Hi,Welcome. I'm Dr. Bruce and I've been a small animal veterinarian for over 12 years. Thank you for your question about Roxie and Bentley. I'm going to be honest in saying that Blastomycosis is a fungal disease that can appear in certain areas with more frequency, but it really isn't something to get too worried about. There really isn't any prevention for it more so than just avoiding areas where it is highly prevalent. Usually the cases I see are ones that were in water areas. There is definite testing for it with a urine antigen screening that your vet can send out. I wouldn't be too worried to send it out in a non-clinical case.
Here is a great link on it.