Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2006
Publication Date: 11/13/2006
Citation: Wakamatsu, N., King, D.J., Kapczynski, D.R., Seal, B.S., Brown, C. 2006. Experimental pathogenesis for chickens, turkeys, and pigeons of exotic Newcastle disease virus from an outbreak in California during 2002-2003. Veterinary Pathology. 43(6):925-933. Interpretive Summary: The occurrence of Exotic Newcastle disease (END) in poultry is reportable to international regulatory agencies, impacts international trade, and is a major problem world-wide. Severe clinical disease is often the first evidence of an END outbreak. However, the severity of disease is known to vary among bird species infected with the same Newcastle disease virus strain. Infection of susceptible chickens, turkeys, and racing pigeons with an END virus isolate from the 2002 END outbreak in California demonstrated a wide range of clinical effects. Severe disease with high mortality occurred in chickens and disease free turkeys, commercial turkeys had generally mild disease with no mortality, and evidence of disease was rare in racing pigeons. Although evidence of severe clinical disease remains an important indicator of a reportable disease like END, a comprehensive END control program must incorporate surveillance to detect virus infected birds especially among those species where clinical disease is not a predictable outcome of an infection.
Technical Abstract: Exotic Newcastle disease virus (NDV) isolated from chickens during the 2002-2003 California outbreak was inoculated into 4-week-old specific-pathogen-free (SPF) White Leghorn chickens, 3-week-old SPF Beltsville White turkeys, 6-week-old commercial Broad Breasted White turkeys, and 10- to 20-week-old racing pigeons, and the clinicopathologic features of disease were compared. Birds were monitored clinically and euthanized sequentially with collection of tissues. Tissues were examined by histopathology, by immunohistochemistry to detect viral nucleoprotein, and by in situ hybridization to detect viral mRNA. Clinically, infected chickens and SPF turkeys showed severe depression, and all died or were euthanized due to severe clinical signs by day 5 postinoculation. In these birds, histologic lesions were widespread and virus was detected in multiple organs. All infected commercial turkeys showed mild depression, and incoordination was observed in some birds. Histologic lesions were mild and viral distribution was limited. In pigeons, only one bird showed overt clinical disease, and histologic lesions and viral distribution were present in limited organs. Consequently, susceptibility to highly virulent NDV was shown to vary among chickens, SPF turkeys, commercial turkeys, and pigeons. Additionally, we have evidence of CA END virus subclinical infections that suggest pigeons could be subclinical carriers of other virulent NDV.