Molecular Detection of human Noroviruses in Influent and Effluent Samples From Two Biological Sewage Treatment Plants in the Region of Monastir, Tunisia

Abstract

Noroviruses (NoVs) are responsible for numerous cases of waterborne and foodborne gastroenteritis every year. They are released in the sewage and their detection in this environment can reflect the epidemiology of the viral strains circulating in the community. A three-year (2007-2010) survey was conducted in order to evaluate the presence of human NoVs using RT-PCR in 518 sewage samples collected at the entrance and exit of two biological sewage treatment plants located in Monastir region, Tunisia. In this study, we aimed to genetically characterize the most prevalent GI and GII NoV strains, in order to obtain a rough estimate of the efficacy of disinfection treatments and to compare the results with clinical data documented in the same area during the same period. This work confirms the wide circulation and the genetic diversity of NoVs in Tunisia and the widespread distribution of NoV variants in both raw and treated wastewater. Indeed, NoV was detected in 192 (37.1%) sewage samples, among them mixed infections with group A rotavirus were detected in 125 (65.1%) cases. The genotypes of the GI NoVs were GI.1, GI.2, GI.4, GI.5, and GI of unassigned genotype (GI.UA), and the genotypes of the GII NoVs were all GII.12. This study enhances the currently poor environmental virological data gathered in Tunisia, demonstrates the benefit of environmental surveillance as a tool to determine the epidemiology of NoVs circulating in a given community, and underlines the need for the design and support of similar long-term studies in our country, in order to compensate for the absence of a national surveillance system for gastroenteric viruses.

Detection and genotyping of group A rotaviruses isolated from sewage samples in Monastir, Tunisia between April 2007 and April 2010

“…Of note, mixed contaminations with noroviruses were detected in 125/375 (33·3%) samples (Hassine‐Zaafrane et al . ).…”

“…Within 24 h after sample collection, the sewage samples (100 ml each) were concentrated using the adsorption‐elution method recommended by the USA Environmental Protection Agency (Lewis and Metcalf ; EPA ), as previously described (Hassine‐Zaafrane et al . ). The pellets were resuspended in 3 ml of 0·1 mol l −1 phosphate buffered saline (pH 7·2) and a solution containing 10 000 units of penicillin and 10 000 μ g of streptomycin per ml, and 25 μ g ml −1 of Fungizone was added to prevent bacterial and fungal contamination.…”

“…Viral RNA was extracted from 1 ml of raw or treated concentrated sewage using the NucliSENS ® EasyMAG ™ platform (bioMérieux, Marcy L'Etoile, France), according to the manufacturer's instructions as previously described (Hassine‐Zaafrane et al . ). Viral RNA was eluted in 110 μ l elution buffer and stored in aliquots at −40°C.…”

“…The same RNA extracts were also tested for the presence of noroviruses as described in Hassine‐Zaafrane et al . .…”

Removal of Rotavirus and Bacteriophages by Membrane Bioreactor Technology from Sewage

“…Studies performed in Tunisia, revealed that Group A rotavirus (RVA) was detected in 32 % of sewage samples [32]. A recent study indicated a high rate contamination of sewage samples with RV and NoV [16]. So, effective wastewater treatment processes are necessary for removal of RV [26].…”