Infectious bronchitis virus in different avian physiological systems—A field study in Brazilian poultry flocks

Abstract

Avian infectious bronchitis is a highly contagious viral disease with economic effects on poultry agribusiness. The disease presents multi-systemic clinical signs (respiratory, renal, enteric, and reproductive) and is caused by one coronavirus (infectious bronchitis virus, IBV). Infectious bronchitis virus is classified into different serotypes and genotypes (vaccine strains and field variants). This study aimed to evaluate the occurrence of IBV in commercial poultry flocks from 3 important producing regions in Brazil and to determine the tropism of the main circulating genotypes to 3 different avian physiological systems (respiratory, digestive, urinary/reproductive). Clinical samples with suggestive signs of IBV infection were collected from 432 different poultry commercial flocks (198 from broilers and 234 from breeders). The total number of biological samples consisted of organ pools from the 3 above physiological systems obtained of farms from 3 important producing regions: midwest, northeast, and south. Infectious bronchitis virus was detected by reverse-transcription, real-time PCR of the 5' untranslated region. The results showed 179 IBV-positive flocks (41.4% of the flocks), with 107 (24.8%) from broilers and 72 (16.8%) from breeders. There were similar frequencies of IBV-positive flocks in farms from different regions of the country, most often in broilers (average 54%) compared with breeders (average 30.8%). reverse-transcription was more frequently detected in the digestive system of breeders (40%), and in the digestive (43.5%) and respiratory (37.7%) systems of broilers. Infectious bronchitis virus genotyping was performed by a reverse-transcription nested PCR and sequencing of the S1 gene from a selection of 79 IBV-positive flocks (45 from broilers and 34 from breeders). The majority of the flocks were infected with Brazilian variant genotype than with Massachusetts vaccine genotype. These results demonstrate the predominance of the Brazilian variant (mainly in the enteric tract) in commercial poultry flocks from 3 important producing regions in Brazil.

GammacoronavirusandDeltacoronavirusin Quail

“…After this surveillance, some quail farmers began to vaccinate quail against IBV with live attenuated or inactivated vaccines based on the Massachusetts (Mass) serotype. Nevertheless, IB outbreaks continued to occur in vaccinated quail flocks and were caused by Brazilian field strains of a serotype divergent from the vaccine strain, as previously report in chickens (1,2,10,15,23,24,28,29). Avian coronavirus is a Gammacoronavirus that can replicate on most epithelial surfaces, causing an economically significant poultry disease that affects renal, reproductive, and respiratory systems and causes enteritis (5,6,21,28).…”

Avian infectious bronchitis virus in Africa: a review

“…Thereafter, IB was reported in other parts of the world (De Wit et al 2011). Subsequently, some strains of IBV caused pathology in non-respiratory organs (such as kidney and gonads) (Cavanagh 2003;Balestrin et al 2014).…”

Avian Infectious Bronchitis Virus: Immunogenicity Profiles and New Pathotypes in Brazil - Literature Review

“…Além disso, a partir de 2000 e com base na análise das sequências de nucleotídeos do gene S1 de isolados de campo do VBI foram identificados, no Brasil, genótipos diferentes daqueles em que são classificadas as estirpes americanas, europeias, asiáticas e australianas do VBI (Figura 1) (BALESTRIN et al, 2014;CHACÓN et al, 2011;FELIPPE et al, 2010;FRAGA et al, 2013;MONTASSIER et al, 2006MONTASSIER et al, , 2012VILLARREAL et al, 2007VILLARREAL et al, , 2010. Além disso, foram também identificadas estirpes variantes brasileiras do VBI com relação à sequência de nucleotídeos do gene da nucleoproteína (N) (ABREU et al, 2006).…”

“…Consta também, na literatura, que essas estirpes foram isoladas de surtos de BIG, apresentando diversas manifestações clínicas e patológicas, tais como traqueobronquites e aerossaculites, lesões renais e problemas reprodutivos em fêmeas e em machos. Esses achados clínico-patológicos caracterizaram, assim, o potencial de um amplo espectro de patotipos dentre esses isolados do VBI no Brasil (BALESTRIN et al, 2014;CHACÓN et al, 2011;2014;FELIPPE et al, 2010, FRAGA et al, 2013MONTASSIER et al, 2006MONTASSIER et al, , 2012VILLARREAL et al, 2007VILLARREAL et al, , 2010.…”

“…Nesse caso, deve-se ressaltar que as razões para a aprovação dessas novas vacinas contra o VBI foi o fato de que as estirpes dos genótipos BR-I e BR-II do VBI que circulam no Brasil apresentam baixa identidade com a região S1 da estirpe Massachusetts e reduzida proteção cruzada com relação à estirpe vacinal atenuada Massachusetts (CHACÓN et al, 2011;2016;FERNANDO et al, 2013FERNANDO et al, , 2017FRAGA et al, 2013;MONTASSIER et al, 2006;2012;VILLARREAL et al, 2010). Algumas dessas estirpes dos genótipos BR apresentam tropismo para o trato respiratório, outras para os tratos gastrointestinal, reprodutivo e/ou urogenital (BALESTRIN et al, 2014;CHACÓN et al, 2014;VILLARREAL et al, 2010), o que requer uma abordagem mais abrangente na formulação de vacinas visando à geração de estados de imuno-proteção tanto para os compartimentos de mucosa como sistêmicos das aves hospedeiras.…”