A human-derived strain of the agent of human granulocytic ehrlichiosis, a recently described emerging rickettsial disease, has been established by serial blood passage in mouse hosts. Larval deer ticks acquired infection by feeding upon such mice and efficiently transmitted the ehrlichiae after molting to nymphs, thereby demonstrating vector competence. The agent was detected by demonstrating Feulgen-positive inclusions in the salivary glands of the experimentally infected ticks and from field-derived adult deer ticks. White-footed mice from a field site infected laboratory-reared ticks with the agent of human granulocytic ehrlichiosis, suggesting that these rodents serve as reservoirs for ehrlichiae as well as for Lyme disease spirochetes and the piroplasm that causes human babesiosis. About 10% of host-seeking deer ticks were infected with ehrlichiae, and of these, 20% also contained spirochetes. Cotransmission of diverse pathogens by the aggressively human-biting deer tick may have a unique impact on public health in certain endemic sites.

https://www.pnas.org/content/pnas/93/12/6209.full.pdf

Perpetuation of the agent of human granulocytic ehrlichiosis in a deer tick-rodent cycle

Phylogeography is a young, vigorous and integrative field of study that uses genetic data to understand the history of populations. This field has recently expanded into many areas of biology and also into several historical disciplines of Earth sciences. In this review, I present a numerical synthesis of the phylogeography literature based on an examination of over 3000 articles published during the first 20 years of the field (i.e. from 1987 to 2006). Information from several topics needed to evaluate the progress, tendencies and deficiencies of the field is summarized for 10 major groups of organisms and at a global scale. The topics include the geography of phylogeographic surveys, comparative nature of studies, temporal scales and major environments investigated, and genetic markers used. I also identify disparities in research productivity between the developing and the developed world, and propose ways to reduce some of the challenges faced by phylogeographers from less affluent countries. Phylogeography has experienced explosive growth in recent years fuelled by developments in DNA technology, theory and statistical analysis. I argue that the intellectual maturation of the field will eventually depend not only on these recent developments, but also on syntheses of comparative information across different regions of the globe. For this to become a reality, many empirical phylogeographic surveys in regions of the Southern Hemisphere (and in developing countries of the Northern Hemisphere) are needed. I expect the information and views presented here will assist in promoting international collaborative work in phylogeography and in guiding research efforts at both regional and global levels.

/pdf/twenty-years-of-phylogeography-the-state-of-the-field-and-3oxye1mcjy.pdf

Twenty years of phylogeography: the state of the field and the challenges for the Southern Hemisphere.

The mitochondrial 16S rRNA gene sequences of the following eight European Metastriata tick species were obtained by direct polymerase-chain-reaction cycle sequencing and silver-staining methods: Rhipicephalus bursa, R. pusillus, R. sanguineus, R. turanicus, Boophilus annulatus, Dermacentor marginatus, Haemaphysalis punctata, and Hyalomma lusitanicum. This mitochondrial gene seems to be a good marker for the establishment of genetic relationships among closely related tick species, but it does not seem to be useful for comparisons of distantly related taxa. The molecular data provide very strong support for the monophyly of the Rhipicephalinae, including Hyalomma spp. However, the genus Rhipicephalus may not be considered a monophyletic group; in all analyses carried out in this study, R. bursa clustered with Boophilus spp. The high percentage of similarity (98.7%) observed between R. sanguineus and R. turanicus sequences would suggest that these species recently diverged within the Rhipicephalus genus. Phylogenetic analyses showed a monophyletic relationship among Amblyomminae taxa. The relationships between Haemaphysalis species and the true placement of this genus within Metastriata could not be resolved.

Mitochondrial 16S rDNA sequences and phylogenetic relationships of species of Rhipicephalus and other tick genera among Metastriata (Acari: Ixodidae)

Wildlife diseases are in fashion. This is creating an explosion of related knowledge. Despite this, the dynamics of both wildlife and diseases and the changes in livestock and wildlife management make it increasingly difficult to overview the current situation of wildlife diseases in Europe. This paper aims to discuss the available management possibilities and to highlight current research priorities. One area that causes severe concern to authorities is diseases largely under control in domestic populations but still existing as a reservoir in wildlife. Multihost situations are also of concern for wildlife management and conservation, as diseases can affect the productivity and density of wildlife populations with an economic or recreational value. Concern about emerging diseases is rising in recent years, and these may well occur at the fertile livestock-wildlife interface. Wildlife-related zoonoses are a diverse and complex issue that requires a close collabora- tion between wildlife ecologists, veterinarians and public health professionals. A few risk factors can be identified in most of the relevant wildlife diseases. Among them are (1) the introduction of diseases through movements or trans- locations of wild or domestic animals, (2) the consequences of wildlife overabundance, (3) the risks of open air livestock breeding, (4) vector expansion and (5) the expansion or introduction of hosts. Wildlife disease control requires the integration of veterinary, ecology and wildlife management expertise. In addition to surveillance, attempts to control wildlife diseases or to avoid disease transmission between wildlife and livestock have been based on setting up barriers, culling, hygienic measures, habitat manage- ment, vector control, treatments and vaccination. Surveil- lance and descriptive studies are still valuable in regions, species or diseases that have received less attention or are (at least apparently) emerging. Nonetheless, limiting the research effort to the mere reporting of wildlife disease outbreaks is of limited value if management recommenda- tions are not given at the same time. Thus, more experimental approaches are needed to produce substantial knowledge that enables authorities to make targeted management recommendations. This requires policy mak- ers to be more aware of the value of science and to provide extra-funding for the establishment of multidisciplinary scientific teams.

