Continuous in vitro propagation of Cowdria ruminantium (Welgevonden stock)in a canine macrophage-monocyte cell line

The Welgevonden stock of Cowdria ruminantium, aetiologic agent of heartwate r, was continuously propagated in DH82 cells, a continuous canine macrophag e-monocyte cell line. Cultures of DH82 cells were readily infected provided that the culture medium was supplemented with cycloheximide. Cultures were split at regular 3-day intervals and infection rates ranged between 60% an d 95%. Cultures were continuously propagated through more than 125 passages over a period of more than one year.