Importance of bursa/body weight ration in the identification of chickens with bursa lesioned by the infectious bursal disease virus.

Abstract

There is a normal ratio among bursa and body weight (B:BR) in birds that changes with the age. When the bursa is affected by she Cumboro disease virus (CDV) the B:BR ratio is lower. An experiment has been conducted with 233 chickens previously inoculated with CDV at differents age. Seven days after infection the B:BR was calculated and confronted with a normal B:BR uninfected chickens. An index was calculated by dividing the inoculated chickens B:BR by the mean of normal B:BR chickens. When this index was lower than 07 it was considered that there was bursal atrophy. The sensitibility (α) of 83.5% and the especificity (β) of 78,0% for the test were determinated by comparation of the results with the ones obtained with bursal histology examination. The prevalence was 75% compared with the 86% of the histologic test. In conclusion this method can be used to identify chickens with bursal atrophy caused by CDV, in replacement to the histopathologic method.