Avian Influenza Highly Pathogenic H ...

Avian Influenza Highly Pathogenic H5 or H7 Fulminating Form in Laying Hens

Avian Influenza Highly Pathogenic H5 or H7 Fulminating Form in Laying Hens

In most cases, in chickens, the disease is fulminating with some birds found dead prior to observation of any clinical signs (1, 2)

This highly virulent clinical group results from infection by H5 or H7 Avian Influenza virus is expressed as a severe, highly fatal systemic disease that affects most organ systems including the nervous and cardiovascular systems. This is a systemic disease that affects respiratory, reproductive, digestive, nervous, cardiovascular and integumentary (skin) systems. (1, 2)

Clinical manifestation varies depending on the extent of damage to specific organs and tissues. Not all clinical signs are present in every bird. The clinical disease is fulminating with some birds found dead prior to observation of any clinical signs. If the disease is less fulminating and birds survive for 3-7 days, individual birds may exhibit nervous disorders such as tremors of head and neck, inability to stand, torticollis, opisthotonos and other unusual positions of head and appendages. Usually, these signs are more marked in birds that take some time to die. (1, 2)

The flock in the poultry shed or houses may be unusually quiet because of decreased activity and reduction in normal vocalization. Depression is common as well as significant declines in feed and water consumption. A precipitous drop in egg production with typical declines including total cessation of egg production within six days. Respiratory signs are less prominent but can include rales, sneezing, coughing, sinusitis, excessive lacrimation. There are severe edema, necrosis, and hemorrhages of comb and wattles and severe subcutaneous hemorrhages of leg shanks. Swelling of the head, upper neck and feet may be observed which results from subcutaneous edema and may be accompanied by petechial-to-ecchymotic hemorrhages(1, 2)

Observed Clinical Signs Happenings


  • High mortality or increases rapidly
  • Sudden onset  of high flock mortality
  • Some birds being found dead prior to observation of any clinical signs
  • Sudden death

Dead birds

  • Dead birds found in a good bodily condition
  • Sudden death

Flock behaviour

  • Decreased flock mobility or activity
  • The poultry house may be unusually quiet because of decreased activity and reduction in the normal vocalization of the birds.

Avian Influenza Highly Pathogenic H5 or H7 Fulminating Form in Laying Hens DOES NOT show or exhibit or manifest any of the following clinical signs happenings:

  • Egg drop
  • Low mortality or increases gradually
  • Dead birds in Poor bodily  condition
  • Visibly sick birds
  • Increase flock mobility or activity
  • Droppings abnormalities
  • Respiratory abnormalities
  • Neurological Nervous
  • Lameness or unusual movements, incoordination, reluctance to move
  • Eyes abnormalities
  • Head, Comb, Wattles, Face, Nostrils, Sinuses, Mount, Beak, Earlobes, abnormalities (except eyes)
  • Body Parts (Neck, wings, breast, abdomen, shanks, legs, hocks, feet, joints, vent, and skin, abnormalities), skinny body, retarded growth, weight depression
  • Feathers abnormalities
  • Feed Consumption Changes
  • Diet or Feed Changes (Recent Feed delivery, Recent formulation /diet, Other silo or improper storage, another feed brand)
  • Shell quality
  • Internal Egg quality
Causing Agents
Viral infection. Avian Influenza (AI) virus, family Orthomyxoviridae, genus Influenza virus A. HPAI ("highly pathogenic avian Influenza")
Affected Systems/Organs
Systemic disease (entire body) that affects respiratory, reproductive, digestive, cardiovascular, nervous and integumentary (skin) systems.
Bird to bird, contaminated water and objects from infected birds. The virus is transmitted by direct contact between infected and susceptible birds or indirect contact through aerosol droplets or exposure to virus-contanminated fomites. The virus is excreted from the nares, mouth, conjunctiva, and cloaca of infected bird into the environment because the virus replication in the respiratory, intestinal, renal, and/or reproductive organs.
Mainly Affects
Liveability and egg production
Prevention, management, and eradication by slaughter using combination of five following specific components: education, biosecurity, diagnostic and surveillance, elimination of infected poultry.
Suggested Actions
  • Can be confirmed with clinical signs and gross lesions
  • Diagnosis should be confirmed with rapid assays and/or a certified laboratory
  • Veterinary intervention is recommended
  • This is a notifiable disease, veterinary intervention is essential. It is advisable that you run DTECT again to ensure you have answered all the questions correctly. If you suspect that you may have this disease please contact your local authorities immediately.

Impact on Egg quality


Impact on Liveability


Impact on Production


Overall Economic Impact


  1. Y.M. Saif.2008.Disease of Poultry. 12th Edition. page 1162, 167
  2. David E. Swayne. 2013. Diseases of Poultry 13th Edition. page 191, 196
  3. Mark Pattison, Paul F. McMullin, Janet M. Bradbury. Dennis J. Alexander. 2008. Poultry Diseases. 6th Edition.
  4. Paul McMullin. 2004. A Pocket Guide to Poultry Health and Disease. First Edition.
  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. page

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