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Volume 18, Number 12—December 2012

Letter

Hepatitis E Virus Genotype 3 in Shellfish, United Kingdom

Suggested citation for this article

To the Editor: Bivalve mollusks (shellfish), such as mussels and oysters, are filter feeders; they concentrate microorganisms of human and animal origin (up to 100×) from the surrounding environment. Several recent reports have linked the incidence of human infection with hepatitis E virus (HEV) to consumption of undercooked pork, game products, and shellfish (1,2). Infectious HEV has been found in swine manure and wastewater (3); therefore, application of manure to land and subsequent runoff could contaminate coastal water, leading to contamination of shellfish and, subsequently, possible human infection. Because they are filter feeders, bivalve mollusks are biologically relevant sentinels and can indicate potential pathogens that are contaminating the environment. It is essential to ensure that this sustainable resource of coastal areas, where mussels and oysters are farmed or collected wild, is not subjected to environmental contamination that could lead to public health risks.

Risk management for bivalve mollusks, aimed at control of fecal pollution, relies heavily on the use of Escherichia coli as an indicator of fecal (sewage) contamination and is enacted under European food regulations (Regulation 854/2004, www.cefas.co.uk/media/455777/extract_reg_no_854_2004.pdf). However, although these regulations probably reduce the number of infections, especially bacterial infections, they are not viewed as adequately controlling the risk for viral infections. Specific risks are posed by the robustness of viruses in the environment and the different behavior of viruses within bivalve mollusks compared with behavior within bacterial fecal indicators.

HEV is deemed to be inactivated during processing procedures used to prepare mussels for consumption; however, HEV is only 50% inactivated at 56°C and 96% at 60°C for 1 hour, it is stable when exposed to trifluorotrichloroethane, and it is resistant to inactivation by acidic and alkaline conditions (4). Most shellfish are usually eaten raw, but viable virus can also pose a risk to public health in shellfish that are lightly steamed or preserved by smoking and/or in acetic acid. Indeed, a recent study by the Food Standards Agency, in which >800 oyster samples from 39 growing beds in the United Kingdom were collected and screened during 2009–2011, found norovirus at low levels in at least 76% of oysters (5). Other studies identified hepatitis A virus and norovirus in shellfish production areas and in ready-to-eat products in the United Kingdom (1,6). In fact, depuration experiments demonstrated no decrease in titers against hepatitis A virus over a 23-hour cleansing period (7). In addition, acute HEV infection attributed to consumption of shellfish was diagnosed for 33 passengers who recently returned from a cruise (2). However, data have been restricted to questionnaires implicating consumption of shellfish as a source of transmission; no follow-up analyses of the contaminated foodstuff have been conducted. Thus, possible transmission routes for HEV remain poorly studied in the United Kingdom (2).

To determine whether HEV is present in mussels collected locally for human consumption, we examined 48 mussels from 5 tidal locations in Scotland. We collected closed mussels from the west coast of Scotland (11 at Lunderston Bay and 28 at Ardrossan) and the east coast of Scotland (9 at Stannergate, Dundee; Ferryden, Montrose; and the Ythan Estuary at Newburgh).

The site at Ardrossan was near a slaughterhouse and a meat preparation purification plant that processes pigs. The plant was considered a potential source of contamination, and mussels were collected in a 10-m2 area around an outfall (drain/sewage pipe) directly in line with the processing plant.

Figure

Thumbnail of Phylogenetic analysis of HEV open reading frame 2 sequences isolated from Mytilus spp. RNA was isolated from 50–100 mg of digestive gland or gill. Tissue was homogenized in 300 μL phosphate-buffered saline, and viral RNA was isolated by using a viral RNA kit (QIAGEN, Crawley, UK), and PCR was conducted by amplifying nucleotides 6332–6476 as described (8). The nucleotide sequences were aligned and bootstrapped, and phylogenetic neighbor-joining trees were constructed by using the Clu

Figure. . Phylogenetic analysis of HEV open reading frame 2 sequences isolated from Mytilus spp. RNA was isolated from 50–100 mg of digestive gland or gill. Tissue was homogenized in 300 μL...

