Du Plessis, J.L.Verwoerd, Daniel Wynand2014-09-012014-09-0120131990Du Plessis, JL 1990, 'Increased pathogenicity of an Ehrlichia-like agent after passage through Amblyomma hebraeum : a preliminary report’, Onderstepoort Journal of Veterinary Research, vol. 57, no. 4, pp. 233-237.0330-2465http://hdl.handle.net/2263/41868The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.After being passaged through 3 generations of Amblyomma hebraeum, an Ehrlichia-like agent isolated from an adult Hyalomma truncatum female became more pathogenic and elicited a disease in sheep indistinguishable from heartwater. Cross-immunity between this agent and several stocks of Cowdria ruminantium and high levels of antibody elicited by the agent against 2 stocks of C. ruminantium in the indirect fluorescent antibody test, confirmed its close relationship to Cowdria.en©South Africa. Dept. of Agricultural Technical Services. ©University of Pretoria. Dept. of Library Services (digital).Veterinary medicineVeterinary medicine -- South AfricaArticle