Avian Infectious Bronchitis Virus

Abstract

Avian infectious bronchitis (IB) is caused by avian infectious bronchitis virus (IBV) belonging to Coronaviridae family. The disease is prevalent in all countries with almost 100% incidence rate. Chicken and commercially reared pheasant are the natural host for IBV. Virus causes respiratory diseases, poor weight gain, feed efficiency in broiler, damage to oviduct, and abnormal egg production in mature hens resulting in economic losses. IBV also replicates in tracheal and renal epithelial cells leading to prominent tracheal and kidney lesions. Virus undergoes spontaneous mutation leading to continual emergence of new variants. The effectiveness of immunization program is diminished because of poor cross-protection among the serotypes. Identification of circulating serotypes is important in controlling IBV infection. Toll-like receptor 3 (TLR3) and TLR21 are involved in early recognition of virus resulting in induction of inflammatory cytokines. Both humoral and cellular immune responses are important in the control of infection. Humoral immunity plays an important role in recovery and clearance of viral infection. IBV-specific cytotoxic T lymphocytes induce lysis of IBV-infected cells. Effective diagnostic tools are required at field level to identify different IBV variants. Embryonated chicken eggs are effective model for virus isolation. Identification by other specific methods like virus neutralization (VN), hemagglutination inhibition (HI), enzyme linked immunosorbent assay (ELISA), immunohistochemistry, or nucleic acid analysis or by electron microscopy is also indispensable. VN test in tracheal organ culture is the best method for antigenic typing for surveillance purposes. Continuous epidemiological surveillance, strict biosecurity measures, and vaccine effective against various serotypes are necessary for controlling IB in chickens.

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

“…Conversely, after vaccinating with high immunogenic IBV variants, CV percentage is commonly less than 45% [ 32 ]. In this situation, a series of multiple live vaccinations are initially used to boost the birds for 100% seroconversion before killed vaccination, which is a major principle for influence on the persistence of titers rather than measure of percent CV [ 41 , 42 ]. In serology detection systems, ELISA tests are commonly used to determine the trend analysis of protective antibody titers by good vaccination or unexpected serology, which is caused by virulent serotype or variant of IBV.…”

“…Despite this, novel, more infectious variants have emerged, but the amino acid sequence of the spike protein (S1) and genome are unchanged. Cross-reaction is particularly protected in chickens because of the interaction of multiple vaccinations covered by more than one included serotype [ 42 , 81 ]. Birds are challenged by new serotypes that differ from the serotypes of selection vaccines, so they are not fully protected against the prevalent serotype.…”

Drawing Comparisons between SARS-CoV-2 and the Animal Coronaviruses

“…Respiratory animal CoVs, such as CRCoVs, are primarily transmitted via droplet infection, or direct contact with infected dogs, while porcine respiratory coronaviruses (PRCoVs) are derived from enteric CoV TGEV inside the porcine host [ 20 , 42 , 122 ]. Certain CoVs, such as bovine CoV (BCoV) in cattle and IBV of poultry, are shed in both feces and respiratory secretions [ 20 , 123 , 124 ]. Ocular transmission of BCoV, albeit in low titers, has been reported in a single study [ 125 ].…”

“…Prolonged/recurrent shedding of virus/viral RNA without clinical signs, or subclinically from animals, has been reported with certain animal CoVs, mirroring similar findings with SARs-CoV-2; however, these shedding patterns might not always reflect the transmission potential of CoVs [ 17 , 18 , 19 , 20 , 21 , 124 ]. Indirect transmission of CoVs through contaminated surfaces/fomites/environment, feed/water, and/or people have been well documented in animals [ 14 , 17 , 18 , 19 , 20 , 21 , 22 , 42 , 123 , 124 ].…”

Coronaviruses in farm animals: Epidemiology and public health implications

“…The IBV is a highly contagious virus of the upper respiratory tract of chickens, leading to 100% morbidity and a mortality rate ranging from 0% to 82% depending upon several factors such as the age of the birds, their immune status, and the involvement of secondary pathogens (Ramakrishnan & Kappala, 2019). The IBV infects chickens of all ages, although young are most susceptible, and may die directly from the IBV infection or from mixed infections mainly caused by Escherichia coli , leading to heavy losses to the breeding industry (Jackwood, 2012).…”