Prevalence of Hepatitis E Virus Infection in Pigs at the Time of Slaughter, United Kingdom, 2013 - Volume 21, Number 8—August 2015 - Emerging Infectious Disease journal - CDC

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Prevalence of Hepatitis E Virus Infection in Pigs at the Time of Slaughter, United Kingdom, 2013 - Volume 21, Number 8—August 2015 - Emerging Infectious Disease journal - CDC

Volume 21, Number 8—August 2015

Research

Prevalence of Hepatitis E Virus Infection in Pigs at the Time of Slaughter, United Kingdom, 2013

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• Suggested Citation

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• Table 2
• Table 3

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Sylvia Grierson, Judith Heaney, Tanya Cheney, Dilys Morgan, Stephen Wyllie, Laura Powell, Donald Smith, Samreen Ijaz, Falko Steinbach, Bhudipa Choudhury, and Richard S. Tedder 

Author affiliations: Animal and Plant Health Agency, Addlestone, United Kingdom (S. Grierson, T. Cheney, S. Wyllie, L. Powell, F. Steinbach, B. Choudhury); Public Health England, London, United Kingdom (J. Heaney, D. Morgan, S. Ijaz, R.S. Tedder); University of Edinburgh, Edinburgh, Scotland, United Kingdom (D. Smith);University of Surrey, Guildford, United Kingdom (F. Steinbach); University College London, London (R. S. Tedder)

Suggested citation for this article

Abstract

Since 2010, reports of infection with hepatitis E virus (HEV) have increased in England and Wales. Despite mounting evidence regarding the zoonotic potential of porcine HEV, there are limited data on its prevalence in pigs in the United Kingdom. We investigated antibody prevalence, active infection, and virus variation in serum and cecal content samples from 629 pigs at slaughter. Prevalence of antibodies to HEV was 92.8% (584/629), and HEV RNA was detected in 15% of cecal contents (93/629), 3% of plasma samples (22/629), and 2% of both (14/629). However, although HEV is prevalent in pigs in the United Kingdom and viremic pigs are entering the food chain, most (22/23) viral sequences clustered separately from the dominant type seen in humans. Thus, pigs raised in the United Kingdom are unlikely to be the main source of human HEV infections in the United Kingdom. Further research is needed to identify the source of these infections.

Hepatitis E virus (HEV) that infects humans is composed of 4 genotypes (G1–4), each with a different geographic distribution and host range (1). Although G1 and G2 infect humans only, G3 and G4 infect humans and animals. HEV G3 and G4 are distributed worldwide, with G3 most commonly infecting both humans and pigs in Europe (2).From the observed incidence of acute HEV infection in blood donors (3), it is clear that HEV G3 infection in humans in England is far more common than previously thought. Realistic estimates are >100,000 infections annually.

Public Health England instituted enhanced surveillance of HEV infections in England and Wales in 2003 (4) and identified a recent and marked increase in the number of patients seeking treatment for HEV infections. In 2013, a total of 691 cases were identified, of which 477 (69%) were considered indigenous (occurring in persons who had not traveled outside England and Wales). Sequencing of strains from these acutely infected persons has identified an emergent phylogenetic cluster of HEV G3 infection in humans, which is likely to represent a zoonosis acquired through the consumption of undercooked meat (B. Said, pers. comm.).

In an early study in the United Kingdom of porcine samples archived during 1991–2001, antibodies to HEV were detected in 85.5% of 256 samples tested (5). More recent studies across Europe indicate that many pig herds show evidence of HEV G3 infection (6–10). A transient viremia in pigs is associated with dissemination of HEV into muscle and other tissues (11). A recent UK study found HEV RNA in 6 of 63 pork sausages tested, of which 5 were in a single batch of 11 (12), and a case−control study in England and Wales showed that human consumption of processed pork products is associated with an increased risk of acquiring HEV (13). It has long been considered plausible that the persistence of viremia in infected pigs up to the time of slaughter could provide a potential vehicle for zoonotic transmission to humans (14). We conducted surveillance of pigs at slaughter to investigate the epizoology of HEV in the United Kingdom and the extent of infection at the time pigs enter the food chain.

Dr. Grierson is a research scientist in the Department of Virology at the Animal and Plant Health Agency, Weybridge, UK. Her research interests focus on the molecular characterization and epidemiology of veterinary viruses, primarily relating to pig diseases.

Acknowledgments

We thank colleagues at the Public Health England Blood Borne Virus Unit and the Animal and Plant Health Agency for their support and assistance.

The data collection described here was undertaken as part of a national “2013 Zoonoses in UK Pigs Abattoir Study” jointly funded by the Department for Environment, Food, and Rural Affairs; the Food Standards Agency; Veterinary Medicines Directorate; Public Health England (PHE); and UK pig industry levy boards including the British Pig Executive (a division of the Agriculture and Horticulture Development Board), Ulster Pork and Bacon Forum, and Quality Meat Scotland. Representatives from the Animal and Plant Health Agency (formerly known as the Animal Health and Veterinary Laboratories Agency); Department for Environment, Food, and Rural Affairs; and PHE designed the study. The laboratory testing, data collection, analysis, and interpretation of the information presented here were undertaken by staff from PHE and the Animal and Plant Health Agency.

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Figure

• Figure. Phylogeny of genotype 3 hepatitis E viruses (HEVs) from pigs and patients with acute hepatitis in the United Kingdom. Nucleotide sequences of a 304-nt open reading frame 2 fragment (positions...

Tables

• Table 1. Serologic analysis of and viral RNA in cecal and plasma samples in 6 pigs ranked by viremia whose HEV plasma load at slaughter exceeded 102IU/mL, United Kingdom
• Table 2. Serologic status of 129 pigs in whom HEV RNA was detected in plasma, cecal fluid, or both, United Kingdom
• Table 3. Markers in the 4 Wantai antibody-seronegative plasma samples from pigs with concordant HEV RNA in plasma and cecal fluid samples, United Kingdom

Suggested citation for this article: Grierson S, Heaney J, Cheney T, Morgan D, Wyllie S, Powell L, et al. Prevalence of hepatitis E virus infection in pigs at the time of slaughter, United Kingdom, 2013. Emerg Infect Dis. 2015 Aug [date cited]. http://dx.doi.org/10.3201/eid2108.141995

DOI: 10.3201/eid2108.141995