| Popis: |
SUMMARY Parameters of naturally occurring Marek's disease herpesvirus (MDHV) infection in commercial broilers were studied in 2 trials, each involving paired flocks. MD condemnations ranged from 6.0 to 15.3%, though little difference was noted between flock pairs, and the pattern of infection in all 4 flocks was similar. Chicks were apparently free of infection at hatching, despite their origin from infected breeder flocks. MDHV could be demonstrated indirectly as early as 9 or 16 days of age in 2 of the flocks. Infection was detected directly at 4 weeks by the presence of microscopic lesions and the isolation of MDHV. Acquired antibody appeared at 6 to 7 weeks. At processing (8 weeks), MDHV was isolated from 98 of 99 birds tested from all flocks and 78%1 had microscopic lesions. Virus infection appeared related directly to lesion response, though the relationship of these parameters to MD condemnations could not be determined. MDHV was demonstrated in samples of litter and dust from 1 of 4 houses prior to the introduction of chicks, suggesting that this was the most probable source of flock infection. |
