Turkey Coronavirus
Also Known As: TCoV — Bluecomb Disease Virus — Turkey Enteritis Virus — Transmissible Enteritis Virus — Turkey Coronaviral Enteritis — TCE
Introduction
Turkey Coronaviruses are members of the Coronaviridae family are very closely genetically related to Infectious Bronchitis Virus.
Gastrointestinal disease is the main result of coronavirus infection in turkeys.
TCoVs are not zoonotic.
Distribution
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.
Signalment
Poults are most severely affected by coronavirus infection.
Clinical Signs
Disease is most severe and mortality highest in poults. The most common manifestation is of gastrointestinal disease, causing white, green or yellow 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 birds are often seen to be huddling together. There is a rapid drop in egg production in breeders.
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 may carry it for life.
Diagnosis
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 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.
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 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 IBV can also be used successfully for TCoV.
Treatment
Ameliorative therapies include supplying heat, calf milk replacer, potassium chloride added to milk suspension, antibiotics and copper sulphate can all be used to help the affected birds.
Control
No vaccine is available but birds that recover are immune for life.
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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References
Cook, J. (2007) Coronaviridae. In: Poultry Diseases, 6th Edition (eds. Pattison, M., McMullin, P., Bradbury, J., Alexander, D.) Saunders, Elsevier, pp 340-349
Guy, J.S. (2008) Turkey Coronavirus Enteritis. In: Diseases of Poultry, 12th Edition (eds. Saif, Y.M., Fadly A.M., Glissen J.R., McDougald L.R., Nolan L.K., Swayne D.E.) Wiley-Blackwell, pp 330-338
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This article was originally sourced from The Animal Health & Production Compendium (AHPC) published online by CABI during the OVAL Project. The datasheet was accessed on 21 June 2011. |
This article was reviewed by Prof Dave Cavanagh BSc, PhD, DSc on 23/08/11.