Submitted to: Western Poultry Disease Conference
Publication Type: Proceedings
Publication Acceptance Date: May 1, 2002
Publication Date: N/A
Technical Abstract: Marek's disease occurs in adult layer or breeder flocks but it is not clear whether this is the result of recent infection with highly virulent strains or, alternatively, earlier infection that has been exacerbated by immunodepressive stress or other factors. We challenged birds at 18 or 90 weeks of age with highly virulent MDV and measured lesion responses and horizontal transmission. Specific pathogen free chickens were susceptible to transient paralysis and tumors, and spread virus horizontally. However, previously vaccinated or exposed chickens were highly refractory to challenge as adults. This suggests that late breaks are not likely due to recent infections.