Vector Interactions and Molecular Adaptations of Lyme Disease and Relapsing Fever Spirochetes Associated with Transmission by Ticks

Emerging Infectious Diseases. Feb, 2002  |  Pubmed ID: 11897061

Pathogenic spirochetes in the genus Borrelia are transmitted primarily by two families of ticks. The Lyme disease spirochete, Borrelia burgdorferi, is transmitted by the slow-feeding ixodid tick Ixodes scapularis, whereas the relapsing fever spirochete, B. hermsii, is transmitted by Ornithodoros hermsi, a fast-feeding argasid tick. Lyme disease spirochetes are generally restricted to the midgut in unfed I. scapularis. When nymphal ticks feed, the bacteria pass through the hemocoel to the salivary glands and are transmitted to a new host in the saliva after 2 days. Relapsing fever spirochetes infect the midgut in unfed O. hermsi but persist in other sites including the salivary glands. Thus, relapsing fever spirochetes are efficiently transmitted in saliva by these fast-feeding ticks within minutes of their attachment to a mammalian host. We describe how B. burgdorferi and B. hermsii change their outer surface during their alternating infections in ticks and mammals, which in turn suggests biological functions for a few surface-exposed lipoproteins.

Protection Against Lyme Disease Spirochete Transmission Provided by Prompt Removal of Nymphal Ixodes Scapularis (Acari: Ixodidae)

Journal of Medical Entomology. May, 2002  |  Pubmed ID: 12061448

Public health recommendations for Lyme disease prevention generally include daily tick checks and prompt removal of attached ticks as a means of decreasing the risk of acquiring Lyme disease in highly endemic regions. In the current study, we determined whether crushing nymphal ticks during removal with forceps increased the risk of B. burgdorferi transmission, what degree of protection from transmission of B. burgdorferi was provided by removal of nymphal Ixodes scapularis Say at specific intervals, and whether commercial devices marketed for tick removal worked when tested against nymphal I. scapularis. Both removal via gentle pressure (26% transmission) or crushing the tick (30% transmission) caused a significant decrease in transmission as compared with the sham control (70% transmission). The degree of protection provided via tick removal decreased steadily up to 60 h of attachment; between 60 and 66 h, a dramatic falloff in protection occurred to the point where no protection was observed at 66 h. Finally, commercial tick removal devices varied widely in their efficacy for the removal of attached nymphal I. scapudaris.

Borrelia Burgdorferi-specific Monoclonal Antibodies Derived from Mice Primed with Lyme Disease Spirochete-infected Ixodes Scapularis Ticks

Hybridoma and Hybridomics. Jun, 2002  |  Pubmed ID: 12165143

We have generated a panel of IgG monoclonal antibodies (MAbs) directed against Borrelia burgdorferi strain B31 antigens, using a method whereby mice were primed with organisms naturally inoculated by Ixodes scapularis nymphal ticks. Western blot analysis showed that these MAbs recognized several B. burgdorferi B31 antigens, including the complement inhibitor factor H-binding proteins ErpA/I/N and ErpC. Two other MAbs were specific for the RevA protein, and have enabled characterization of that previously unknown protein. The data presented here suggest that the production of MAbs from animals infected by tick-bite is a potentially useful tool for the identification of novel proteins synthesized by B. burgdorferi during mammalian infection.

A Preliminary Linkage Map of the Tick, Ixodes Scapularis

Experimental & Applied Acarology. 2002  |  Pubmed ID: 14570121

A linkage map of the Ixodes scapularis genome was constructed based upon segregation amongst 127 loci. These included 84 random amplified polymorphic DNA (RAPD) markers, 32 Sequence-Tagged RAPD (STAR) markers, 5 cDNAs, and 5 microsatellites in 232 F1 intercross progeny from a single, field-collected P1 female. A preliminary linkage map of 616 cM was generated across 14 linkage groups with one marker every 10.8 cM. Assuming a genome size of approximately 10(9) bp, the relationship of physical to genetic distance is approximately 300 kb/cM in the I. scapularis genome.

Dynamic Changes in Lyme Disease Spirochetes During Transmission by Nymphal Ticks

Experimental & Applied Acarology. 2002  |  Pubmed ID: 14570124

Ticks are not crawling needles, merely delivering infectious agents to vertebrate hosts. A sophisticated interplay takes place between ticks, pathogens, and vertebrate hosts. The relationship between Ixodes ticks and the Lyme disease spirochetes they transmit involves subtle changes in spirochete populations that maximize their chances of being transmitted. An understanding of this complex interplay will, hopefully, allow the development of new tools to block transmission of tick-borne agents.

