An in vitro study of the life cycle of Cowdria ruminantium

Abstract

The life cycle of Cowdria ruminantium was studied in SBE 189 cells by light and electron microcospy. Cultures were infected with a synchronized inoculum and fixed and processed form 15 min to 111 h post-inoculation (PI). After 12 h, single or small groups of large reticulate bodies were identified in intracytoplasmic membrane-bound vacuoles. The latter gradually developed into smaller reticulate bodies with a more granular internal structure. From 66 to 75 h PI, there was a significant increase in colony size. Most colonies contained reticulate bodies even though a few intermediate to electron-dense bodies were evident. Single extracellular reticulate bodies with a peptidoglycan-like layer was observed 84 h PI. At 90 h, abundant intermediate and electron-dense bodies were observed which coincided with lysis of tissue culture cells. In this study, Cowdria ruminantium, therefore, had a developmental cycle of approximately 4 days.