Occurrence and genetic diversity of Cryptosporidium and Giardia in urban wastewater treatment plants in north-eastern Spain

Abstract

This study was designed to investigate the presence and removal efficiency of Cryptosporidium and Giardia in wastewater treatment plants at the 20 most populated towns in Aragón (north-eastern Spain). Samples of influent and effluent wastewater and dewatered sewage sludge were collected seasonally from 23 plants and processed according to USEPA Method 1623. All samples from raw and treated wastewater tested positive for Giardia, at an average concentration of 3247±2039cysts/l and 50±28cysts/l, respectively. Cryptosporidium was identified in most samples from both raw (85/92) and treated (78/92) wastewaters in a concentration significantly lower than Giardia, at both influent (96±105oocysts/l) and effluent samples (31±70oocysts/l) (P<0.001). The (oo)cyst counts peaked in summer in most plants. The removal efficiency was higher for Giardia (1.06-log to 2.34-log) than Cryptosporidium (0.35-log to 1.8-log). Overall, high removal efficiency values were found for Giardia after secondary treatment based on activated sludge, while tertiary treatment (microfiltration, chlorination and/or ultraviolet irradiation) was needed to achieve the greatest removal or inactivation of Cryptosporidium. Most samples of treated sludge were positive for Giardia (92/92) and Cryptosporidium (45/92), at an average concentration of 20-593cysts/g and 2-44oocyst/g, respectively. The molecular characterization of Cryptosporidium oocysts and Giardia cysts were attempted at the SSU rRNA/GP60 and bg/tpi loci, respectively. G. duodenalis sub-assemblage AII was identified in all plants, with a large proportion of samples (15/47) harboring mixed assemblages (AII+B). Nine Cryptosporidium species and six subtypes were identified, with C. parvum IIaA15G2R1 being the most prevalent. The presence of significant numbers of (oo)cysts in samples of final effluents and treated sludge reveals the limited efficacy of conventional treatments in removing (oo)cysts and highlights the potential environmental impact and public health risks associated with disposal and reclamation of wastewater.

Diversity of Cryptosporidium spp. in wild rodents from the Canary Islands, Spain

“…The results obtained in our study suggest that Cryptosporidium sp. 1 may correspond to one unnamed Cryptosporidium genotype isolated from an environmental sample in Aragon (north-eastern Spain) and another unnamed genotype isolated from a storm event water sample from New York [82,83]. It was not possible to identify to the species level Cryptosporidium sp.…”

Wastewater-based epidemiology—surveillance and early detection of waterborne pathogens with a focus on SARS-CoV-2, Cryptosporidium and Giardia

“…Australia (King et al 2015a;Zahedi et al 2018), Brazil andPeru (Ulloa-Stanojlović et al 2016;Martins et al 2019), China (Feng et al 2009;Li et al 2012;Huang et al 2017), Japan (Hashimoto et al 2006;Hirata and Hashimoto 2006), Switzerland and Germany (Ward et al 2002), the USA (Xiao et al 2001;Zhou et al 2003) and Tunisia (Ben Ayed et al 2012) (Table 2). While in Europe, a number of studies have reported that C. parvum is the dominant species in wastewater (Hänninen et al 2005;Spanakos et al 2015;Imre et al 2017;Ramo et al 2017). In other countries such as China, Iran, Tunisia and the USA, livestock-associated species such as C. andersoni and C. xiaoi dominate in wastewater samples (Xiao et al 2001;Liu et al 2011;Ben Ayed et al 2012;Hatam-Nahavandi et al 2016;Ma et al 2019) (Table 2).…”

Propagation of Giardia duodenalis cysts in immunosuppressed CF-1 mice

“…Giardia duodenalis is a protozoan parasite that commonly causes waterborne gastrointestinal illness in humans, with outbreaks across the world (Efstratiou et al, 2017). Giardia cysts are often found in wastewater and biosolid samples at high concentrations, and remains an important waterborne pathogen (King et al, 2016;Ramo et al, 2017a;Ramo et al, 2017b;Rhodes et al, 2015). Since the cyst is the only stable life stage in the environment, viable G. duodenalis cysts are required to study this pathogen in environmental matrices.…”