Lance A. Durden

Birds Disperse Ixodid (Acari: Ixodidae) and Borrelia burgdorferi-Infected Ticks in Canada

Abstract A total of 152 ixodid ticks (Acari: Ixodidae) consisting of nine species was collected from 82 passerine birds (33 species) in 14 locations in Canada from 1996 to 2000. The Lyme disease spirochete Borrelia burgdorferi Johnson, Schmidt, Hyde, Steigerwaldt & Brenner was cultured from the nymph of a blacklegged tick, Ixodes scapularis Say, that had been removed from a common yellowthroat, Geothlypis trichas L., from Bon Portage Island, Nova Scotia. As a result of bird movement, a nymphal I. scapularis removed from a Swainson’s thrush, Catharus ustulatus incanus (Godfrey), at Slave Lake, Alberta, during spring migration becomes the new, most western and northern record of this tick species in Canada. Amblyomma longirostre Koch, Amblyomma sabanerae Stoll, and Ixodes baergi Cooley & Kohls are reported for the first time in Canada. Similarly, Amblyomma americanum L., Amblyomma maculatum Koch, and Ixodes muris Bishopp & Smith are reported for the first time on birds in Canada. After removal of an I. muris gravid female from a song sparrow, Melospiza melodia Wilson, at St. Andrews, New Brunswick, eggs were laid, which developed into larvae, and this new tick-host record demonstrates that birds have the potential to start a new tick population. We conclude that passerine birds disperse several species of ixodid ticks in Canada, and during spring migration translocate ticks from the United States, and Central and South America, some of which are infected with B. burgdorferi.

Ticks parasitizing humans in Georgia and South Carolina

From 1990 through 1995, 913 ticks removed from 460 human patients in Georgia or South Carolina were identified and recorded. The majority of these specimens (758, 83.0%) were lone star ticks, Amblyomma americanum. One hundred and four (11.4%) American dog ticks Dermacentor variabilis, 36 (3.9%) blacklegged ticks Ixodes scapularis, 9 (1.0%) Gulf coast ticks Amblyomma maculatum, and 6 (0.7%) brown dog ticks Rhipicephalus sanguineus were also recovered. All active stages (larvae, nymphs, and adults) of A. americanum were represented, whereas nymphs and adults of D. variabilis and I. scapularis and only adults of A. maculatum and R. sanguineus were recorded. Compared with data published for other regions in the U.S.A., A. americanum was a much more prevalent parasite of humans in the current survey. Only 1 (3%) of the I. scapularis collected was a nymph. Because these tick species are vectors of zoonotic pathogens or cause tick paralysis in humans, the data have epidemiological significance.

Gulf Coast Ticks (Amblyomma maculatum) and Rickettsia parkeri, United States

Geographic distribution of Rickettsia parkeri in its US tick vector, Amblyomma maculatum, was evaluated by PCR. R. parkeri was detected in ticks from Florida, Georgia, Kentucky, Mississippi, Oklahoma, and South Carolina, which suggests that A. maculatum may be responsible for additional cases of R. parkeri rickettsiosis throughout much of its US range.

An enzootic transmission cycle of Lyme borreliosis spirochetes in the southeastern United States

Lyme borreliosis, or Lyme disease (LD), is a tick-borne zoonotic infection of biomedical significance, caused by Borrelia burgdorferi sensu lato (s.l.) spirochetes and transmitted by Ixodes species ticks. It usually circulates among wildlife vertebrate reservoirs and vector ticks but may infect humans, causing multisystem problems. In far western and northern North America, the host reservoirs, tick vectors, and genospecies of Borrelia are well known but not so in the southern U.S., where there is controversy as to the presence of “true” LD. Here we report the presence of the LD spirochete B. burgdorferi sensu stricto (s.s.) and Borrelia bissettii, three main reservoir hosts, and two enzootic tick vectors in the southeastern U.S. The two enzootic tick vectors, Ixodes affinis and Ixodes minor, rarely bite humans but are more important than the human biting “bridge” vector, Ixodes scapularis, in maintaining the enzootic spirochete cycle in nature. We also report extraordinary longevities and infections in the reservoir rodents Peromyscus gossypinus, Sigmodon hispidus, and Neotoma floridana.