/pdf/diseases-shared-between-wildlife-and-livestock-a-european-i8rd9v8yvo.pdf

Diseases shared between wildlife and livestock: a European perspective

Borrelia burgdorferi sensu lato, the spirochete that causes human Lyme borreliosis (LB), is a genetically and phenotypically divergent species. In the past several years, various molecular approaches have been developed and used to determine the phenotypic and genetic heterogeneity within the LB-related spirochetes and their potential association with distinct clinical syndromes. These methods include serotyping, multilocus enzyme electrophoresis, DNA-DNA reassociation analysis, rRNA gene restriction analysis (ribotyping), pulsed-field gel electrophoresis, plasmid fingerprinting, randomly amplified polymorphic DNA fingerprinting analysis, species-specific PCR and PCR-based restriction fragment length polymorphism (RFLP) analysis, and sequence analysis of 16S rRNA and other conserved genes. On the basis of DNA-DNA reassociation analysis, 10 different Borrelia species have been described within the B. burgdorferi sensu lato complex: B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii, Borrelia japonica, Borrelia andersonii, Borrelia valaisiana, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, and Borrelia bissettii sp. nov. To date, only B. burgdorferi sensu stricto, B. garinii, and B. afzelii are well known to be responsible for causing human disease. Different Borrelia species have been associated with distinct clinical manifestations of LB. In addition, Borrelia species are differentially distributed worldwide and may be maintained through different transmission cycles in nature. In this paper, the molecular methods used for typing of B. burgdorferi sensu lato are reviewed. The current taxonomic status of B. burgdorferi sensu lato and its epidemiological and clinical implications, especiallly correlation between the variable clinical presentations and the infecting Borrelia species, are discussed in detail.

Molecular Typing of Borrelia burgdorferi Sensu Lato: Taxonomic, Epidemiological, and Clinical Implications

To evaluate the role of migratory birds in the long-distance dispersal of Ixodes dammini ticks and in the spread of Lyme disease, a 6-year study of migrating birds to an offshore New England island was conducted during 1989-1994. I. dammini are not endemic on this island, therefore allowing assessment of long-distance tick dispersal rather than local infestation. Of 11,324 spring migrants examined, 1.2% were infested with I. dammini. Of 8607 fall migrants examined, 0.2% were infested. Of nymphal ticks examined, 20% were infected with Borrelia burgdorferi. OspB DNA sequencing of 6 B. burgdorferi isolates was identical to sequences of 2 strains common in coastal Maine. It is evident that bird migration allows for long-distance dispersal of I. dammini from areas where they are endemic to areas where they are not and that a few bird species account for the majority of tick dispersal. The likelihood of establishment of enzootic Lyme disease by this mechanism is discussed.

/pdf/role-of-bird-migration-in-the-long-distance-dispersal-of-2rts3ga2aa.pdf

Role of bird migration in the long-distance dispersal of Ixodes dammini, the vector of lyme disease

Discriminating between Ixodes Ticks by Means of Mitochondrial DNA Sequences

We analyzed the geographic distribution of the Ixodes ricinus-like ticks in eastern North America by comparing the mitochondrial 16S rDNA sequences of specimens sampled directly from the field during the 1990s. Two distinct lineages are evident. The southern clade includes ticks from the southeastern and middle-eastern regions of the United States. The range of the northern clade, which appears to have been restricted to the northeastern region until the mid-1900s, now extends throughout the northeastern and middle-eastern regions. These phyletic units correspond to northern and southern taxa that have previously been assigned specific status as Ixodes dammini and Ixodes scapularis, respectively. The expanding range of I. dammini appears to drive the present outbreaks of zoonotic disease in eastern North America that include Lyme disease and human babesiosis.

https://www.pnas.org/content/pnas/92/14/6284.full.pdf

Distribution of the Ixodes ricinus-like ticks of eastern North America.

Borrelia burgdorferi is a spirochete pathogen transmitted among warm-blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.

/pdf/sequence-variation-in-the-outer-surface-protein-genes-of-45lcw1u3o8.pdf

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi.

We sequenced the OspB genes of 51 Borrelia burgdorferi isolates from five sites along the coast of Maine. Seven unique nucleotide sequences were observed, with an average pairwise difference of 0.47%. Five unique amino acid sequences were represented, differing at up to five residues. Multiple strains were observed at three sites, and most strains were found at more than one site. Multiple strains were recovered from a single rat on Monhegan Island. High strain diversity of B. burgdorferi may play a role in determining the abundance of this spirochete.

OSPB Sequence Variation of Borrelia Burgdorferi Along the Coast of Maine

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