What is a cerebral pathogenicity index test (ICPI)?
The Intracerebral pathogenicity index is a test to see how virulent a virus is. 0.05ml of a diluted virus is injected intracerebrally into each of 10 one-day-old chicks. The birds are examined every 24 hours for 8 days. At each observation the birds are scored: 0 if normal, 1 if sick, and 2 if dead. The ICPI is the mean score per bird per observation over the 8-day period. The most virulent viruses will give a maximum score of 2.0, whereas slower strains will give values close to 0.0.
