- © 2011 Marshfield Clinic
Non-Rural Point Source Blastomycosis Outbreak Near a Yard Waste Collection Site
- John R. Pfister, MS*,
- John R. Archer, MS†,
- Shelly Hersil, BS, CHES‡,
- Tammi Boers, RS‡,
- Kurt D. Reed, MD, MGIS§,
- Jennifer K. Meece, PhD||,
- Jennifer L. Anderson, BS||,
- Joshua W. Burgess, PhD#,
- Thomas D. Sullivan, PhD**,
- Bruce S. Klein, MD**,
- L. Joseph Wheat, MD†† and
- Jeffrey P. Davis, MD†
- *Wisconsin State Laboratory of Hygiene, Madison, WI, USA
- †Bureau of Communicable Disease and Emergency Response, Wisconsin Division of Public Health, Madison, WI, USA
- ‡Lincoln County Health Department, Merrill, WI, USA
- §Northwestern University Feinberg School of Medicine, Chicago, IL, USA
- ||Marshfield Clinic Research Foundation, Marshfield, WI, USA
- #University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- **School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA
- ††MiraVista Diagnostics, Indianapolis, IN, USA
- Corresponding Author:
Jeffrey P. Davis, MD; Bureau of Communicable Disease and Emergency Response; Wisconsin Division of Public Health; 1 W. Wilson St., Room 318; Madison, Wisconsin 53701; Tel: (608) 267-9003; Fax: (608) 261-4976; E-mail: jeffrey.davis{at}wisconsin.gov
Abstract
Background: Blastomycosis is a potentially fatal infection caused by the fungus Blastomyces dermatitidis. During January 1 through March 5, 2006, twenty-one laboratory confirmed cases of blastomycosis were reported among residents of an endemic area in north-central Wisconsin; a striking increase compared with previous years. The objective of the study was to determine if an observed increase in blastomycosis among residents of an urban area in north-central Wisconsin was caused by a point-source exposure and to identify its source.
Methods: We compared epidemiologic features, and signs and symptoms of B. dermatitidis infection among 46 historic (1999–2005) and 21 possible outbreak case patients. In addition, a case-control study was conducted to compare risk factors of the outbreak case patients with those of 64 age, gender, and geographically-matched control subjects. We conducted site inspections, evaluated meteorological data, genetically compared outbreak and non-outbreak isolates, and attempted environmental detection of B. dermatitidis using polymerase chain reaction, in vitro isolation, and in vivo isolation by tail vein injection of mice.
Results: The unusual risk profile of this outbreak included: residence within non-rural city limits with limited time spent outdoors and an equivalent gender ratio and young median age among case patients consistent with common source rather than unrelated exposures. Thirteen of fourteen outbreak-associated clinical isolates of B. dermatitidis clustered in the same genetic group by PCR-RFLP analysis. Inspections near the cluster center suggested a yard waste collection site as the probable exposure source. B. dermatitidis nucleic acid was detected in one of 19 environmental samples. Environmental and meteorological conditions and material management practices were identified that may have facilitated growth and dispersal of B. dermatitidis conidia near this residential area.
Conclusions: Results of our investigation of this large non-rural outbreak of blastomycosis suggest bioaerosol hazards may exist near yard waste collection and composting facilities, especially where pine tree litter is present, in B. dermatitidis endemic areas.
