标题：Mortality rates from a Nigerian isolate of the Infectious Bursa Disease Virus and passive haemagglutination antibody titer that protects chicks against challenge with the virus isolate
摘要：To determine passive
haemagglutination (PHA) antibody titer that would protect chicks against
Nigerian isolates of the Infectious Bursa
Disease Virus (IBDV), five groups of chicks aged 30 days which had
different antibody titers were challenged with a Nigerian isolate of virulent
IBDV. Mortality rates of the different groups were plotted against their
respective mean PHA antibody titers. A group with zero antibody titer had a
mortality rate of 75% while those with PHA antibody titers of 185.6, 243.2,
256 and 307.2 had mortality rates of 40%, zero, zero and zero respectively.
Linear equation generated for a line of best fit of the graph of mortality
rates of the chicks on their IBD antibody titers gave antibody titer (X) at
which mortality (Y) would be zero as 300. A mortality of 75% and the high antibody level needed to protect chicks suggest that the isolate may be a
hypervirulent strain.
