Avian Influenza Highly Pathogenic ( ...

Avian Influenza Highly Pathogenic (HPAI) H5 or H7 in Laying Hens

Happenings / Clinical Signs

Clinical manifestation varies depending on the extent of damage to specific organs and tissues (i.e. not all clinical signs are present in every bird)

Morbidity and mortality rates are very high (50-89%) and can reach 100% in some flocks

Mortality

  • In most cases the disease is fulminating with some birds being found dead prior of observation of any clinical signs
  • Typically, the virus spread rapidly among poultry housed on the floor with peak mortality (70-100%)  occurring in 3-5 days of first clinical signs
  • In poultry housed cages, the virus spreads slower through the house with peak mortality taking 10-15 days
  • When death is peracute, no gross lesions may be observed

Dead birds

  • Good body fleshing condition
  • The mortality occurring in 3-5 days of first clinical signs in birds housed on the floor
  •  In birds housed in cages,  the peak mortality taking 10-15 days

Visibly sick birds

  • Many visibly sick birds

Nervous

If the disease is less fulminating and the birds survive 3-7 days may exhibit nervous disorders:

  • Tremors of head and neck
  • Inability to stand
  • Torticollis
  • Opisthotonus
  • Unusual positions of the head and appendages

Behaviour

  • The poultry houses may be unusually quiet because of decreased activity and reduction of normal vocalization of the birds
  • Depression

Egg Drop

  • Egg production declines rapidly
  • Precipitous drops in egg production occurs with typical  declines including total  cessation of egg production within six days

Respiratory

  • Respiratory signs spread fast
  • Respiratory signs are less prominent than with Low Pathogenic  Avian Influenza Virus
  • Rales
  • Sneezing
  • Coughing

Head

  • Multifocal necrosis and haemorrhages of comb and wattles
  • Severe edema, necrosis, and haemorrhages of comb and wattles
  • Periorbital  edema may be seen accompanied by petechial-to-ecchymotic hemorrhages
  • Swelling of the head , face and upper neck accompanied by petechial-to-ecchymotic hemorrhages
  • Necrotic foci, haemorrhage, and cyanosis of the non- feathered skin especially wattles and comb

Body Parts (Neck, wings, breast, abdomen, shanks, legs, hock, feet, joints, vent, and skin)

  • Severe subcutaneous haemorrhages of leg shanks
  • Edematous , haemorrhagic and necrotic lesion in the skin
  • Swelling of the upper neck
  • Necrotic foci, haemorrhage, and cyanosis of the no feathered skin

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.

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.

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. 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

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.
Spread
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
Solution
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

0

Impact on Liveability

5


Impact on Production

5

Overall Economic Impact

5



Y.M. Saif.2008.Disease of Poultry. 12th Edition. page 167

David E. Swayne. 2013.  Diseases of Poultry 13th Edition. page 196

Mark Pattison, Paul F. McMullin, Janet M. Bradbury. Dennis J. Alexander. 2008. Poultry Diseases. 6th Edition.

Paul McMullin. 2004. A pocket Guide to Poultry Health and Disease. First Edition.

Steven Leeson, John D. Summers. 2008. Commercial Poultry Nutrition. Third Edition.

Donald D. Bell, Williams D. Weaver. 2009.  Commercial Chicken Meat and Egg Production. Fifth Edition.

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