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PubMed2001

A relapsing fever group spirochete transmitted by Ixodes scapularis ticks.

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.

Animals↗
PubMed2001

Effects of acorn production and mouse abundance on abundance and Borrelia burgdorferi infection prevalence of nymphal Ixodes scapularis ticks.

Risk of exposure to Lyme disease is a function of the local abundance of nymphal Ixodes ticks that are infected with the etiological agent, the spirochete Borrelia burgdorferi. We monitored abundance of white-footed mice (the principal B. burgdorferi reservoir in the eastern and central United States) and acorns (a critical food resource for mice), and Ixodes scapularis ticks, as well as ambient temperature (cumulative growing degree days) and growing season precipitation, in a forested landscape of southeastern New York State from 1994 to 2000. We found that acorn production in autumn strongly influenced abundance of white-footed mice the following summer and that abundance of mice in summer, when larval ticks are active, influenced the abundance of infected nymphs the following year. Consequently, the abundance of infected nymphal ticks can be predicted from acorn production 1.75 years earlier. Monitoring of natural fluctuations in acorn production thus supports results of prior acorn addition experiments that were conducted at small spatial scales. Growing degree days and precipitation either had no significant effect on density of nymphs or marginally increased the explanatory power of models that included acorns or mouse density as independent variables. We conclude that, at our study site in New York, the risk of human exposure to Lyme disease is affected by mouse density in the prior year and by acorn production 2 years previously.

Animal Feed↗
PubMed2002

Diversity of Ixodes-borne Borrelia species--clinical, pathogenetic, and diagnostic implications and impact on vaccine development.

Among Borrelia spirochetes carried by hard ticks belonging to the various Ixodes species, at least 10 species can be distinguished. Of these, Borrelia burgdorferi sensu stricto is involved in human Lyme borreliosis in North America and Europe, and Borrelia garinii and Borrelia afzelii in human disease in Europe and Asia. The pathogenetic significance of the other species is uncertain. Although some of the Borrelia species are restricted to certain tick species, Ixodes ricinus, the vector of Lyme borreliosis in Europe, can be infested by at least five different species, including all three pathogenic species. There is evidence that different Borrelia species are preferentially found in different hosts: In Europe, B. afzelii is frequently found in small mammals, whereas B. garinii and Borrelia valaisiana are often found in birds. This could very well be related to differential sensitivity of these species to complement-mediated bactericidal activity of different hosts. Borrelial complement regulator acquiring proteins, among them OspE or Erp proteins, bind to host factor H and related proteins, and this binding protects against activation of complement by the spirochetal surface. The binding is different for proteins originating from different species and is also depending on the host origin of factor H. In Europe, B. garinii is mainly found in neuroborreliosis, whereas in skin disease B. afzelii is more frequently found. The reason is unclear. The majority of human sera cross-react between proteins of different Borrelia species, but some sera react only with proteins from one of the species. This holds especially for reactivity with OspC. A vaccine against B. burgdorferi sensu stricto has been licensed, but was recently redrawn from the market because of commercial reasons. A vaccine protecting against all three pathogenic species is not yet available.

Animals↗
PubMed2004

Occurrence of Borrelia afzelii and Borrelia garinii in Ixodes ricinus ticks from southern Moravia, Czech Republic.

During the years 1996-2000, a total of 2398 Ixodes ricinus ticks were collected in three areas of southern Moravia and eastern Bohemia, Czech Republic, and examined by dark-field microscopy for the presence of spirochetes. The prevalence of B. burgdorferi sensu lato in Ixodes ricinus ticks varied and depended upon the year. In 1996, the prevalence 6.8% was observed, during 1997 and 1998, it increased to 8.4% and 12.3%, respectively. The lowest prevalence was observed in 1999 (3.6%), and in 2000 it increased to 4.0%. The mean rate of infection was 6.5%, and the proportions of infected ticks were 12.2% in 263 male ticks, 8.3% in 289 female ticks, 6.0% in 1621 nymphs, and 1.3% in 225 larvae. From the total of 156 highly infected ticks (>100 spirochetes per sample) transferred into BSK-H medium for isolation attempts, 13 isolates were obtained. PCR-RFLP and electrophoresis (SDS-PAGE) were used for the identification and characterization of Borrelia strains. Ten tick isolates were identified as Borrelia afzelii, and the other three isolates were found to be Borrelia garinii. The results indicate the epidemiological importance of B. afzelii and B. garinii in central Europe, and emphasize the role of I. ricinus in the ecology of B. burgdorferi and in the epidemiology and epizootiology of Lyme disease.

