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Human Enteric Viruses Associated with Molluscan Shellfish in Coastal Waters

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Title Human Enteric Viruses Associated with Molluscan Shellfish in Coastal Waters
 
Creator Umesha, K.R.
 
Contributor Venugopal, M.N.
Indrani Karunasagar
Karunasagar, I.
Maragal, M.M.
 
Subject ---
 
Description Ph.D. Thesis
Rapid population growth and urbanization occurring along the coast have led to the
increased discharge of sewage into coastal surface waters in many parts of the world. Although
this discharge is mitigated by wastewater treatment plants in industrialized countries, the
effluents from these plants and uncontrolled spillage still release substantial amounts of
pathogens. Bivalve mollusks (including muscles, clams and oyster) growing in such
contaminated waters accumulate pathogenic bacteria and viruses, and can present a significant
health risk when consumed raw or lightly cooked.
The present study was carried out to know the occurrence of enteric viruses in bivalve
mollusks and cultured shrimp along west coast of India. Samples comprising of oysters, clams
and water were collected biweekly from two sites (Site 1: Sasthan, Site 2: Mulki). Shrimp
(P. monodon) samples were collected from culture ponds along the west coast of India and
were analyzed for the presence of human pathogenic enteric viruses, fecal coliforms and MS-2
phage.
Molecular techniques like RT-PCR and PCR were used for the detection of viruses
while soft agar overlay method for the detection of MS-2 phage and MPN methods for fecal
coliforms were employed. Enteroviruses were detected in 38% of oyster and 49% of clam
samples from site 1 and 36% of oyster and 43% of clam samples from site 2. Enteroviruses
were also detected in 15% of shrimp samples. However, none of these samples were found
positive for polioviruses. This result indicates that the shellfish growing waters are
contaminated with non-polio enteroviruses.
Adenoviruses were detected in 18% of oysters and 27% of clam samples from site 1 and
16% of oyster and 27% of clam samples from site 2 by nested PCR. The sequence analysis of
nested PCR products revealed that the strain isolated from shellfish share 96% sequence
identify with adenovirus 41 and 91% with adenovirus 40. It has been reported that adenoviruses
are more often detected than enteroviruses in coastal waters and domestic sewage. However,
our results showed that the enteroviruses are distributed more frequently in bivalve molluscan
shellfish than adenovirus along southwest coast of India.
The presence of both Adenoviruses and Enteric viruses was detected in 26 samples, 45
samples were positive only for enteroviruses and 11 samples were positive only for
adenoviruses. This result indicates that adenoviruses might not serve as an indicator of viral
pollution. None of the samples analyzed were found positive for noroviruses, rotaviruses and
HAV.
Physiological functions, accumulation and elimination of microbes in bivalves are
affected by temperature and salinity. In the present study, the frequency of occurrence of
enteroviruses and adenoviruses was high between May to December. It was interesting to note
that the salinity of shellfish harvesting waters was low (Avg. 11.7 ‰ in site 1 and 9.25 ‰ in
site 2) and river inflow was high during the same period. However, the variation in temperature
was minimal during this period (Average 29C).
The total and fecal coliform counts in the shellfish growing areas failed to meet the
standards set by NSSP of US and fecal coliforms showed negative associated with both MS-2
phage and enteric viruses. Hence fecal coliforms alone may not serve as an indicator of human
enteric viral pollution.
The detection of MS-2 phage as indicator of viral pollution in shellfish and their
growing water was carried out in two sites, and we found association between the occurrence of
MS-2 phage and enteroviruses in oyster samples and no association in clam samples. MS-2
phage showed no association with the occurrence of adenoviruses in both oyster and clam
samples from both the sampling sites.
 
Date 2016-07-04T16:17:15Z
2016-07-04T16:17:15Z
2007-01-12
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/68442
 
Language en
 
Format application/pdf
 
Publisher Karnataka Veterinary, Animal and Fisheries Sciences University, Bidar