Abstract
BackgroundInfectious bronchitis is highly contagious and constitutes one of the most common and difficult poultry diseases to control. IBV is endemic in probably all countries that raise chickens. It exists as dozens of serotypes/genotypes. Only a few amino acid differences in the S1 protein of vaccine and challenge strains of IBV may result in poor protection. Tropism of IBV includes the respiratory tract tissues, proventriculus and caecal tonsils of the alimentary tract, the oviduct and the kidney.ResultsInfectious bronchitis virus (IBV) strain closely related to Massachusetts (Mass) serotype was isolated from broiler chickens suffering from severe renal and respiratory distresses. The isolate was serologically identified by Dot-ELISA and further characterized by RT-PCR then genotyped using S1 gene sequence analysis. Alignment of the S1 sequence of the isolate with 16 IBV strains revealed high homology to isolates related to Mass serotype. Inoculation with the strain reproduced the disease in experimental 1-day-old chickens and resulted in 20% mortality, severe renal and moderate respiratory distresses. Marked histopathological changes in both kidney and trachea were observed in experimentally infected chickens. A protection study using the H120 live attenuated vaccine showed low protection rate in spite of high S1 sequence homology (97%). Protection based criteria were: virus re-isolation attempts from trachea, tracheal and renal histopathology as well as IBV antigens detection by immunofluorescent antibody technique in kidney sections.ConclusionPeriodical evaluation of cross-protective capabilities of IBV vaccine(s) versus recently recovered field isolates should be performed to ensure optimum control of IBV.
Highlights
Infectious bronchitis is highly contagious and constitutes one of the most common and difficult poultry diseases to control
The S1 protein forms the N-terminal portion of the peplomer and contains antigenic epitopes mainly within three hypervariable region (HVR) [4,5,6]
Neutralizing and serotype specific epitopes are associated within the defined HVRs
Summary
Infectious bronchitis is highly contagious and constitutes one of the most common and difficult poultry diseases to control. IBV is endemic in probably all countries that raise chickens. Avian infectious bronchitis virus (IBV) is a highly contagious pathogen of chickens that replicates primarily in the respiratory tract and in some epithelial cells of the gut, kidney and oviduct [1]. (page number not for citation purposes) http://www.virologyj.com/content/3/1/78 tein (N), membrane glycoprotein (M), spike glycoprotein (S) and small membrane protein (E). The S1 protein forms the N-terminal portion of the peplomer and contains antigenic epitopes mainly within three HVRs [4,5,6]. Neutralizing and serotype specific epitopes are associated within the defined HVRs [4,7,8]
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