Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 22, 2010
Publication Date: March 1, 2011
Citation: Susta, L., Miller, P.J., Afonso, C.L., Brown, C.C. 2011. Clinicopathological characterization in poultry of three strains of Newcastle disease viruses isolated from recent outbreaks. Veterinary Pathology. 48(2):349-360. Interpretive Summary: Three virulent Newcastle disease viruses were put into four-week old specific pathogen free (SPF) Leghorns to evaluate their virulence and the lesions cause by these viruses. The distribution of the virus, the clinical disease and gross and histological lesions observed were different for each of the viruses even though they are all categorized as virulent. One virus is a representative virus that can be found currently circulating in cormorants in the U.S.A. Knowing what clinical signs and lesions to expect if this virus was to infect chickens is especially important for the U.S. Poultry Industry. Another of the viruses is the virulent Australian virus that has been shown to have mutated into virulence from low virulence in chickens in Australia. Pathology with this virus in chickens has not yet been described. The last virus is a virus that is typical of viruses currently circulating in Asia. The North and South America have not yet reported this genotype of virus being isolated. It is critical that we observe lesions and disease caused by these types of viruses in chickens to know what to expect if there was an outbreak. Histopathological lesions for each of the viruses are described. Differences and similarities are noted.
Technical Abstract: Newcastle disease is a severe threat to the poultry industry and is caused by Newcastle disease virus (NDV), a member of the genus Avulavirus, Family Paramyxoviridae. The NDV is rapidly evolving, with several new genotypes having been discovered in the last few years. Characterization of these strains is important to evaluate field changes, to anticipate new outbreaks and to develop adequate control measures. In this paper three Newcastle disease isolates (APMV-1/duck/ Vietnam, Long Bien /78/2002 [Long Bien], APMV-1/chicken/Australia/9809-19-1107/1998[Australia], APMV-1/double crested cormorant/ U.S., Nevada/ 19529-04/ 2005 [Nevada Cormorant]) from recent outbreaks were investigated via clinicopathological assessment, immunohistochemistry, in situ hybridization and serology in experimentally infected 4-week-old chickens. Phylogenetic studies showed that Australia isolate belongs to Class II genotype I, Long Bien to Class II genotype VIId and Nevada Cormorant to Class II genotype V. Even though all three viruses had a virulent fusion protein cleavage site and an ICPI values greater than 1.5, they all differed in their ability to cause clinical signs, lesions, and in their viral distribution. Long Bien isolate showed the most severe clinicopathological picture, and the most widespread viral distribution (as shown by IHC and ISH). The Australia isolate and Nevada Cormorant isolates had a milder pathological phenotype, with viral replication restricted to only a few organs. Although Nevada Cormorant is considered a velogen by standard pathogenicity indices, it behaved more like a mesogen. The variability in clinicopathological characteristics despite the similarity in ICPI, suggest that full clinicopathological assessment is necessary to fully characterize new isolates, and that there are differences in pathogenesis among viruses of different genotypes.