Comparison of the effects of infectious bronchitis and infectious laryngotracheitis on the chicken respiratory tract.

In infectious bronchitis (IB) virus infection of the chicken the upper and lower respiratory tracts were damaged, but infectious laryngotracheitis (ILT) virus caused lesions only in the upper respiratory tract. Secondary infection with Escherichia coli was apparent in the trachea of birds inoculated with either virus but was more striking in those given IB virus. Serum alpha 1-acid glycoprotein, an acute-phase protein, occurred in higher concentrations in chickens inoculated with IB virus than in those given ILT virus.