Metagenomic-based Surveillance of Pacific Coast tick Dermacentor occidentalis Identifies Two Novel Bunyaviruses and an Emerging Human Ricksettsial Pathogen

Abstract An increasing number of emerging tick-borne diseases has been reported in the United States since the 1970s. Using metagenomic next generation sequencing, we detected nucleic acid sequences from 2 novel viruses in the family Bunyaviridae and an emerging human rickettsial pathogen, Rickettsia philipii, in a population of the Pacific Coast tick, Dermacentor occidentalis in Mendocino County sampled annually from 2011 to 2014. A total of 250 adults of this human-biting, generalist tick were collected from contiguous chaparral and grassland habitats, and RNA from each individually extracted tick was deep sequenced to an average depth of 7.3 million reads. We detected a Francisella endosymbiont in 174 ticks (70%), and Rickettsia spp. in 19 ticks (8%); Rickettsia-infected ticks contained R. rhipicephali (16 of 250, 6.4%) or R. philipii (3 of 250,1.2%), the agent of eschar-associated febrile illness in humans. The genomes of 2 novel bunyaviruses (>99% complete) in the genera Nairovirus and Phlebovirus were also identified and found to be present in 20–91% of ticks, depending on the year of collection. The high prevalence of these bunyaviruses in sampled Dermacentor ticks suggests that they may be viral endosymbionts, although further studies are needed to determine whether they are infectious for vertebrate hosts, especially humans, and their potential role in tick ecology

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