EIMERIA-MEDIA - SELECTION AND CHARACTERIZATION OF A PRECOCIOUS LINE

A precocious line of Eimeria media was obtained by selection for early development of oocysts in rabbits. The prepatent period was reduced f rom 108 to 72 h. The precocious line was less pathogenic than the orig inal strain, and its multiplication rate was lower. Rabbits given oocy sts of the precocious line were totally immune to challenge with the o riginal strain as assessed by change in weight gain but were partially protected as assessed by oocyst output. Selection for precocious deve lopment was accompanied by morphological changes in the sporulated ooc ysts; each sporocyst contained only one large refractile body instead of the two smaller bodies seen in the original strain.