DNA Evidence of Borrelia Lonestari in Amblyomma Americanum (Acari: Ixodidae) in Southeast Missouri

Journal of Medical Entomology. Jul, 2003  |  Pubmed ID: 14680133

Amblyomma americanum collected near Lake Wappapello, Missouri, tested positive for Borrelia lonestari using polymerase chain reaction and sequence analyses of B. lonestari 16S rRNA and flagellin (flaB) genes. Twelve pools containing a total of 214 nymph or adult ticks contained evidence of infection with B. lonestari (minimum prevalence 5.6%). These data suggest that persons in southeast Missouri are at risk for exposure to B. lonestari after A. americanum tick bite, a possible cause of erythema migrans-like rash illness in this region. Derivation of the complete coding sequence for B. lonestari flaB is also reported.

Survey of Ticks Collected in Mississippi for Rickettsia, Ehrlichia, and Borrelia Species

Journal of Vector Ecology : Journal of the Society for Vector Ecology. Dec, 2003  |  Pubmed ID: 14714667

From November 1999 through October 2000, we tested ticks collected from vegetation as well as from deer, dogs, and humans for spotted fever group (SFG) rickettsiae, Ehrlichia chaffeensis, and Borrelia spp. spirochetes. A total of 149 adult ticks representing four species was collected from 11 collection sites from southwestern to northern Mississippi. Amblyomma americanum was most commonly collected (n=68), followed by Ixodes scapularis (n=53). The bird tick, Ixodes brunneus (usually rare), was the third most commonly collected tick (n=17). Eleven Dermacentor variabilis were also collected. Ticks were cut longitudinally to make smears on three microscope slides. The remaining body parts were frozen at -65 degrees C for additional testing. Tick smears were stained by direct immunofluorescence assays (DFA) for Rickettsia spp. and Borrelia spp., while indirect immunofluorescence assays (IFA) were used for Ehrlichia spp. The corresponding tick for each positive smear was evaluated using PCR analysis. None of the 149 ticks tested was DFA positive for Borrelia spp. However, smears of 30 (20%) and 32 (22%) ticks reacted with anti-E. chaffeensis sera and anti-R. rickettsii conjugate (known to react with several members of the spotted fever group), respectively. None of the ticks staining with the IFA for Ehrlichia was positive for E. chaffeensis using PCR. However, 23 (72%) of 32 FA-positive ticks for SFG rickettsiae yielded amplicons of the appropriate size when tested using a PCR assay for SFG rickettsiae, corresponding to an overall infection rate with SFG rickettsiae among the collected ticks of 15%. Smears of 12 (71%) of 17 I. brunneus revealed abundant bacilliform bacteria. PCR amplification of DNA from a single I. brunneus containing these bacteria was performed using universal primers for the 16S rRNA gene as well as Borrelia-specific primers. The predominant sequence obtained using the universal primers did not match any sequence in GenBank, but it showed 91% identity with an endosymbiont of Acanthoamoeba. Other sequences represented in the top 50 Basic Local Alignment Search (BLAST) scores were primarily from soil bacteria, although some similarity to several Anaplasma species and Ehrlichia risticii was indicated. The significance of this finding remains undetermined.

Bacteriolytic Activity of Selected Vertebrate Sera for Borrelia Burgdorferi Sensu Stricto and Borrelia Bissettii

The Journal of Parasitology. Dec, 2003  |  Pubmed ID: 14740924

An in vitro assay to evaluate the bacteriolytic activity of the complement pathway was applied to 2 strains of Borrelia bissettii, CO501 and DN127, and compared with that of B. burgdorferi sensu stricto B31. Sera from mule deer (Odocoileus hemionus) and the Western Fence lizard (Sceloporus occidentalis) were completely borreliacidal for B. burgdorferi and for both strains of B. bissettii. Serum from Bobwhite quail (Colinus virginianus) was nonlytic for B. burgdorferi and partially lytic for B. bissettii strains, CO-501 and DN127. Serum from a New Zealand White rabbit (Oryctolagus cuniculus) was partially lytic for all 3 strains of Borrelia, whereas serum from white-footed mice (Peromyscus leucopus) were nonlytic for all 3 Borrelia strains. The spectrum of complement sensitivity of B. bissettii appears to be similar to that of European B. afzelii in that tested rodent serum is not lytic to these 2 genospecies. Interestingly, both B. bissettii and B. afzelii have been found to be closely associated with rodents. Complement sensitivity demonstrated in these experiments may suggest and possibly predict specific reservoir-host associations.

