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==Introduction==

==Introduction==

Turkey Coronaviruses are members of the '''[[Coronaviridae]]''' family and fall into two categories: '''Bovine Coronavirus-like turkey isolates (TCoV-B)''' and '''IBV-like Turkey Coronaviruses (TCoV-I).''' The TCoV-I viruses are very closely genetically related to '''[[Avian Infectious Bronchitis|Infectious Bronchitis Virus]].'''

Turkey Coronaviruses are members of the '''[[Coronaviridae]]''' family are very closely genetically related to '''[[Avian Infectious Bronchitis|Infectious Bronchitis Virus]].'''

'''[[Avian Alimentary System - Anatomy & Physiology|Gastrointestinal]] [[:Category:Alimentary Diseases - Birds|disease]]''' is the main result of coronavirus infection in turkeys.

'''[[Avian Alimentary System - Anatomy & Physiology|Gastrointestinal]] [[:Category:Alimentary Diseases - Birds|disease]]''' is the main result of coronavirus infection in turkeys.

==Distribution==

==Distribution==

Turkey Coronaviral enteritis, (TCE) caused by TCoV-B, has only been confirmed in the '''USA and Canada''' but TCoV-I has recently been isolated in Britain.

Turkey Coronaviral enteritis, (TCE) has been reported in North American, Europe (including the UK) and Brazil.

Transmission is via the '''faecal-oral route''' and can be spread by people, vehicles and vermin.

Transmission is via the '''faecal-oral route''' and can be spread by people, vehicles and vermin.

==Signalment==

==Signalment==

'''Poults''' are most severely affected by coronavirus infection.  

'''Poults''' are most severely affected by coronavirus infection.  

==Clinical Signs==

==Clinical Signs==

Disease is most severe and mortality highest in poults. The most common manifestation is of [[:Category:Alimentary Diseases - Birds|gastrointestinal disease]], causing '''white, green or yellow [[Diarrhoea|diarrhoea]], anorexia, inappetance and malaise.''' Concurrent dehydration, hypothermia, pyrexia and weakness may occur. The skin of adult birds is often seen to darken. Birds often exhibit a '''drooped wing appearance'''. Morbidity is usually 100% and bird are often seen to be huddling together.  

Disease is most severe and mortality highest in poults. The most common manifestation is of [[:Category:Alimentary Diseases - Birds|gastrointestinal disease]], causing '''white, green or yellow [[Diarrhoea|diarrhoea]], anorexia, inappetance and malaise.''' Concurrent dehydration, hypothermia, pyrexia and weakness may occur. The skin of adult birds is often seen to darken. Birds often exhibit a '''drooped wing appearance'''. Morbidity is usually 100% and bird are often seen to be huddling together. There is a rapid drop in egg production in breeders.

 

Neurological disease develops in some birds, producing a head tilt, depression and ataxia.

TCoV is also '''one of a group of pathogens''' associated with '''Poult Enteritis and Mortality Syndrome (PEMS)''' which affects poults up to '''one month old''' in the USA causing huge spikes in mortality.

TCoV is also '''one of a group of pathogens''' associated with '''Poult Enteritis and Mortality Syndrome (PEMS)''' which affects poults up to '''one month old''' in the USA causing huge spikes in mortality.

Recovery begins after approximately 5 days but it may take several weeks to regain weight. Recovered birds will not become ill again but do '''shed the virus for months afterwards and carry it for life.'''  

Recovery begins after approximately 5 days but it may take several weeks to regain weight. Recovered birds will not become ill again but do '''shed the virus for months afterwards and may carry it for life.'''  

==Diagnosis==

==Diagnosis==

Clinical signs are suggestive but not diagnostic of TCE or PEMS. Starvation and other viral pathogens can appear very similarly.

Clinical signs are suggestive but not diagnostic of TCE or PEMS. Starvation and other viral pathogens can appear very similarly.

At '''post-mortem''', birds with TCE have '''swollen, pale, flaccid duodenums with a mononuclear cell infiltrate''' intraluminally. Epithelial lesions are most severe in the jejunum. '''Villous stunting and atrophy''' is evident on histological analysis. Nucleoli may appear pronounced in infected cells. Goblet cells decrease in number and epithelial separation may be seen.<ref>Adams, N. R., Ball, R. A., Hofstad, M. S (1970) '''Intestinal lesions in transmissible enteritis of turkeys.''' ''Avian Diseases'', 14:392-399.</ref>

At '''post-mortem''', birds with TCE have '''swollen, pale, flaccid duodenums and jejunums with a mononuclear cell infiltrate''' intraluminally. Epithelial lesions are most severe in the jejunum. '''Villous stunting and atrophy''' is evident on histological analysis. Nucleoli may appear pronounced in infected cells. Goblet cells decrease in number and epithelial separation may be seen.<ref>Adams, N. R., Ball, R. A., Hofstad, M. S (1970) '''Intestinal lesions in transmissible enteritis of turkeys.''' ''Avian Diseases'', 14:392-399.</ref>

'''Electron microscopy''' can be used to look for Coronaviral particles in gut contents but this is often challenging. '''Indirect [[Immunofluorescence]] and immunoperoxidase staining''' using antibodies from convalescent turkeys can demonstrate TCoV in intestinal sections. A '''modified [[ELISA testing|ELISA]]''' is capable of detecting antibodies to TCoV, derived from a commercially available test, which is promising for disease screening in the future. '''Reverse PCR''' designed for [[Avian Infectious Bronchitis|IBV]] can also be used successfully for TCoV-Is.

'''Electron microscopy''' can be used to look for coronaviral particles in gut contents but this is often challenging. '''Indirect [[Immunofluorescence]] and immunoperoxidase staining''' using antibodies from convalescent turkeys can demonstrate TCoV in intestinal sections. A '''modified [[ELISA testing|ELISA]]''' is capable of detecting antibodies to TCoV, derived from a commercially available test, which is promising for disease screening in the future. '''Reverse PCR''' designed for [[Avian Infectious Bronchitis|IBV]] can also be used successfully for TCoV.

==Treatment==

==Treatment==

No [[Vaccines|vaccine]] is available but birds that recover are immune for life.

No [[Vaccines|vaccine]] is available but birds that recover are immune for life.

Because of the carrier state, farms should be '''depopulated''' after a TCE outbreak. Access to farms should be limited as part of '''general biosecurity''' measures and it should be considered that marketed birds have unknown TCoV status.

Because of persistence within the flock, farms should be '''depopulated''' after a TCE outbreak. Access to farms should be limited as part of '''general biosecurity''' measures and it should be considered that marketed birds have unknown TCoV status.

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