The influence of age on the response of ring-necked pheasants to infection with marble spleen disease virus.

Ring-necked pheasants that were negative for maternal antibody against type II avian adenoviruses were orally inoculated with 5.0 x 10(2) tissues-culture-infective doses of marble spleen disease (MSD) virus at 1-week intervals through 6 weeks of age, and at 9 and 13 weeks of age. Groups of four virus-inoculated birds and two control birds were necropsied at 4, 6, 8, and 10 days postinoculation, and the spleens were evaluated for gross and microscopic lesions. No lesions consistent with MSD were present in birds inoculated at 1, 2, 3, or 4 weeks of age. A single bird in the group inoculated at 5 weeks of age had gross and microscopic lesions of MSD. Five birds in the group inoculated at 6 weeks of age had lesions of MSD. The patterns of lesion development in the 6-week-old birds were similar to those produced in the 9- and 13-week-old birds inoculated with MSD virus. The reason for the lack of gross or microscopic lesion development during the first 4 weeks of life is unknown.