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A species of Borrelia spirochetes previously unknown from North America has been found to be transmitted by Ixodes scapularis ticks. Infected ticks are positive for Borrelia spp. by DFA test but negative for Borrelia burgdorferi by polymerase chain reaction (PCR) using species-specific primers for 16S rDNA, outer surface protein A, outer surface protein C, and flagellin genes. A 1,347-bp portion of 16S rDNA was amplified from a pool of infected nymphs, sequenced, and compared with the homologous fragment from 26 other species of Borrelia. The analysis showed 4.6% pairwise difference from B. burgdorferi, with the closest relative being Borrelia miyamotoi (99.3% similarity) reported from Ixodes persulcatus in Japan. Phylogenetic analysis showed the unknown Borrelia to cluster with relapsing fever group spirochetes rather than with Lyme disease spirochetes. A 764-bp fragment of the flagellin gene was also compared with the homologous fragment from 24 other Borrelia species. The flagellin sequence of B. burgdorferi was 19.5% different from the unknown Borrelia and showed 98.6% similarity with B. miyamotoi. A pair of PCR primers specifically designed to amplify a 219-bp fragment of the flagellin gene from this spirochete was used to survey field-collected I. scapularis nymphs from five northeastern states (Connecticut, Rhode Island, New York, New Jersey, and Maryland). Positive results were obtained in 1.9-2.5% of 712 nymphs sampled from four states but in none of 162 ticks collected from Maryland. Transovarial transmission was demonstrated by PCR of larval progeny from infected females with filial infection rates ranging from 6% to 73%. Transstadial passage occurred from larvae through adults. Vertebrate infection was demonstrated by feeding infected nymphs on Peromyscus leucopus mice and recovering the organism from uninfected xenodiagnostic larvae fed 7-21 days later. Considering the frequency of contact between I. scapularis and humans, further work is needed to determine the potential public health significance of yet another zoonotic agent transmitted by this tick species.

Twenty eight species of Ixodidae have been found on man in South America (21 Amblyomma, 1 Boophilus, 2 Dermacentor, 2 Haemaphysalis, 1 Ixodes and 1 Rhipicephalus species). Most of them are rarely found on man. However, three species frequently parasitize humans in restricted areas of Argentina (A. neumanni reported from 46 localities), Uruguay (A. triste from 21 sites) and Argentina-Brazil (A. parvum from 27 localities). The most widespread ticks are A. cajennense (134 localities in Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela), A. ovale (37 localities in Argentina, Brazil, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela) and A. oblongoguttatum (28 sites in Brazil, Colombia, French Guiana, Guyana, Suriname and Venezuela). Amblyomma aureolatum (18 localities in Argentina, Brazil, French Guiana and Paraguay), A. cajennense, and A. triste are vectors of rickettsioses to man in South America. A better understanding of the respective roles of these and other tick species in transmitting pathogens to humans will require further local investigations. Amblyomma ticks should be the main subjects of these studies followed by species of Boophilus, Dermacentor, Haemaphysalis and Rhipicephalus species. In contrast with North America, Europe and Asia, ticks of the genus Ixodes do not appear to be major players in transmitting diseases to human. Indeed, there is only one record of an Ixodes collected while feeding on man for all South America.

Bartonella species were isolated from the blood of 63 of 325 Rattus norvegicus and 11 of 92 Rattus rattus from 13 sites in the United States and Portugal. Infection in both Rattus species ranged from 0% (e.g., 0/87) to approximately 60% (e.g., 35/62). A 337-bp fragment of the citrate synthase (gltA) gene amplified by polymerase chain reaction was sequenced from all 74 isolates. Isolates from R. norvegicus were most similar to Bartonella elizabethae, isolated previously from a patient with endocarditis (93%-100% sequence similarity), followed by Bartonella grahamii and other Bartonella species isolated from Old World rodents (Clethrionomys species, Mus musculus, and Rattus species). These data suggest that Rattus species are a reservoir host for pathogenic Bartonella species and are consistent with a hypothesized Old World origin for Bartonella species recovered from Rattus species introduced into the Americas.

