Pathological changes in laying hens inoculated with the JPA-1 strain of egg drop syndrome-1976 virus.

Rhode Island Red laying hens were inoculated with the JPA-1 strain of egg drop syndrome-1976 virus and examined pathologically 1, 3, 5, 7, 10, 14, 21, 28 and 80 days postinoculation (p.i.). Eggs with a discolored or soft shell or no shell were laid over a period from 10 to 24 days p.i. Egg production failed transiently in some affected birds after 13 days p.i. At autopsy, the uterus revealed remarkable edema and swelling of the mucosal folds together with the deposition of whitish exudate in the cavity 14 days p.i. Microscopically, intranuclear inclusion bodies were found in epithelial cells of the uterus, isthmus and vaginal gland region 10 and 14 days p.i. There were also severe degeneration and desquamation of the epithelial cells, atrophy of the uterine glands and remarkable infiltration of heterophils, lymphocytes and plasmacytes accompanied with extensive edema. Twenty-one days after inoculation, lymphoid follicles were formed in the mucosal folds of some part of the oviduct. Electron microscopic examination revealed various amounts of virus particles 68 approximately 80 nm in diameter mainly in the nuclei of the epithelial cells on the mucosa and in the exudate, and also in the cytoplasm of macrophages in the uterus.