Investigation of an Infectious Bursal Disease Virus Outbreak at a Broiler Farm in Tottori Prefecture and the Measures Taken to Control the Disease

Chie Cho, Yuko Tsuka, Moegi Kuroda, Natsuki Akashi, Tsuneyuki Masuda, Shigeki Yamamoto, Yoshifumi Inoue

In December 2018, there was an increase in mortality and wastage rates in a meat-processing plant due to colibacillosis at a broiler farm that rears 140 thousand chickens in Tottori prefecture. Bursal atrophy and hepatic encapsulitis were observed after a postmortem examination, and infectious bursal disease virus (IBDV) genes were detected by polymerase chain reaction analysis of bursal specimens. Histopathological analysis revealed diffuse, severe follicle atrophy in the bursa, and immunostaining revealed lymphoid cell-associated IBDV antigens in the atrophic bursa, which indicated that there was subclinical onset of IBD in the flock. Sequence analysis revealed that the detected IBDV showed genetically high similarity with the vaccine strain used on the farm. Countermeasures against IBD, including improved vaccination methods and cleaning and disinfecting the houses, successfully reduced the mortality rates.

J. Jpn. Soc. Poult. Dis.