Two-year monitoring of Cryptosporidium parvum and Giardia lamblia occurrence in a recreational and drinking water reservoir using standard microscopic and molecular biology techniques

Abstract

Starting in 2006, a monitoring of Giardia lamblia and Cryptosporidium parvum occurrence was conducted for 2 years in the largest drinking water reservoir of Luxembourg (Esch-sur-Sûre reservoir) using microscopy and qPCR techniques. Parasite analyses were performed on water samples collected from three sites: site A located at the inlet of the reservoir, site B located 18 km downstream site A, at the inlet of the drinking water treatment plant near the dam of the reservoir and site C where the finished drinking water is injected in the distribution network. Results show that both parasites are present in the reservoir throughout the year with a higher occurrence of G. lamblia cysts compared to C. parvum oocysts. According to our results, only 25% of the samples positive by microscopy were confirmed by qPCR. (Oo)cyst concentrations were 10 to 100 times higher at site A compared to site B and they were positively correlated to the water turbidity and negatively correlated to the temperature. Highest (oo)cyst concentrations were observed in winter. In contrast, no relationship between the concentrations of (oo)cysts in the reservoir and rain events could be established. Though a correlation has been observed between both parasites and faecal indicators in the reservoir, some discrepancies highlight that the latter do not represent a reliable tool to predict the presence/absence of these pathogenic protozoa. In summer 2007, the maximal risk of parasite infection per exposure event for swimmers in the reservoir was estimated to be 0.0015% for C. parvum and 0.56% for G. lamblia. Finally, no (oo)cysts could be detected in large volumes of finished drinking water.

Occurrence, Source, and Human Infection Potential of Cryptosporidium and Giardia spp. in Source and Tap Water in Shanghai, China

“…The presence of more empty oocysts (ghosts) in the filtration method was possibly also partially responsible for the lower occurrence of Cryptosporidium oocysts detected by PCR in this study, because the ghosts could still be detected by microscopy but not by PCR. In a recent study in Luxembourg, only 25% of the samples positive by microscopy were confirmed by PCR (23).…”

“…In addition, organic matter was found to be significantly correlated with Cryptosporidium and Giardia occurrence in surface water in Argentina (1). Total coliform, fecal coliform, or E. coli was reported to correlate with Cryptosporidium and Giardia occurrence in source water samples in several studies in Italy, Luxembourg, Spain, United States, Canada, and Argentina (1,12,23,31,39,49). In some other studies, no correlation between total coliform or E. coli and Cryptosporidium was reported (7,8).…”

“…The biological or environmental basis for this observation, however, is not clear, and the small sample size of the study could have contributed to some of the observed associations. Nevertheless, the correlation between the occurrence of Cryptosporidium and Giardia and conductivity was reported in samples of recreational rivers in Malaysia (5) and in a drinking water reservoir in Luxembourg (23). In addition, organic matter was found to be significantly correlated with Cryptosporidium and Giardia occurrence in surface water in Argentina (1).…”

“…Giardia recoveries were 72 to 77% for calcium carbonate when 85 cysts/liter were used to seed river or tap water (46). PCR-based techniques have been used increasingly for detection and characterization of Cryptosporidium oocysts and G. duodenalis cysts in water (3,13,23,27,58,61). Unlike Method 1623, recent PCR methods can differentiate Cryptosporidium and Giardia species that infect humans from those that do not infect humans.…”

Comparative Study on Waterborne Parasites between Malaysia and Thailand: A New Insight

“…However, studies reported that seasonal and climate changes (during the four seasons) in certain countries do not contribute to the correlation between these two waterborne parasites. 35,36 One limitation of this study was the use of the IMS technique. This technique was chosen because it has high sensitivity, is commercially available, and it effectively purifies waterborne protozoans from other debris.…”