Abortion in a heifer associated with the intra-uterine transmission of Cowdria ruminantium-like organisms following heartwater vaccination.

A Nguni heifer aborted a 6-month-old foetus 35 days after intravenous inoculation with Onderstepoort heartwater vaccine. Histopathological examination of the brain revealed numerous suspected Cowdria ruminantium organisms in the endothelial cells of the blood vessels. The organisms were ultrastructurally and immunohistochemically compatible with Cowdria ruminantium, although, owing to autolysis and cross-reactions, the possibility that they represent another rickettsial or related organism could not be completely excluded. As far as we could ascertain this is the first recorded case of suspected intra-uterine transmission of Cowdria ruminantium in ruminants.