RESUMO
BACKGROUND: A novel Ehrlichia, closely related to Ehrlichia ruminantium, was recently discovered from Panola Mountain State Park, GA, USA. We conducted a study to determine if this agent was recently introduced into the United States. METHODS: We developed a sensitive PCR assay based on the conserved gltA (citrate synthase) gene and tested DNA samples extracted from 1964 field-collected and 1835 human-biting Amblyomma americanum from 23 eastern states of the USA. RESULTS: The novel agent was detected in 36 ticks collected from 10 states between 1998 and 2006. Infected ticks were collected both from vegetation (n = 14, 0.7%) and from humans (n = 22, 1.2%). Fragments of the conserved gltA gene and the variable map1 gene were sequenced from positive samples. Two distinct clades, with 10.5% nucleic acid divergence over the 730 bp map1 sequence, were identified. CONCLUSION: These data suggest that the Panola Mountain Ehrlichia was not recently introduced to the United States; this agent has an extensive distribution throughout the range of its tick vector, has been present in some locations for several years, and displays genetic variability. Furthermore, people in several states were exposed to this agent through the bite of infected ticks, underscoring the potential public health risk of this emerging ehrlichiosis.
Assuntos
Ehrlichia/classificação , Ehrlichia/isolamento & purificação , Variação Genética , Ixodidae/microbiologia , Animais , Antígenos de Bactérias/genética , Proteínas de Bactérias/genética , Citrato (si)-Sintase/genética , DNA Bacteriano/análise , DNA Bacteriano/isolamento & purificação , Ehrlichia/genética , Geografia , Georgia , Humanos , Proteínas de Membrana/genética , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase , Análise de Sequência de DNARESUMO
An Aedes aegypti-specific, fluorogenic probe hydrolysis (Taq-Man), polymerase chain reaction assay was developed for real-time screening using a field-deployable thermocycler. Laboratory-based testing of A. aegypti, A. aegypti (Trinidad strain), Culex pipiens, Culex quinquefasciatus, Anopheles stephensi, and Ochlerotatus taeniorhynchus individual adult mosquitoes and mixed pools (n = 10) demonstrated 100% concordance in both in vitro sensitivity (six of six samples) and specificity (10 of 10 samples). A single adult A. aegypti was identified in a pool of 100 non-A. aegypti mosquitoes. The limit of detection of A. aegypti egg pools was five individual eggs. Field testing was conducted in central Honduras. An A. aegypti and Culex spp. panel of individual and mixed pools (n = 30) of adult mosquitoes, pupae, and larvae demonstrated 100% concordance in sensitivity (22 of 22 samples) and 97% concordance in specificity (29 of 30 samples), with one false-positive result. Field testing of an A. aegypti and Culex spp. blind panel (n = 16) consisting of individual and mixed pools of adult mosquitoes, pupae, and larvae demonstrated 90% concordance in sensitivity (nine of 10 samples) and 88% concordance in specificity (14 of 16 samples).
