Experimental infection of lambs with an equine granulocytic Ehrlichia species resembling the agent that causes human granulocytic ehrlichiosis (HGE)

Five lambs were inoculated with a granulocytic Ehrlichia species originally isolated from a Swedish horse with granulocytic ehrlichiosis (EGE). The 16 S rRNA gene sequence of the Swedish Ehrlichia sp, causing EGE was identical to the sequence of the agent causing human granulocytic ehrlichiosis (HGE) . After the inoculation, infected neutrophils and a low serologic response were seen in all lambs, but no clinical symptoms were observed. In one lamb 17% of the neutrophils were infected without a corresponding fever. Six we eks later the lambs were inoculated with an ovine isolate off. phagocytophi la. After challenge with E. phagocytophila the lambs reacted with fever and infected granulocytes. The results presented herein show that the equine E hrlichia isolate was infective for lambs but generated weak immune response and no distinctive protection from subsequent challenge with E, phagocytop hila.