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Hepatitis-splenomegaly Syndrome

Layer Hepatitis, HS Syndrome, Big Liver And Spleen Disease Viru

Hepatitis-splenomegaly (HS) syndrome, also known as layer hepatitis, is a liver infection caused by the avian hepatitis E virus (HEV). Avian HEV is a nonenveloped, positive-sense, single-stranded RNA virus. It is genetically related to but distinct from human and swine HEVs.

What is the Hepatitis E Virus (HEV)

HEV is an important but extremely understudied pathogen. It has been identified in a number of animal species, including chickens, rabbits, rats, deer, pigs, possibly cattle and sheep. Pigs are a recognized reservoir for HEV. There is potential for cross-species and zoonotic transfer to humans. The virus has been identified in commercial laying hens in North America, China, and Spain. In the United States, HEV was widespread among clinically healthy laying hens throughout North America.

Clinical signs of HS syndrome in Chickens

Chickens with HS syndrome are suffering from varying degrees of liver damage. Affected broiler breeder hens in Shandong, China were found with regressive ovaries, extensive necrosis and hemorrhage of the liver, and enlarged liver and spleen. Liver disease often causes chickens to accumulate bloody fluid in their abdomen, vasculitis, and amyloidosis in the liver.

Clinical Signs

Loss of appetite
Swollen abdomen
Reduced egg production


  • History
  • HEV serum antibody testing
  • RT-PCR


Supportive care



  • Biosecurity
  • Miniize contact with pig feces

Scientific References

Risk Factors

  • Pig manure