Submitted to: International Marek's Disease Symposium Abstracts and Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 9, 2000
Publication Date: N/A
Two Argentine isolates (NULP-1 and NULP-4) of Marek's disease virus (MDV) were compared as reported by Calnek et al (1998) in MD genetically susceptible P-2a strain chickens. Criteria of immunosuppression were (1) atrophy of the thymus and bursa of Fabriciou as measured by organ weight and (2) histopathologic evidence of necrosis and lymphoid cell depletion. Preliminary results from NULP-1 showed its pathogenicity was very similar to RB1B (classified as the vv pathotype of MDV) and was intermediate between isolates JM-16 and RK-1. The vv+ isolate, NULP-4, caused the most severe damage to lymphoid organs in terms of atrophy and histopathologic changes. Other strains from the United States were tested following the same hypothesis. Preliminary results suggest the hypothesis is partially supported since there is a direct relationship between MD virulence and immunosuppressive properties in some strains.