Detection and Molecular Characterization of Hepatitis A Virus from Tunisian Wastewater Treatment Plants with Different Secondary Treatments

Abstract

Hepatitis A virus (HAV) is the main causative agent of hepatitis infection associated with waterborne outbreaks worldwide. In Tunisia, there is no specific surveillance system for HAV and current secondary wastewater treatment processes are unable to remove viral particles, which present a potential public health problem. Qualitative and quantitative analysis of HAV in 271 raw and treated wastewater samples from five sewage treatment plants (STPs) during 13 months was performed. Moreover, the efficiency of three secondary wastewater treatment processes (conventional activated sludge, extended aeration, and oxidation ditch activated sludge) was evaluated. Data obtained demonstrated that HAV is endemic in Tunisia and circulates with high prevalence in both raw (66.9%) and treated (40.7%) wastewater. HAV circulates throughout the year in the coastal areas, with the highest rates found during summer and autumn, whereas in central Tunisia, high levels were shown in autumn and winter. Total virus removal was not achieved, since no difference in mean HAV loads was observed in effluents (6.0 ؋ 10 3 genome copies [GC]/ml) and influents (2.7 ؋ 10 3 GC/ml). The comparison of the HAV removal values of the three different wastewater treatment methods indicates that extended aeration and oxidation ditch activated sludge had better efficiency in removing viruses than conventional activated sludge did. Molecular characterization revealed that the vast majority of HAV strains belonged to subgenotype IA, with the cocirculation of subgenotype IB in wastewater treatment plants that collect tourism wastewater. IMPORTANCEThis report provides important data on the incidence, behavior, seasonality, and genotype distribution of HAV in the environment in Tunisia, as well as the risk of infection derived from its occurrence in effluents due to inadequate wastewater treatment. In addition, these findings seem to confirm that the prevalence of HAV depends on socioeconomic level, sanitary conditions in the communities, sewage facilities, the locality, and the climate. The wide dispersion of HAV in effluents proves the inefficacity of the current wastewater treatment processes used in Tunisia to remove virus; therefore, establishment of tertiary treatment processes or replacement of the medium-charge activated sludge (conventional activated sludge) by the low-charge version (oxidation ditch activated sludge) is absolutely needed. Rapid detection of the HAV genome in wastewater may provide a timely warning sign to health authorities to implement population protection measures. H epatitis A virus (HAV) is one of the most important human waterborne viruses and constitutes the main cause of human enteric hepatitis transmitted via the fecal-oral route (1). It is widely prevalent in the world, as millions of new cases of HAV infections occur worldwide every year (2). It was previously demonstrated that areas with inadequate water supply and poor wastewater facilities and hygienic conditions generally have very high HAV prevalence (3, 4). Th...

Sapovirus in Wastewater Treatment Plants in Tunisia: Prevalence, Removal, and Genetic Characterization

“…The viral rate detected in the central Tunisian WWTPs was 38.9% for Sidi-Bouzid (optional aerated lagoon) and 35.2% for Sbeitla (activated sludge). These results are partially in line with those found in previous studies (5,21), where hepatitis A virus (HAV) detection was in general higher in inland regions of the country.…”

“…Tunisia has developed its WWTPs only to secondary-level treatments. Our study showed that SaV is widely circulating in the country, in accordance with previous results for other enteric viruses, such as HAV (5,21). Tunisia does not have a gastroenteritis outbreak reporting system or routine surveillance, and it has been suggested that socioeconomic status and hygiene level of the population are key points in the epidemiologic pattern of enteric viruses, due to the seroprevalence observed in rural areas (35,36).…”

“…Nevertheless, the predominant trend on our study was a higher number of SaV-contaminated samples detected during the summer season, both in coastal and in inland WWTPs. These results can be explained by the increase in tourist activities from both domestic and the European Union tourists (5,21).…”

“…All WWTPs follow the requirements of the Tunisian law on environmental impact assessment and regulations on the quality of discharges and reuse of treated water. Physicochemical indicators to determine the quality parameters as well as the WWTP processes and characteristics of each area according to the National Office of Sanitation (ONAS) of Tunisia were described in more depth elsewhere (5,21).…”

“…The reduction of enteric viruses in wastewater treatment plants (WWTPs), however, is mostly inefficient (3) and is relatively poor compared with that of fecal indicator microorganisms such as Escherichia coli (4). In several countries in Africa, including Tunisia, the quality of treated wastewater is still poor, even though advanced WWTPs have been installed (5). During the last decade, the insufficiently treated wastewater, contaminated with enteric viruses, has been used in Tunisia for agricultural irrigation and the refilling of aquifers to help palliate the lack of water resources (6); this combination of factors might become a threat for public health.…”