Avian Influenza A and Paramyxo Viruses Complicating Respiratory Disease Diagnosis in Poultry

Prior to 1956, laboratory diagnosticians in the United States could reasonably rely on differentiating and identifying Newcastle disease virus (NDV) as the etiologic agent causing a respiratory infection in chickens or turkeys by demonstrating that the isolate hemagglutinated chicken red blood cells (rbc). Unfortunately, this simple means of differentiation is no longer possible. In other parts of the world, a presumptive diagnosis of Newcastle disease virus by demonstrating hemagglutination of rbc's with infectious fluids of embryos has been complicated by the presence of Fowl Plague, a disease which preceded Newcastle disease as a poultry pathogen. In 1949, Dinter isolated a hemagglutinating virus from chickens in Germany, identified as virus N, which produced a pneumoencephalitis-like disease in young chicks. This agent was found to be an antigenic variant of the fowl plague virus (8,9). Other agents that hemagglutinate chicken rbc were recovered not only from poultry but also from swine and horses (2,14,15,23). These agents belong to the myxovirus group. More specifically, all except NDV and strain yucaipa of the paramyxovirus group show some cross-antigenic relationship with the complement-fixating soluble nucleic acid component (G) of type A (PR8) influenza virus (1,2).