Infectious bronchitis virus (IBV) is a species of virus from the genus ''

Gammacoronavirus ''Gammacoronavirus'' (Gamma-CoV) is one of the four genera (''Alphacoronavirus, Alpha''-, ''Betacoronavirus, Beta-'', ''Gamma-'', and ''Deltacoronavirus (genus), Delta-'') of coronaviruses. It is in the subfamily ''Orthocoronavirinae'' of the fa ...

'' that infects

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s. It causes

avian infectious bronchitis Avian infectious bronchitis (IB) is an acute and highly contagious respiratory disease of chickens. The disease is caused by avian infectious bronchitis virus (IBV), a coronavirus (Coronaviridae, Orthocoronavirinae, genus ''Gammacoronavirus'', sub ...

, a highly infectious disease that affects the

respiratory tract The respiratory tract is the subdivision of the respiratory system involved with the process of conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respirato ...

, gut,

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

and

reproductive system The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are al ...

. IBV affects the performance of both meat-producing and egg-producing chickens and is responsible for substantial economic loss within the poultry industry.

Classification

IBV is in the genus ''

'', or group 3, with a non-segmented, positive-sense single-stranded RNA

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

. It was previously the type species of its genus '' Igacovirus''. When there was only one genus of coronaviruses, the genus ''Coronavirus'', it was the type species of the group of all known coronaviruses.

Recombination

When two strains of

coronavirus Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the comm ...

IBV infect a host they may recombine during genome replication. Recombination appears to contribute to the genetic variation of the IBV

found in nature.

Pathology

Respiratory system

When inhaled, virus will attach to

glycoprotein Glycoproteins are proteins which contain oligosaccharide (sugar) chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known a ...

receptors containing

sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone. The term "sialic acid" () was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this group is ''N''-acetylneuraminic acid ...

on ciliated epithelial cells of the respiratory epithelium. The respiratory replication will result in loss of ciliary activity, mucus accumulation, necrosis and desquamation, causing respiratory distress, râles and

asphyxia Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects all the tissues and organs, some more rapidly than others. There are m ...

. Local virus replication will result in viremia, spreading the infection into other tissues and organs. Other respiratory diseases of chickens (''

Mycoplasma gallisepticum ''Mycoplasma gallisepticum'' (MG) is a bacterium in the class Mollicutes and the family Mycoplasmataceae. It causes chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys, chickens, game birds, pigeons, and passerin ...

'', avian infectious laryngotracheitis ( Gallid alphaherpesvirus 1), Newcastle disease (avian paramyxovirus 1),

Avian metapneumovirus Avian metapneumovirus (aMPV), also known as turkey rhinotracheitis or swollen head syndrome, causes a variety of disease syndromes in birds, depending on the bird species and virus type (A, B, C or D). First detected in 1978 in South Africa, the ...

infection may be confused clinically to infectious bronchitis.

Kidney

Through viremia, some nephrotropic strains (most of high virulence) could infect the kidney epithelium in tubules and

nephron The nephron is the minute or microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and a cup-shaped structu ...

, causing kidney failure. At gross examination, kidneys may appear swollen and pale in color and with urates in

ureters The ureters are tubes composed of smooth muscle that transport urine from the kidneys to the urinary bladder. In an adult human, the ureters typically measure 20 to 30 centimeters in length and about 3 to 4 millimeters in diameter. They are lin ...

Reproductive system

In hens, the viremic IBV will also reach the

oviduct The oviduct in vertebrates is the passageway from an ovary. In human females, this is more usually known as the fallopian tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, or will dege ...

, causing lesions in the magnum (the egg-white gland) and in the uterus (the egg-shell gland), leading to a sharp decline of egg production, shell-less, fragile or roughened shells eggs (uterus lesion) with watery whites (magnum lesion). Infection of chickens at puberty, during the oviduct development, will impede oviduct formation and destroy future laying capacity, resulting in "false layers". However, other diseases affecting layer chickens could lead to that condition.

Vaccines

There are both

attenuated vaccine An attenuated vaccine (or a live attenuated vaccine, LAV) is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable (or "live"). Attenuation takes an infectious agent and alters it so that it becomes harmless or le ...

s and

inactivated vaccine An inactivated vaccine (or killed vaccine) is a type of vaccine that contains pathogens (such as virus or bacteria) that have been killed or rendered inactive, so they cannot replicate or cause disease. In contrast, live vaccines use pathogens ...

s available. Their effectiveness is diminished by poor cross-protection. The nature of the protective immune response to IBV is poorly understood, but the surface spike protein, the amino-terminal S1 half, is sufficient to induce good protective immunity. Experimental vector IB vaccines and genetically manipulated IBVs—with heterologous spike protein genes—have produced promising results, including in the context of in ovo vaccination.