Abstract
Giardia duodenalis and Cryptosporidium spp. are two of the most prominent aetiological agents of waterborne diseases. Therefore, efficient and affordable methodologies for identifying and quantifying these parasites in water are increasingly necessary. USEPA Method 1623.1 is a widely used and validated protocol for detecting these parasites in water samples. It consists of a concentration step, followed by parasite purification and visualization by immunofluorescence microscopy. Although efficient, this method has a high cost particularly due to the immunomagnetic separation (IMS) step, which is most needed with complex and highly contaminated samples. Based on this, the present study aimed to determine whether it is possible to maintain the efficiency of Method 1623.1 while reducing the amount of beads per reaction, using as a matrix the challenge water recommended by the World Health Organization. As for Giardia cysts, a satisfactory recovery efficiency (RE) was obtained using 50% less IMS beads. This was evaluated both with a commercial cyst suspension (56.1% recovery) and an analytical quality assessment (47.5% recovery). Although RE rates obtained for Cryptosporidium parvum did not meet Method 1623.1 criteria in any of the experimental conditions tested, results presented in this paper indicated the relevance of the described adaptations, even in challenge water.
Highlights
Some 2.2 billion people around the world do not have safely managed drinking water services, 4.2 billion people are deprived of safely managed sanitation services, and 3 billion lack basic handwashing facilities (WHO )
The cysts of G. duodenalis and oocysts of C. parvum were clearly observed against the background in all samples (Figure 1), regardless of the condition of the test, following the first and second acid dissociations
The Shapiro–Wilk test indicated that data for percent C. parvum recovery without adding beads did not follow a normal distribution
Summary
Some 2.2 billion people around the world do not have safely managed drinking water services, 4.2 billion people are deprived of safely managed sanitation services, and 3 billion lack basic handwashing facilities (WHO ). The repeated prevalence of these protozoa in surface water denotes significant risks to human health, especially due to their low ID50 (the number of cysts and/or oocysts needed to infect 50% of exposed people), which has been estimated to fall between 10 and 2,000 for C. parvum (Robert-Gangneux & Dardé ) and between 10 and 100 for G. duodenalis (Rendtorff ). In this context, assessing the microbiological quality of drinking water is mandatory to ensure its safety for consumption (WHO )
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