Transmission and passage in horses of the agent of human granulocytic ehrlichiosis

John E. Madigan, Philip J. Richter, Robert B. Kimsey, Jeffrey E. Barlough, Johan S Bakken, J. Stephen Dumler

Research output: Contribution to journalArticlepeer-review

102 Scopus citations


The human granulocytotropic ehrlichia and Ehrlichia equi produce similar diseases in their respective host species (humans, horses). Currently, the phylogenetic and biologic relationships of these 2 uncultured pathogens remain unclear. Previous studies have revealed nucleotide sequence similarity approaching identity at the level of the 16S ribosomal RNA gene. To investigate the biologic similarities of these 2 ehrlichiae, the susceptibility of horses to the human agent was tested by intravenous inoculation of infected human blood. The results demonstrate that the human granulocytotropic ehrlichia produces a disease in the horse indistinguishable from that caused by E. equi, providing biologic evidence that these 2 organisms are highly related and potentially conspecific. It is possible that cases of human illness now attributed to human granulocytotropic ehrlichia may in fact be caused by 1 or more strains of an ehrlichia known chiefly as an equine pathogen.

Original languageEnglish (US)
Pages (from-to)1141-1144
Number of pages4
JournalJournal of Infectious Diseases
Issue number4
StatePublished - Oct 1995


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