Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/2/2012
Publication Date: 8/2/2012
Citation: Auten, K.M., Heidari, M., Dunn, J.R. 2012. Positive correlation between replication rate and pathotype of Marek’s disease virus strains in maternal antibody negative chickens. Meeting Abstract. Merial-NIH National Veterinary Scholar Sympsoium. Comparative Medicine: The Key to Translation, August 2-5, 2012, Loveland, Colorado.
Technical Abstract: Marek’s disease (MD) is a highly contagious lymphoproliferative disease of chickens associated with large economic losses worldwide. The etiological agent, Marek’s disease virus (MDV), can be divided into three pathotypes: virulent (v), very virulent (vv), and very virulent plus (vv+). While previous work has shown that a vv+MDV strain has a significantly higher replication rate than a vMDV strain, this has not been evaluated on a broad spectrum of viruses. Currently, pathotyping of new strains of MDV requires both a long period of time and a large number of birds. Confirming a positive correlation of virus replication and pathotype may lead to faster and cheaper alternative pathotyping methods or at least as a screening assay for choosing isolates to be pathotyped. The current study investigated the relationship between replication rates and pathogenicity using five representative MDV strains from each of the pathotypes v, vv, and vv+ (fifteen total strains). Fifteen maternal antibody negative chickens were challenged with each of the fifteen strains at hatch. Based on the results of a pilot study to determine the appropriate days and tissue samples for differentiating virus strains, brain, lung, and bursa of Fabricius were sampled from five birds of each strain at 9, 11, and 13 days post challenge. Multiplex qPCR was performed on the DNA isolates to measure the ratio of MDV-specific glycoprotein B (gB)/chicken GAPDH. Viral replication levels appeared to be correlated with virulence, as higher levels of viral replication were seen in the vvMDV and vv+MDV strains relative to the vMDV strains for all three tissues at most time points. Thymus and bursa weights were measured for all birds and significant thymus and bursal atrophy was observed in vv+MDV strains compared to vMDV strains at all three time points.