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 nested 
PCR. The prevalence of infection ranged from 0 to 2.5% for E. chaffeensis, 0 to 
3.9% for E. ewingii, 0 to 2.2% for PME, 17 to 83.1% for R. amblyommii, and 0 to 
3.1% for B. lonestari. There were 46 (4.1%) individual adults positive for two 
agents, and two females that were each positive for three agents. Two larval 
batches were positive for both B. lonestari and R. amblyommii, indicating the 
potential for transovarial transmission of both agents from a single female. 
Although infrequent in occurrence, the dynamics of coinfections in individual 
ticks should be explored further, given the potential implications for 
differential diagnosis and severity of human illness.