Changes

== Diagnosis  ==

== Diagnosis  ==

Clinical signs are indicative of the disease. The government should be notified immediately and all premises shut down if the disease is suspected.  

Laboratory diagnosis is essential when dealing with suspected cases of AI due to the lack of classical clinical signs, zoonotic potential, and need to differentiate between HPAI and LPAI as well as the virus subtype. The diagnosis is based on isolation and characterisation of the virus. Tracheal/ cloacal swabs or faeces are taken from live birds and suspended in antibiotic solution before being inoculated into the allantoic cavity of 9-11 day old embroyanted chicks.  Taking lower respiratory tract samples is important, as the virus may not be found in the upper respiratory tract. Faecal or organ samples from dead birds can also be used. Following incubation the allantoic fluid is tested for haemagglutination, a positive result (i.e. haemagglutination is present) indicating viral infection. An immunodiffusion test can be used to confirm the presence of influenza A virus, using antiserum to the nucleocapsid or matrix antigens.  Polyclonal chicken antisera can be used to further identify the virus subtype by observing which specific antiserum inhibits the haemagglutinating activity of the virus (haemagglutination inhibition).  

 

Haemoagglutination inhibition (HI) should be performed on serological samples to detect a four fold increase in the viral antibodies. Samples should be taken at the acute phase, when the virus is first suspected and then a convalescent stage sample taken around two weeks later to detect the increase in antibodies.  

Virulence assessment can be performed by injecting chickens with infective allantoic fluid and observing the presence/absence and severity of disease for 10 days.

Paired serum samples can be taken in order to identify seroconversion. One sample is taken in the acute phase of infection before antibodies are produced and another 2-3 weeks later. A fourfold increase in antibody levels (usually identified by haemagglutination inhibition) will show that infection with the virus has occurred. This can only provide a retrospective diagnosis but can be useful in identifying which flocks have been exposed to AI, especially in cases where it is an asymptomatic infection. 

Due to continual antigenic drift and shift specificity and sensitivity of diagnostics is a big problem.

== Control  ==

== Control  ==