Detection of Bacterial Agents in Amblyomma americanum (Acari: Ixodidae) from Georgia, USA, and the use of a Multiplex Assay to Differentiate Ehrlichia chaffeensis and Ehrlichia ewingii

ABSTRACT Amblyomma americanum, the lone star tick, is the most common and most aggressive human biting tick in the Southeastern United States. It is known to transmit the agents of human ehrlichioses, Ehrlichia chaffeensis and Ehrlichia ewingii. In addition, it carries agents of unspecified pathogenicity to humans, including Rickettsia amblyommii, Borrelia lonestari, and the newly emerging Panola Mountain Ehrlichia (PME). Surveillance of these ticks for recognized or emerging pathogens is necessary for assessing the risk of human infection. From 2005 to 2009, we surveyed A. americanum ticks from four locations in the state of Georgia. Ticks (1,183 adults, 2,954 nymphs, and 99 larval batches) were tested using a multiplex real-time polymerase chain reaction (PCR) assay designed to detect and discriminate DNA from Rickettsia spp., E. chaffeensis, and E. ewingii, This assay was capable of detecting as few as 10 gene copies of the aforementioned agents. Ticks were also tested for PME and B. lonestari by neste...