EIMERIA-COECICOLA CHEISSIN 1947 - ENDOGENOUS DEVELOPMENT IN GUT-ASSOCIATED LYMPHOID-TISSUE

Coccidia-free rabbits were inoculated with different doses of a pure s train of Eimeria coecicola and samples of gut were taken at 80, 96, 11 2, 128, 144, and 160 h postinoculation. The use of a very low infectiv e dose (2-20 oocysts) was sufficient to study the last merogony. The n umber of merozoites in meronts increased when the infective dose decre ased. Only the first merogony of this coccidium in lymphocytes or M-ce lls of gut-associated lymphoid tissue (GALT) has previously been descr ibed. Three other generations of meronts are described herein. All the se endogenous stages were observed in the epithelium of the vermiform appendix, sac culus rotundus, and Peyer's patches, especially at the b ases of the domes. However, in heavily infected tissues the gamonts we re seen throughout the epithelium of the GALT. The third- and fourth-g eneration meronts were of two types. As in other eimerian species of t he rabbit, type A meronts produced thick polynucleated merozoites, whe reas type B meronts gave rise to large numbers of thin merozoites with one nucleus. Microgamonts were polynucleated and less numerous than m acrogamonts. Type A meronts were also polynucleated and less numerous at the end of the merogony. Therefore, types A and B could correspond to a sexual phenotype differentiation occuring during the two asexual phases of multiplication.