MOLECULAR PHYLOGENETIC ANALYSES INDICATE THAT THE IXODES RICINUS COMPLEX IS A PARAPHYLETIC GROUP

The Ixodes ricinus species complex is a group of ticks distributed in almost all geographic regions of the world. Lyme borreliosis spirochetes are primarily transmitted by tick species within this complex. It has been hypothesized that the Lyme vector ticks around the world are closely related and represent a monophyletic group. This implies that vector competence in ixodid ticks for Lyme agents might have evolved only once. To test this hypothesis, we used a molecular phylogenetic approach. Two fragments of mitochondrial 16S ribosomal deoxyribonucleic acid were sequenced from 11 species in the I. ricinus complex and from 16 other species of Ixodes. Phylogenetic analysis using Bayesian methodology indicated that the I. ricinus complex is not a monophyletic group unless 3 additional Ixodes species are included in it. The known major vectors of Lyme disease agents in different areas of the world are not sister taxa. This suggests that acquisition of the ability to transmit borreliosis agents in species of Ixodes may have multiple origins.

Migratory songbirds disperse ticks across Canada, and first isolation of the Lyme disease spirochete, Borrelia burgdorferi, from the avian tick, Ixodes auritulus.

During a 3-yr comprehensive study, 196 ixodid ticks (9 species) were collected from 89 passerine birds (32 species) from 25 localities across Canada to determine the distribution of avian-associated tick species and endogenous Lyme disease spirochetes, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt, and Brenner. We report the following first records of tick parasitism on avian hosts: the rabbit-associated tick, Ixodes dentatus Marx, from Manitoba and Ontario; the mouse tick, Ixodes muris Bishopp and Smith, from British Columbia; and the blacklegged tick, Ixodes scapularis Say, from New Brunswick. Moreover, we provide the first record of the Neotropical tick, Amblyomma humerale Koch (1 nymph), in Canada and its parasitism of any bird. This tick was compared morphologically with nymphs of other Neotropical Amblyomma spp., and genetically, using a 344-bp fragment of the 12S rDNA sequence of 41 New World Amblyomma species. The first collections of the western blacklegged tick, Ixodes pacificus Cooley and Kohls, from passerine species in Alberta and British Columbia, are also reported. Notably, we further report the first isolation of B. burgdorferi from the bird tick, Ixodes auritulus Neumann, collected from an American robin, Turdus migratorius L., on Vancouver Island. Furthermore, B. burgdorferi-positive I. auritulus larvae were collected from a reservoir-competent fox sparrow, Passerella iliaca (Merrem). Our findings indicate that ground-dwelling passerines, in particular, are parasitized by certain ixodid ticks and play an important role across Canada in the wide dispersal of B. burgdorferi-infected ticks and increased risk of Lyme disease exposure.

Invasion: Exotic Ticks (Acari: Argasidae, Ixodidae) Imported into the United States. A Review and New Records

Abstract A review of the literature and unpublished records from the U.S. National Tick Collection on the importation of ticks from foreign lands reveals that at least 99 exotic tick species assignable to 11 genera have been either detected and destroyed at ports of entry or inadvertently imported into the United States in the past half century. This number includes four argasid and 95 ixodid species, some of which are important vectors of agents that cause disease to both man and animals. If one includes Aponomma sp. and Hyalomma sp. and the subspecies of Rhipicephalus, the total exceeds 100 taxa. It is notable that the number of imported tick species recorded herein exceeds the total number of tick species native to the United States. It appears that the soft tick genera Argas, Antricola and Nothoaspis have not been imported, although at some point in time Argas persicus (Oken) was introduced because it is resident although not often collected. The hard tick genera Anomalohimalaya, Cosmiomma, Margaropus, Nosomma and Rhipicentor, and the nuttalliellid genus Nuttalliella have also not been imported.

Widespread Dispersal of Borrelia burgdorferi–Infected Ticks Collected from Songbirds Across Canada

