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BACKGROUND: Freshwater cyanobacterial harmful algal blooms (HABs) and the toxins they may produce are of increasing concern in recreational and drinking waters due to their potential public health risk. In order to assess the scope and magnitude of this problem, the Wisconsin Department of Health Services, the Wisconsin Department of Natural Resources (DNR) and the Wisconsin State Laboratory of Hygiene (WI SLH) undertook a five-year surveillance effort to evaluate the public health burden of HABs and to better characterize environmental conditions during these blooms.
METHODS: With project funding from the Centers for Disease Control and Prevention (CDC), the collaborative interagency team developed several new case reporting pathways, including automated call notifications from the Wisconsin Poison Center, a web-based illness survey, direct contact with ill individuals, and referrals from partner agencies (including DNR, WI SLH and local health departments). These illness reports were reviewed by program staff to ensure that they fit the case definition of a HAB-related illness. When the time between reporting and exposure was less than five days, follow-up water sampling was conducted to determine the environmental conditions at the time of the exposure. Environmental sampling was led by regional DNR staff collection of water samples and shipment to WI SLH, where they were analyzed for cyanobacteria cell densities, cyanotoxin levels, and a suite of water quality parameters. In Wisconsin, health advisories for HAB-related exposure are issued based on the World Health Organization guidance for cyanobacteria cell densities in recreational waters.
RESULTS: Between 2009 and 2013, the Wisconsin Department of Health Services received 144 complaints of human and animal illness associated with exposure to HABs. The most common HAB-related illnesses reported were gastrointestinal distress, dermal rash, respiratory irritation and cold-like symptoms. Cyanotoxins were detected in over 56% (26 of 46) of the environmental samples analyzed, with microcystin-LR, -LA and -RR the most common toxins in Wisconsin surface waters.
CONCLUSIONS: Expanded outreach efforts to health-care professionals, veterinarians, local lake associations and the general public helped increase reporting of HAB-related illnesses and awareness of the potential hazard associated with algal blooms. In the absence of continued federal funding, the information gathered in this surveillance effort has helped the interagency team prioritize surveillance and outreach activities to address the public health burden of HABs and implement interventions to exposures to harmful blue-green algae and their toxins.