared here on the blog, Six Mile Lake Provincial Park is one of our go-to campgrounds and we visit it every year.

Before you head out on your next outdoor adventure, here is some important information that you should know to keep both you and your dog safe.

two dogs laying outside on a raised dog bed | Blastomycosis in Dogs
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What is Blastomycosis?

Blastomycosis is a fungal infection caused by inhaling the Blastomyces dermatitidis fungal spores. It is also commonly referred to as ‘Blasto’. After the spores have been inhaled, they move through the respiratory tract settling in the airways. Here they reproduce, eventually spreading throughout the body. If the infection isn’t caught and addressed, it can even spread to the major organs in your dog’s body which is often fatal. In some isolated cases, the fungal spores enter the body through an open wound. Similar to when they are inhaled, they will then reproduce and spread throughout the body.

Humans can also inhale the fungal spores and suffer from Blastomycosis. While cats can become infected as well, but it is rare.  

The fungi responsible for this infection can usually be found in the soils or in decaying matter such as rotting logs and vegetation. It is prevalent in warmer, moist environments including the midwest, the Great Lakes region, around Georgian Bay, the Ottawa area, and in Northwestern Ontario. When the soil is stirred up, the fungal spores are released into the air putting those in close contact with the area at risk. Blastomycosis in dogs is more common than infection in people largely due to the fact that our canine companions are closer to the surface of the soil.

What are the Symptoms of Blastomycosis in Dogs?

Early identification and treatment of infection will give your dog the best chance of survival. As a responsible dog owner, this means that you need to be familiar with the most common Blastomycosis symptoms in dogs. This is especially important if you know that you are spending time in a high-risk area.

The most common signs of Blastomycosis in dogs include:

  • Loss of appetite
  • Weight loss
  • Coughing
  • Congestion
  • Difficulty breathing
  • Fever
  • Leg pain or lameness
  • Depression
  • Draining skin lesions
  • Hard bumps under the skin
  • Enlarged lymph nodes
  • Eye infections, squinting, or sudden blindness
  • Testicular inflammation
  • Seizures

If you notice any combination of these symptoms, contact your veterinarian immediately. Explain where you have been and whether you are aware of confirmed cases in the area. This will help your vet to assess whether your dog’s illness is a result of Blastomycosis or another medical cause.

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Can Blastomycosis be Treated?

Blastomycosis treatment in dogs requires administering anti-fungal medications such as fluconazole and itraconazole. For most dogs, this will include an average of 2 to 6 months of ongoing treatment. Blastomycosis skin lesions may require additional medication to prevent bacterial infection. In more serious cases, your dog may need to be hospitalized to address the more severe symptoms that have developed.

Even after the treatment period, some dogs will relapse when the medications are stopped and develop symptoms once again. For other dogs, the symptoms that they experienced, like blindness, may be permanent.  Therefore, you dog will need to follow up appointments and testing to ensure that the treatment was successful. Dogs that have been infected are at a greater risk of infection again in the future.

What is the Survival Rate of Blastomycosis?

Despite the long recovery, treatment for Blastomycosis in dogs is relatively effective when the infection has been caught early and the prognosis is good. The estimated recovery rate for Blastomycosis in dogs is between 50% and 75%. The costs of treating Blastomycosis run in the thousands of dollars. However, if it is left untreated a dog’s prognosis is significantly worse. Many untreated cases will be fatal.

Can Dogs Spread Blastomycosis to Other Dogs?

In order to be infected, a dog must be in contact directly with the Blastomyces dermatitidis fungal spores. Once the spores have infected a dog, they enter a different form which allows them to spread throughout the body, but this form is not infectious to other animals or to humans. This means that you will not need to segregate your pet from the family during treatment. But you should consider the locations that you have visited, including your own backyard, to try to determine the source of the infection as others can be infected from the soils in that area.

Can Dogs Get Blastomycosis in Winter?

If you enjoy camping or hiking in the colder winter months, you may be wondering if there is still a risk of Blastomycosis in dogs. While some illnesses and infections do go dormant when the temperatures drop, the same can’t be said for the fungi responsible for this infection. Studies show that there is no consistent seasonality, meaning that exposure can happen at any time. Although the time when veterinarians see the highest number of cases is around the early fall or later winter. This would indicate that dogs were initially exposed in the warmer months.

dog digging in the dirt | Blastomycosis in Dogs
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How Do I Stop My Dog from Getting Blastomycosis?

Unfortunately, there is no vaccination or guaranteed prevention of Blastomycosis short of avoiding areas where your dog can be exposed. This likely isn’t what you were hoping to hear if you enjoy camping or hiking in an area that is a known exposure site, like we do. Luckily, there are some steps that you can take to reduce the risk as well as to prevent a more serious infection.

Avoid Areas Where the Ground Has Been Disturbed

Are they currently doing work at your favourite park or hiking trail that requires excavation or significant digging? These activities stir up the soil which releases the fungal spores into the area. Even walking by construction sites like these can put you or your dog at risk.

Other higher risk areas where exposure is greater include farms, hunting areas, and along the banks of lakes and streams.

Prevent Digging and Sniffing

If you know that you are in a high-risk area, you want to take steps to prevent your dog from inhaling the spores. One reason that dogs are at a higher risk for infection is that they often have their noses to the ground, exploring the area around them. This means that, if the spores are disturbed, there is a higher likelihood that they are going to breath them in. When possible, stop your dog from sniffing excessively or digging in the soil.

Seek Veterinary Help Early

The best prognosis for your dog involves starting treatment as early as possible. This means identifying the signs of an infection and bringing your dog to your veterinarian immediately. The sooner that your dog is examined, the better.

Were you aware of the risks of Blastomycosis in dogs? Has your dog previously been infected? We would love to hear about your experiences in the comments.

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