Occurrences of Giardia cysts in beach water

A total of 64 beach water samples with various bacteriological quality (Gra des 1 to 4) were analysed for their bacteriological and parasitological con tents (E coli and Giardia cysts respectively). Results indicated that Giard ia cysts were detected in less than 10% of the Grade 1 beach water samples with E coil concentrations of <24/100mL. For Grades 2, 3 & 4 beach water sa mples, Giardia cysts were found, respectively, in 85, 50 and 64% of the sam ples. Except for one beach water sample which had an unusually high concent ration of Giardia cysts (23 cysts/L), they were generally present at modera te concentrations (<10 cysts/L) in all other beach water samples. Despite m oderate levels of Giardia cysts present in beach water of different grades, the potential health risk faced by swimmers bathing in local beach water n eeds to be carefully assessed as Giardia is known to have a low infectious dose. (C) 1998 IAWQ Published by Elsevier Science Ltd. All rights reserved.