title: Comparison of human and southern sea otter (Enhydra lutris nereis) health risks for infection with protozoa in nearshore waters.
abstract: Cryptosporidium and Giardia spp. are waterborne, fecally-transmitted pathogens that cause economic loss due to gastroenteritis and beach closures. We applied quantitative microbial risk assessment (QMRA) to determine the health risks for humans and sea otters due to waterborne exposure of Cryptosporidium and Giardia spp. when swimming in three types of surface waters: river, stormwater and wastewater effluent during the wet and dry seasons in the central coast of California. This is the first application of QMRA to estimate both the probability of infection in Southern sea otters and the probability of illness in humans, using microbial source tracking (MST) as a variable. Children swimming close to stormwater discharges had an estimated Cryptosporidium-associated illness probability that exceeded the accepted U.S. EPA criteria (32 illnesses/1000 swimmers or 3.2%). Based on the assumption that sea otters are as susceptible as humans to Cryptosporidium infection, the infection probabilities were close to 2% and 16% when sea otters were swimming at the end of points of rivers and stormwater discharges, respectively. In the case of Giardia, infection probabilities of 11% and 23% were estimated for sea otters swimming at the end of point of wastewater discharges, assuming that sea otters are as susceptible as gerbils and humans, respectively. The results of this QMRA suggest that 1) humans and sea otters are at risk when swimming at outflow sites for rivers, stormwater and treated wastewater effluent; 2) reduced loads of viable protozoan cysts and oocysts in recreational water can lessen the probability of infection of humans and sea otters; and 3) the risk of infection of humans and sea otters can be reduced with the treatment of wastewater to decrease oocyst and cyst viability before effluent is released into the sea.
authors.affiliation: Pathology, Microbiology and Immunology Department, School of Veterinary Medicine, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA; Escuela de Medicina Veterinaria, Facultad de Ecologia y Recursos Naturales, Universidad Andres Bello, Republica 440, 8370251 Santiago, Chile.
authors.forename: A D
authors.initials: AD
authors.lastname: Adell
authors.affiliation: National Institute of Water and Atmospheric Research (NIWA), P.O. Box 11-115, Hillcrest, Hamilton, New Zealand.
authors.forename: G
authors.initials: G
authors.lastname: McBride
authors.affiliation: Department of Civil and Environmental Engineering, University of California, One Shields Avenue, Davis, CA 95616, USA; Singapore Centre for Environmental Life Sciences Engineering (SCELSE), School of Civil and Environmental Engineering, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.
authors.forename: S
authors.initials: S
authors.lastname: Wuertz
authors.affiliation: Pathology, Microbiology and Immunology Department, School of Veterinary Medicine, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA; One Health Institute, School of Veterinary Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Conrad
authors.affiliation: One Health Institute, School of Veterinary Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA. Electronic address: wasmith@ucdavis.edu.
authors.forename: W A
authors.initials: WA
authors.lastname: Smith
mesh_terms: D000818:Animals; D003458:Cryptosporidium; D005872:Giardia; D006801:Humans; D033661:Oocysts; D010041:Otters; D014481:United States; D014871:Water Microbiology
keywords: Bacteroidales; QMRA; Recreational water; Stormwater; Wastewater; Zoonoses