Association of Borrelia Garinii and B. Valaisiana with Songbirds in Slovakia

Applied and Environmental Microbiology. May, 2003  |  Pubmed ID: 12732554

In Europe, 6 of the 11 genospecies of Borrelia burgdorferi sensu lato are prevalent in questing Ixodes ricinus ticks. In most parts of Central Europe, B. afzelii, B. garinii, and B. valaisiana are the most frequent species, whereas B. burgdorferi sensu stricto, B. bissettii, and B. lusitaniae are rare. Previously, it has been shown that B. afzelii is associated with European rodents. Therefore, the aim of this study was to identify reservoir hosts of B. garinii and B. valaisiana in Slovakia. Songbirds were captured in a woodland near Bratislava and investigated for engorged ticks. Questing I. ricinus ticks were collected in the same region. Both tick pools were analyzed for spirochete infections by PCR, followed by DNA-DNA hybridization and, for a subsample, by nucleotide sequencing. Three of the 17 captured songbird species were infested with spirochete-infected ticks. Spirochetes in ticks that had fed on birds were genotyped as B. garinii and B. valaisiana, whereas questing ticks were infected with B. afzelii, B. garinii, and B. valaisiana. Furthermore, identical ospA alleles of B. garinii were found in ticks that had fed on the birds and in questing ticks. The data show that songbirds are reservoir hosts of B. garinii and B. valaisiana but not of B. afzelii. This and previous studies confirm that B. burgdorferi sensu lato is host associated and that this bacterial species complex contains different ecotypes.

How Can We Prevent Lyme Disease?

The New England Journal of Medicine. Jun, 2003  |  Pubmed ID: 12802029

Inability of Outer-surface Protein C (OspC)-primed Mice to Elicit a Protective Anamnestic Immune Response to a Tick-transmitted Challenge of Borrelia Burgdorferi

Journal of Medical Microbiology. Jul, 2003  |  Pubmed ID: 12808075

A one-inoculation regimen of recombinant outer-surface protein C (OspC), which has been demonstrated to elicit protective immunity against a tick-borne challenge of Borrelia burgdorferi, was administered to outbred mice. Following seroconversion, the serum antibody titre against OspC was allowed to wane with time until there was little or no detection of anti-OspC antibodies by immunoblot. The mice were then challenged with an infectious dose of B. burgdorferi by tick transmission. Eleven of 12 OspC-primed mice subsequently became infected by B. burgdorferi, demonstrating that a protective anamnestic response was not generated in these mice following the introduction of infectious OspC-expressing spirochaetes.

Genetic Variation at the VlsE Locus of Borrelia Burgdorferi Within Ticks and Mice over the Course of a Single Transmission Cycle

Journal of Bacteriology. Aug, 2003  |  Pubmed ID: 12867452

The Lyme disease spirochete, Borrelia burgdorferi, causes a persistent infection in the vertebrate host even though infected animals mount an active immune response against the spirochete. One strategy used by the spirochete to evade vertebrate host immunity is to vary the structure and expression of outer membrane antigens. The vlsE locus represents the best-studied example of antigenic variation in B. burgdorferi. During vertebrate host infection, recombination between the active vlsE locus and silent, partial vlsE copies leads to gene conversion events and the generation of novel alleles at the expression site. In the present study, we followed a population of B. burgdorferi organisms moving through vertebrate host and tick stages to complete one transmission cycle. The major goal of the study was to determine if the vlsE locus was subject to different selective pressure and/or recombination frequency at different stages of the spirochete's life cycle. We report here that the vlsE genetic diversity generated within the rodent host was maintained through the larval and nymphal tick stages. Therefore, naturally infected ticks are likely to transmit spirochete populations with multiple vlsE alleles into naive vertebrate hosts. Although vlsE genetic diversity in mice was maintained through tick stages, the dominant vlsE alleles were different between tick stages as well as between individual ticks. We propose that population-level bottlenecks experienced by spirochetes, especially during the larval-to-nymphal molt, are responsible for individual infected ticks harboring different dominant vlsE alleles. Although vlsE genetic diversity is maintained through tick stages, the VlsE protein is unlikely to be of functional importance in the vector, because the protein was expressed by very few (<1%) bacteria in the vector.

