How to cite this article: Vet. Res. (2008) 39:40
DOI: 10.1051/vetres:2008017

Estimation of hepatitis E virus transmission among pigs due to contact-exposure

Martijn Bouwknegt^{1, 2}, Klaas Frankena², Saskia A. Rutjes¹, Gerard J. Wellenberg³, Ana Maria de Roda Husman¹, Wim H.M. van der Poel³ and Mart C.M. de Jong<sup>2, 3

1</sup>  Laboratory for Zoonoses and Environmental Microbiology, Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment, Bilthoven, The Netherlands
²  Quantitative Veterinary Epidemiology Group, Wageningen Institute of Animal Sciences, Wageningen, The Netherlands
³  Animal Sciences Group of Wageningen UR, Department of Infectious Diseases, Lelystad, The Netherlands

Received 19 August 2007; accepted 19 March 2008; published online 27 March 2008

Abstract - Locally acquired hepatitis E in humans from industrialized countries has been repeatedly suggested to originate from pigs. Pigs may serve as a reservoir of hepatitis E virus (HEV) for humans when a typical infected pig causes on average more than one newly infected pig, a property that is expressed by the basic reproduction ratio R₀. In this study, R₀ for HEV transmission among pigs was estimated from chains of one-to-one transmission experiments in two blocks of five chains each. Per chain, susceptible first-generation contact pigs were contact-exposed to intravenously inoculated pigs, subsequently susceptible second-generation contact pigs were contact-exposed to infected first-generation contact pigs, and lastly, susceptible third-generation contact pigs were contact-exposed to infected second-generation contact pigs. Thus, in the second and third link of the chain, HEV-transmission due to contact with a contact-infected pig was observed. Transmission of HEV was monitored by reverse transcriptase polymerase chain reaction (RT-PCR) on individual faecal samples taken every two/three days. For susceptible pigs, the average period between exposure to an infectious pig and HEV excretion was six days (standard deviation: 4). The length of HEV-excretion (i.e. infectious period) was estimated at 49 days (95% confidence interval (CI): 17-141) for block 1 and 13 days (95% CI: 11-17) for block 2. The R0 for contact-exposure was estimated to be 8.8 (95% CI: 4-19), showing the potential of HEV to cause epidemics in populations of pigs.

Key words: hepatitis E virus / transmission / contact-exposure / reproduction ratio / pigs

Corresponding author: martijn.bouwknegt@rivm.nl

© INRA, EDP Sciences 2008