Occurrence of Giardia lamblia in recreational streams in Basel-Landschaft, Switzerland

Little is known about the environmental occurrence of the pathogenic organism Giardia lamblia in Switzerland. To provide a better insight into the importance of G. lamblia, a cheap, effective and easy to handle detection method was validated and evaluated in a series of field studies. G. lamblia was detected in 97.5% of surface water samples taken from two streams (Birs and Ergolz) located in the canton Basel-Landschaft, Switzerland. Since higher numbers of G. lamblia cysts were found after waste water treatment plants, human wastes appeared to be an important source of contamination. A correlation of G. lamblia with Escherichia coli and enterococci was observed. However, a linear equation to predict the number of G. lamblia cysts, given a concentration of E. coli or enterococci, did not prove to be suitable (r-squared = 0.27; r-squared = 0.24).