Vector Competence of Ixodes Pacificus and I. Spinipalpis (Acari: Ixodidae), and Reservoir Competence of the Dusky-footed Woodrat (Neotoma Fuscipes) and the Deer Mouse (Peromyscus Maniculatus), for Borrelia Bissettii

Journal of Medical Entomology. May, 2003  |  Pubmed ID: 12943110

We investigated the experimental vector competence of Ixodes pacificus Cooley and Kohls and Ixodes spinipalpis Hadwen and Nuttall, and the reservoir competence of the dusky-footed woodrat (Neotoma fuscipes Baird) and the deer mouse (Peromyscus maniculatus [Wagner]), for Borrelia bissettii Postic, Marti Ras, Lane, Hendson, and Baranton. Both rodent species are capable reservoirs for B. bissettii; infection rates for I. pacificus or I. spinipalpis nymphs fed as larvae on infected animals ranged from 50 to 57%. Moreover, both I. pacificus and I. spinipalpis are efficient vectors of B. bissettii. Viable infections were recorded from all rodents known to be exposed to one or more infected nymphs of I. spinipalpis (seven deer mice, two white mice) or I. pacificus (seven deer mice). In contrast, none of four New Zealand white rabbits fed upon by 90 I. pacificus nymphs with a probable B. bissettii infection rate of >50% became infected or seroconverted. The attachment and feeding success of laboratory-reared nymphs similarly confined with deer mice in muslin-covered wire-mesh cages for 24 h ranged from 0% for I. pacificus to 17-73% for I. spinipalpis. Notably, the I. pacificus nymphs were physiologically capable of feeding; nymphs failing to attach to rodents fed readily when placed in feeding capsules upon rabbits. We conclude that the dusky-footed woodrat and the deer mouse are capable experimental reservoir hosts of B. bissettii, and that both I. spinipalpis and I. pacificus are efficient experimental vectors of B. bissettii. However, the reluctance of I. pacificus nymphs to feed on certain rodents may limit its importance as an enzootic vector of B. burgdorferi sensu lato spirochetes.

Dynamic Changes in Borrelia Burgdorferi Populations in Ixodes Scapularis (Acari: Ixodidae) During Transmission: Studies at the MRNA Level

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). 2003  |  Pubmed ID: 14511582

Many B. burgdorferi genes are regulated at the level of transcription during B. burgdorferi passage from ticks to mammals. Particular spirochete outer surface proteins of interest are OspA, OspC, and vlsE. The messenger RNA (mRNA) levels produced by these three genes were determined by a quantitative reverse transcription PCR (q-RT-PCR) procedure for spirochete populations in nymphal I. scapularis midguts and salivary glands at specific intervals during the feeding process. The mRNA values were compared to that of a standard, the mRNA levels of the constitutively expressed Flagellin (fla) gene. The levels of OspA and vlsE did not increase markedly in the midgut during feeding, but the mRNA levels of OspC increased significantly during feeding. In tick salivary glands, OspA mRNA levels actually decreased during feeding, while OspC levels increased six orders of magnitude. The mRNA levels of vlsE in tick salivary glands increased significantly only during the last 2 days of tick feeding. Overall, OspA mRNA was more abundant in tick midguts, whereas OspC and vlsE mRNA was more abundant in tick salivary glands. Further studies on the regulation of B. burgdorferi transcription activity during the act of transmission will lead to a better understanding of spirochete transmission dynamics, and hopefully facilitate the development of novel ways of interrupting the spread of Lyme disease.

