Download Infectious Bursal Disease Jul 2011

Infectious bursal disease
Fact sheet
Introductory statement
Infectious bursal disease (IBD) or Gumboro disease is an acute, contagious viral infection in chickens. It
primarily causes severe immunosuppression in young chickens and disease and mortality in 3–6 week old
chickens1. IBD causes lymphoid depletion in wild birds but generally infection is sub-clinical.
Infectious bursal disease virus (IBDV) multiplies rapidly in developing B lymphocytes in the bursa of Fabricius
leading to immunosuppression and increase susceptibility to other diseases 2. IBD has been observed for over
40 years but it continues to be a potential threat to the Australia poultry industry and worldwide.
Aetiology
IBDV belongs to the genus Avibirnaviurs of the family Birnaviridae3. The virus genome consists of two
segments of double stranded RNA. There are two recognised serotypes of IBDV (1 and 2). Serotype 1 is
pathogenic only to chickens, and can be further divided into classical virulent, attenuated, antigenic virulent
and very virulent IBD virus based on their virulence and antigenicity 2. Recent serological evidence of serotype
1 IBDV infection in wild birds suggests that wild birds may place a role in the epidemiology of IBDV by serving
as a reservoir for the virus3. Serotype 2 viruses are naturally avirulent and do not cause clinical disease in
chickens and turkeys4.
Natural hosts
The natural hosts of IBDV are the domestic fowl including chickens and turkeys. Other wild birds like healthy
ducks, guinea fowl, quail and pheasants have been found to be naturally infected by serotype 1 IBDV5. There
is no evidence that IBD virus can infect other animals, including humans1.
World distribution
Classical serotype 1 IBDV strains are endemic throughout the world. Very virulent IBD is endemic in parts of
southern Asia, Indonesian island region, South America, Middle East and Africa 1.
Occurrence in Australia
IBD was first identified in Australia in 1974. The classical strains reported in Australia are genetically different
from the classical strains found overseas.
Epidemiology
Birds that are 3-6 weeks of age are the most susceptible to clinical disease. The IBDV is susceptible to
mutation, highly resistant to heat and chemicals and can persist in faeces, bedding, contaminated feed and
water for up to four months in certain conditions. Mode of transmission is primarily through faecal oral route,
with aerosol spread considered to be less important. There is no evidence that IBD can be transmitted in
embryos or semen1.
The viral incubation period is about 2-3 days and can be shed as soon as 24 hours following infection and can
last up to two weeks1. The disease is highly contagious, can spread through the movement of poultry
products, equipment, feed bags, vehicles and people, and to a lesser extent, through aerosols of
dust1.Transmission of IBD between wild birds and poultry is likely to be due to scavenging of dead chickens,
ingestion of contaminated water, or exposure of respiratory or conjunctival membranes to contaminated
poultry dust5.
Classical serotype 1 IBD infection in wild birds is believed to be subclinical. Recent research shows that wild
birds play a role in the epidemiology of IBDV by acting as a reservoir for the virus 3.
Serotype 1 IBDV antibodies have been detected in Australian wild birds including carrion crows and rock
pigeons which were found around barns and domestic chicken flocks4. There is no data that suggest IBDV is
transmitted by wild birds in Australia, however direct or indirect transmission of the virus between wild birds
and domestic chickens probably occurs4. It is strongly believed that the serotype IBDV 1 is highly host specific
to chickens. However, IBDV has been isolated from a sparrow in China, which suggests that wild birds may
have an important role in the natural history of IBDV.
Reports have shown that serotype 2 of IBDV is more prevalent in many species of wild birds, with the natural
host considered to be turkeys4.
Clinical signs
The susceptibility of birds (other than chickens) to serotype 1 IBD viruses is uncertain 1. IBD infection in wild
birds is believed to be subclinical with no associated clinical signs. In turkeys there is no data that reports
infections with very virulent IBD (vvIBD) or exotic antigenic variant IBD (eavIBD).
In chickens however, acute forms of infection causes depression, debilitation and dehydration 1. Infected birds
can produce watery diarrhoea and develop swollen and blood-stained vents. Mortality rates vary with
virulence of the strain involved, the challenge dose as well as the flock's ability to mount an effective immune
response1. Infection with less virulent strains may not show overt clinical signs but the chickens may develop
fibrotic or cystic bursa of Fabricus that can prematurely atrophy (before six months of age) and/or may die of
infections by agents that would not usually cause disease in immunocompetent chickens.
