Infectious Bronchitis Coronavirus Infection in Chickens: Multiple System Disease with Immune Suppression

Abstract

In the early 1930s, infectious bronchitis (IB) was first characterized as a respiratory disease in young chickens; later, the disease was also described in older chickens. The etiology of IB was confirmed later as being due to a coronavirus: the infectious bronchitis virus (IBV). Being a coronavirus, IBV is subject to constant genome change due to mutation and recombination, with the consequence of changing clinical and pathological manifestations. The potential use of live attenuated vaccines for the control of IBV infection was demonstrated in the early 1950s, but vaccine breaks occurred due to the emergence of new IBV serotypes. Over the years, various IBV genotypes associated with reproductive, renal, gastrointestinal, muscular and immunosuppressive manifestations have emerged. IBV causes considerable economic impacts on global poultry production due to its pathogenesis involving multiple body systems and immune suppression; hence, there is a need to better understand the pathogenesis of infection and the immune response in order to help developing better management strategies. The evolution of new strains of IBV during the last nine decades against vaccine-induced immune response and changing clinical and pathological manifestations emphasize the necessity of the rational development of intervention strategies based on a thorough understanding of IBV interaction with the host.

Immune Responses in Laying Hens after an Infectious Bronchitis Vaccination of Pullets: A Comparison of Two Vaccination Strategies

“…Depending on the IBV strain, lung, kidney and reproductive tract tissue functions can be impacted [5][6][7][8]. This prompted us to examine whether two commonly used IB vaccination strategies in Canadian layer operations systemically induce an adequate immune response in various body systems.…”

“…The genome is approximately 27.6 kilobases (kb) long and codes for large replicase polyprotein, as well as structural proteins (i.e., spike (S) glycoprotein, membrane (M) protein, nucleocapsid (N) protein, and small envelope protein (E) [2,4]. IB has clinical and pathological consequences in multiple body systems such as respiratory, renal, and reproductive tracts [5][6][7][8]. Initially, IBV targets the upper respiratory epithelial cells and leads to respiratory clinical manifestations [5,9].…”

“…Initially, IBV targets the upper respiratory epithelial cells and leads to respiratory clinical manifestations [5,9]. In the kidneys, the ciliated epithelial cells of nephrons are infected by nephropathogenic IBV strains, which results in clinical signs such as weight loss, watery droppings, and an increased incidence of mortality [7,8,10,11]. In the reproductive tract, IBV targets the cells of oviducts in chickens, potentially causing hens to lay eggs with shell abnormalities and thus decreasing egg production [6,12,13].…”

Factor Influences for Diagnosis and Vaccination of Avian Infectious Bronchitis Virus (Gammacoronavirus) in Chickens

“…The upper respiratory tract (UTI) is the principal site of IBV replication; subsequently, viremia causes viral multiplication to disseminate to other tissue through blood circulation [ 44 , 45 , 46 ]. IBV can be persistent in the long term in the cecal tonsils and kidneys due to the continuous cross-infection of infected or immune flocks [ 44 , 47 ].…”

Metagenomic sequencing determines complete infectious bronchitis virus (avian Gammacoronavirus) vaccine strain genomes and associated viromes in chicken clinical samples

“…Infectious bronchitis virus (IBV) is a gammacoronavirus of the subgenus Igacovirus (ICTV 2020, [ 1 ]) causing an acute, highly contagious upper respiratory tract disease with potential systemic complications in chickens posing a major economic burden on the poultry industry [ 2 ]. The virus replicates in the respiratory, digestive, excretory, and reproductive system, resulting in a variety of pathogenic effects and both respiratory and gastrointestinal viral excretions are possible (reviewed in [ 3 , 4 ]). In addition to respiratory signs, decreased egg quality and production are common.…”