The skin of outdoor workers in North Carolina

Abstract

Background: Tick-Transmitted rickettsial diseases, such as ehrlichiosis and spotted fever rickettsiosis, are significan sources of morbidity and mortality in the southern United States. Because of their exposure in tick-infested woodlands outdoor workers experience an increased risk of infection with tick-borne pathogens. As part of a doubl blind randomized-controlled field trial of the effectiveness of permethrin-Treated clothing in preventing tic bites, we identified tick species removed from the skin of outdoor workers in North Carolina and tested th ticks for Rickettsiales pathogens Methods: Ticks submitted by study participants from April-September 2011 and 2012 were identified to species an life stage, and preliminarily screened for the genus Rickettsia by nested PCR targeting the 17-kDa protein gene Rickettsia were further identified to species by PCR amplification of 23S-5S intergenic spacer (IGS) fragment combined with reverse line blot hybridization with species-specific probes and through cloning and nucleotid sequence analysis of 23S-5S amplicons. Ticks were examined for Ehrlichia and Anaplasma by nested PCR directed at th gltA, antigen-expressing gene containing a variable number of tandem repeats, 16S rRNA, and groESL genes Results: The lone star tick (Amblyomma americanum) accounted for 95.0 and 92.9% of ticks submitted in 201 (n = 423) and 2012 (n = 451), respectively. Specimens of American dog tick (Dermacentor variabilis), Gulf Coas tick (Amblyomma maculatum) and black-legged tick (Ixodes scapularis) were also identified. In both years o our study, 60.9% of ticks tested positive for 17-kDa. "Candidatus Rickettsia amblyommii", identified in all four tic species, accounted for 90.2% (416/461) of the 23S-5S-positive samples and 52.9% (416/787) of all samples tested Nucleotide sequence analysis of Rickettsia-specific 23S-5S IGS, ompA and gltA gene fragments indicated that ticks principally A. americanum, contained novel species of Rickettsia. Other Rickettsiales, including Ehrlichia ewingii E. chaffeensis, Ehrlichia sp. (Panola Mountain), and Anaplasma phagocytophilum, were infrequently identified, principally i A. americanum Conclusions: We conclude that in North Carolina, the most common rickettsial exposure is to R. amblyommii carrie by A. americanum. Other Rickettsiales bacteria, including novel species of Rickettsia, were less frequently detected i A. americanum but are relevant to public health nevertheless.