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Title: Pathotyping of Australian isolates of Marek's disease virus in commercial broiler chickens vaccinated with herpesvirus of turkeys (HVT) or bivalent (HVT/SB1) vaccine and associated with viral load in the spleen and feather dander
Contributor(s): Walkden-Brown, Steve W (author)orcid ; Islam, Aminul (author); Islam, Afm Fakhrul (author); Burgess, Susan (author); Groves, Peter John (author); Cooke, Julie (author)
Publication Date: 2013
DOI: 10.1111/avj.12084
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Abstract: Objective: To pathotype Australian isolates of Marek's disease virus (MDV) in commercial broiler chickens using standard methods and to evaluate early markers of pathotype. Methods: A complete 3 x 4 factorial experiment with two replicates was conducted using 648 Cobb broiler chickens in 24 isolators. The experimental factors were vaccination (unvaccinated, herpesvirus of turkeys (HVT), bivalent (HVT + SB1 strain of serotype 2 MDV) and MDV challenge (unchallenged or 500 plaque-forming units of isolates MFP57, 02LAR or FT158). Mortality, body weight, immune-organ weights and viral load were measured to 56 days post challenge (dpc). Vaccinal protective index (PI) and virulence rank (VR) were calculated based on gross Marek's disease (MD) pathology. Results: The PIs provided by the HVT and bivalent vaccines against challenge with MPF57, 02LAR, and FT158 were 84.6% 56%, 61.4% and 82.2%, 60.8%, 57.7%, respectively, leading to putative pathotypes of virulent MDV for MPF57 and very virulent MDV for 02LAR and FT158. Significantly more of the unvaccinated chickens (85.7%) had MD lesions than chickens vaccinated with either the HVT (26.8%) or bivalent vaccine (27.6%). Strong linear relationships were observed between the incidence of MD at 56 dpc and MDV load in the spleen at 7 dpc (R² = 0.71) and MDV load in the isolator exhaust dust at 14 dpc (R² = 0.57) and 21 dpc (R² = 0.51). Immune organ weights had a weaker association with subsequent MD incidence. Conclusion: Pathotyping results in broiler chickens with maternal antibody broadly agreed with those in specific-pathogen-free chickens in other studies, with some important differences. MDV load in the spleen at 7 dpc and in isolator dust at both 14 and 21 dpc was a powerful early predictor of subsequent MD incidence.
Publication Type: Journal Article
Source of Publication: Australian Veterinary Journal, 91(8), p. 341-350
Publisher: Wiley-Blackwell Publishing Ltd
Place of Publication: United Kingdom
ISSN: 0005-0423
Field of Research (FOR): 070712 Veterinary Virology
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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School of Environmental and Rural Science

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