Assessment of the Presence of Hepatitis E Virus in Surface Water and Drinking Water in Portugal

Abstract

Hepatitis E virus (HEV) is a non-enveloped single-stranded positive-sense RNA virus, belonging to the Hepeviridae family, resistant to environmental conditions, and transmitted by the consumption of contaminated water. This virus is responsible for both sporadic and epidemic outbreaks, leading to thousands of infections per year in several countries, and is thus considered an emerging disease in Europe and Asia. This study refers to a survey in Portugal during 2019, targeting the detection and eventual quantification of enteric viruses in samples from surface and drinking water. Samples positive for HEV RNA were recurrently found by reverse transcription quantitative PCR (RT-qPCR), in both types of matrix. The infectivity of these samples was evaluated in cultured Vero E6 cells and RNA from putative viruses produced in cultures evidencing cytopathic effects and was subjected to RT-qPCR targeting HEV genomic RNA. Our results evidenced the existence of samples positive either for HEV RNA (77.8% in surface water and 66.7% in drinking water) or for infectious HEV (23.0% in surface water and 27.7% in drinking water). These results highlight the need for effective virological control of water for human consumption and activities.

Monitoring Waterborne Pathogens in Surface and Drinking Waters. Are Water Treatment Plants (WTPs) Simultaneously Efficient in the Elimination of Enteric Viruses and Fecal Indicator Bacteria (FIB)?

“…In Portugal, NoV and HAV RNAs had not yet been found in drinking water, namely in a recent study [44]. However, another enteric virus (HEV) was detected in the drinking water sampled in this study, as was already referred to above for surface water samples [48]. Concerning other countries, Kukkula et al (1999) [35] detected NoV II RNA in drinking water from various sources in Finland and, more recently, Blanco et al (2017) [36] detected NoV I and NoV II RNA in drinking water in Spain, in concentrations (327.0-660.0 gc/L) higher than in the present study.…”

“…HAV RNA, not detected in the present study in surface waters, was detected in Peri Lagoon in Brazil [58] at relatively high concentrations (1.1 × 10 2 to 4.3 × 10 3 gc/L). In Portugal, Teixeira et al (2020) [44] did not detect viruses in superficial water intended for drinking water production, but Salvador et al (2020) [48] reported, for surface water samples included in this study (from the river and the dam reservoir), the detection of hepatitis E virus (HEV), which is an enteric virus not included in the present study.…”

“…However, while HAV RNA was not detected in dam reservoir samples, its detection occurred once, yet at a low concentration, in the drinking water of WTP_D. Although bearing in mind that RNA concentration was always normalized to the volumes of sampled water, its detection may have been due to the considerably higher volumes of drinking water sampled (620 L in this particular sample of WTP_D), relative to surface water (Figure 1), thus increasing the possibility of finding viruses in this water matrix [48,64]. In relation to NoV II RNA, the results evidenced its resistance to water treatment, although its decrease was very variable, having even been detected in drinking water a few months after its detection in the surface water that feeds the WTP.…”

“…The water from the river and dam reservoir was treated at WTP_R and WTP_D, respectively. The WTPs used different treatment schemes, as described in Salvador et al (2020) [48], the main differences being in the first pre-oxidation step, carried out with ozone in WTP_R and with chlorine in WTP_D; and the inclusion of an adsorption step with activated carbon, in WTP_R. Both WTPs include a final disinfection with chlorine.…”

“…Most of the procedures followed in this study were performed as described in Salvador et al (2020) [48]. Briefly, the Nanoceram filters (Argonite; Sanford, FL, USA) with the samples of concentrated water were eluted with beef extract (BD Bioscience; Franklin Lakes, NJ, USA) and the eluted solutions were subjected to an organic flocculation process followed by centrifugation and filtration through 0.22-µm pore-size Acrodisc Syringe filters (PALL Corporation; Ann Arbor, Michigan, USA).…”