Animals↗
PubMed2006

Co-detection of Bartonella henselae, Borrelia burgdorferi, and Anaplasma phagocytophilum in Ixodes pacificus ticks from California, USA.

Presence of Bartonella DNA was explored in 168 questing adult Ixodes pacificus ticks from Santa Cruz County, California. Bartonella henselae type I DNA was amplified from 11 ticks (6.55%); previously, two (1.19%) were found to be infected with Borrelia burgdorferi and five (2.98%) with Anaplasma phagocytophilum. Detection of B. henselae was not dependent on co-infection. The present study offers additional evidence that Ixodes spp. ticks may act as hosts and possibly vectors for B. henselae.

Anaplasma phagocytophilum↗
PubMed1996

Ixodes pacificus (Acari: Ixodidae) as a vector of Ehrlichia equi (Rickettsiales: Ehrlichieae).

Ehrlichia equi, a rickettsia described from horses in California 30 yr ago, causes equine granulocytic ehrlichiosis throughout the Americas and possibly Europe. Here, we report experimental transmission of E. equi from infected to susceptible horses through bites of western blacklegged ticks, Ixodes pacificus (Cooley & Kohls). In preliminary field studies, only I. pacificus consistently infested horses and vegetation at 3 locations with contemporary cases of equine ehrlichosis, and in particular, I. pacificus was the only species found attached to all of the infected horses. Exposure to bites of ticks in the genus Ixodes poses previously unrecognized and serious health risks to humans and animals.

Animals↗
PubMed1998

Occurrence of Ixodes scapularis (Acari: Ixodidae) on a selected segment of the Appalachian Trail.

A 918-km section of the Appalachian National Scenic Trail from the West Virginia-Maryland border to the Massachusetts-Vermont border was surveyed for the presence of Ixodes scapularis Say. The trail and its edges were drag-sampled during 4 hikes between May and October 1991. Trips were designed to survey areas of the Appalachian Trail when I. scapularis might be questing and to revisit states endemic for Lyme disease during differing times. After sampling for ticks, meteorological and ecological characteristics were measured at each site. In total, 1,776 km of the Appalachian Trail were hiked during 88 d and resulted in sampling 489 sites. All life stages of Ixodes scapularis (n = 46) were collected from 21 sites within a 331-km range of the Appalachian Trail between Salisbury, CT, to Delaware Water Gap, PA. This segment of Appalachian Trial is easily accessible to a large urban population and should be posted with tick warning signs to alert the public to the presence of I. scapularis.

Animals↗
PubMed1998

Ehrlichial DNA amplified from Ixodes ricinus (Acari: Ixodidae) in France.

Granulocytic ehrlichia 16S rDNA was amplified for the 1st time from an Ixodes ricinus (Linne) tick collected in Europe. Sequence analysis of polymerase chain reaction products from the 16S rRNA gene demonstrated the organism from which it originated to be closely related to the agent of human granulocytic ehrlichiosis, an emerging disease that was recently described in the United States; Ehrlichia phagocytophila, the agent of tick-borne fever of ruminants in Europe; and Ehrlichia equi. the agent of the worldwide equine granulocytic ehrlichiosis. These granulocytic ehrlichiae have been associated with Ixodes spp. ticks that may act as vectors. It remains to be determined if each of these granulocytic ehrlichiae, that may constitute variants of the same species, is responsible for a specific disease in animals and in humans.

Animals↗
PubMed2000

Characterization of a new spotted fever group rickettsia detected in Ixodes ricinus (Acari: Ixodidae) collected in Slovakia.

