Transmission of Hepatitis E from Pigs to Humans
THE NETHERLANDS - Researchers studied the course of hepatitis E virus (HEV) infection in pigs by direct contact and inoculation. They identified urine and meat as possible sources for pig-to-pig and pig-to-human HEV transmission.
Worldwide, hepatitis E virus (HEV) genotype 3 is observed in pigs and transmission to humans is implied. To estimate public health risks from contact with pigs or the consumption of pork products, the transmission routes and dynamics of infection should be identified. Hence, the course of HEV-infection in naturally infected pigs merits further study.
Martijn Bouwknegt from the National Institute for Public Health and the Environment in Bilthoven, the Netherlands, and colleagues undertook this research.
To resemble natural transmission, 24 HEV-susceptible pigs were infected either by one-to-one exposure to intravenously inoculated pigs (C1-pigs; n=10), by one-to-one exposure to contact-infected pigs (C2-pigs: n=7; C3-pigs: n=5) or due to an unknown non-intravenous infection route (one C2-pig and one C3-pig).
The course of HEV-infection for contact-infected pigs was characterized by:
- faecal HEV RNA excretion that started at day 7 (95 per cent confidence interval: 5-10) post-exposure and lasted 23 (19-28) days
- viraemia that started after 13 (8-17) days of faecal HEV RNA excretion and lasted 11 (8-13) days and
- antibody development that was detected after 13 (10-16) days of faecal HEV RNA excretion.
The time until onset of faecal HEV RNA excretion and onset of viraemia was significantly shorter for intravenously inoculated pigs compared to contact-infected pigs, whereas the duration of faecal HEV RNA excretion was significantly longer.
At 28 days post-infection, HEV RNA was detected less frequently in organs of contact-infected pigs than intravenously inoculated pigs. For contact-infected pigs, HEV RNA was detected in 20 of 39 muscle samples that were proxies for pork at retail and in 4 of 7 urine samples.
Conclusions
The course of HEV infection differed between infection routes, suggesting that contact-infection could be a better model for natural transmission than intravenous inoculation. Urine and meat were identified as possible HEV-sources for pig-to-pig and pig-to-human HEV transmission.
Reference
Bouwknegt M., S.A. Rutjes, C.B.E.M. Reusken, N. Stockhofe-Zurwieden, K. Frankena, M.C.M. de Jong, A.M. de Roda Husman and W.H.M. van der Poel. 2009. The course of hepatitis E virus infection in pigs after contact-infection and intravenous inoculation. BMC Veterinary Research 2009, 5:7doi:10.1186/1746-6148-5-7.
Further Reading
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