Tissue tropism of a Thailand strain of high-pathogenicity avian influenza virus (H5N1) in tissues of naturally infected native chickens (Gallus gallus), Japanese quail (Coturnix coturnix japonica) and ducks (Anas spp.).

The tropism of a Thailand strain of highly pathogenic avian influenza H5N1 virus was demonstrated on tissues (lung, trachea, heart, liver, spleen, pancreas, rectum, kidney, brain, skeletal muscle, duodenum, and oviduct) from naturally infected native chickens (Gallus gallus), Japanese quail (Coturnix coturnix japonica) and ducks (Anas spp.) by indirect immunofluorescence assay. In chickens and quail, the distribution and localization of nucleoprotein viral antigen was similar and detected at the highest level in cardiac myocytes, at 88% (chickens) and 89% (quail), and respiratory, digestive and urinary systems all showed high levels of antigen. Antigen in duck tissues were detected at significantly lower levels (P < 0.05) with the exception of brain and skeletal muscle samples. In most cases, antigen in duck tissue was absent in the digestive organs but present in respiratory organs, which supports the hypothesis that aerosol and oral-oral transmission are the main method of highly pathogenic avian influenza virus transmission from this species.