ARS | Publication request: TpE: PANOLA MOUNTAIN EHRLICHIA: A NOVEL TICK-TRANSMITTED PATHOGEN IN THE USA CLOSELY RELATED TO EHRLICHIA RUMINANTIUM, CAUSAL AGENT OF HEARTWATER DISEASE IN RUMINANTS

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: September 5, 2008
Publication Date: September 22, 2008
Citation: Loftis, A., Mixson-Hayden, T., Stromdahl, E., Mahan, S., Yabsley, M., Garrison, L., Reeves, W.K., Williamson, P., Fitak, R., Levin, M. 2008. TpE: PANOLA MOUNTAIN EHRLICHIA: A NOVEL TICK-TRANSMITTED PATHOGEN IN THE USA CLOSELY RELATED TO EHRLICHIA RUMINANTIUM, CAUSAL AGENT OF HEARTWATER DISEASE IN RUMINANTS. Meeting Abstract.

Technical Abstract: Ehrlichia ruminantium, the economically most important pathogen in the genus Ehrlichia, is enzootic in sub-Saharan Africa and occurs on islands in the Caribbean. The pathogen causes heartwater disease in ruminants and might also cause illness in humans. We recently found a novel Ehrlichia, genetically and antigenically similar to E. ruminantium, in the USA. The agent was identified in a goat experimentally infested with field-collected ticks (Amblyomma americanum) from Panola Mountain State Park, Georgia, USA. Phylogenetic analysis targeting five different genes suggested it might be either a divergent strain of E. ruminantium or a closely related, novel species. Goats were susceptible to the Panola Mountain Ehrlichia (PME) and developed febrile illness similar to the mildest manifestation of E. ruminantium, "heartwater fever." Colony-reared nymphal A. americanum and A. maculatum maintained PME transstadially and transmitted the pathogen between goats. The organism was detected in the blood of a person who fell ill after the bite of a nymphal Amblyomma; clinical signs responded to doxycycline therapy. To determine the geographic range of PME, we developed a PCR assay based on the citrate synthase (gltA) gene and tested 1964 field-collected and 1803 human-biting A. americanum from the Eastern USA. PME was detected in 35 ticks collected between 1998 and 2006, both from vegetation and from humans, from 11 states. Fragments of the gltA and major antigenic protein 1 (map1) genes were sequenced, and two distinct map1 clades were identified with overlapping geographic ranges. The Panola Mountain Ehrlichia has an extensive distribution throughout the range of its tick vector within the USA. The pathogen was shown to infect both livestock and people in the USA and represents a potential emerging health risk.