A portion of mitochondrial 12S rDNA sequences (337-355 base pairs) and 63 morphological characters of 36 hard-tick species belonging to 7 genera were analyzed to determine the phylogenetic relationships among groups and species of Rhipicephalus and between the genera Rhipicephalus and Boophilus. Molecular and morphological data sets were first examined separately. The molecular data were analyzed by maximum parsimony (MP), maximum likelihood, and neighbor-joining distance methods; the morphological data were analyzed by MP After their level of congruence was evaluated by a partition homogeneity test, all characters were combined and analyzed by MP. The branches of the tree obtained by combining the data sets were better resolved than those of the trees inferred from the separate analyses. Boophilus is monophyletic and arose within Rhipicephalus. Boophilus species clustered with species of the Rhipicephalus evertsi group. Most of the clustering within Rhipicephalus was, however, consistent with previous classifications based on morphological data. Morphological characters were traced on the molecular reconstruction in order to identify characters diagnostic for monophyletic clades. Within the Rhipicephalus sanguineus complex, the sequences of specimens morphologically identified as Rhipicephalus turanicus were characterized by a high level of variability, indicating that R. turanicus-like morphology may cover a spectrum of distinct species.

BackgroundAmblyomma cajennense F. is one of the best known and studied ticks in the New World because of its very wide distribution, its economical importance as pest of domestic ungulates, and its association with a variety of animal and human pathogens. Recent observations, however, have challenged the taxonomic status of this tick and indicated that intraspecific cryptic speciation might be occurring. In the present study, we investigate the evolutionary and demographic history of this tick and examine its genetic structure based on the analyses of three mitochondrial (12SrDNA, d-loop, and COII) and one nuclear (ITS2) genes. Because A. cajennense is characterized by a typical trans-Amazonian distribution, lineage divergence dating is also performed to establish whether genetic diversity can be linked to dated vicariant events which shaped the topology of the Neotropics.ResultsTotal evidence analyses of the concatenated mtDNA and nuclear + mtDNA datasets resulted in well-resolved and fully congruent reconstructions of the relationships within A. cajennense. The phylogenetic analyses consistently found A. cajennense to be monophyletic and to be separated into six genetic units defined by mutually exclusive haplotype compositions and habitat associations. Also, genetic divergence values showed that these lineages are as distinct from each other as recognized separate species of the same genus. The six clades are deeply split and node dating indicates that they started diverging in the middle-late Miocene.ConclusionsBehavioral differences and the results of laboratory cross-breeding experiments had already indicated that A. cajennense might be a complex of distinct taxonomic units. The combined and congruent mitochondrial and nuclear genetic evidence from this study reveals that A. cajennense is an assembly of six distinct species which have evolved separately from each other since at least 13.2 million years ago (Mya) in the earliest and 3.3 Mya in the latest lineages. The temporal and spatial diversification modes of the six lineages overlap the phylogeographical history of other organisms with similar extant trans-Amazonian distributions and are consistent with the present prevailing hypothesis that Neotropical diversity often finds its origins in the Miocene, after the Andean uplift changed the topology and consequently the climate and ecology of the Neotropics.

In addition to being a major nuisance biter, the lone star tick, Amblyomma americanum (L.), is increasingly recognized as an important vector of pathogens affecting humans, domestic animals, and wildlife. Despite its notoriety, efforts have been lacking to define the spatial occurrence of A. americanum in the continental United States with precision beyond that conveyed in continental-scale distribution maps. Here we present a county-level distribution map for A. americanum generated by compiling collection records obtained from a search of the published literature and databases managed by the USDA, U.S. National Tick Collection, and Walter Reed Biosystematics Unit. Our decadal and cumulative maps, which visually summarize 18,121 collections made between 1898 and 2012, show that A. americanum is either established (≥six ticks or ≥two life stages) or reported (

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