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Title: Potential Evidence of a Unique Marek's Disease Virus Strain Circulating in Pennsylvania

item Dunn, John
item GINGERICH, ERIC - University Of Pennsylvania

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2010
Publication Date: 10/18/2010
Citation: Dunn, J.R., Gingerich, E. 2010. Potential evidence of a unique Marek's disease virus strain circulating in Pennsylvania [abstract]. In: 5th International Workshop on the Molecular Pathogenesis of Marek's Disease Virus and 1st Symposium on Avian Herpesviruses, October 17-20, 2010, Athens, Georgia, p. 103.`

Interpretive Summary:

Technical Abstract: In 2007, virus isolates were grown and characterized from two flocks in Pennsylvania experiencing higher than normal mortality attributed to Marek’s disease. The first flock was 28-week old commercial white layers vaccinated with HVT + Rispens, and the second flock was 36-week old commercial brown layers vaccinated with HVT + SB-1. Testing for purity by immunohistochemistry revealed that both isolates reacted to both H19 and T65 monoclonal antibodies. Although all serotype 1 MDV strains except Rispens are known to react with H19 antibody, T65 has previously only been shown to react with Rispens, GA and three Chinese MDV field isolates. Sequencing within the MDV pp38 gene confirmed the similarity of amino acids with these previous strains causing the altered epitope reactivity. Pathotyping results indicated the isolates were not unusually virulent compared to other recent field strains. In 2010, a virus isolate was grown from a different nearby Pennsylvania flock of 36-week old commercial white layers vaccinated with HVT + Rispens. Once again, this isolate reacted to both H19 and T65 antibodies. The rarity of the pp38 sequence found in these field isolates suggests that the viruses isolated in Pennsylvania in 2007 and 2010 may be of the same origin. Additional studies would be useful to determine whether this really is a focus or not and, if so, how extensive is the focus and how is the virus transmitted between flocks. These findings also confirm that the T65 antibody is not specific for Rispens, therefore results when using T65 should be interpreted with caution.