engleski

Infectious bursal disease: the re-emerging problem

Infectious bursal disease (IBD), also known as Gumboro disease, hit the poultry production twice in the last several decades. The first time in 1962 when the disease was recognised, causing around 5% mortality in chickens aged three weeks and older, and severe, prolonged immunosuppression of chickens infected at an early age. The vaccines became available and during following decades the disease turned to mainly subclinical infection causing less than 1% mortality. The second stroke occurred in the late 80's in Western Europe changing dramatically IBD situation. The emerged highly virulent IBD (hvIBDV) virus soon spread all around world causing mortality up to 25% in broilers and 60 % in layers. Moreover, clinical signs as well as mortality were observed in very young birds, even as young as seven days. Mild live vaccines, which were in wide use, were not able to protect against this infection. Isolated virus showed to be of classical type, but mentioned biological characteristics of hvIBDV forced poultry industry to switch from mild to more invasive vaccinal strains, almost overnight. The vaccination programmes required some adjustment, too. IBD virus is very stable in the environment, thus once introduced in poultry house will continue to cause disease in flock after flock, despite vigorous disinfection. So, in contrast to some other viral diseases, vaccination is the principal method used for the control of IBD infection in chickens. Vaccination programmes have to be carefully designed considering the actual IBD situation in particular farm, level and uniformity of maternally derived antibodies, type of birds as well as type of vaccine. Also, protection of young birds by vaccination is directed in two ways: hyperimmunization of parent flocks using inactivated vaccines and vaccination of progeny using live vaccines. There are a lot of types of available live vaccines ranging from mild to so called 'hot' vaccines. Generally, immunogenicity of the live vaccines ie. serologic response correlate with adverse effect regarding bursa damage. According to own experiences, hvIBD can be well controlled if timing for vaccination and live intermediate vaccines in progeny are used. It is important to mention that satisfactory result may not be expected in the first vaccinated flock, but after several consequently vaccinated flocks in the same poultry house.

Infectious bursal disease; highly virulent virus; vaccination

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