Human and canine blastomycosis: A common source infection.

Area of Science:

• Mycology
• Veterinary Medicine
• Infectious Diseases

Background:

• Blastomycosis is a fungal infection caused by Blastomyces.
• Endemic areas are typically in the Mississippi and Ohio River valleys and the St. Lawrence River valley.
• Human and animal infections are often linked to environmental exposures.

Purpose of the Study:

• To report a suspected common-source outbreak of blastomycosis in humans and dogs.
• To identify a potential new endemic area for blastomycosis in Ontario, Canada.
• To document the first Canadian report of a shared source for human and canine blastomycosis.

Main Methods:

• Case investigation and clinical assessment.
• Serological testing for human cases.
• Veterinary diagnosis for canine cases.
• Geographical and temporal analysis of exposure.

Main Results:

• One human and one canine case of confirmed blastomycosis occurred in fall 1993.
• An additional human case (seropositive) and four probable canine cases were identified.
• All cases had visited the same island in Bayfield Inlet, Georgian Bay, during summer/early fall 1993.
• This represents the first reported common source of human and canine blastomycosis in Canada.
• Evidence suggests a new endemic region for blastomycosis.

Conclusions:

• The island in Bayfield Inlet is a likely common source of Blastomyces exposure.
• This outbreak indicates a potential new endemic area for blastomycosis in Ontario.
• Simultaneous human and canine infections underscore the importance of environmental risk assessment.