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Diagnosis
In diagnosing IBD in wild birds the agar gel precipitation (AGP) test has been documented. The virus
neutralisation test is more recommended for use to determine the prevalence of antibodies to serotype 1 and
2 of IBDV4.
The virus neutralisation test is considered advantageous for screening as it has higher sensitivity and
specificity5. In addition, when using the AGP test for examining the seroprevalence of IBDV in wild birds,
problems such as cross reacting of the serotype 1 and 2 of IBDV can occur 4.
Clinical pathology
There is no reported information associated with clinical pathology in wild birds infected with IBD viruses.
Pathology
No macroscopic lesions were observed at necropsy in the bursa of Fabricius or in secondary lymphoid organs
in artificially inoculated wild birds. Furthermore, no evidence of disease, changes in behaviour, or mortality
were evident.
Laboratory diagnostic specimens
Specimen samples that can be collected for diagnosis are fresh serum, caecal tonsils and kidney tissues3, 4.
Laboratory procedures
See diagnosis.
Treatment
No treatment is necessary as infection does not cause disease in wild birds.
Prevention and control
IBDV is unlikely to be persistent in wild bird population; therefore the main source of IBDV would be present
on poultry farms or the surrounding environment as a result of contamination from infected and shedding
chickens. The primary focus for prevention and control should hence be on biosecurity of poultry farms, and
can include vaccination. IBD vaccines that contain both classical and variant IBD serotype 1 viruses are now
licensed1. Active immunisation with classical serotype 1 vaccine provides good protection against vvIBDV 6.
Control should also be implemented in keeping poultry stock in a closed system to prevent contact with wild
birds that may then act as a source of infection for other susceptible poultry flocks. The species that may be
implicated in the spread of IBD are ducks, gulls, crows and pigeons5. Though there is very little evidence that
demonstrates that there is spread between farms in outbreaks.
Surveillance and management
Wildlife disease surveillance in Australia is coordinated by the Wildlife Health Australia. The National Wildlife
Health Information System (eWHIS) captures information from a variety of sources including Australian
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government agencies, zoo and wildlife parks, wildlife carers, universities and members of the public.
Coordinators in each of Australia's States and Territories report monthly on significant wildlife cases identified
in their jurisdictions. NOTE: access to information contained within the National Wildlife Health Information
System dataset is by application. Please contact [email protected].
There are currently no formal surveillance programs for IBDV in wild birds in Australia. Poultry farmers,
particularly back-yard poultry farmers should be encouraged to protect their stock from exposure to wild
birds to minimise risk of infection. Evidence of infection or exposure of Australian wild birds to IBDV would be
considered interesting and unusual and would be captured in the National Wildlife Health Information System
(eWHIS). We would encourage any readers with definitive information to submit these data to the system.
Statistics
In 1983 serum samples were collected from 392 native water birds of 11 species from several areas of
Western Australia during the period of 1977 to 19797. The samples were used for serological tests like plaque
reduction and haemagglutination-inhibition (HI) tests as well as AGP tests. Sera from 7 species were tested
with plaque reduction tests for serotype 1 and gave positive results in 2/4 fleshy footed shearwaters, 1/1
silver gull and 11/38 black ducks5.
Human health implications
There is no scientific evidence that indicates IBD virus can infect humans.
Conclusions
IBDV is not considered a direct risk to wild bird populations, as there are few reports of IBD causing
devastation in wild bird populations and thus their possible ecological impact appears to be of little
importance5. The epidemiological significance in several studies have concluded that different free living and
migratory bird species might naturally become infected by IBDV strains that are potentially pathogenic to
chickens2,7. In addition, different bird species naturally infected with IBDV not only could become the carriers
or reservoirs in IBDV transmission but also may play a role in the emergence of variant IBDV2. A recent study
of wild birds in Africa has concluded that the close relationship of wild birds and chicken origin IBDV based on
the genomic structure indicates that wild birds can play a role in the epidemiology and spread of IBDV in
nature8.
This demonstrates that more research and surveys for seroprevalence would contribute to understanding the
epidemiological impact of wild birds carrying IBD and its importance to poultry health.
References and other information
1.
2.
Animal Health Australia (2009). Disease strategy: Infectious bursal disease caused by very virulent
IBD virus or exotic antigenic variant strains of IBD virus (Version 3.0), Australian Veterinary
Emergency Plan (AUSVETPLAN), Edition 3, Primary Industries Ministerial Council, Canberra, ACT.
http://www.animalhealthaustralia.com.au/fms/Animal%20Health%20Australia/AUSVETPLAN/IBD22PROOF(2Jun09).pdf Accessed 14 May 2010
Wang YS, Wang ZC, Tang YD et al. Comparison of four infectious bursal disease viruses isolated from
different bird species. Archives of Virology. 2007; 152(10):1787–1797.
