Gumboro disease – a persisting global problem
Gumboro disease was first described in the 1960’s in Gumboro, Delaware, USA. Many scientific authors also refer to it as Infectious Bursal Disease (IBD) as the virus invades and replicates in the Bursa of Fabricius.
Soon after the first discovery of Gumboro disease it became clear that biosecurity and cleaning and disinfection are not sufficient to control the disease, and vaccines were quickly developed and widely used.
These vaccines proved to be efficacious as the clinical signs of the disease disappeared.
Over the last 50 years the economic development in many countries has increased the number of birds placed per farm and had led to stricter biosecurity and surveillance programs.
Gumboro disease, despite the wide use of vaccines and increased biosecurity, is however still very much present and ranks among the top five diseases in almost all countries globally.
One of the reasons for this dominance is that the Gumboro disease virus is a very persistent virus surviving in poultry houses in the absence of chickens during downtime periods.
Past, present, future
After the initial outbreak in the US, Gumboro clinical disease was reported in many other countries in the 1960s and 1970s. The clinical form later disappeared and the condition became mainly sub-clinical between 1970s and 1985. More virulent forms were later reported around the same time with a very immune-suppressive form of Gumboro disease in the USA (starting around 1985), which then later spread to Latin America.
The very virulent form of the Gumboro disease spread around the same time to Western Europe, North Africa,the Middle East and Asia, see map ‘Isolation of Gumboro disease virus on a global level’. In the late 1990’s and the late 2000’s.
The very virulent form of Gumboro disease spread to Latin America and California. Today the very virulent form of Gumboro disease is still present in many countries, and variant strains of Gumboro disease are present in several countries, leading to sub-clinical forms of Gumboro disease.
Stop the Gumboro cycle
As the Gumboro virus is a very persistent virus, in many case sit is already present inside the farm, which can lead to a field challenge when new birds are placed. The characteristics of this challenge in chickens (age of birds, severity, consequences, etc.), will vary from house to house but the challenge will occur. In this case vaccination, should aim at both protecting the chickens and preventing the Gumboro challenge from getting out of control.
When considering a sound Gumboro vaccination program the main objectives must be:
- Ensure continuous protection of the chickens against farm infection of Gumboro disease, or ‘Prevention of Infection’,
- Protect against the clinical signs of infection or ‘Clinical Protection’,
- Prevent or significantly reduce the amount of virus shed after challenge or ‘Reduction of shedding of the Gumboro field virus’,
- Prevent the build-up of a higher virus pressure, production cycle after production cycle,
- Prevent the evolution of the farm Gumboro disease towards a virus that could escape the protection program.
The last two points are important for the reduction of the shedding of the Gumboro field virus, since the goal of a strong Gumboro vaccination program should be to stop the Gumboro Cycle.