METHODS: Surveillance for blastomycosis in Minnesota is passive. MDH receives case reports from health care providers (HCPs), infection preventionists (IPs), clinical laboratories, and veterinarians in multiple formats. MDH staff contact HCPs and veterinarians to obtain clinical and demographic data before interviewing case-patients or pet owners for symptom and exposure histories. Confirmed human and veterinary cases are defined as a Minnesota resident with B. dermatitidis organisms cultured or visualized from tissue or body fluid; or, a positive urine or serum antigen test and compatible clinical signs and symptoms. Case data are entered into an Access database. Surveillance data for both human and veterinary cases are posted on the MDH website. Clusters of human and/or veterinary cases are investigated. In 2014, environmental samples were collected during 3 cluster investigations, and tested by PCR for B. dermatitidis.
RESULTS: During 1999-2015, 540 human cases (range, 22-49 cases per year) and 1,224 veterinary cases (range, 52-99 cases per year) of blastomycosis were reported in Minnesota. Both human and veterinary cases were diagnosed year-round. The median age of human cases was 45 (range, 3-93 years), and 69% of cases were male. 96% of veterinary cases were canine and 4% were feline. Of the canine cases, 55% were male and 69% were neutered or spayed. Ten clusters of human or veterinary cases were investigated (range, 0-3 investigations per year); only 2 of the clusters occurred in the same Minnesota county. 60% to 95% of environmental samples were PCR positive for B. dermatitidis at 3 case-cluster sites tested in 2014.
CONCLUSIONS: Surveillance of both veterinary and human blastomycosis cases has compelling advantages. Blastomycosis-endemic regions may be more accurately mapped; geographic and temporal clusters of canine cases may be sentinels for human disease risk.