E. ondiri is believed to be endemic in wild ruminants, particularly bushbuck, and it sporadically overspills into domestic cattle grazing forest edges or scrubs.
The route of infection is not known, but E. ondiri can be seen in circulating granulocytes (neutrophils and eosinophils) and monocytes while cattle are ill, and in the spleen at necropsy. Electron microscopic studies have shown that E. ondiri can also infect endothelial and Kupffer cells, and it may be free in capillary lumens in the heart.
It is believed that E. ondiri initially multiplies in the spleen, with subsequent spread to other areas. Damage to the vascular endothelium would explain the hemorrhages and edema, as in many other rickettsial infections.
- Kiptoon JC & Mugera GM (1983) Invasion of capillary endothelial cells by Ehrlichia ondiri. Vet Rec 112(3):59-60