abstract:  Millions of Lyme disease vector ticks are dispersed annually by songbirds across Canada, but often overlooked as the source of infection. For clarity on vector distribution, we sampled 481 ticks (12 species and 3 undetermined ticks) from 211 songbirds (42 species/subspecies) nationwide. Using PCR, 52 (29.5%) of 176 Ixodes ticks tested were positive for the Lyme disease spirochete, Borrelia burgdorferi s.l. Immature blacklegged ticks, Ixodes scapularis, collected from infested songbirds had a B. burgdorferi infection prevalence of 36% (larvae, 48%; nymphs, 31%). Notably, Ixodes affinis is reported in Canada for the first time and, similarly, Ixodes auritulus for the initial time in the Yukon. Firsts for bird-parasitizing ticks include I. scapularis in Quebec and Saskatchewan. We provide the first records of 3 tick species cofeeding on passerines (song sparrow, Swainsons thrush). New host records reveal I. scapularis on the blackpoll warbler and Nashville warbler. We furnish the following first Canadian reports of B. burgdorferi–positive ticks: I. scapularis on chipping sparrow, house wren, indigo bunting; I. auritulus on Bewicks wren; and I. spinipalpis on a Bewicks wren and song sparrow. First records of B. burgdorferi–infected ticks on songbirds include the following: the rabbit-associated tick, Ixodes dentatus, in western Canada; I. scapularis in Quebec, Saskatchewan, northern New Brunswick, northern Ontario; and Ixodes spinipalpis (collected in British Columbia). The presence of B. burgdorferi in Ixodes larvae suggests reservoir competency in 9 passerines (Bewicks wren, common yellowthroat, dark-eyed junco, Oregon junco, red-winged blackbird, song sparrow, Swainsons thrush, swamp sparrow, and white-throated sparrow). We report transstadial transmission (larva to nymph) of B. burgdorferi in I. auritulus. Data suggest a possible 4-tick, i.e., I. angustus, I. auritulus, I. pacificus, and I. spinipalpis, enzootic cycle of B. burgdorferi on Vancouver Island, British Columbia. Our results suggest that songbirds infested with B. burgdorferi–infected ticks have the potential to start new tick populations endemic for Lyme disease. Because songbirds disperse B. burgdorferi–infected ticks outside their anticipated range, health-care providers are advised that people can contract Lyme disease locally without any history of travel.

The arthropod, but not the vertebrate host or its environment, dictates bacterial community composition of fleas and ticks

Bacterial community composition in blood-sucking arthropods can shift dramatically across time and space. We used 16S rRNA gene amplification and pyrosequencing to investigate the relative impact of vertebrate host-related, arthropod-related and environmental factors on bacterial community composition in fleas and ticks collected from rodents in southern Indiana (USA). Bacterial community composition was largely affected by arthropod identity, but not by the rodent host or environmental conditions. Specifically, the arthropod group (fleas vs ticks) determined the community composition of bacteria, where bacterial communities of ticks were less diverse and more dependent on arthropod traits—especially tick species and life stage—than bacterial communities of fleas. Our data suggest that both arthropod life histories and the presence of arthropod-specific endosymbionts may mask the effects of the vertebrate host and its environment.

Evolutionary history of mammalian sucking lice (Phthiraptera: Anoplura)

BackgroundSucking lice (Phthiraptera: Anoplura) are obligate, permanent ectoparasites of eutherian mammals, parasitizing members of 12 of the 29 recognized mammalian orders and approximately 20% of all mammalian species. These host specific, blood-sucking insects are morphologically adapted for life on mammals: they are wingless, dorso-ventrally flattened, possess tibio-tarsal claws for clinging to host hair, and have piercing mouthparts for feeding. Although there are more than 540 described species of Anoplura and despite the potential economical and medical implications of sucking louse infestations, this study represents the first attempt to examine higher-level anopluran relationships using molecular data. In this study, we use molecular data to reconstruct the evolutionary history of 65 sucking louse taxa with phylogenetic analyses and compare the results to findings based on morphological data. We also estimate divergence times among anopluran taxa and compare our results to host (mammal) relationships.ResultsThis study represents the first phylogenetic hypothesis of sucking louse relationships using molecular data and we find significant conflict between phylogenies constructed using molecular and morphological data. We also find that multiple families and genera of sucking lice are not monophyletic and that extensive taxonomic revision will be necessary for this group. Based on our divergence dating analyses, sucking lice diversified in the late Cretaceous, approximately 77 Ma, and soon after the Cretaceous-Paleogene boundary (ca. 65 Ma) these lice proliferated rapidly to parasitize multiple mammalian orders and families.ConclusionsThe diversification time of sucking lice approximately 77 Ma is in agreement with mammalian evolutionary history: all modern mammal orders are hypothesized to have diverged by 75 Ma thus providing suitable habitat for the colonization and radiation of sucking lice. Despite the concordant timing of diversification events early in the association between anoplurans and mammals, there is substantial conflict between the host and parasite phylogenies. This conflict is likely the result of a complex history of host switching and extinction events that occurred throughout the evolutionary association between sucking lice and their mammalian hosts. It is unlikely that there are any ectoparasite groups (including lice) that tracked the early and rapid radiation of eutherian mammals.