Tissue Tropism of Three Cloacal Isolates and Massachusetts Strain of Infectious Bronchitis Virus

Abstract

Three virus isolates (ECV-1, -2, and -3) recovered from cloacae of chickens in flocks that experienced drops in egg production were identified as infectious bronchitis virus (IBV), based on characteristic embryo lesions, chloroform sensitivity, coronavirus morphology, and serology. Because these isolates were recovered from the cloacae of the hens, their tissue tropism was compared with the prototype strain of IBV, Massachusetts-41 (M-41), in experimentally inoculated chickens. During the 39-day period postinoculation (PI), virus isolation was attempted from digestive and respiratory tracts, kidney, and cloacal swabs. ECV-1, ECV-2, and M-41 were more frequently recovered from the cecal tonsils than from other tissues. ECV-1, ECV-3, and M-41 were also recovered from kidney for up to 39 days PI. ECV-2 and ECV-3 had a limited distribution in respiratory tissues, being isolated only sporadically from trachea, bronchus, and lung. Surprisingly, ECV-2 was isolated from esophagus at 2, 16, 30, and 39 days PI; otherwise, its distribution in other tissues was sporadic. Results confirmed that IBV, including M-41, can infect a variety of tissues and that some isolates may be recovered frequently from digestive tract tissues, particularly from the cecal tonsils.