Temporal and spatial distribution of blastomycosis cases among humans and dogs in Illinois (2001-2007)

Objective-To compare the temporal and spatial distribution of cases of blastomycosis among humans and dogs in Illinois. Design-Retrospective cross-sectional survey. Sample-Human and canine populations in Illinois from 2001 through 2007. Procedures-For each year, human population data were obtained from the US Census Bureau, and the total number of dogs was estimated by use of a human population-based formula. Data regarding infections with Blastomyces dermatitidis in humans were accessed from the Illinois Department of Public Health. Data regarding B dermatitidis infections in dogs were acquired through a survey of a random sample of the 747 veterinary medical practices in Illinois. Statistical analyses of human and canine data were performed by use of t tests, ANOVA, odds ratio assessment, and regression modeling. Results-Estimated annual incidence of human cases of blastomycosis in Illinois increased from 3.8 to 10.7 cases/1 million persons/y from 2001 through 2007. Analysis of data from 221 veterinary practices revealed that the mean estimated annual incidence of canine cases of blastomycosis was 8.3 times the mean estimated annual incidence of human cases, with a similar pattern of change and regional distributions. Thirty-eight counties reported either human or canine cases but not both. Conclusions and Clinical Relevance-The estimated annual incidence of blastomycosis in humans and dogs in Illinois increased during the period of interest. Veterinarians, physicians, and public health agencies should be encouraged to communicate with each other regarding diagnoses of blastomycosis in either species to facilitate early diagnosis and treatment.