Cultivation of Eimeria bovis in Three Established Cell Lines and in Bovine Tracheal Cell Line Cultures

Monolayer established cell line cultures of bovine kidney (Madin-Darby, 1958), human intestine (Intestine 407), and mouse fibroblasts (L cells), as well as bovine tracheal cell line cultures, were inoculated with E. bovis sporozoites and observed for a maximum of 21 days. Mature first-generation schizonts developed in each of the cell types, except for the L cells. In these, large numbers of sporozoites entered cells but only a few transformed into trophozoites; the most advanced stage seen was a trinucleate schizont. In the tracheal cells, relatively numerous schizonts developed and mature schizonts were first observed 8 days after inoculation. Thus, the rate of development of the schizont in the tracheal cells was unusually rapid, exceeding even that in calves. Some mature schizonts were relatively large; the maximum, 292 by 118 µ, was observed in an 18-day culture. Intracellular merozoites and early schizonts of the second generation were found in 18- and 19-day cultures of tracheal cells. Many schizonts occurred also in established kidney cell line cultures, but the rate of development was slower than that in tracheal cells, and the first mature schizonts were observed in a 14-day culture. The largest mature schizont seen (55 by 38 µ) was in a 21-day culture. In the intestinal cells, relatively small numbers of schizonts developed; the rate of development was approximately the same as that in kidney cells. The largest mature schizont observed, 109 by 55 µ, was seen in a 13-day culture. Of the four cell types studied, the bovine tracheal cells appear to provide the best conditions for development of E. bovis.