Two previously undescribed rickettsiae were detected in Ixodes ricinus Ricketts by polymerase chain reaction. Ixodes ricinus Slovakia (IRS) 3 and IRS4 were identified in ticks collected in northeastern and southwestern Slovakia, respectively. Sequences of the 16S rRNA citrate synthase (gltA) and outer membrane protein rOmpA (ompA) encoding genes of both strains were nearly identical but were distinct from those of all other known rickettsiae. Phylogenetic relationships inferred from the comparison of these sequences with those of other members of the genus Rickettsia indicate that IRS3 and IRS4 constitute a new rickettsial genotype and form a separate cluster among the spotted fever group rickettsiae.

Animals↗
PubMed2005

Three multiplex assays for detection of Borrelia burgdorferi sensu lato and Borrelia miyamotoi sensu lato in field-collected Ixodes nymphs in North America.

Two hundred fifty New Jersey field-collected Ixodes scapularis Say ticks and 17 Colorado Ixodes spinipalpis Hadwen & Nuttall ticks were tested using three separate multiplex real-time polymerase chain reaction (PCR) assays. One assay targets the rrs-rrlA IGS region of Borrelia spp. to detect Borrelia burgdorferi sensu lato (s.l.) and Borrelia miyamotoi s.l. The second assay targets the ospA region of B. burgdorferi s.l. to detect B. burgdorferi sensu stricto (s.s.), Borrelia bissettii, and Borrelia andersonii. The final assay targets the glpQ region of B. miyamotoi s.l. to differentiate B. miyamotoi LB-2001 and Borrelia lonestari. A testing scheme combining these tests yielded 18% of tested I. scapularis ticks surveyed from New Jersey positive for B. burgdorferi s.s., 3.2% I. scapularis ticks positive for B. miyamotoi LB-2001, and 41.2% I. spinipalpis ticks positive for B. bissettii surveyed from Colorado.

Animals↗
PubMed2006

Molecular analysis of microbial communities identified in different developmental stages of Ixodes scapularis ticks from Westchester and Dutchess Counties, New York.

Ixodes scapularis ticks play an important role in the transmission of a wide variety of pathogens between various mammalian species, including humans. Pathogens transmitted by ticks include Borrelia, Anaplasma and Babesia. Although ticks may harbour both pathogenic and non-pathogenic microflora, little is known about how the diversity of the microflora within ticks may influence the transmission of pathogens. To begin addressing this question, we examined the composition of bacterial communities present in Ixodes scapularis collected from Westchester and Dutchess Counties, New York State, at different developmental and nutritional stages. Genetic fingerprints of bacterial populations were generated by temporal temperature gradient gel electrophoresis (TTGE) separation of individual polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments, followed by DNA sequence analysis for bacterial identification. The fingerprints of the TTGE bands were grouped into five clusters. The most abundant DNA sequence found in all the samples was Rickettsia, followed by Pseudomonas and Borrelia. Ralstonia, Anaplasma, Enterobacterias, Moraxella, Rhodococcus and uncultured proteobacterium were present as well. We also determined the prevalence of Anaplasma phagocytophilum and Borrelia burgdorferi by PCR and DNA sequence analysis. Statistical analyses indicated significant variations in the bacterial communities depending on tick developmental stage and degree of engorgement. We suggest that these two elements affect microbial diversity within the tick and may in turn influence pathogen transmission to humans and animals after tick bite.

Animals↗
PubMed2003

Candidatus Ehrlichia walkerii: a new Ehrlichia detected in Ixodes ricinus tick collected from asymptomatic humans in Northern Italy.

Ixodes ricinus harbors many infectious agents pathogenic for humans. A cause of fever is found in less than 50% of patients exposed to ticks. Investigations on 359 Ixodes ticks removed from asymptomatic patients in Northern Italy revealed the presence of a new ehrlichial agent in 10 ticks. Comparison of the 16S rRNA and the gltA gene sequences showed the organism is most closely related to Ehrlichia ruminantium. We propose this new Ehrlichia be named "candidatus Ehrlichia walkerii."

Animals↗
PubMed2000

New Ehrlichia species closely related to Ehrlichia chaffeensis isolated from Ixodes ovatus ticks in Japan.