Comparison of Disseminated and Nondisseminated Strains of Borrelia Burgdorferi Sensu Stricto in Mice Naturally Infected by Tick Bite

Infection and Immunity. Sep, 2004  |  Pubmed ID: 15322021

Clinical isolates of Borrelia burgdorferi sensu stricto have been categorized into disseminated and nondisseminated groups based on distinct ribosomal spacer restriction fragment length polymorphism genotypes (RSTs). In order to determine whether transmission by tick bite would alter the dissemination dynamics and disease produced by distinct genotypes, disseminated isolates (RST1), nondisseminated isolates (RST3), and a standard laboratory strain (B-31) were established in a murine cycle utilizing infections transmitted by ticks. B-31 spirochetes circulated in the blood of inbred C3H/HeJ mice longer than in the blood of outbred mice. The majority of C3H mice exposed to RST1-infected ticks contained cultivable spirochetes in their blood for up to 17 days; in contrast, mice exposed to RST3 isolates demonstrated a precipitous decline in infection after day 7 postexposure. A quantitative PCR (q-PCR) assay demonstrated that the densities of spirochetes in blood were similar for the RST1 and RST3 isolates, except during the 2nd week postexposure, when the RST1 isolates displayed a markedly higher density in blood. Spirochete load in the heart and bladder of infected mice was measured by q-PCR at 8 weeks postexposure; the numbers of spirochetes in these tissues were similar for mice infected with either disseminated or nondisseminated strains. Similarly, histopathology samples of heart, bladder, and joint tissue obtained at 8 weeks postexposure did not reveal greater pathology in mice infected with the disseminated isolates. We conclude that although the spirochetemia induced by tick-transmitted disseminated isolates was more intense and of longer duration than that induced by nondisseminated isolates, the resultant pathologies produced by these strains were ultimately similar.

Rapid Detection Methods and Prevalence Estimation for Borrelia Lonestari GlpQ in Amblyomma Americanum (Acari: Ixodidae) Pools of Unequal Size

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). 2005  |  Pubmed ID: 16011431

DNA was extracted from pools of Amblyomma americanum ticks collected from vegetation at two sites in Fort Leonard Wood, Missouri and tested for the presence of Borrelia spp. Two new methods were developed to detect Borrelia lonestari DNA by targeting the glycerophosphodiester phosphodiesterase (glpQ) gene. The first method detected B. lonestari DNA using a SYBR green I melting curve analysis of the PCR product obtained with glpQ gene primers. The second method, a glpQ TaqMan assay, detected and confirmed the presence of B. lonestari glpQ-specific sequences. Twenty-two of 95 tick pools collected at site A148 contained B. lonestari DNA. None of 19 pools from site A241 contained B. lonestari DNA. No B. burgdorferi sensu lato DNA was detected using a SYBR green I melting curve analysis of the PCR product obtained with outer surface protein A (ospA) primers. The overall B. lonestari infection prevalence (with 95% confidence interval) at site A148 was estimated using two algorithms: minimum infection rate 4.14% (2.45, 5.84) and maximum likelihood with correction 4.82% (3.11, 7.16). The merits of each are discussed. Sequencing of the entire B. lonestari glpQ and partial 16S rRNA genes revealed two genetic variants circulating in this population of A. americanum from Missouri.

Strategies for Reducing the Risk of Lyme Borreliosis in North America

International Journal of Medical Microbiology : IJMM. May, 2006  |  Pubmed ID: 16524769

The incidence of Lyme borreliosis continues to increase in the United States. In 1991, when Lyme borreliosis first became a nationally reportable disease to the Centers for Disease Control and Prevention (CDC), a total of 9470 cases were reported; in contrast, by 2002 a total of 23,763 cases were reported, >2.5x the total in 1991. Area-wide acaricides can be highly effective in killing nymphal Ixodes scapularis, with >95% of nymphs killed in studies using cyfluthrin, deltamethrin, or carbaryl. The majority of residents living in households within the area hyperendemic for Lyme borreliosis will not, however, consider the use of area-wide acaricides. A survey of communities in 4 states (Connecticut, Massachusetts, New Jersey, New York) demonstrated that <25% of the populace have used area-wide acaricides on their own property. In searching for alternative methods of reducing Lyme borreliosis risk, host-targeted methods have been proven to be effective. Newly developed methods include the use of acaricides applied to deer feeder stations. This method is called the 4-poster method and has been shown in trials to reduce populations of nymphal I. scapularis by 69%. In addition, rodent-targeted bait boxes containing fipronil have been shown to eliminate ticks on mice and negatively impact the population of questing I. scapularis and reduce the proportion of these ticks infected with Borrelia burgdorferi sensu stricto. Host eradication can also be utilized. On Monhegan Island, Maine, white-tailed deer were totally eradicated from the island from 1999 to 2000. By 2004, no immature I. scapularis could be found on rodents on Monhegan Island. Landscape management practices can also be utilized to reduce the risk of Lyme borreliosis as can personal protection procedures including regular tick checks. These practices have been nicely summarized in a new Tick Management Handbook produced by Dr. Kirby C. Stafford III with the Connecticut Agricultural Experiment Station. Although there is no magic bullet available to completely eliminate the risk of Lyme borreliosis from large geographic areas, the use of Integrated Pest Management (IPM) practices holds the prospect for reducing and managing Lyme borreliosis risk in the future.

