Epsilon Archive for Student Projects

Abstract

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