| dc.description.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 pro tozoan 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.
© 2016 Elsevier Ltd. All rights reserved. | |
