Outbreak of Cryptosporidiosis Centers for Disease Control and Prevention Associated With a Man-Made

Water at RWVs can become contaminated by "CTU SBDU the parasite when infected persons with diar­ In July 2008, clusters of laboratory-confirmed rhea swim, when contaminated animal feces cryptosporidiosis cases and reports of gastrointestinal illness in persons who are introduced either directly or through wa­ visited a lake were reported to Tarrant County Public Health. In response, ter run-off, and as a result of deficiencies in epidemiologic, laboratory, and environmental health investigations were human waste sanitation systems. Cryptosporidium has been associated with initiated. A matched case-control study determined that swallowing the lake three-quarters of reported outbreaks of gastro­ water was associated with illness (adjusted odds ratio = 16.3; 95% confidence enteritis associated with treated RWVs (e.g., interval: 2.5–infinity). The environmental health investigation narrowed pools and interactive fountains) in the U.S. down the potential sources of contamination. Laboratory testing detected (1999–2008) (Hlavsa et al., 2011). The para­ site’s extreme tolerance of chlorine allows it Cryptosporidium hominis in case-patient stool specimens and Cryptosporidium to survive for 3.5–10.6 days in treated RWVs species in lake water. It was only through the joint effort that epidemiologic, where the free chlorine level is maintained at laboratory, and environmental health investigators could determine that >1 1–3 parts per million (ppm) (Shields, Hill, human diarrheal fecal incidents in the lake likely led to contamination of the Arrowood, & Beach, 2008) as recommended water. This same collaborative effort will be needed to develop and maintain by the Centers for Disease Control and Pre­ vention (CDC). A standard protocol has been an effective national Model Aquatic Health Code. developed to remediate contaminated treated RWVs through a process called hyperchlo­ rination, whereby the free chlorine contact Introduction By July 11, five laboratory-confirmed cases of time of 15,300 mg-min/L is achieved (e.g., On July 8, 2008, Tarrant County Public cryptosporidiosis were identified among lake maintaining free chlorine level at 20 ppm for Health (TCPH) was notified of an outbreak visitors and five separate groups reported gas­ 765 minutes) at water pH <7.5 and tempera­ of gastrointestinal illness among attendees of trointestinal symptoms after visiting the lake. ture >25°C (Shields et al., 2008). a picnic at a lake that was a man-made chlo­ Cryptosporidiosis is caused by the proto­ Because of the clusters of laboratory-con­ rinated recreational water venue (RWV). On zoan parasite Cryptosporidium and is charac­ firmed cryptosporidiosis cases and reports of July 9, a second group of lake visitors report­ terized by watery diarrhea typically lasting gastrointestinal symptoms anecdotally asso­ ed similar illness. On July 10, a local clini­ one to four weeks in immunocompetent in­ ciated with visiting the lake on the same day, cian called TCPH to report a cluster of three dividuals (Hunter et al., 2004). Cryptosporid­ TCPH launched an investigation in collabo­ patients with laboratory-confirmed Crypto­ ium can be transmitted by the fecal-oral route ration with the Texas Department of State sporidium infection; all had visited the lake. through the ingestion of contaminated water. Health Services (DSHS) and CDC. The ob­