* No externally validated assays are available.
** Culture, which can be exceedingly difficult, should only be performed by experienced laboratories using biosafety level 3 containment. In-house fungal culture should never be attempted in animals that might have blastomycosis.
Infection typically occurs from inhalation of the mold spores, which can be found in the environment in endemic regions. These spores convert to yeast form in the lungs, propagate, and disseminate hematogenously, potentially causing pulmonary or extrapulmonary disease, often involving the skin, eyes, and lymph nodes.
The yeast form of B dermatitidis is not transmissible to other animals (including humans) under normal circumstances, as it must be directly inoculated into tissue to cause disease. Risks posed by the yeast form are predominantly associated with bites, needlestick injuries, or other sharps injuries. Transmission of B dermatitidis to a veterinarian has occurred as a result of a needlestick injury following a fine-needle aspiration of an infected site.1 While infection via this route has been rarely reported, it should be considered because of the typically lax sharps-handling practices often seen in veterinary hospitals and the relatively high incidence of needlestick injuries.2,3 Particular care should be taken with sharps handling in any animal with suspected blastomycosis, especially after fine-needle aspiration of a lesion.
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A bite from an infected animal is another potential route of transmission, as this can inoculate the yeast form into tissue.4,5
Another potential (but unproven) concern is reversion of the yeast form to the infectious mold form on bandage materials or exudates deposited in the environment. Yeast–to–mycelial conversion can occur within 3 to 4 days at room temperature, suggesting there could be a risk associated with contaminated surfaces or materials. This route of transmission, however, has not been documented.
Basic infection-control practices (eg, prompt disposal of bandages, regular bandage changing, proper waste disposal, routine cleaning and disinfection) should greatly minimize any theoretical risk for transmission of B dermatitidis.