Avian infectious bronchitis virus
Encyclopedia
Avian infectious bronchitis virus (IBV) http://www.ictvdb.rothamsted.ac.uk/ICTVdB/03.019.0.01.001.htm is a coronavirus
Coronavirus
Coronaviruses are species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae. Coronaviruses are enveloped viruses with a positive-sense single-stranded RNA genome and a helical symmetry. The genomic size of coronaviruses ranges from approximately 16 to 31...

 which infects chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

, causing the associated disease, infectious bronchitis
Avian infectious bronchitis
Avian infectious bronchitis is an acute and highly contagious respiratory disease of chickens. The disease is caused by avian infectious bronchitis virus , a coronavirus, and characterized by respiratory signs including gasping, coughing, sneezing, tracheal rales, and nasal discharge. In young...

 (IB. It is a highly infectious avian pathogen which affects the respiratory tract
Respiratory tract
In humans the respiratory tract is the part of the anatomy involved with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...

, gut
Gut (zoology)
In zoology, the gut, also known as the alimentary canal or alimentary tract, is a tube by which bilaterian animals transfer food to the digestion organs. In large bilaterians the gut generally also has an exit, the anus, by which the animal disposes of solid wastes...

, kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

 and reproductive system
Reproductive system
The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes...

s of chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

s.

Classification

IBV is a coronavirus
Coronavirus
Coronaviruses are species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae. Coronaviruses are enveloped viruses with a positive-sense single-stranded RNA genome and a helical symmetry. The genomic size of coronaviruses ranges from approximately 16 to 31...

, recently relocated to genus Gammacoronavirus http://ictvonline.org/virusTaxonomy.asp?version=2009, with a non-segmented, positive-sense single-stranded RNA genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

.

Respiratory system

When inhaled, virus will attach to glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...

 receptors containing sialic acid
Sialic acid
Sialic acid is a generic term for the N- or O-substituted derivatives of neuraminic acid, a monosaccharide with a nine-carbon backbone. It is also the name for the most common member of this group, N-acetylneuraminic acid...

 on ciliated epithelial cells of the respiratory epithelium. The respiratory replication will result in loss of ciliary activity http://www.youtube.com/watch?v=40Vxq5I22pM&feature=related, mucus acumulation, necrosis and desquamation, causing respiratory distress, râles and asphyxia
Asphyxia
Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...

. Local virus replication will result in viremia, spreading the infection into other tissues and organs. Other respiratory diseases of chickens (Mycoplasma gallisepticum
Mycoplasma gallisepticum
Mycoplasma gallisepticum is a bacterium belonging to the class Mollicutes and the family Mycoplasmataceae. It is the causative agent of chronic respiratory disease in chickens and infectious sinusitis in turkeys, chickens, game birds, pigeons, and passerine birds of all ages.-Transmission:MG is...

, avian infectious laryngotracheitisGallid herpesvirus 1
Gallid herpesvirus 1
Gallid herpesvirus 1 is a virus of the family Herpesviridae that causes avian infectious laryngotracheitis. It was originally recognized as a disease of chickens in the United States in 1926...

, Newcastle disease
Newcastle disease
Newcastle disease is a contagious bird disease affecting many domestic and wild avian species. First found in Newcastle, United Kingdom in 1926, then by Burnet in 1943 in Australia in connection with laboratory infection where the virus was isolated from a ocular discharge of a patient to show the...

, Avian metapneumovirus 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
Nephron
The renal tubule is the portion of the nephron containing the tubular fluid filtered through the glomerulus. After passing through the renal tubule, the filtrate continues to the collecting duct system, which is not part of the nephron....

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

Reproductive system

Viremic IBV will also reach the oviduct
Oviduct
In non-mammalian vertebrates, the passageway from the ovaries to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body...

, 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. 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.
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