The endogenous development of virulent strains and attenuated precocious lines of Eimeria tenella and E. necatrix.

摘要: Studies were made of the endogenous development H strains E. tenella and necatrix, precocious lines derived from them. Second-generation meronts both matured at a faster rate than those parent strains. The first- second-generation line necatrix significantly smaller contained fewer merozoites corresponding stages These observations provide reasons for precocity, partial explanation attenuation, these lines. Virulent ofEimeria spp. chicken may be attenuated in 2 ways: firstly, by repeated passage embryos to produce embryo- adapted and, secondly, selection early maturation oocysts during serial "precocious" At- tenuation virulence an eimerian due alteration de- velopmental stages, e.g., morphology or lo- cation tissues, their production numbers. For example, embryo-adapted (Long, 1972) reproduces poorly chickens its second- generation are small develop epithelium 1973) contrast strain which large located lamina propria. Similarly, Eimeria spp., obtained chicken, depleted numbers reduced size (Jef- fers, 1975; McDougald Jeffers, 1976;