IMMUNOCYTOCHEMICAL STUDY OF THE PATHOGENESIS OF PACHECOS PARROT DISEASE IN BUDGERIGARS

Thirty-five budgerigars were infected with the Psittacid herpesvirus 1 (RSL-1 strain, ATCC) to study the pathogenesis of Pacheco's disease. Intramuscular (i.m.) and oral (p.o.) infection routes were used in 21 and 14 animals respectively. Animals were euthanized on days 1, 2, 3, 4, 6 and 8 post-inoculation (p.i.) and complete postmortem examination s and histological studies were performed. The presence of viral antig en in tissues was detected by immunohistochemical techniques using a r abbit polyclonal antibody. In the i.m.-infected birds, lesions were fi rst detected on the third day p.i. and included necrotizing hepatitis and splenitis, both associated to the presence of viral antigen. Necro tic and inflammatory lesions as well as viral antigen were detected in many organs after the fourth day p.i. (oesophagus, crop, pancreas, ki dney, adrenal gland, thyroid and parathyroid glands, thymus, ovary and feathers) proving generalization of the disease. Chronology of the in fection was similar in the p.o.-infected birds. However, two main diff erences were observed between the groups: In the p.o. group, viral ant igen was first detected in cloacal mucosa (3rd day p.i.), liver and sp leen; and viral entry into target cells and dissemination to the rest of the tissues was slower in this group. In addition, detection of vir al antigen in feather follicular epithelial cells and in granulosa cel ls of ovarian follicles are findings that could be of relevance to the transmission of the virus.