Avian Hepatitis E Virus Infections, ...

Avian Hepatitis E Virus Infections, or Big Liver and Spleen Disease, or Hepatitis Splenomegaly Syndrome in Laying Hens

Avian Hepatitis E Virus Infections, or Big Liver and Spleen Disease, or Hepatitis Splenomegaly Syndrome in Laying Hens

Hepatitis-splenomegaly (HS) syndrome is a disease of layer and broiler breeders characterized by increased mortality and decrease of egg production and is primarily caused by avian hepatitis E virus. (1, 2, 3)

Morbidity (percentage of sick birds) and mortality in the field are relatively low, although subclinical avian infections are widespread in chicken flocks. (1, 2, 3)

In some outbreaks, there has been a drop in egg production of up to 20%, but in other outbreaks, egg production has not been affected. (1, 2, 3)

HS syndrome is characterized by above-normal mortality of 30-72 weeks of age, with the highest incidence occurring between 40-50 weeks of age. Weekly mortality increases approximately 0.3% to 1.0% for several weeks (3-4 weeks). (1, 2, 3)

Diseased birds may have pale combs and wattles, depression, anorexia, and soiled vent feathers or pasty droppings. Small eggs with thin and poorly pigmented shells. Internal qualities are unaffected. (1, 2, 3)

The clinical signs for HS in Australia also vary from subclinical infection to egg drops that may reach 20% and accompanied by up to 1% mortality per week over a period of 3--4 weeks. (1, 2 )

Affected flocks in the United States and Europe appear to have milder or subclinical infections compared to those in Australia. (1, 2 )

In the USA the disease has been associated with “primary feather drop syndrome”, were broiler breeders fall to peak during production, show delayed sexual maturity and moult primary feathers. (1, 2, 3)

Observed Clinical Signs Happenings

Hepatitis Splenomegaly Syndrome is characterized by above-normal mortality of 30-72 weeks of age

Morbidity and mortality in the field are relatively low

 Visibly sick birds

  • Few visibly sick birds
  • Affected birds show depression
  • Soiled vent feathers or pasty droppings
  • Pale combs and wattles

Egg drop

  • Egg production drops gradually
  • A sudden, rapid drop in egg production may be the first indication of infection in a flock, lasting for up to 3—4 weeks.
  • Failure to attain peak production may be the first sign
  • Egg drop may reach 20% and accompanied by up to 1% mortality per week
  • Egg production may be affected, usually (usually 4-10%)

Mortality

  • Low mortality or increases gradually
  • above-normal mortality of 30-72 weeks of age
  • Weekly mortality increases to approximately 0.3%  for several weeks
  • Sometimes mortality reach 1% mortality per week over a period of 3-4 weeks
  • Highest incidence occurring between 40-60 weeks of age

 Dead Birds

  • Prior to death, affected birds are usually in good bodily condition with pale combs and wattles
  • Sometimes the dead bird is in poor bodily condition

Head Comb Wattles Face Nostrils Sinuses Mount Beak Earlobes

  • Pale combs and wattles

Droppings

  • Soiled vent feathers or pasty droppings
  • Feces smeared on feathers around the vent
  • Dirty or Pasty vents or feathers with droppings around the vent

Feathers

  • Soiled vent feathers or pasty droppings
  • Feces smeared on feathers around the vent
  • Dirty or Pasty vents or feathers with droppings around the vent
  • Induce a moult
  • Many birds in the flock may exhibit loss of primary feathers resembling moulting.
  •  Moult primary feathers (premature moulting)

Egg quality

  • Egg size decreased or reduced
  • Pale or loss of colour in brown-shelled eggs
  • Small eggs with thin and poorly pigmented shells
  • Small eggs
  • Smaller than normal Eggs
  • Thin-shelled and soft-shelled or porous eggs
  • Ungraded or second's eggs increased
  • Egg specific gravity score lower (should be above 1.080 (1.068 thin shells)

 

Avian Hepatitis E Virus Infections, or Big Liver and Spleen Disease, or Hepatitis Splenomegaly Syndrome in Laying Hens DOES NOT exhibit or manifest any of the following clinical signs happenings:

  1. High mortality or increases rapidly
  2. Dead birds in a Skinny bodily condition), sometimes
  3. Many visibly sick birds
  4. Flock behaviour activity change
  5. Respiratory abnormalities
  6. Neurological Nervous
  7. Lameness or unusual movements, incoordination, ataxia
  8. Eyes abnormalities
  9. Body Parts (Neck, wings, breast, abdomen, shanks, legs, hocks, feet, joints, vent, and skin, abnormalities), skinny body, retarded growth, weight depression
  10. Feed Consumption Changes
  11. Feed Consumption Pattern
  12. Feed intake increased
  13. Feed intake reduced or refusal
  14. Diet or Feed Changes (Recent Feed delivery, Recent formulation /diet, Other silo or improper storage, Another feed brand)
  15. Internal Egg defects
Causing Agents
Viral Infection. Avian Hepatitis E virus infection. Herpesvirus.
Affected Systems/Organs
Reproductive, Digestive system. Liver and Spleen.
Spread
Natural infections have only been demonstrated in birds over 24 weeks of age though it is possible that transmission from parents and/or infection in rear occur with a subsequent period of latency.
Mainly Affects
Egg Production, Egg Quality and Liveability
Solution
Trough cleaning and disinfection after depletion of an affected flock. Good biosecurity. All in/all out production.
Suggested Actions
  • Can be confirmed with clinical signs and gross lesions
  • Can be dealt with in house
  • Technical assistance recommended
  • Diagnosis should be confirmed with rapid assays and/or a certified laboratory
  • Veterinary intervention is recommended

Impact on Egg quality

1

Impact on Liveability

1


Impact on Production

1

Overall Economic Impact

1



  1. Y.M. Saif.2008.Disease of Poultry. 12th Edition. page 444
  2. David E. Swayne. 2013. Diseases of Poultry 13th Edition. page 496
  3. Mark Pattison, Paul F. McMullin, Janet M. Bradbury. Dennis J. Alexander. 2008. Poultry Diseases. 6th Edition. 413
  4. Paul McMullin. 2004. A Pocket Guide to Poultry Health and Disease. First Edition. page 85
  5. Steven Leeson, John D. Summers. 2008. Commercial Poultry Nutrition. Third Edition.
  6. Donald D. Bell, Williams D. Weaver. 2009.  Commercial Chicken Meat and Egg Production. Fifth Edition.
  7. Gail Damerow 1994. The Chicken Health Handbook.

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