Transfer of Borrelia Burgdorferi S.s. Infection Via Blood Transfusion in a Murine Model

The Journal of Parasitology. Aug, 2006  |  Pubmed ID: 16995409

Without antibiotic treatment, the Lyme-disease-causing bacterium, Borrelia burgdorferi can be cultured from the peripheral blood of human patients nearly 6 wk post-tick bite. To determine if Lyme disease spirochetes can be transmitted from a spirochetemic donor mouse to a naive recipient during blood transfusion, blood taken from immunocompetent infected mice was transfused into either immunodeficient (SCID) mice, inbred immunocompetent animals (C3H/HeJ), or outbred mice. Nine of 19 (47.7%) immunodeficient mice, 7 of 15 (46.8%) inbred immunocompetent mice, and 6 of 10 (60.0%) outbred mice became infected with B. burgdorferi after transfusion. Our results indicate that it is possible to acquire B. burgdoferi infection via transfused blood in a mouse model of Lyme borreliosis.

Repellent Activity of Fractioned Compounds from Chamaecyparis Nootkatensis Essential Oil Against Nymphal Ixodes Scapularis (Acari: Ixodidae)

Journal of Medical Entomology. Sep, 2006  |  Pubmed ID: 17017233

Preliminary repellent activity of 14 natural products isolated from essential oil components extracted from the heartwood of Alaska yellow cedar, Chamaecyparis nootkatensis (D. Don) Spach., were evaluated against nymphal Ixodes scapularis Say in a laboratory bioassay and compared with technical grade N,N-diethyl-3-methylbenzamide (deet). Four hours after treatment, nootkatone and valencene-13-ol had repellent concentration (RC)50 values of 0.0458 and 0.0712% (wt:vol), respectively; two additional Alaska yellow cedar compounds, nootkatone 1 --> 10 epoxide and carvacrol had reported RC50 values of 0.0858 and 0.112%, respectively. The observed RC50 value for deet was 0.0728% (wt:vol). Although not statistically significantly more active than deet, the ability of these natural products to repel ticks at relatively low concentrations may represent a potential alternative to synthetic commercial repellents.

Response of Nymphal Ixodes Scapularis, the Primary Tick Vector of Lyme Disease Spirochetes in North America, to Barriers Derived from Wood Products or Related Home and Garden Items

Journal of Vector Ecology : Journal of the Society for Vector Ecology. Dec, 2006  |  Pubmed ID: 17249361

Forest products were tested to see if they functioned as a barrier to nymphal Ixodes scapularis. These products could potentially be used to define a border between high density and low density tick zones on residential properties in Lyme disease endemic regions of North America. Common home and garden items were also tested. Three wood products effectively acted as barriers to nymphal I. scapularis: Alaska Yellow Cedar sawdust, Alaska Yellow Cedar woodchips, and cellulose. These three products were then weathered to determine how long they remained active. Cellulose and Alaska Yellow Cedar woodchips lost their activity almost immediately (within three days); in contrast, Alaska Yellow Cedar sawdust impeded crossing by nymphal ticks for up to one month. Creating barriers at the woods-lawn interface may someday play a role in integrated campaigns to prevent Lyme disease but will not serve as a stand-alone measure to block transmission of Lyme disease spirochetes.

