Detection of Cryptosporidium spp. and Giardia spp. in Environmental Water Samples: A Journey into the Past and New Perspectives

Abstract

Among the major issues linked with producing safe water for consumption is the presence of the parasitic protozoa Cryptosporidium spp. and Giardia spp. Since they are both responsible for gastrointestinal illnesses that can be waterborne, their monitoring is crucial, especially in water sources feeding treatment plants. Although their discovery was made in the early 1900s and even before, it was only in 1999 that the U.S. Environmental Protection Agency (EPA) published a standardized protocol for the detection of these parasites, modified and named today the U.S. EPA 1623.1 Method. It involves the flow-through filtration of a large volume of the water of interest, the elution of the biological material retained on the filter, the purification of the (oo)cysts, and the detection by immunofluorescence of the target parasites. Since the 1990s, several molecular-biology-based techniques were also developed to detect Cryptosporidium and Giardia cells from environmental or clinical samples. The application of U.S. EPA 1623.1 as well as numerous biomolecular methods are reviewed in this article, and their advantages and disadvantages are discussed guiding the readers, such as graduate students, researchers, drinking water managers, epidemiologists, and public health specialists, through the ever-expanding number of techniques available in the literature for the detection of Cryptosporidium spp. and Giardia spp. in water.

Molecular Identification of Protozoan Sarcocystis in Different Types of Water Bodies in Lithuania

“…Due to the large morphological and genetic differences between genera or even species of parasitic protozoa, universal methods for identification of these parasites in various environmental samples have not been developed yet. The concentration of many protozoa species in water samples is relatively low [ 37 ]; therefore, detection requires very sensitive techniques, such as molecular methods. While some protozoa are undetectable in water samples under a microscope [ 38 ], molecular methods for the identification of parasitic protozoa are not fully developed [ 27 , 37 ].…”

“…The concentration of many protozoa species in water samples is relatively low [ 37 ]; therefore, detection requires very sensitive techniques, such as molecular methods. While some protozoa are undetectable in water samples under a microscope [ 38 ], molecular methods for the identification of parasitic protozoa are not fully developed [ 27 , 37 ]. It should be noted that molecular-based techniques are not standardized for the diagnosis of Sarcocystis and other parasitic protozoa in water samples [ 10 , 37 ].…”

“…While some protozoa are undetectable in water samples under a microscope [ 38 ], molecular methods for the identification of parasitic protozoa are not fully developed [ 27 , 37 ]. It should be noted that molecular-based techniques are not standardized for the diagnosis of Sarcocystis and other parasitic protozoa in water samples [ 10 , 37 ]. Therefore, a wide variety of methodologies, e.g., conventional PCR and derivatives, DNA hybridization, loop-mediated isothermal amplification (LAMP), or quantitative PCR, are used [ 10 , 27 , 39 , 40 ].…”

“…During environmental sample testing, discrimination between DNA from a living cell versus DNA from a dead one might be considered impossible. Consequently, the prevalence of parasites in the samples collected can be overestimated [ 37 ]. Oocysts or sporocysts of protozoan Sarcocystis parasites are also known to be resistant to various environmental conditions (freezing, low humidity, high temperatures, etc.)…”

Cryptosporidiosis outbreaks linked to the public water supply in a military camp, France

“…in aquatic samples. These techniques are more sensitive and would require less water sample volume than the microscopic examination [ 36 ].…”