Experimental infection of vaccinated slaughter ostriches with virulent Newcastle disease virus

A virulent Newcastle disease virus (NDV) isolate from an outbreak in commercial poultry, with virulence indices of MDT = 47-48 h; IVPI = 2,17 and ICPI = 1,8; was used to inoculate 10x vaccinated (standard poultry vaccines) as well as 10x unvaccinated slaughter ostriches via intratracheal, ocular and nasal routes, in a controlled environment. All unvaccinated ostriches developed clinical signs (mainly respiratory); two of them died while the other eight recovered. No vaccinated ostriches developed any clinical signs. All remaining (18) ostriches were slaughtered 14 d after the last mortality. Virulent NDV could be re-isolated from the dead birds, but not from organs, muscle (fresh), muscle (24 h chilled), gastro-intestinal tract, bone-marrow or respiratory system taken from the slaughtered ostriches. It is suggested that it would be extremely unlikely that the international trade in ostrich meat could act as a mechanism for spreading virulent NDV from endemic to non-endemic parts of the world.