Infectious bursal disease is an acute, highly contagious viral disease of young chickens. It is most often found in highly concentrated poultry producing areas. It causes marked morbidity and mortality in affected flocks. Although the disease causes severe losses, its affect on reducing the bird's ability to develop immunity to other diseases may be the most serious effect produced by this disease.
The transmission or spread of the disease can occur by direct contact (bird to bird), contaminated litter and feces, caretaker, contaminated air, equipment, feed, servicemen and possible insects and wild birds. It is extremely contagious.
Birds have ruffled feathers, a slight tremor at onset of the disease, strained defecation, loss of appetite and are dehydrated. Affected birds have a tendency to sit and when forced to move, have an unsteady gait. Vent picking is common and a whitish diarrhea frequently develops. A sudden rise in body temperature is followed by a drop to subnormal temperature, prostration and death. Birds surviving the initial infection will recover rapidly within two weeks.
Postmortem lesions include dehydration and changes in the bursa, skeletal muscle, liver and kidneys. All affected birds have bursal changes characterized by swelling, change in shape (oblong), color (pink, yellow, red, black) and the formation of a gelatinous film around the bursa. Within a few days the bursa shrinks to half its normal size or smaller.
Diagnosis of infectious bursal disease is based on flock history and postmortem lesions. Laboratory procedures may be used to substantiate the diagnosis.
Vaccines are available but must be carefully used. If given correctly, good immunity can be developed. There is no specific treatment for infectious bursal disease and indiscriminate medication with certain drugs may severely aggravate mortality. Supportive measures such as increasing heat, ventilation and water consumption are beneficial.