Spain: Last relevant results on swine hepatitis E virus

HEV infection in humans is one of the most important causes of acute clinical hepatitis in developing countries. Transmission of the virus occurs primarily by the faecal-oral route through contaminated drinking water in areas with poor sanitary conditions. Although the case fatal rate is generally low (<1%), it can reach up to 25% in pregnant women.

The existence of sporadic HEV infection cases in individuals of industrialized countries with no history to travel to endemic areas has suggested the possibility of an animal reservoir. After the first description of swine HEV in USA, sequence analyses have shown high nucleotide identity between swine and human isolates from the same geographic area. The facts that human clinical hepatitis E has been associated with consumption of undercooked meat products and swine HEV strains can infect non-human primates provide more evidence that HEV should be considered an agent with zoonotic potential.

Research on HEV (swine and other species) at CReSA has been carried out since 2003. During 2009 the group has published five papers based on the last results obtained. Below the main results of these papers are summarized.

• The most likely natural route of infection of swine HEV by oral inoculation of pigs was explored and the potential infection by direct contact exposure was investigated. Pigs orally inoculated with a single HEV dose got infection, although few animals had evidence of infection. Moreover, the virus was successfully transmitted to direct contact exposed pigs.
  En: Pigs orally inoculated with swine hepatitis E virus are able to infect contact sentinels. Casas M, Pina S, de Deus N, Peralta B, Martín M, Segalés J. Vet. Microbiol. 2009 Mar 13. [Epub ahead of print]
  
  
• Avian HEV sequences in chickens from Europe have been reported by the first time. Further studies are needed to elucidate the clinical significance of avian HEV infections in Europe.
  En: Evidence of widespread infection of avian hepatitis E virus (avian HEV) in chickens from Spain.
  Peralta B, Biarnés M, Ordóñez G, Porta R, Martín M, Mateu E, Pina S, Meng XJ. Vet. Microbiol. 2009 May 28; 137(1-2):31-6.
  
  
• A truncated ORF2 capsid HEV antigen derived from a genotype 3 strain was developed in insect cells and insect larvae. Seropositivity by ELISA in the studied animal populations was 71.4% for pigs, 0.60% for goats, 1.92% for sheep, and 11.11% for cats. None of the 1170 cattle samples or 166 rodent samples analyzed was positive.
  En: Anti-HEV antibodies in domestic animal species and rodents from Spain using a genotype 3-based ELISA. Peralta B, Casas M, de Deus N, Martín M, Ortuño A, Pérez-Martín E, Pina S, Mateu E. Vet. Microbiol. 2009 May 28; 137(1-2):66-73.
  
  
• A serological retrospective study carried out using archived sera (samples gathered between 1985 and 1997) showed that HEV was present and widespread in Spanish swine farms at least since 1985. Any significant changes in prevalence were detected from 1 year to another and therefore, HEV infection in swine should be considered endemic in Spain.
  En: Retrospective serological study on hepatitis E infection in pigs from 1985 to 1997 in Spain. Casas M, Pujols J, Rosell R, de Deus N, Peralta B, Pina S, Casal J, Martín M. Vet. Microbiol. 2009 Mar 30; 135(3-4):248-52
  
  
• Evolutive pressure analysis indicates that microevolution of HEV seems to be driven by negative selection. Further studies should be carried out in order to clarify the HEV origin and evolution.
  En: Genetic characterization of the complete coding regions of genotype 3 hepatitis E virus isolated from Spanish swine herds. Peralta B, Mateu E, Casas M, de Deus N, Martín M, Pina S. Virus Res. 2009 Jan; 139(1):111-6.

The HEV research has been funded by different sources: CReSA (2003-2004), MEC (AGL2004-06688/GAN) and Porcivir Consolider-Ingenio (CDS2006-00007).