ARS | Publication request: Characterization of Newcastle disease virus isolated from cormorant and gull species in the United States in 2010

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2011
Publication Date: February 8, 2012
Citation: Diel, D.G., Miller, P.J., Wolf, P.C., Mickley, R.M., Musante, A.R., Emanueli, D.C., Shively, K.J., Afonso, C.L. 2012. Characterization of Newcastle disease virus isolated from cormorant and gull species in the United States in 2010. Avian Diseases. 56:128-133.

Interpretive Summary: Newcastle disease virus (NDV) is the causative agent of Newcastle disease (ND), one of the most important diseases of poultry worldwide. Occurrence of Newcastle disease may negatively impact the poultry industry due to high mortality rates and to restrictions in trade of poultry products. In the United States, Newcastle disease is considered exotic in domestic poultry; however the virus has been frequently associated with disease in wild birds, especially cormorants, which represents a constant risk for the introduction of the disease in poultry flocks. In the present study, we describe the characterization of thirteen NDV viruses obtained during die-offs of cormorants and gulls in the States of Minnesota, Massachusetts, Maine, New Hampshire and Maryland in 2010. Our studies demonstrate that all viruses obtained in 2010 are very similar to viruses that caused mortality in cormorants in Minnesota in 2008. Interestingly, as described for the viruses responsible for the outbreak in 2008, a diagnostic test routinely used by USDA to detect Newcastle disease virus infection failed to detect the viruses that caused the outbreaks in 2010. However, all 2008 and 2010 viruses were detected by a diagnostic test specifically developed for viruses obtained from cormorants. These observations indicate the need of a specific diagnostic test to detect Newcastle disease viruses that infect cormorants. During the 2010 mortality events, gulls presenting symptoms of Newcastle disease and which tested positive for the virus were captured on the east shore of Maryland in an area that is located only 60 miles away from the Delmarva Poultry Industry, which is an area with a high concentration of poultry farms. These findings demonstrate that in order to prevent the introduction of Newcastle disease from wild birds into domestic poultry farms it is very important to enforce strict biosecurity measures in the poultry farms.

Technical Abstract: Newcastle disease virus (NDV), a member of the genus Avulavirus of the family Paramyxoviridae, is the causative agent of Newcastle disease (ND) a highly contagious disease that affects many species of birds and which frequently causes significant economic losses to the poultry industry worldwide. Virulent NDV is exotic in poultry in the U.S.; however, the virus has been frequently associated with outbreaks of ND in cormorants, which poses a significant threat to poultry species. Here we present the characterization of thirteen NDV isolates obtained from outbreaks of ND affecting cormorants and gulls in the states of Minnesota, Massachusetts, Maine, New Hampshire and Maryland in 2010. All 2010 isolates are closely related to the viruses that caused the ND outbreaks in Minnesota in 2008, following the new evolutionary trend observed in cormorant NDV isolates since 2005. Similarly to the results obtained with the 2008 isolates, the USDA validated F-gene real-time RT-PCR assay failed to detect the 2010 cormorant viruses, whereas all viruses were detected by a cormorant-specific F-gene real-time RT-PCR assay. Notably, NDV-positive gulls were captured on the eastern shore of Maryland, which represents a significant geographic expansion of the virus since its emergence in North America, and poses a significant threat to the Delmarva Poultry Industry located within 60 miles of the outbreak. These findings highlight the need for constant epidemiological surveillance for NDV in wild bird populations, and for consistent biosecurity measures to prevent the introduction of the agent into domestic poultry flocks.