الفهرس 
cover englishOnly 14 pages are availabe for public view
 |  | from | 286 |  |  |
| | | from | 286 | | |
Abstract
In this study, the pathogenesis of two live attenuated CIAV vaccines was experimentally investigated using two hundred one-day-old, specific-pathogen-free (SPF) chicks, which were allocated into five groups (40 chicks each). group 1 was orally vaccinated with attenuated cux-1 strain in drinking water. group 2 was kept as a contact non-vaccinated group to group 1. group 3 was intramuscularly vaccinated with attenuated 26P4 strain. group 4 was kept as a contact non-vaccinated group to group 3, and group 5 served as a negative control group. Five birds from each group were sacrificed on the 3rd, 7th, 15th, 22nd, 29th, 36th and 41st day-post-vaccination (dpv). Tissue specimens from bone marrow, thymus, spleen, cecal tonsils, bursa of Fabricius, liver, pancreas, proventriculus and duodenum were collected from three birds for histopathology, lesion scoring and immunohistochemistry. On 7th dpv, bone marrow and thymus were subjected to TUNEL assay (Terminal deoxynucleotidyl transferase dUTP nick end labeling) to demonstrate the characteristic apoptotic patterns of CIAV. Using ELISA (Enzyme Linked Immuno Sorbent Assay) at 3rd, 7th, 15th, 22nd, 29th, 36th and 50th dpv, CIAV vaccines specific antibodies responses were measured in collected serum from 5 chicks per group. Liver specimens were collected on the 7th, 15th and 21st dpv for real time-PCR (qPCR), to detect and quantitate the CAV genomic DNA.
Fecal swabs from all groups at 41st and 50th dpv were also subjected to qPCR to detect and quantify the viral genome shedding. Finally, the attenuated 26P4 strain was inoculated in embryonated SPF eggs, and the collected embryo and CAM (chorioallantoic membrane) were subjected to histopathology and immunoperoxidase techniques. Mortalities occurred in both vaccinated groups and their contact groups. Frothy diarrhea, ulcer, S/C haemorrhages, cannibalism and signs of mild depression were the most developed clinical signs in groups 1, 2, 3 and 4. Pale bone marrow and atrophy of the thymus were the most characteristic post-mortem changes in groups 1, 2, 3 and 4. Microscopically, changes characteristic of CIAV were observed, and the most affected organs were bone marrow, thymus, liver and spleen; respectively. The demonstrated histopathological lesions started as early as the 3rd dpv in almost all organs of concern in all 4 groups. Immunofluorescence labelling of CIAV antigen demonstrates virus in all examined organs in both vaccinated and contact groups, with the bone marrow as the most substantial positive. Chicks of group 1 and 3 started to be seropositive at 15th dpv while group 2 and 4 at 22nd dpv. CIAV genome was detected in livers and fecal swabs of vaccinated and contact groups on concerned days. Indeed, live attenuated CIAV vaccines (either by oral or parenteral route) are pathogenic to 1-day-old chicks and they could spread horizontally and transmitted to contact chicks, inducing mortalities and immunosuppression.