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