Comparing Presence of Avian Paramyxovirus-1 Through Immunohistochemistry in Tracheas of Experimentally and Naturally Infected Chickens

SUMMARY. Tracheas from chickens infected both in the field and experimentally with lentogenic Newcastle disease virus (also known as avian paramyxovirus-1 [APMV-1] and referred to here as “lentogenic NDV”) were examined histopathologically to score degree of pathologic changes and by immunohistochemistry to determine presence of viral protein. In the field cases there was often a striking lack of correlation between severity of tracheal lesions and amount of immunohistochemical signal for APMV-1 protein. Experimental cases had minimal pathologic changes and also minimal immunohistochemical signal. Positive cells were often associated with surface deciliation. It may be that lentogenic NDV has only a minor role as a respiratory pathogen, merely compromising the mucosa to allow other respiratory pathogens to infect and worsen the clinical and pathologic presentation.