Abstract

    Infectious bursal disease virus was isolated from bursae of broilers suffering from Gumboro disease and was designated as field virus (FV). The virus was confirmed through agar gel precipitation test (AGPT) and counter current immunoelectrophoresis (CCIE). The virus was titrated by using reverse passive haemagglutination (RPHA) test and egg infective dose fifty (EID₅₀)_. The FV was inoculated into 9-to 11-day-old embryonated chicken eggs through chorio-allantoic membrane (CAM). At each passage, the virus in the chorio-allantoic fluid (CAF) and embryos was confirmed by AGPT and titrated by RPHA test. Geometric mean titer (GMT) of the virus in CAF was 37 to 64 in 1-3^rd passage, 111 to 239 in 4-7^th passages. In 8 to 15^th passages, virus titer remained from 294 to 588 and in 16-24^th passages virus titer ranged from 675 to 2195. Similarly, virus titer in the embryos was 1024 to 512 in 1^st -10^th passages, while the virus titer in passages 11-24^th ranged from 478 to 111. Embryos were monitored for lesions and mortality. Severe lesions were present on the CAM in 1^st-7^th passages, while moderate to mild haemorrhages were seen in 8^th to 16^th passages and  in 17^{th _} 24^th passages  no lesions were observed.

Key words: Infectious bursal disease virus, adaptation, embryonated eggs, chorioallantoic fluid.