Infectious Disease
Increases in blastomycosis incidence in humans and dogs by ecoregion in Minnesota, 1999-2023 Vanessa M. Slack* Vanessa M. Slack Slack Slack University of Michigan
Blastomycosis, an emerging infectious disease caused by inhalation of Blastomyces fungal spores, often presents as a respiratory infection but can disseminate, causing severe disease with a mortality rate of 8-10%. Examining incidence changes across ecological regions may yield insights into climate or environmental profiles associated with endemicity and emergence. We analyzed surveillance data reported to Minnesota Department of Health (1999-2023) to assess trends in blastomycosis incidence rates (IRs) in humans and dogs across 7 EPA-defined ecological regions spanning wetlands, plains, and forests. Between 1999-2023, 1,111 human and 2,825 dog cases were reported; statewide incidence increased 1.6 times for humans and 3.1 times for dogs. The 2 forest regions (N. Central Hardwood Forests and N. Lakes and Forests) comprised 80% of human cases (n=447 and n=443) and 88% of dog cases (n=900 and n=1589). IRs and ratios (IRRs) in both humans and dogs were highest in 2019-2023 compared to previous years, except N. Glaciated Plains, which has not reported a human case since 2004. Human IRRs (2019-2023 vs. 1999-2003) ranged from 1.7 (95%CI: 1.2-2.0) in N. Lakes and Forests to 9.4 in Lake Agassiz Plain (95%CI: 0.54-164), while dog IRRs ranged from 2.9 in N. Glaciated Plains to 21.0 in N. MN Wetlands. Compared to 2014-2018, recent incidence increased most rapidly for humans in W. Corn Belt Plains and N. Central Hardwood Forests (IRRs 2.7, 95%CI: 1.2-6.0 and 2.4, 95%CI: 1.6-3.0); dog incidence increased most rapidly in N. MN Wetlands (IRR: 2.7) and doubled in 4 regions: N. Central Hardwood Forests, N. Lakes and Forests, Lake Agassiz Plain, and W. Corn Belt Plains (IRRs: 1.9, 2.0, 2.2 and 2.2). These findings show that rising cases are a statewide concern for humans and dogs. While the 2 forest regions dominate the epidemiology of blastomycosis in the state, increases in all ecoregions should motivate statewide control measures such as awareness messaging for earlier diagnoses.