Seven Ehrlichia strains (six HF strains and one Anan strain) that were obtained from laboratory mice by intraperitoneally inoculating homogenates of adult Ixodes ovatus collected in Japan were characterized. 16S rRNA sequences of all six HF strains were identical, and the sequences were 99.7, 98.2, and 97.7% identical to those of Anan strain, Ehrlichia chaffeensis (human monocytic ehrlichiosis agent), and E. muris, respectively. Partial GroEL amino acid sequencing also revealed that the six HF strains had identical sequences, which were 99.0, 98.5, and 97.3% identical to those of E. chaffeensis, the Anan strain, and E. canis, respectively. All HF strains were lethal to mice at higher dosages and intraperitoneal inoculation, whereas the Anan or E. muris strain induced only mild clinical signs. Light and electron microscopy of moribund mice inoculated with one of the HF strains revealed severe liver necrosis and the presence of numerous ehrlichial inclusions (morulae) in various organs. The study revealed that members of E. canis genogroup are naturally present in Ixodes ticks. HF strains that can cause severe illness in immunocompetent laboratory mice would be valuable in studying the pathogenesis and the roles of both cellular and humoral immune responses in ehrlichiosis caused by E. canis genogroup.

Amino Acid Sequence↗
PubMed2001

Identification of Ehrlichia spp. and Borrelia burgdorferi in Ixodes ticks in the Baltic regions of Russia.

The presence and distribution of Ehrlichia spp. and Borrelia burgdorferi sensu lato was demonstrated among ixodid ticks collected in the Baltic regions of Russia, where Lyme borreliosis is endemic. A total of 3,426 Ixodes ricinus and 1,267 Ixodes persulcatus specimens were collected, and dark-field microscopy showed that 265 (11.5%) I. ricinus and 333 (26.3%) I. persulcatus ticks were positive. From these samples, 472 dark-field-positive and 159 dark-field-negative ticks were subjected to PCR and subsequent reverse line blot hybridization. Fifty-four ticks (8.6%) carried Ehrlichia species, and 4 (0.6%) carried ehrlichiae belonging to the Ehrlichia phagocytophila complex, which includes the human granulocytic ehrlichiosis agent. The E. phagocytophila complex and an Ehrlichia-like species were detected only in I. ricinus whereas Ehrlichia muris was found exclusively in I. persulcatus, indicating a possible vector-specific infection. Borrelia garinii was found predominantly in I. persulcatus, but Borrelia afzelii was evenly distributed among the two tick species. Only two I. ricinus ticks carried B. burgdorferi sensu stricto, while Borrelia valaisiana and a newly identified B. afzelii-like species were found in 1.7 and 2.5% of all ticks, respectively. Of the dark-field-positive ticks, only 64.8% yielded a Borrelia PCR product, indicating that dark-field microscopy may detect organisms other than B. burgdorferi sensu lato. These observations show that the agent of human granulocytic ehrlichiosis may be present in ticks in the Baltic regions of Russia and that clinicians should be aware of this agent as a cause of febrile disease.

Animals↗
PubMed2006

Comparison of direct fluorescent antibody staining and real-time polymerase chain reaction for the detection of Borrelia burgdorferi in Ixodes scapularis ticks.

Borrelia burgdorferi, the agent responsible for causing Lyme disease in humans and animals, is transmitted via the bite of infected Ixodes spp. ticks. Ticks removed from humans and animals are routinely tested by diagnostic laboratories to determine if they are infected with these bacteria. The objective of this study was to compare the efficacy of 2 commonly used methods, direct fluorescent antibody staining and real-time polymerase chain reaction (PCR), for the detection of B. burgdorferi in Ixodes scapularis ticks. One hundred and twenty-seven adult I. scapularis ticks collected in Connecticut, a Lyme disease endemic area, were tested, and results were compared. Results showed 24.8% ticks tested positive for Borrelia spp. by fluorescent antibody testing and 32.5% ticks were positive for B. burgdorferi by real-time PCR testing. When ticks were grouped into categories by level of engorgement (unengorged, partially engorged, and fully engorged), 95% of unengorged ticks, 90.5% of partially engorged, and 86.8% of engorged ticks tested were in agreement. Ten of the 127 ticks examined were too dehydrated to be tested by the fluorescent antibody technique; half of these tested positive by PCR. Real-time PCR appears to be the better of these 2 methods for the diagnosis of this bacterial infection in I. scapularis ticks.

