Experimental infection of four horses with Ehrlichia phagocytophila

Four clinically healthy horses which were negative for antibodies to Ehrlic hia phagocytophila, the agent of bovine ehrlichiosis, were infected experim entally with E phagocytophila-containing bovine leucocytes, administered in travenously. The horses were examined daily for four weeks, and blood sampl es were collected daily for cytological, haematological and biochemical exa mination and for a nested polymerase chain reaction (PCR). An indirect immu nofluorescence test was used to determine when the horses seroconverted and the duration of positive titres. There were no abnormal clinical, haematol ogical or biochemical findings in any of the four horses and all the PCRs y ielded negative results. However, all the horses seroconverted with recipro cal titres of up to 1280, and the positive titres persisted for up to five months.