Abstract
BackgroundIn the Eastern and Upper Midwestern regions of North America, Ixodes scapularis (L.) is the most abundant tick species encountered by humans and the primary vector of B. burgdorferi, whereas in the southeastern region Amblyomma americanum (Say) is the most abundant tick species encountered by humans but cannot transmit B. burgdorferi. Surveys of Borreliae in ticks have been conducted in the southeastern United States and often these surveys identify B. lonestari as the primary Borrelia species, surveys have not included Arkansas ticks, canines, or white-tailed deer and B. lonestari is not considered pathogenic. The objective of this study was to identify Borrelia species within Arkansas by screening ticks (n = 2123), canines (n = 173), and white-tailed deer (n = 228) to determine the identity and locations of Borreliae endemic to Arkansas using PCR amplification of the flagellin (flaB) gene.MethodsField collected ticks from canines and from hunter-killed white-tailed were identified to species and life stage. After which, ticks and their hosts were screened for the presence of Borrelia using PCR to amplify the flaB gene. A subset of the positive samples was confirmed with bidirectional sequencing.ResultsIn total 53 (21.2%) white-tailed deer, ten (6%) canines, and 583 (27.5%) Ixodid ticks (252 Ixodes scapularis, 161 A. americanum, 88 Rhipicephalus sanguineus, 50 Amblyomma maculatum, 19 Dermacentor variabilis, and 13 unidentified Amblyomma species) produced a Borrelia flaB amplicon. Of the positive ticks, 324 (22.7%) were collected from canines (151 A. americanum, 78 R. sanguineus, 43 I. scapularis, 26 A. maculatum, 18 D. variabilis, and 8 Amblyomma species) and 259 (37.2%) were collected from white-tailed deer (209 I. scapularis, 24 A. maculatum, 10 A. americanum, 10 R. sanguineus, 1 D. variabilis, and 5 Amblyomma species). None of the larvae were PCR positive. A majority of the flaB amplicons were homologous with B. lonestari sequences: 281 of the 296 sequenced ticks, 3 canines, and 27 deer. Only 22 deer, 7 canines, and 15 tick flaB amplicons (12 I. scapularis, 2 A. maculatum, and 1 Amblyomma species) were homologous with B. burgdorferi sequences.ConclusionsData from this study identified multiple Borreliae genotypes in Arkansas ticks, canines and deer including B. burgdorferi and B. lonestari; however, B. lonestari was significantly more prevalent in the tick population than B. burgdorferi. Results from this study suggest that the majority of tick-borne diseases in Arkansas are not B. burgdorferi.
Highlights
In the Eastern and Upper Midwestern regions of North America, Ixodes scapularis (L.) is the most abundant tick species encountered by humans and the primary vector of B. burgdorferi, whereas in the southeastern region Amblyomma americanum (Say) is the most abundant tick species encountered by humans but cannot transmit B. burgdorferi
In Arkansas, ticks and reservoir species were screened for Borrelia in nine northeast Arkansas counties using indirect fluorescence antibody (IFA), both I. scapularis and A. americanum were identified as potential vectors, and deer mice (Peromyscus spp.) and marsh rice rats (Oryzomys palustris Harlan) as potential reservoir hosts [23]
Identification of Borrelia DNA in the tick population A total of 2123 ticks were included in this study and represented five tick species; I. scapularis (33%), A. americanum (31%), R. sanguineus (16 %), D. variabilis (9%), and A. maculatum (8%)
Summary
In the Eastern and Upper Midwestern regions of North America, Ixodes scapularis (L.) is the most abundant tick species encountered by humans and the primary vector of B. burgdorferi, whereas in the southeastern region Amblyomma americanum (Say) is the most abundant tick species encountered by humans but cannot transmit B. burgdorferi. In the Eastern and Upper Midwestern regions of North America, Ixodes scapularis (L.) is the most abundant tick species encountered by humans and the primary vector of Borrelia burgdorferi (causative agent of Lyme disease), whereas in the southeastern region Amblyomma americanum (Say) is the most abundant tick species encountered by humans but it cannot transmit B. burgdorferi [1,2]. Health professionals often question cases of Lyme disease from the southeastern United States because symptoms may be confused with other tick-borne illnesses and not all patients produce the erythema migrans or bull’s eye rash used for diagnosis [15,17] These cases are rarely fatal, but can cause cardiac, neurological and joint problems [17]. The exact cause for the reduced incidence for Lyme disease in the southern United States is unknown, but hypotheses include the abundance of other tick species in the area, the habitat, host dynamics, and tick genetics [2,24]
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