Abstract:
This study describes the isolation, serotyping and genotyping of 54 infectious bronchitis virus
(IBV) cases predominantly in KwaZulu-Natal and compared to several isolates from other
South African provinces between 2011 and 2012 and several historic isolates. The results
indicate the division of isolates into two different genotypes of IBV within the province,
Massachusetts (Mass)-like and QX-like. The IBV Mass-like genotype was the most prevalent
and was detected in 79% of the full spike protein S1 gene sequences. Variation up to 22.3%
was detected within local Mass-type strains, supporting the hypothesis that multiple IBV
serotypes may co-circulate in the same region simultaneously. Additionally, more conservation
was observed amongst Mass serotypes versus QX-like serotypes, implying that vaccine use
can influence the variability within the IBV population; this is deduced from the fact that
the only live vaccine registered for use in South Africa at the time of the study was of Mass
origin and no QX-like vaccines were available for use. This study offers the first published
consolidation of IBV isolates from an area of South Africa and identifies variation within the
IBV population of the broiler flock within the study area over a 2-year period.
