veterinary zone

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.

Transmission
Airborne transmission in the direction of prevailing wind. The spread of infection is rapid in a flock. Some birds become carriers and shedders of the virus through secretions and discharges for many months after the infection. IB virus persists in contaminated chicken houses for approximately four weeks. contaminated litter and feces, caretaker, contaminated air, equipment, feed, servicemen and possible insects and wild birds. It is extremely contagious.

Antemortem findings:
1. Indifference and depression
2. Sneezing, gasping and coughing
3. Nasal discharge
4. Abnormal respiratory sounds (rales)
5. Weakness and huddling near the light source
6. Reduced egg production in laying birds. Low egg quality and soft egg shells are noted.
7. Mortality due to kidney disease caused by the nephrotropic strain of the IB virus.
8. Inflammation of the air sacs may be a complication of IB.

Postmortem lesions
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
Diagnosis of infectious bursal disease is based on flock history and postmortem lesions. Laboratory procedures may be used to substantiate the diagnosis.

Differential diagnosis
Newcastle disease, laryngotracheitis (LT) and infectious coryza. Laryngotracheitis spreads slowly in a flock although respiratory signs are more severe than in infectious bronchitis. LT is not seen in young chicken.

Treatment
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.