Animals↗
PubMed2006

Natural infection, transovarial transmission, and transstadial survival of Rickettsia bellii in the Tick Ixodes loricatus (Acari: Ixodidae) from Brazil.

An Ixodes loricatus engorged female, infected with Rickettsia bellii, was collected from an opossum (Didelphis aurita) in Mogi das Cruzes, São Paulo State, Brazil. Two consecutive laboratory tick generations (F(1) and F(2)) reared from this single engorged female were evaluated for Rickettsia infection by polymerase chain reaction (PCR) targeting specific Rickettsia genes. Immature ticks fed on naïve Wistar rats (Rattus norvegicus) and adult ticks fed on opossum (D. aurita), both free of ticks and rickettsial infection. PCR performed on individual ticks from the F(1) (20 larvae, 10 nymphs, and 10 adults) and the F(2) (30 larvae, 30 nymphs, and 15 adults) yielded expected bands compatible with Rickettsia. All the PCR products that were sequenced, targeting gltA gene, resulted in sequences identical to each other and 99.7% (349/350) similar to the corresponding sequence of R. bellii in GenBank. The R. bellii infection on ticks from the second laboratory generation (F(2)) was confirmed by other PCR protocols and successful isolation of R. bellii in cell culture. We report for the first time a Rickettsia species infecting I. loricatus, and the first report of R. bellii in the tick genus Ixodes. We conclude that there was an efficient transovarial transmission and transstadial survival of this Rickettsia species in the tick I. loricatus. Our results suggest that R. bellii might be maintained in nature solely by transovarial transmission and transstadial survival in ticks (no amplifier vertebrate host is needed), since there has been no direct or indirect evidence of infection of vertebrate hosts by R. bellii.

Animals↗
PubMed2002

Nymphal diapause and its photoperiodic control in the tick Ixodes scapularis (Acari: Ixodidae).

It is shown experimentally that the option between developmental diapause and non-diapause development in nymphs of Ixodes scapularis Say, 1821 (Middle Atlantic population) is determined by photoperiodic conditions according to a two-step photoperiodic reaction of short-day long-day type. Diapause arrest of development is induced by an impact of either long day upon unfed nymphs, or short day upon engorged nymphs, while non-diapause development completed in 2-2.5 months at 20 degrees C needs the change from short-day to long-day conditions. Some ecophysiological aspects of mechanisms controlling seasonal development of ticks belonging to Ixodes ricinus complex are discussed.

Animals↗
PubMed2000

Parasitism by Ixodes didelphidis and I. loricatus (Acari: Ixodidae) on small wild mammals from an Atlatic Forest in the State of Sao Paulo, Brazil.

From January 1995 to June 1996, ticks were studied in a fragment of Atlantic Forest in a residential area in the city of Itapevi, State of Sao Paulo, Brazil. Cases of human Lyme disease-like illness were registered in this area during the spring of 1992. The monthly relative density of ticks was determined and the influence of seasonal climatic conditions was evaluated as well as the relationship between ticks and hosts. Ticks (n = 88) were collected from small mammals captured (n = 134) in monthly trappings where the traps were operated for five consecutive days. Immature ticks (n = 42, 47.7%) were identified as Ixodes spp. The adult ticks (n = 46, 52.3%) were identified as Ixodes didelphidis Fonseca and Aragão (n = 19, 21.6%), I. loricatus Neumann (n = 26, 29.5%) and Amblyomma cajennense (F.) (n = 1, 1.1%). The monthly correlations between tick numbers and meteorological data were not significant. The correlation between the different stages of ticks and the two seasons (cold-dry and warm-rainy) indicated that both immature and adult ticks showed a seasonal pattern of abundance. The highest numbers of immature ticks were observed on rodents, during the cold-dry season (from April to September) with a peak in August 1995. Adults ticks were predominant during the warm-rainy season (from October to March) with a peak in January 1995. Adult ticks were only collected on marsupials.

Animals↗