A deadly dimorph: what you need to know about Blastomyces spp.

Maxx had just returned from spending a holiday weekend at a camp near Geraldton, Ontario when his owners noticed he just “wasn’t himself.” He began coughing and then “started licking his paws a lot.” When his paws began to bleed, that was enough for Maxx to be taken to the vet. He had symptoms of fever, swollen lymph nodes, high white blood cell counts, lesions over his entire body – “including inside his adorable ears” - swelling limbs and paws. These symptoms, along with a positive fungal spore test confirmed a diagnosis: Blastomycosis. Things progressed quickly, too quickly it seemed. Maxx was put on aggressive antifungal therapy. Shortly after his visits to the vet, his right eye became swollen, and Maxx returned to the vet, who confirmed that Blastomyces spp. was spreading to his eye. Even after three days of eye drops and aggressive oral drugs, his right eye became so cloudy and painful that it had to be surgically removed. Maxx’s story, adapted from the local daily newspaper in Thunder Bay, Ontario, is familiar among dog owners. Blastomycosis infection rates for dogs are ten times higher than humans; they are the second most common host of this deadly fungal pathogen. Working as a medical laboratory technologist and supervisor of the Mycology Department at Public Health Ontario Laboratories (PHOL) in Thunder Bay, Ontario, I see approximately 1800 human specimens requesting fungus culture testing yearly. Anywhere between 30 and 50 of those are typically new patients diagnosed with Blastomyces dermatitidis or Blastomyces gilchristii (Blastomyces spp.). Since I began working at PHOL in June of 2000, I have taken an interest in the Mycology Department and enjoy working with fungal cultures. My interest peaked in 2005 when the Thunder Bay District Health Unit (TBDHU) requested us to spike soil samples with cultures of Blastomyces spp. for anonymous trial testing at another laboratory that performed the Polymerase Chain Reaction (PCR) test. The TBDHU wanted a method to test soil samples in and around the Thunder Bay area. Fewer than three years later, the investigation was “unearthed.” Of the 45 soil samples collected, 12 tested positive for the fungus (Dunn, 2008). It was then that my passion for the research of this and other deadly human fungal pathogens began. This literature review is a summarization of the progression of research from the discovery of the species Blastomyces dermatitidis through to our current understanding of the disease blastomycosis and the organisms involved in this potentially deadly infection, Blastomyces spp. For more than a century, many dedicated researchers have added to the current knowledge of this pathogen. Building from this knowledge, four significant areas are contributing to our present understanding of Blastomyces spp. These areas involve the diagnosis, prognosis, treatment and prevention of blastomycosis. Each of these areas link to the four sections of this literature review: The tasks of the laboratory, the infection in the host, the monitoring by the physician and veterinarian, and the health unit’s public awareness. From these sections, the review will conclude with a discussion of where the future lies with this deadly Risk Group 3 (RG3) (Public Health Agency of Canada, 2015, Chapter 2.3.1.3) fungal pathogen