Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2011
Publication Date: 12/30/2011
Citation: Brown, C.C., Jones, M.E., Cattoli, G., Cardenas-Garcia, S., Miller, P.J., Afonso, C.L. 2011. Experimental characterization of West African Newcastle disease virus [abstract]. RESOLAB Annual Directors Meeting. p. 1. Interpretive Summary:
Technical Abstract: Four West African strains and one South African strain of virulent Newcastle disease virus (NDV) were characterized through a two-phase experiment. Strains investigated were Burkina Faso/2415-580/2008, Nigeria/228-7/2006, Niger/1377/2006, and Goose/South Africa/08100426/2008. Phylogenetic analysis shows that the West African viruses cluster in NDV class II, genotype XIII, while the South African virus is grouped in class II, genotype VII. The objective of Phase 1 was to determine the viability and virulence of the viruses through an experimental infection study. The objective of Phase 2 was to determine if standard vaccination protocols are protective against these strains. For Phase 1, each strain was inoculated into 4-week-old specific pathogen free white leghorn chickens via a standard eyedrop method. For all strains, all experimentally-infected birds died or were euthanized by day 4 post-infection due to the severity of disease. Gross and histologic examination of all birds revealed severe necrosis of lymphoid tissues (spleen, thymus, Bursa of Fabricius, cecal tonsils), intestinal hemorrhage, and eyelid edema and hemorrhage. Immunohistochemical staining of lymphoid tissues revealed widespread viral antigen associated with lesions, in all cases. For Phase II, one-day-old specific-pathogen-free (SPF) white leghorn chicks were vaccinated with a live vaccine, and boosted 17 days later. Vaccines consisted of either V4 or La Sota administered at standard doses. Chicks were challenged with either the Burkina Faso or South Africa strains at 22 days of age, and oropharyngeal and cloacal swabs were collected 2 and 4 days post-challenge. All vaccinated birds survived challenge from both viral strains, with no clinical signs noted. Results demonstrate that the three West African and the South African NDV strains are highly virulent. However, vaccination with live viruses of genotype 1 (V4) or genotype II (La Sota) is protective under experimental conditions with SPF birds. Further tests to determine the degree of post-challenge viral shedding and to assess antibody response to vaccination are pending, as is a full immunohistochemical evaluation of lesions.