New Records of Immature Ixodes Scapularis from Mississippi

Journal of Vector Ecology : Journal of the Society for Vector Ecology. Dec, 2006  |  Pubmed ID: 17249363

Integrated Use of 4-Poster Passive Topical Treatment Devices for Deer, Targeted Acaricide Applications, and Maxforce TMS Bait Boxes to Rapidly Suppress Populations of Ixodes Scapularis (Acari: Ixodidae) in a Residential Landscape

Journal of Medical Entomology. Sep, 2007  |  Pubmed ID: 17915516

In fall 2003, we began testing an integrated control strategy to rapidly achieve and sustain reduced numbers of Ixodes scapularis Say (Acari: Ixodidae) in a residential area. We combined two host-targeted technologies in conjunction with single, barrier acaricide applications to sequentially attack each postembryonic life stage of the tick. Granular deltamethrin applied to the lawn-forest interface of participant properties resulted in 100% control of host-seeking nymphs. Nymphal and larval tick burdens on targeted small mammal hosts at treated properties were reduced by 92.7 and 95.4%, respectively, after the first year (2004) of combined interventions. Over the same period, populations of host-seeking nymphs, larvae, and adults were reduced by 58.5, 24.8, and 77.8%, respectively. After interventions in 2005, tick burdens on small mammals were maintained at similar levels, whereas control of host-seeking nymphs, larvae, and adults increased to 94.3, 90.6, and 87.3%, respectively. Prospects for widespread use of these technologies to protect the public's health are discussed.

A Hard Tick Relapsing Fever Group Spirochete in a Brazilian Rhipicephalus (Boophilus) Microplus

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). 2007  |  Pubmed ID: 17979536

Tick-borne diseases usually comprise a complex epidemiological and ecological network connecting the vector, pathogen, and a group of host species. Symptoms associated with Lyme disease have been reported in Brazil, but no Borrelia sp. has been definitively related to these events. Here we have identified a B. lonestari/B. theileri-related spirochete DNA in the cattle tick Rhipicephalus (Boophilus) microplus from Brazil. Four hundred R. microplus and 80 Amblyomma cajennense ticks were screened, and only 1 horse-fed R. microplus was infected. A Borrelia sp. 16S rDNA sequence was amplified by polymerase chain reaction (PCR) from the total tick DNA with 99% similarity to B. theileri and B. lonestari. Partial flaB sequence was also obtained, demonstrating 96% similarity to the B. lonestari flagellin gene, and the resultant putative amino acid sequence demonstrated 97% identity to B. lonestari flagellin. Moreover, partial glpQ sequence demonstrated 92% similarity to the B. lonestari gene, with a putative amino acid sequence 90% identical to the B. lonestari glycerophosphodiester phosphodiesterase. Phylogenetic analyses clearly include this Brazilian Borrelia sp., denoted "Borrelia," sp-BR in a group of spirochetes aligned with B. theileri and B. lonestari. Thus, hard tick relapsing fever group spirochetes represent a clade of widespread bacteria and herein we describe the first molecular identification of a Borrelia sp. in South America.

Novel Relapsing Fever Spirochete in Bat Tick

Emerging Infectious Diseases. Mar, 2008  |  Pubmed ID: 18325285

A Doxycycline Hyclate Rodent Bait Formulation for Prophylaxis and Treatment of Tick-transmitted Borrelia Burgdorferi

The American Journal of Tropical Medicine and Hygiene. May, 2008  |  Pubmed ID: 18458316

The prophylactic and curative potential of doxycycline hyclate formulated in a rodent bait at concentrations of 250 and 500 mg/Kg was evaluated in a murine model of Lyme borreliosis. Both bait formulations prevented tick-transmitted Borrelia burgdorferi infection in 100% of C3H/HeJ mice (N = 16), as well as cured acute, established infection in mice (N = 8) exposed to bait for 14 days. Spirochete infection was cleared in 88.9% to 100% of infected nymphs feeding on mice fed 250 and 500 mg/Kg antibiotic bait formulations, respectively. These data provide evidence for exploring alternative techniques to prevent transmission of Lyme disease spirochetes.

MLST of Housekeeping Genes Captures Geographic Population Structure and Suggests a European Origin of Borrelia Burgdorferi

Proceedings of the National Academy of Sciences of the United States of America. Jun, 2008  |  Pubmed ID: 18574151