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3.
4.
5.
6.
7.
8.
Jin Jeon W, Lee EK, Joh SJ et al. Very virulent infectious bursal disease virus isolated from wild birds in
Korea Epidemiological implications. Virus Research. 2008; 137:153-156
Motohiko, O, Takashi, W, Tsuyoshi, Y et al. Seroprevalence of Infectious Bursal Disease in Free-Living
Wild Birds in Japan. Journal of Veterinary Medical Science. 1998; 60: 11: 1277-1279.
Gilchrist, P. Involvement of free-flying wild birds in the spread of the viruses of avian influenza,
Newcastle disease and infectious bursal disease from poultry products to commercial poultry.
World’s Poultry Science Journal. 2005; 61; 198-210.
World Organisation of Animal Health (OIE). Chapter 2.3.12: Infectious Bursal Disease (Gumboro
disease). Manuals of diagnostic tests and vaccines for terrestrial manuals. 2008.
http://www.oie.int/esp/normes/mmanual/2008/pdf/2.03.12_IBD.pdf Accessed 4 May 2010
Wilcox, G.E, Flower, R.L.P, Baxendale, W and Mackenzie, J.S. Serological survey of wild birds in
Australia for the prevalence of antibodies to egg drop syndrome 1976 (EDS-76) and infectious bursal
disease viruses. Avian pathology. 1983; 12; 135-139.
Kasanga CJ, Yamaguchi T, Wambura PN, Munangandu HM, Ohya K, Fukushi H (2008) Detection of
infectious bursal disease virus (IBDV) genome in free-living pigeon and guinea fowl in Africa suggests
involvement of wild birds in the epidemiology of IBDV, Virus Genes 36;521-529
Other information
Adewuyi OA, Durojaiye OA and Adene DF (1989). The status of guinea fowls (Numida meleagris) in the
epidemiology of infectious bursal disease (IBD) of poultry in Nigeria. Journal of Veterinary Medicine B36:43–
48.
Firth GA (1974). Occurrence of an infectious bursal syndrome within an Australian poultry flock. Australian
Veterinary Journal 50:128–130.
Lukert PD and Saif YM (2003). Infectious bursal disease. In: Diseases of Poultry, 11th edition, Saif YM, Barnes
HJ, Glisson JR, Fadly AM, McDougald LR and Swayne DE (eds), Iowa State Press, Ames, Iowa, 161–179.
van den Berg TP, Ona A, Morales D and Rodriguez JF (2001). Experimental inoculation of game/ornamental
birds with a very virulent strain of IBDV. In: II. International Symposium on Infectious Bursal Disease and
Chicken Infectious Anaemia, Institut fur Geflugelkrankheiten, Giessen, Germany, 236–246.
Acknowledgements
We are very grateful to the many people who had input into this fact sheet and would specifically like to
thank Pato Chan and Leigh Nind.
Updated: 20 July 2011
To provide feedback on this fact sheet
We are interested in hearing from anyone with information on this condition in Australia, including laboratory
reports, historical datasets or survey results that could be added to the National Wildlife Health Information
System. If you can help, please contact us at [email protected].
Wildlife Health Australia would be very grateful for any feedback on this fact sheet. Please provide detailed
comments or suggestions to [email protected]. We would also like to hear from you if
WHA Fact sheet: Infectious bursal disease | July 2011 | 5
you have a particular area of expertise and would like to produce a fact sheet (or sheets) for the network (or
update current sheets). A small amount of funding is available to facilitate this.
Disclaimer
This fact sheet is managed by Wildlife Health Australia for information purposes only. Information contained
in it is drawn from a variety of sources external to Wildlife Health Australia. Although reasonable care was
taken in its preparation, Wildlife Health Australia does not guarantee or warrant the accuracy, reliability,
completeness, or currency of the information or its usefulness in achieving any purpose. It should not be
relied on in place of professional veterinary consultation. To the fullest extent permitted by law, Wildlife
Health Australia will not be liable for any loss, damage, cost or expense incurred in or arising by reason of any
person relying on information in this fact sheet. Persons should accordingly make and rely on their own
assessments and enquiries to verify the accuracy of the information provided.
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