Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Survival curve after challenge with lethal DPV strain CHv. Ten ducks from the vaccinated group or negative-control group were orally challenged with 1,000 LD50 of DPV strain CHv on the 6th week after the first immunization. Mortality was monitored daily for 10 days after challenge. The figure was drawn as a Kaplan-Meier survival curve. The y axis shows the cumulative (Cum) survival calculated by the Kaplan-Meier method (P < 0.01).
