Annual and Diurnal Profiles of Cryptosporidium and Giardia in River Water in Japan

A quantitative survey was performed to understand the annual and diurnal profiles of <I>Cryptosporidium</I> and <I>Giardia</I>, representative waterborne infectious protozoans, in river water which is used for drinking water sources in Japan. To investigate the annual profiles, 84 river water samples were collected at 7 sites in the tributary rivers of the Tone River basin in Japan from June 2008 to February 2010. <I>Cryptosporidium</I> and <I>Giardia</I> were detected in 59 (70%) and 64 (76%) out of the 84 samples (10 liters each), showing the highest concentration of 344 oocysts/10 L and 144 cysts/10 L, respectively. Annual variation of the concentrations of <I>Cryptosporidium</I> and <I>Giardia</I> was high. The ratio of the maximum concentration to the mean value at each sampling site ranged from 2-8 except for one sampling site in which the frequency of detection was extremely low. To investigate diurnal profiles, 15 river water samples were collected at 3 sites in the tributary rivers of the Tone River on October 9<SUP>th</SUP>, 2008. The maximum concentrations of <I>Cryptosporidium</I> and <I>Giardia</I> in some sampling sites were approximately 10-fold higher than the lowest value. The correlation between the anaerobic spore-forming bacteria and these infectious protozoans was stronger than other microbial indicators (total coliforms, <I>Escherichia coli</I> and heterotrophic bacteria).