^a A live, avirulent vaccine consisting of the three major serotypes (1, 2, and 5) of R anatipestifer.

^b A formalin-inactivated cell suspension of the three major serotypes (1, 2, and 5) of R anatipestifer is recommended for preventive immunization on farms where the disease is endemic or epidemic. An Escherichia coli bacterin can also be used where field challenge warrants. Ducklings should not be vaccinated within 21 days of slaughter.