A total of 36 (92%) of the 39 mussels from the west coast were positive by PCR for HEV, and 5 (55%) of the 9 from the east coast were positive. The mean value of HEV RNA detected in the samples was 4.25 log10 IU/mL (range 3.73–5.2 log10 IU/mL), and the assay was validated by using the current candidate HEV World Health Organization standard (http://whqlibdoc.who.int/hq/2011/WHO_BS_2011.2175_eng.pdf). Phylogenetic analysis showed that most bivalve mollusk sequences clustered with HEV genotype 3 from humans and swine (Figure; Technical Appendix [PDF - 218 KB - 2 pages]). Also, HEV sequences isolated specifically from a UK human source corresponded with sequences isolated from the bivalve mollusks. The presence of a swine-like HEV genotype 3 in freshwater bivalve mollusks has also been reported in Japan and South Korea (1,9).

Worldwide, an estimated 40,000 persons die and another 40,000 experience long-term disability as a result of consuming raw or undercooked shellfish (10). This study, demonstrating the presence of HEV in mussels collected locally in Scotland for human consumption, raises concern as to whether these shellfish are a potential source of infection, as reported (2). The association between environmental contamination with HEV and possible transmission by eating shellfish warrants investigation.

Claire Crossan, Paul J. Baker, John Craft, Yasu Takeuchi, Harry R. Dalton, and Linda ScobieComments to Author 
Author affiliations: Author affiliations: Glasgow Caledonian University, Glasgow, Scotland, UK (C. Crossan, P.J. Baker, J. Craft, L. Scobie); University College London, London, UK (Y. Takeuchi); European Centre for Environment and Human Health, University of Exeter Medical School, Truro, UK (H.R. Dalton)

Acknowledgment

This work was supported by European Commission FP6 funded project LSHB-CT-2006-037377 and by the Chief Scientist Office Scotland project reference ETM/32.

References

  1. Kamar N, Bendall R, Legrand-Abravanel F, Xia NS, Ijaz S, Izopet J, Hepatitis E. Lancet. 2012;379:247788. DOIPubMed
  2. Said B, Ijaz S, Kafatos G, Booth L, Thomas HL, Walsh A, Hepatitis E outbreak on cruise ship. Emerg Infect Dis. 2009;15:173844. DOIPubMed
  3. McCreary C, Martelli F, Grierson S, Ostanello F, Nevel A, Banks M. Excretion of hepatitis E virus by pigs of different ages and its presence in slurry stores in the United Kingdom. Vet Rec. 2008;163:2615. DOIPubMed
  4. Emerson SU, Arankalle VA, Purcell RH. Thermal stability of hepatitis E virus. J Infect Dis. 2005;192:9303. DOIPubMed
  5. Lowther JA, Gustar NE, Powell AL, Hartnell RE, Lees DN. A two-year systematic study to assess norovirus contamination in oysters from commercial harvesting areas in the United Kingdom. Appl Environ Microbiol. 2012;78:58127. DOIPubMed
  6. Baker K, Morris J, McCarthy N, Saldana L, Lowther J, Collinson A, An outbreak of norovirus infection linked to oyster consumption at a UK restaurant, February 2010. J Public Health (Oxf). 2011;33:20511. DOIPubMed
  7. McLeod C, Hay B, Grant C, Greening G, Day D. Inactivation and elimination of human enteric viruses by Pacific oysters. J Appl Microbiol. 2009;107:180918. DOIPubMed
  8. Erker JC, Desai SM, Mushahwar IK. Rapid detection of hepatitis E virus RNA by reverse transcription–polymerase chain reaction using universal oligonucleotide primers. J Virol Methods. 1999;81:10913. DOIPubMed
  9. Li TC, Miyamura T, Takeda N. Detection of hepatitis E virus RNA from the bivalve Yamato-Shijimi (Corbicula japonica) in Japan. Am J Trop Med Hyg. 2007;76:1702 .PubMed
  10. Shuval H. Estimating the global burden of thalassogenic diseases: human infectious diseases caused by wastewater pollution of the marine environment. J Water Health. 2003;1:5364 .PubMed

Figure

Technical Appendix

Suggested citation for this article: Crossan C, Baker PJ, Craft J, Takeuchi Y, Dalton HR, Scobie L. Hepatitis E virus genotype 3 in shellfish, United Kingdom [letter]. Emerg Infect Dis [Internet]. 2012 Dec [date cited]. http://dx.doi.org/10.3201/eid1812.120924

DOI: 10.3201/eid1812.120924

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Table of Contents – Volume 18, Number 12—December 2012

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Linda Scobie, Department of Life Sciences, Glasgow Caledonian University, Cowcaddens Rd, Glasgow, G4 0BA, UK





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