Most of the infectious disease topics that we’ve covered on Worms & Germs involve bacteria or viruses. Fungal diseases (other than ringworm) are often overlooked because they are less common, and because they tend to be more of a concern in certain areas only. However, when fungal infections occur they can cause serious problems.
Blastomyces dermatitidis is a dimorphic fungus (meaning it can exist in the form of a mold or a yeast) that lives in the soil in some areas. It is more common in wet, sandy, acid soils that have a high organic content. Animals (and people) can become infected by exposure to the mold form of the fungus in the soil. If the fungal spores are inhaled, it can result in severe pneumonia. Blastomycosis (infection with Blastomyces) can be difficult to diagnose and very difficult (and expensive) to treat. So while blastomycosis is rare in general, it is still an important disease, especially in areas where it is more common.
Recently, a study was published in the journal Medical Mycology (Chen et al, 2008, 46: 843-852), regarding blastomycosis in dogs in Tennessee. This was a case-control study that compared dogs with blastomycosis to dogs that did not have the disease. Here are some of the results:
- Male dogs were 2.7 times as likely to be affected as females.
- Working and sporting dogs were at higher risk (4.6 and 6.2 times as likely, respectively).
- Dogs 2-4 years of age were at highest risk.
- Close proximity to water was also a significant risk factor for infection.
In Ontario, blastomycosis seems to be most common around Georgian Bay. In the US, it is more common in central and northern states, with most cases reported in Wisconsin, Tennessee, Mississippi, Kentucky and Arkansas.
Blastomycosis can also occur in people, but blastomycosis cannot be transmitted from dogs to humans (or between any animal species). Only the mold form of the fungus that lives in the soil is infectious.