History, signs, and lesions may be suggestive of LPAI, but are similar to other diseases. With HPAI, lesions are more useful in a presumptive diagnosis. Confirmation of AI requires laboratory tests including serology and virus detection. Confirmation of HPAI requires inoculating susceptible chickens with the virus and molecular characterization of the cleavage site.
Influenza virus usually can be isolated in chick embryos from tissue or swab samples of trachea, lung, air sac, sinus exudate, or cloaca. The virus hemagglutinates chicken red blood cells. The AGID test can be used to identify type A internal antigen of the virus or to demonstrate an increase in antibody titer between acute and convalescent sera.
Influenza must be differentiated from other poultry diseases including Newcastle disease, other paramyxovirus infections, mycoplasmosis, chlamydial infections, and fowl cholera. Highly pathogenic AI should be differentiated from velogenic viscerotropic Newcastle disease. Because AI viruses causing highly pathogenic AI are considered exotic to the United States, they are reportable to the USDA, and confirmation by virus isolation is essential.
If you have sick birds in Minnesota you can contact the University of Minnesota Veterinary Diagnostic Laboratory at 1-800-605-8787. There is a national toll free number: 1-866-536-7593
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