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Caused by a herpesvirus
Hosts
- The most important disease of unvaccinated backyard chicken flocks
Pathogenesis
- Replicates initially in the lungs and B cells
- Enters feather follicles: produces virus-laden dander that is shed into litter
- Reaches T cells, causing proliferation without virus protein production
- T cells localize in brain or nerves causing encephalitis
- End stage: massive visceral tumors
Epidemiology
- More virulent strains evolving: presents a challenge to vaccinal immunity
Control
- Removal of litter between batches of chicks
- Vaccines administered in ovo at 18 days