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Also Known As – '''''Gumboro disease''''' – '''''Infectious Avian Nephrosis''''' – '''''Infectious Bursitis'''''
[[Category:To Do - Steph]]
Caused By - ''Infectious Bursal Disease Virus'' – ''IBDV''
==Introduction==
Infectious bursal disease is a '''highly contagious [[Viruses | viral]]''' disease of birds caused by an avibirnavirus.
The virus can survive in a wide range of environmental conditions, remains viable from pH 2-12 and is activated only in 70⁰C for 30minutes. It is also resistant to some disinfectants.
IBDV can '''survive''' in poultry houses for '''122 days''' after removal of infected birds and in contaminated water or feed for 52 days.
Of the two known serotypes of IBDV, only '''Serotype I''' is pathogenic, causing bursal disease in '''chicks''' by '''selectively''' infecting the cells of the '''[[Bursa of Fabricius]]'''.
This disease is '''notifiable''' to the World Organisation for Animal Health [www.oie.int/ (OIE)]
==Signalment==
IBDV can infect chickens, ducks, geese and guineafowl but only '''chickens''' show clinical signs of disease.
Lethal infection is usually seen in chicks '''3-6 weeks old''' due to IBDV being to restricted to cells at a certain stage of development.
==Distribution==
Worldwide
The main route of transmission is '''faecal-oral''' and the virus is shed for up to 2 weeks post-infection in large amounts.
The role of wild birds as a mechanical vector is poorly understood.
IBDV can also be spread by the [[Nematodes | nematode]] parasite, Alphitobius diaperinus.
IBD is not thought to be zoonotic.
==Clinical Signs==
One of the main effects of IBDV infection is '''mortality'''. This can be in chicks at 3-6 weeks old or later on as a result of severe '''immunosuppression''' allowing other disease to proliferate, in particular, [[Escherichia coli | ''E. coli'']] and gangrenous dermatitis.
Viral virulence varies massively and thus so can disease severity. Initial outbreaks are usually the most severe and recurrent disease milder with lower mortality.
'''[[Diarrhoea]]''', recumbency, '''dehydration''', neurological signs and ruffling of the feathers form a typical presentation of IBDV.
==Diagnosis==
Acute disease is usually recognised in a flock by '''rapid onset, high morbidity''' ([[Diarrhoea | diarrhoea]]) with a spike in mortality and '''rapid recovery'''. Diagnosis is confirmed by post-mortem or laboratory testing.
On '''post-mortem examination''', carcasses are '''dehydrated''', often with '''darkened pectoral muscles'''. Many '''petechiae''' may be present in the thigh and pectoral muscle masses.
Mucus may also be present within the [[Alimentary System Overview - Anatomy & Physiology | intestines]]. In advanced disease, renal changes may be evident due to prolonged dehydration.
Grey foci may also be present on an enlarged [[Spleen - Anatomy & Physiology | spleen]].
The [[Bursa of Fabricius | '''bursa of fabricius''']] will usually initially be '''enlarged, oedematous and haemorrhagic.''' Its colour turns from white to cream and a '''yellow transudate''' covers its serosa early in infection.
From 7-8 days following infection, the [[Bursa of Fabricius | bursa]] '''atrophies''' and becomes approximately '''1/3''' of its original weight.
IBDV antigen can be detected in cloacal bursa or splenic samples by '''Agar Gel Precipitation''' or '''Immunofluorescence'''.
'''Antibody [[ELISA testing | ELISA]]''' can be used for serological diagnosis within a flock. A mimimum of 30 samples is required.
==Treatment==
'''No treatment''' is available and recovery is usually rapid in an infected flock.
==Control==
'''Hygienic''' measures with appropriate disinfectants are imperative.
'''Vaccination''' is also usually required. Both live and inactivated forms are available. Timing is difficult due to interference of maternal immunity, but oil adjuvanted vaccines can extend maternal immunity to 5 weeks. Vaccination can cause immunosuppression and a degree of bursal damage.
==References==
<references/>
Animal Health & Production Compendium, '''Infectious Bursal Disease datasheet''', accessed 05/06/2011 @ http://www.cabi.org/ahpc/
Animal Health & Production Compendium, '''Infectious Bursal Disease Virus datasheet''', accessed 05/06/2011 @ http://www.cabi.org/ahpc/