In the clinical acute form vvIBDV , the disease causes significant economic losses due to mortality, reduced performance and immunosupression that lead to increased susceptibility to other diseases. The IBD virus is extremely resistant to environmental conditions and chemicals. Therefore the control of the disease must take into consideration strict biosecurity combined with an effective vaccination program. The following articles review the available knowledge about the disease, the virus, the clinical signs and the role of different elements of the immune system. At the conclusion of these articles, a prevention program is offered, which includes elements of biosecurity and a comprehensive list of vaccination programs for breeders, broilers and commercial layers that in my experience have worked effectively in Asian countries.
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Infectious bursal disease IBD, Gumboro is an acute, highly contagious viral infection in chickens manifested by inflammation and subsequent atrophy of the bursa of Fabricius, various degrees of nephroso-nephritis and immunosuppression. Clinically the disease is seen only in chickens older than 3 weeks. The feathers around the vent are usually stained with faeces containing plenty of urates.
The period of most apparent clinical symptoms and high death rate is at the age of 3 - 6 weeks. IBD could however be observed as long as chickens have a functioning bursa up to the age of 16 weeks. In chickens younger than 3 weeks, IBD could be subclinical, but injured bursa leads to immunosuppression. Also, diarrhoea, anorexia, depression, ruffled feathers, especially in the region of the head and the neck are present.
A natural IBD infection is mostly observed in chickens. Most isolates of the IBD virus in turkeys are serologically different from those in chickens. In premises, once contaminated with the IBD virus, the disease tends to recur, usually as subclinical infection. The dead bodies are dehydrated, often with haemorrhages in the pectoral, thigh and abdominal muscles. Two serotypes are known to exist, but only serotype 1 is pathogenic. The virus is highly resistant to most disinfectants and environmental onditions.
In contaminated premises, it could persist for months and in water, forage and faeces for weeks. The incubation period is short and the first symptoms appear days after infection. The lesions in the bursa of Fabricius are progressive.
In the beginning, the bursa is enlarged, oedematous and covered with a gelatinous transudate. IBD virus has a lymphocidic effect and the most severe injuries are in the lymph follicles of the bursa of Fabricius. Most commonly, IBD begins as a serous bursitis.
IBD lesions undergo various stages of serous haemorrhagic to severe haemorrhagic inflammation. The course of the disease is days and the peak mortality occurs in the middle of this period. In some cases, the bursa is filled with coagulated fibrinous exudate that usually forms casts with the shape of mucosal folds. In birds surviving the acute stage of the disease, the bursa is progressively atrophying.
Microscopically, an atrophy of follicles into the bursa is observed secondary to inflammatory and dystrophic necrobiotic alterations. The kidneys are affected by a severe urate diathesis. In an acute outbreak and manifestation of the typical clinical signs, the diagnostics is not difficult. The diagnosis could be confirmed by detection of typical gross lesions throughout a patho-anatomical study.
The application of live vaccines in chickens is a key point in the prevention of IBD and should be related to the levels of maternal antibodies.
Infectious bursal disease
Diarrhoea with urates in mucus. Post-mortem lesions Oedematous bursa may be slightly enlarged, normal size or reduced in size depending on the stage , may have haemorrhages, rapidly proceeds to atrophy. Haemorrhages in skeletal muscle especially on thighs. Diagnosis Clinical disease - History, lesions, histopathology.
Gumboro Disease - overview
There are two distinct serotypes of the virus, but only serotype 1 viruses cause disease in poultry. Viruses belonging to one of these antigenic subtypes are commonly known as variants, which were reported to break through high levels of maternal antibodies in commercial flocks, causing up to 60 to percent mortality rates in chickens. With the advent of highly sensitive molecular techniques, such as reverse transcription polymerase chain reaction RT-PCR and restriction fragment length polymorphism RFLP , it became possible to detect the vvIBDV, to differentiate IBDV strains, and to use such information in studying the molecular epidemiology of the virus. IBDV genome consists of two segments, A and B, which are enclosed within a nonenveloped icosahedral capsid.
Infectious Bursal Disease, IBD, Gumboro
Good Practice At one time the disease was considered as primarily affecting commercial broiler flocks. A virulent strain appeared in Europe in and since then it has become an important disease of layer and breeding flocks. Widespread vaccination is now conducted, and the immunocompetence status of breeder flocks and hatcheries is determined by the degree of exposure to the virus. Flocks maintained under strict biosecurity are particularly susceptible to field exposure as they would not previously have been exposed to the disease. The virus which causes Gumboro disease usually affects the lymph cells in the cloaca, tonsils and spleen. Image source: www. There are a range of vectors including wild birds, vermin and humans.
Infectious Bursal Disease in Poultry
Infectious bursal disease IBD, Gumboro is an acute, highly contagious viral infection in chickens manifested by inflammation and subsequent atrophy of the bursa of Fabricius, various degrees of nephroso-nephritis and immunosuppression. Clinically the disease is seen only in chickens older than 3 weeks. The feathers around the vent are usually stained with faeces containing plenty of urates. The period of most apparent clinical symptoms and high death rate is at the age of 3 - 6 weeks. IBD could however be observed as long as chickens have a functioning bursa up to the age of 16 weeks.