The Characteristics of The Precocious Line Nn-P125 of Eimeria necatrix

Abstract

The precocious line, Nn-P125, was assayed on its characteristics relevant to an attenuated live vaccine. The Nn-P125 line was attenuated to such an extent that all chickens did not exhibit any clinical signs by oral inoculation with 9 x 10⁴ oocysts/bird. In contrast, the same number of oocysts of the parent strain killed all the birds inoculated. The prepatent period of the line was shortened about one day as compared with that of the parent Nn strain. These characteristics of Nn-P125 were stable throughout repeated relaxed passages in chickens. The line has an immunological potential to the extent of that chickens received 25 or more oocysts/bird resisted the challenge conducted 4 weeks after vaccination. Chicks aged 3 days or more were found to be suitable for vaccination. Based on these results, the Nn-P125 line was recognized to be an appropriate seed of an attenuated live vaccine against Eimeria necatrix infection.