Infectious bronchitis in Brazil : a minor field study in Bastos municipality, Sao Paulo

Abstract: Infectious Bronchitis (IB) is a highly contagious viral respiratory and productiondepressant disease distributed world wide. The disease is caused by the InfectiousBronchitis Virus (IBV), a positive RNA strand Avian Coronavirus within thegenus Gammacoronavirus. Due to a combination of high mutation rate and atendency of recombination a constant emergence of new genotypes and serotypesis seen. In Brazil, a country with an extensive poultry production and majorproblems with disease control, the diversity of circulating strains are wide andoutbreaks of clinical disease despite intensive use of vaccines are common. Theaim of this study was to investigate the presence of IBV and to identify genotypesof isolated IBVs in a limited number of layer flocks in Bastos, São Paulo, as partof the screening for circulating genotypes in the country. As a minor part theBiosecurity measures (precautions) was observed. In addition, a literature studywas performed on IB and IBV. Organ samples from four farms were collected aspools of trachea, lungs, kidneys, reproductive tract and enteric content and wereanalyzed using Reverse Transcriptase Polymerase Chain Reaction (RT-PCR).Over fifty percent of the samples were positive for IBV and three samples wereidentified as 4/91-genotype using Genotype-specific PCR. Due to problems withthe RT-PCR that was targeting part of the S1-gene, the genotypes of the rest of thepositive samples could not be determined using DNA sequencing. They wereinstead identified as not belonging to Massachusetts, D274 or 4/91 genotypesusing Genotype-specific RT-PCR. Considering the results of previous studies inBrazil stating that a national Brazilian Variant dominates, the possibility that theunidentified genotypes belonged to the national genotype were considered high.