Survey of Borreliae in ticks, canines, and white-tailed deer from Arkansas, U.S.A.

<p>Abstract</p> <p>Background</p> <p>In the Eastern and Upper Midwestern regions of North America, <it>Ixodes scapularis</it> (L.) is the most abundant tick species encountered by humans and the primary vector of <it>B. burgdorferi,</it> whereas in the southeastern region <it>Amblyomma americanum</it> (Say) is the most abundant tick species encountered by humans but cannot transmit <it>B. burgdorferi.</it> Surveys of Borreliae in ticks have been conducted in the southeastern United States and often these surveys identify <it>B. lonestari</it> as the primary <it>Borrelia</it> species, surveys have not included Arkansas ticks, canines, or white-tailed deer and <it>B. lonestari</it> is not considered pathogenic. The objective of this study was to identify <it>Borrelia</it> 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 (<it>flaB)</it> gene.</p> <p>Methods</p> <p>Field 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 <it>Borrelia</it> using PCR to amplify the <it>flaB</it> gene. A subset of the positive samples was confirmed with bidirectional sequencing.</p> <p>Results</p> <p>In total 53 (21.2%) white-tailed deer, ten (6%) canines, and 583 (27.5%) Ixodid ticks (252 <it>Ixodes scapularis</it>, 161 <it>A. americanum</it>, 88 <it>Rhipicephalus sanguineus</it>, 50 <it>Amblyomma maculatum,</it> 19 <it>Dermacentor variabilis,</it> and 13 unidentified <it>Amblyomma</it> species) produced a <it>Borrelia flaB</it> amplicon. Of the positive ticks, 324 (22.7%) were collected from canines (151 <it>A. americanum,</it> 78 <it>R. sanguineus</it>, 43 <it>I. scapularis,</it> 26 <it>A. maculatum,</it> 18 <it>D. variabilis</it>, and 8 <it>Amblyomma</it> species) and 259 (37.2%) were collected from white-tailed deer (209 <it>I. scapularis,</it> 24 <it>A. maculatum,</it> 10 <it>A. americanum,</it> 10 <it>R. sanguineus</it>, 1 <it>D. variabilis</it>, and 5 <it>Amblyomma</it> species). None of the larvae were PCR positive. A majority of the <it>flaB</it> amplicons were homologous with <it>B. lonestari</it> sequences: 281 of the 296 sequenced ticks, 3 canines, and 27 deer. Only 22 deer, 7 canines, and 15 tick <it>flaB</it> amplicons (12 <it>I. scapularis</it>, 2 <it>A. maculatum</it>, and 1 <it>Amblyomma</it> species) were homologous with <it>B. burgdorferi</it> sequences.</p> <p>Conclusions</p> <p>Data from this study identified multiple Borreliae genotypes in Arkansas ticks, canines and deer including <it>B. burgdorferi</it> and <it>B. lonestari;</it> however, <it>B. lonestari</it> was significantly more prevalent in the tick population than <it>B. burgdorferi</it>. Results from this study suggest that the majority of tick-borne diseases in Arkansas are not <it>B. burgdorferi.</it></p

Different populations of blacklegged tick nymphs exhibit differences in questing behavior that have implications for human lyme disease risk.

Animal behavior can have profound effects on pathogen transmission and disease incidence. We studied the questing (= host-seeking) behavior of blacklegged tick (Ixodes scapularis) nymphs, which are the primary vectors of Lyme disease in the eastern United States. Lyme disease is common in northern but not in southern regions, and prior ecological studies have found that standard methods used to collect host-seeking nymphs in northern regions are unsuccessful in the south. This led us to hypothesize that there are behavior differences between northern and southern nymphs that alter how readily they are collected, and how likely they are to transmit the etiological agent of Lyme disease to humans. To examine this question, we compared the questing behavior of I. scapularis nymphs originating from one northern (Lyme disease endemic) and two southern (non-endemic) US regions at field sites in Wisconsin, Rhode Island, Tennessee, and Florida. Laboratory-raised uninfected nymphs were monitored in circular 0.2 m2 arenas containing wooden dowels (mimicking stems of understory vegetation) for 10 (2011) and 19 (2012) weeks. The probability of observing nymphs questing on these stems (2011), and on stems, on top of leaf litter, and on arena walls (2012) was much greater for northern than for southern origin ticks in both years and at all field sites (19.5 times greater in 2011; 3.6-11.6 times greater in 2012). Our findings suggest that southern origin I. scapularis nymphs rarely emerge from the leaf litter, and consequently are unlikely to contact passing humans. We propose that this difference in questing behavior accounts for observed geographic differences in the efficacy of the standard sampling techniques used to collect questing nymphs. These findings also support our hypothesis that very low Lyme disease incidence in southern states is, in part, a consequence of the type of host-seeking behavior exhibited by southern populations of the key Lyme disease vector