Avian influenza (fowl plague)

Occurrence: Worldwide.
Species affected: All.
Age affected: All.
Causes: Type A Orthomyxoviruses.
Effects: Reportable disease. Respiratory distress, coughing, sneezing, rales, depression, sinusitis, emaciation, feed refusal, nervous signs and diarrhoea. In layers, there is a drop in egg production and shell quality. Mortality is rapid with virulent strains.


Clinical signs

The incubation period is hours to days, depending on age, sex, species affected, concurrent infections and pathogenicity of virus. Respiratory distress, coughing, sneezing, rales, depression, sinusitis, emaciation, off feed, nervous disorder, and diarrhoea may be seen. Rapid mortality, up to 100%, occurs with virulent high pathogenic strains (fowl plague) (H5 and H7 subtypes). Multiple pathotypes can occur. Low pathogenic strains causing only a mild respiratory disease, but their presence in flocks can lead to trade restrictions among countries. A drop in egg production and shell quality, watery eyes, excessive lacrimation, oedema of head and face, and cyanosis may be observed.


Postmortem lesions

Lesions include mucous in trachea, air sacculitis, swollen head or wattles, egg peritonitis, sinusitis, watery lungs, and fibrinous enteritis. Pericarditis, necrosis of skin and GI tract; haemorrhages on wattles, combs and legs; necrotic foci on liver, spleen, kidney and lungs, and haemorrhages at junction of proventriculus and gizzard can be seen with fowl plaque.


The AGP and ELISA tests can be used for determining the presence of antibody in the sera. Isolation and identification of virus from trachea or vent in embryonating eggs or tissue culture is needed.  Test haemagglutinating ability of the virus mixed with chicken sera containing antibodies against influenza. The virus can be sub-typed using specific sera against all known HA and N or new real time PCR tests using subtype specific probes can make a diagnosis in 2 hours. It simulates mycoplasmosis, turkey coryza, VVND, ILT, ornithosis, and fowl chlorea.

Treatment & control

Killed vaccine is available some countries. Quarantine, depopulation and eradication of virulent form is mandated under law in most countries. Strict biosecurity is needed. Control of live bird markets in important to prevent the spread of the virus. Wild free flying water fowl can spread AIVs all over the world. Recombinant AI vaccines available, which contain the H5 gene cloned into fowl pox, NDV, or HVT vectors. The H5N1 highly pathogenic viruses can jump species causing disease in a number of them including humans. H7 viruses have also been shown to cause disease in humans.

Broad-spectrum antibiotics are helpful to control secondary bacteria. 

Avian influenza insights

Keeping the Avian Influenza virus out

During the most recent Avian Influenza summit, a part of the International Egg Commissions leadership conference in Berlin, the egg industry’s world leaders discussed all the ins and outs of the current Avian Influenza threat. Keeping the virus out, that should be at the forefront of every producer’s mind.

Vaccination against AI

The avian influenza threat has changed recently, disrupting trade, inducing high levels of mortality and causing enormous economic losses. This has changed the discussion on whether to vaccinate or not. Dr Yannick Gardin of Ceva: “There are many dogmas surrounding the control of Avian flu. Countries who decided to vaccinate were viewed as the bad countries, this label is no longer appropriate.”

Lessons learned from the recent US HPAI epornitic

The last confirmed case of H5N2 highly pathogenic avian influenza (HPAI) was diagnosed in Iowa in a commercial layer complex on June 17th. All indications are that outbreaks of this strain - which emerged in early March in Missouri and later devastated flocks in Minnesota, the Dakotas, Iowa and Nebraska - have ended. Now it is time to draw conclusions.

"Facing a new world order"

The current avian influenza situation has rung the alarm bells across the globe. The American poultry and egg industry is suffering losses. James Sumner, 
president of the USA Poultry & Egg Export Council is worried: “We are facing an entire new world order.”

Most read items on avian influenza in 2015