Infectious bronchitis virus (IBV) is the causative agent of avian infectious bronchitis, which is characterized by respiratory, reproductive, and renal signs. However, the role of IBV as an enteric pathogen in still controversial. In Brazil, antigenic groups of IBV divergent from the Massachusetts serotype used for vaccination schedules in that country have already been demonstrated. The present study aimed to assess the different genotypes of IBV in Brazilian commercial poultry flocks by partial sequencing of the S1 amino-terminus coding region using enteric contents as samples and examine their relationship with the vaccine serotype currently in use. Samples of enteric contents were taken as pools of five birds from each of 18 poultry farms (17 broiler and one laying farm) from five Brazilian states between 2002 and 2006. Birds were presenting watery diarrhea and poor general condition but were without respiratory, renal, or reproductive signs. Conventional antibacterial and anticoccidial therapies were unsuccessful and, furthermore, all samples proved negative for rotavirus, reovirus, and astrovirus. Eleven IBV samples were isolated in embryonated eggs and resulted in S1 sequences. Phylogenetic analysis showed that these segregated into an exclusive cluster, close to serotype D274, but distant from Massachusetts. Mean amino acid identity amongst these Brazilian strains was 94.07%; amongst these and serotypes D274, 4/91, and Massachusetts, mean amino acid identity was 77.17%, 69.94%, and 68.93%, respectively. In conclusion, the presence of genotype variant strains of IBV in Brazilian poultry flocks has been demonstrated and might be the reason for the unsuccessful control of IBV in Brazil. Furthermore, these results also strengthen the implications of IBV in enteric diseases of poultry.

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1. The possibility that infectious bronchitis virus (IBV) variants isolated from broilers with enteric and respiratory problems have a different tropism and pathological outcome from those IBV strains causing classical respiratory disease was investigated. 2. IBV variants were isolated from broiler flocks with enteric and respiratory problems in two regions of Brazil. The USP-10 isolate, of enteric origin, was inoculated via the oral oroculonasal routes into IBV-antibody-free broilers and specific pathogen-free (SPF) chickens to determine tissue tropism and pathogenicity and compared with an IBV variant (USP-50) isolated from chickens showing signs of respiratory disease only. 3. Both USP-10 and USP-50 strains caused similar pathological patterns by either route of inoculation. Both variants were detected in respiratory and non-respiratory tissues, including the kidney, intestine and testis. 4. Broilers were more susceptible to infection than SPF chickens, and seroconversion was detected in all of the chicks.