ARS | Publication request: Application of the "best fit" pathotyping assay for evaluation of Russian isolates of Marek's disease virus

Submitted to: Workshop on Molecular Pathogenesis of Marek's Disease and Avian Immunology
Publication Type: Abstract Only
Publication Acceptance Date: August 5, 2006
Publication Date: August 5, 2006
Citation: Dudnikova, E., Norkina, S., Vlasov, A., Slobodchuk, A., Lee, L.F., Witter, R.L. 2006. Application of the "best fit" pathotyping assay for evaluation of Russian isolates of Marek's disease virus. 4th International Workshop on Molecular Pathogenesis of Marek's Disease Virus. p. 40.

Technical Abstract: The objective of this study was to investigate the validity of the "best fit" pathotyping assay for testing of field isolates of Marek's disease (MD) virus. Twenty serotype 1 MD viruses were isolated from breeder and commercial flocks in 8 regions of the Russian Federation. These isolates were pathotyped using a simplified form of the ADOL pathotyping assay using vaccinated and nonvaccinated SPF chickens from a local source. Lesion responses were compared with those induced by reference strains JM/102W, Md5, and 648A representing pathotypes v, vv and vv+, respectively. Based on comparison to reference strains, we determined the pathotype of 6 isolates as "vv+", 13 isolates as "vv" and 1 isolate as "v". All 20 isolates were isolated from poultry farms with outbreaks of clinical MD or with MD lesions being detected on processing. Most of the Russian isolates possessed high virulence, almost equal to that of recent isolates in United States. Lesion responses induced by the 3 reference strains consistently differentiated the respective pathotypes in nonvaccinated chickens and in chickens vaccinated with HVT alone or with a bivalent HVT + 301B/1 vaccine. Variation between replicate trials was minimal. Interpretation of the data was straightforward although the criteria of the most important for classification of an isolate depended in part on the virulence of the isolate. These results indicate that the "best fit" pathotyping assay can be conducted with local chicken strains and yields data that is consistent with the ADOL method.