Emergence and molecular characterization of the avian infectious bronchitis virus GI‐23 in commercial broiler farms from South America

Abstract

Avian infectious bronchitis virus (IBV) is the etiological agent of a highly contagious disease in the poultry industry. The spike protein (S1 subunit) is responsible for the molecular diversity of the virus and many genetic types, and lineages are described worldwide. IBV genetic type I—strain 23 (GI‐23) has spread across different continents (including Asia, Europe and Africa), causing multiple outbreaks and severe economic losses throughout the poultry industry in the last decade. The present study aimed to report the emergence and molecular characterization of GI‐23 in South Brazil, being detected for the first time in South America. Eighty‐two broiler flocks presenting clinical suspicion of infectious bronchitis were selected for this study. Tracheal, renal and intestinal samples were collected for IBV detection and genotyping. A total of 57 flocks were positive for IBV by generic RT‐qPCR targeting 5' untranslated region and 31 also tested positive for GI‐11 by a specific RT‐qPCR targeting S1 gene for this lineage. The remaining 26 IBV‐positive samples were genotyped by partial and one by complete S1 gene/protein sequencing. Phylogenetic analysis demonstrated that all of them clustered into a specific branch of the GI‐23. S1 protein sequence analysis evidenced that all Brazilian GI‐23 IBVs had the two characteristic amino acid substitutions A93T and S/H118P/L, but other changes were also observed, such as S37F (n = 21; 81%), G117S (n = 17, 65%), P122S (n = 16; 61%) and W71R (n = 9; 35%). This study brings new insights into the epidemiology of the IBV GI‐23 in the world, highlighting its emergence and molecular characteristics in Brazil, South America.

Pathogenicity of GI-23 Avian Infectious Bronchitis Virus Strain Isolated in Brazil

“…Unclassified variants in the GI-1 and GI-11 lineages were sequenced and the phylogenetic analysis ( Figure 1 ) showed new viral strains, classified as GI-23. This result is in agreement with earlier research reported by Ikuta et al (2022) [ 26 ]. Although, in general, the amino acid sequences obtained in the present study were very similar to the sequences presented by Ikuta et al (2022) [ 35 ] ( Table 1 of such work), through the analyses carried out in the present study, some differences were found.…”

“…Among the group assigned as “not classified”, nine isolates were subjected to S1 glycoprotein gene sequencing. In the phylogenetic analysis, we used a sequence dataset of the strains frequently found in Brazil and GI-23 [ 26 ]. According to the phylogenic relationship shown in Figure 1 , all nine isolates were grouped within the GI-23 strain.…”

“…The Genbank sequence I.D. OP113954.1 (IBV SB2805), was the first IBV sequence that showed a pattern similar to other sequences of the GI-23 group in Brazil [ 26 ]. * Indicate the sequences obtained from the samples isolated and analyzed in the present study.…”

“…Recently, there has been an increase in cases of respiratory diseases in chicken-producing regions of Brazil (states of Paraná, Rio Grande do Sul, Santa Catarina, São Paulo, Goiás and Ceará). Through molecular diagnosis, the presence of the GI-23-type strain was detected in samples from poultry farms with different production performances and no other sanitary problem [ 26 ]. Consequently, there was a significant increase in slaughter condemnations.…”

Key Aspects of Coronavirus Avian Infectious Bronchitis Virus

“…Currently, GI-17 (DMV/1639-like strains) is the major variant of IBV circulating in US commercial poultry; it was initially isolated in 2011 and began causing significant diseases in 2014/2015 [ 17 ]. In Latin America, lineages GI-1, GI-11, GI-16, and GI-23 are coexisting at present in Brazil, and the prevalent genotypes are GI-13 (793B-type) and GI-16 (Q1) in Chile [ 28 , 29 , 37 ]. In Africa, such as Egypt, Morocco, and Nigeria, the co-epidemic lineages include GI-1 (Mass-type) and GI-13 (793B-type); in addition to this, there are Egyptian IBV variants 1, 2 (GI-23) in Egypt, Moroccan isolates (GI-21) in Morocco, and QX-type (GI-19) strains in Nigeria [ 20 , 49 , 50 , 51 ].…”