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Pathogenicity Assessment of Seven Variants of Infectious Bronchitis Virus Isolated from Commercial Broiler Chickens during 2013 in Egypt
Authors: Mahmoud E. Sediek
Number of views: 379
The aim of this study was to evaluate the pathogenicity of seven variants of IBV isolates (Coded,
11, 15, 21, 13, 19, 22, 24) using commercial broiler chickens. These isolates isolated from 25
commercial broiler flocks raised in El-Behera and Kafr-Elsheikh governorates in 2013, and were
identified by the AGPT against reference IBV Beaudette antiserum and RT-PCR and characterized
by partial sequence analysis of S1 gene as variant 2 IBV strains. The results at 2 weeks of PI
revealed that all isolates were able to induce serological response and respiratory signs in the form
of conjunctivitis, mainly of a frothy type, associated with lacrimation, edema and cellulitis of the
periorbital tissues, sneezing, coughing, tracheal rales and gasping were observed in all infected
groups in a varying degrees and varying times of appearance and disappearance. In addition the
birds appeared lethargic, reluctant to move. No mortalities were recorded during the course of
experiment in all groups. The main lesions of PI were slight increase of mucin, congestion and
presence of nasal exudate in the trachea and small patches of pneumonia in chickens challenged
with 4 IBV isolates only (NO. 15, 21, 22, 24). Renal lesions (nephritis and enlarged kidney) which
were induced in chickens challenged with 3 isolates (NO. 15, 21 and 24) were not as pronounced
as seen in the field. Histopathological finding of PI, exhibited tracheal lesions with inflammatory
cells infiltration in the lamina propria and submucosa, edema in the submucosa, desquamation of
the lining epithelial of the mucosa and activation of goblet cells. In addition to renal lesions with
interstitial nephritis which characterized by infiltration of inflammatory cells (heterophils,
lymphocytes and plasma cells) in the interstitial tissue.