Distribution of influenza A virus (IAV) nucleoprotein antigen in the gastrointestinal tract and bursa of Fabricius of mallards exposed to a H14N5 IAV through intranasal inoculation or contact exposure.

Viral antigen was not identified in larynx, trachea, lung, brain, kidney, adrenal glands, pectoral skeletal muscle, heart, or liver. 1– = no staining; + = staining of a few cells; ++ = staining of moderate numbers of cells; +++ = staining of numerous cells.