Avian influenza virus (AIV) and Newcastle disease virus (NDV) are the two most important viruses affecting poultry worldwide, said first-named author Mary Pantin-Jackwood of the Southeast Poultry Research Laboratory. She added that co-infections of poultry with AIV and NDV are a problem from both the clinical point of view and the diagnosis of these viruses.

The goal of her study, with colleagues at the Laboratory, was to examine the interaction between AIV and NDV in infected poultry species. They conducted experiments in which chickens and turkeys were infected with lentogenic, mesogenic or velogenic strains of NDV, and with low pathogenicity (LP) or high pathogenicity (HP) AIV, as relevant to specific ecosystems, by giving the viruses simultaneously or sequentially.

Pathogenesis (clinical signs, lesions), presence of the viruses in tissues, duration and titre of virus shedding for each virus, transmission to contact birds, and seroconversion to both viruses was evaluated.

Chickens co-infected with a lentogenic NDV vaccine strain (LaSota) and an LPAIV responded similarly to infection as chickens infected with the viruses given separately. However, an effect on virus shedding was observed in co-infected birds. In turkeys, previous exposure to LPAIV prevented infection with NDV.

More importantly, previous infection of chickens with mesogenic or velogenic NDV interfered with HPAIV infection but the virulence of the NDV strain and the timing of HPAIV inoculation affected the outcome of infection.

The researchers concluded that previous or simultaneous infection of NDV and AIV can interfere with the replication dynamics and the disease caused by these viruses in poultry.

August 2013