The presence of Giardia and cryptosporidium in surface waters and effluents in Israel

During a period of 9 months (May 1995-January 1996), various environmental sources were investigated for the presence of Giardia and Cryptosporidium in Israel. Out of 15 samples from five streams, 12 were positive for Cryptosporidium (80%) with an average concentration of 0.04-1.9 oocysts/1 and 8 were positive for Giardia (53.3%) with 0.05-0.78 cysts/1. Two springs were also tested and found positive for Cryptosporidium and (0.54 oocysts/1) only. The main drinking water reservoir of Israel, Lake Kineret, was also sampled 6 times at two sites. Cryptosporidium was isolated in 4/6 samples (66.6%) at an average concentration of 0.3-1.09 oocysts/1 while Giardia was present in 5/6 samples (83.3%), 0.135-16.2 cysts/1. Drinking water entering a filtration pilot plant was also tested and found positive for Cryptosporidium in 23/35 samples (0-317 oocysts/1) and 8/35 for Giardia (0-16.7 cysts/1). In order to evaluate some potential inputs of contamination of the drinking water sources, two possible contributors were tested: domestic sewage and cowshed effluents. In sewage effluents, 3/3 samples were positive for both Cryptosporidium and Giardia. The oocysts and cysts were present at 8.3-8.05/1 and 5-27.3/1 respectively. In cowshed effluents, 1/6 samples was positive for Cryptosporidium at a high concentration (3630 oocysts/1) but no Giardia cysts were found. The levels of Cryptosporidium and Giardia oocysts and cysts isolated from these environmental samples may present a public health hazard although no major outbreaks have so far been reported in Israel.