Author(s): Salvador, Daniel
Date: 2021
Persistent ID: http://hdl.handle.net/10451/52484
Origin: Repositório da Universidade de Lisboa
Subject(s): vírus entéricos; RT-qPCR; vírus da hepatite E; Norovirus; ensaios de infecciosidade; enteric viruses; hepatitis E virus; Norovirus; infectivity assays
Monitoring the water quality is a requisite to prevent outbreaks related to waterborne diseases, predominantly caused by enteric pathogens, such as bacteria and viruses. Enteric RNA viruses are transmitted to humans usually via the fecal-oral route and water is recognized as an important transmission vehicle. This project aimed to monitor Enterovirus, Norovirus from two genogroups (NoV GI and NoV GII), hepatitis A virus (HAV), and hepatitis E virus (HEV), in water matrices in Portugal: natural water from two surface sources; drinking water of two Water Treatment Plants (WTPs), and at the water distribution network; untreated and treated wastewater of three Wastewater Treatment Plants (WWTPs). Samples of surface and drinking water were collected in May 2018 and in a sampling campaign from January to December 2019. Wastewater samples were collected between November 2019 and March 2020. The detection and quantification of viral RNA were performed by a reverse transcription quantitative PCR (RT-qPCR) approach and the infectivity of RT-qPCR positive samples was evaluated in cultured Vero E6 cells. Surface water and drinking water samples were also taken for the analysis of fecal indicator bacteria (FIB) by cultural methods. Viral RNAs from Enterovirus, HAV, HEV, NoV I and NoV were detected and quantified in the two sources of surface water, river and dam reservoir (23 in 27 samples), as well as in drinking water sampled at the outlet of WTP_R, WTP_D and the distribution network (27 in 36 samples). HEV and HAV RNAs were the most and the least frequently detected, respectively. RNAs of Enterovirus and NoV I detected in surface waters, appeared to be eliminated with the treatment at both WTPs. However, HEV, NoV II, and HAV RNAs (0–109,687.5 gc/L), found in surface water samples, were still detected in drinking water, although usually at lower concentrations (0–5,617.1 gc/L). Our results also evidenced the existence of samples positive for infectious HEV (8 in 19 samples analyzed), in both types of water matrix. On the other hand, FIB were only detected in surface water, having been eliminated by WTPs to non-detectable values in the drinking water. Only a positive correlation was found between enteric viruses and FIB; this was in surface water, between NoV I and intestinal enterococci. In untreated wastewater, viral RNA was detected in all samples collected, being Enterovirus and NoV II RNAs the most frequently detected (14 in 14 samples). Norovirus was the viral genus whose representatives evidenced the highest RNA concentrations (5,448,041.8 gc/L). In treated wastewater, all collected samples were positive for RNA from at least one of the viruses under study, NoV II and NoV I having been the most frequently detected (14 in 14 samples and 13 in 14, respectively). Viral RNA was differently eliminated in the three WWTPs, depending on the type of treatment used, having been confirmed that the highest rates of reduction were achieved with tertiary treatment (31.4–100%). In this context, it is very important to consider the insertion of enteric viruses in the mandatory/regulatory analysis of water quality and to maintain their monitoring over time with the aim to prevent risks of transmission in the community.
