4 ǀ HEV IN ENVIRONMENTAL SAMPLES
The persistence and transmission of HEV in the environment are still poorly studied.88 Genotypes 1 and 2 are mainly found in regions with limited resources and poor sanitation resulting in the contamination of water supplies and food.1,16-17 In India, the HEV outbreaks were caused by highly polluted water between 1978 and 2013.24 However, the role of water in the transmission of zoonotic cases of HEV has only been suspected, but the detection of genotype 3 in shellfish and seemingly shellfish-related outbreaks have recently raised the question and discussions on this issue of public health concern among researchers and scientists.89-90 The above statement is supported by some studies from developed countries; seems to show higher HEV seroprevalence in people exposed to water or in shellfish consumers.91-92
Besides the evidence of HEV infection in humans via ingestion of seafood (shellfish, mussels), captive dolphins, which generally feed on fish, have been reported to be positive for HEV by serology (anti-HEV Ig), HEV RNA testing and findings of liver disorders with virus strains identified as genotype 3, which raises concerns of environmental contamination of food or wastewater as source of HEV.93
To date, the waterborne HEV-3 transmitting remains to be explicated. A current study in Germany recognized that work-related contact with wastewater can be associated with autochthonous hepatitis E, indicating the possible role of water in transmitting HEV-3.94 Animal and human hosts of HEV-3 might pollute wastewater matrices by the secretion of faeces in developed countries. The spread of HEV particles to the environment can pollute surface waters, which could possibly be an HEV infection source for humans and animals.88
HEV has been identified in urban sewage samples in various countries in Spain, Italy, and the Netherlands.95-97 Recently, in European countries a number of studies have been carried out for HEV detection in urban sewages.98-106
Beyer and colleagues determined the occurrence of HEV in water sources in urban areas of Germany. Wastewater samples were found positive by RT-qPCR for genotypes HEV-3c and 3f, where HEV-3c was identified among the most dominant genotype. Approximately, 75% of samples from the urban river showed the detection of HEV RNA.107
In another study, HEV prevalence was monitored in effluent and influent water in drinking and wastewater treatment plants (WWTPs). The performance of various methods was assessed for concentrating HEV in effluent and influent water from both treatment plants. The prevalence of HEV in inflowing water samples varies based on the WWTPS and RT-qPCR analysis, while no HEV was identified in effluent water.108 A large-scale study of 9 years (2011-2019) was executed into urban sewage in Italy for gaining a deep insight into the HEV epidemiology. In this investigation, 1374 sewage samples were collected from 48 different WWTPs, which are situated in 20 distinct regions of Italy. The RT-qPCR analysis quantified the HEV RNA detection in 74 urban sewage samples. Among these, 56 and 18 samples showed the detection of G3 and G1, respectively. G3 strains were detected throughout the investigation period, whereas the detection of G1 strains occurred only in 2011-2012 samples. The findings illustrate substantial viral circulation in the Italian people with a prevalence of G3 strains.106
In a 5-year integrated environmental and human HEV surveillance study, 169 cases were confirmed with HEV with an annual occurrence of 0.72 cases/1,000,000. Among 65 HEV RNA-positive samples, 66%, 32%, and 1% were detected to be genotype HEV3, HEV1, and HEV4, respectively.105 For the first time, HEV circulation was demonstrated in the northwest of Argentina to indicate the presence of the virus in water samples from the Arias–Arenales River in Salta city. HEV circulation was detected by nested PCR, IgM and IgG, and ELISA. Results revealed the detection of HEV-RNA in 1.6% of the tested samples, belonging to HEV genotype 3. Three samples showed the presence of IgM, while the IgG anti-HEV prevalence was recorded to be 9%.109
Heldt and colleagues collected 250 water and 68 sediment samples from the Sinos River tributaries, along with 50 pork products samples sold in the Sinos River, Brazil, and investigated for the detection and characterization of HEV genome by RT-PCR and nucleotide sequencing. Among the tested samples, HEV genotype 3 was identified in 36% of food samples, whereas no water or sediment evidence of the circulation of HEV. The outcome indicates polluted pork products as a possible route for HEV infection and necessitates a careful assessment of swine herds and food safety.110
Numerous evidence and research information demonstrate that HEV is widespread in both industrialized and developing countries representing a devastating threat to public health worldwide.30Animal-based HEVs are appeared to trigger HEV infections in the developed nations that require the development of vaccines for preventing the spread of HEV infection to humans.111Clemente-Casares and colleagues reviewed the European countries-based environmental, animal, and human data collected since the 90s.22 Based on the serological data, it was inferred that the HEV virus quite frequently infects the European community, and some animal species, i.e., deer, wild boars, and pigs are host reservoirs. Identification of virus in polluted pork products and mussels indicate the circulation of HEV strains from water to food chain. In water, the HEV in natural conditions may be inactivated by temperature and sunlight (UV). The virus may be removed by the physical treatment of water or disinfection methods.88 The HEV cases caused by genotype 1 can be controlled and prevented by improving the personal hygiene practices, and proper sanitation in developing countries.24