Lyme borreliosis, caused by the tick-borne bacterium Borrelia burgdorferi, has become the most common vector-borne disease in North America over the last three decades. To understand the dynamics of the epizootic spread and to predict the evolutionary trajectories of B. burgdorferi, accurate information on the population structure and the evolutionary relationships of the pathogen is crucial. We, therefore, developed a multilocus sequence typing (MLST) scheme for B. burgdorferi based on eight chromosomal housekeeping genes. We validated the MLST scheme on B. burgdorferi specimens from North America and Europe, comprising both cultured isolates and infected ticks. These data were compared with sequences for the commonly used genetic markers rrs-rrlA intergenic spacer (IGS) and the gene encoding the outer surface protein C (ospC). The study demonstrates that the concatenated sequences of the housekeeping genes of B. burgdorferi provide highly resolved phylogenetic signals and that the housekeeping genes evolve differently compared with the IGS locus and ospC. Using sequence data, the study reveals that North American and European populations of B. burgdorferi correspond to genetically distinct populations. Importantly, the MLST data suggest that B. burgdorferi originated in Europe rather than in North America as proposed previously.

Knowledge, Attitudes, and Behaviors Regarding Lyme Disease Prevention Among Connecticut Residents, 1999-2004

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). Dec, 2008  |  Pubmed ID: 18637724

Lyme disease, caused by the tick-transmitted bacterium Borrelia burgdorferi, is the most common vector-borne disease in the United States. We surveyed residents of three Connecticut health districts to evaluate the impact of intensive community-wide education programs on knowledge, attitudes, and behaviors to prevent Lyme disease. Overall, 84% of respondents reported that they knew a lot or some about Lyme disease, and 56% felt that they were very or somewhat likely to get Lyme disease in the coming year. During 2002-2004, the percentage of respondents who reported always performing tick checks increased by 7% and the percentage of respondents who reported always using repellents increased by 5%, whereas the percentage of respondents who reported avoiding wooded areas and tucking pants into socks decreased. Overall, 99% of respondents used personal protective behaviors to prevent Lyme disease. In comparison, 65% of respondents reported using environmental tick controls, and increased use of environmental tick controls was observed in only one health district. The majority of respondents were unwilling to spend more than $100 on tick control. These results provide guidance for the development of effective Lyme disease prevention programs by identifying measures most likely to be adopted by residents of Lyme disease endemic communities.

Indicators for Elevated Risk of Human Exposure to Host-seeking Adults of the Rocky Mountain Wood Tick (Dermacentor Andersoni) in Colorado

Journal of Vector Ecology : Journal of the Society for Vector Ecology. Jun, 2008  |  Pubmed ID: 18697314

The human-biting adult stage of the Rocky Mountain wood tick (Dermacentor andersoni) can cause tick paralysis in humans and domestic animals and is the primary tick vector in the intermountain west of the pathogens causing Colorado tick fever, Rocky Mountain spotted fever, and tularemia. We conducted drag sampling studies in Poudre Canyon and Rocky Mountain National Park of Larimer County, CO, to determine microhabitat use patterns by host-seeking D. andersoni adults and find environmental factors signaling elevated risk of tick exposure. Big sagebrush (Artemisia tridentata) was found to serve as a general indicator of areas with elevated risk of exposure to host-seeking D. andersoni adults; this likely results from a shared climate tolerance of big sagebrush and D. andersoni. Grass was the favored substrate for host-seeking ticks. Drag sampling of open grass or grass bordering rock or shrub produced abundances of D. andersoni adults significantly higher than sampling of brush. Sampling sites in Rocky Mountain National Park, relative to Poudre Canyon, were characterized by more intense usage by elk (Cervus elaphus) but decreased brush coverage, smaller brush size, and lower abundances of host-seeking D. andersoni adults. There has been a tremendous increase in the population of elk in Rocky Mountain National Park over the last decades and we speculate that this has resulted in an ecological cascade where overgrazing of vegetation by elk is followed by suppression of rodent populations, decreased tick abundance, and, ultimately, reduced risk of human exposure to D. andersoni and its associated pathogens.

Transmission Dynamics of Borrelia Burgdorferi S.s. During the Key Third Day of Feeding by Nymphal Ixodes Scapularis (Acari: Ixodidae)

Journal of Medical Entomology. Jul, 2008  |  Pubmed ID: 18714875

Nymphal Ixodes scapularis Say are the principal vectors of Lyme disease spirochetes (Borrelia burgdorferi sensu stricto) in the eastern United States. Physicians frequently face the decision of whether or not to administer prophylactic antibiotics to human tick bite victims in Lyme disease endemic regions, based on the overall probability that such bites will result in infection with B. burgdorferi s.s. We evaluated the transmission dynamics of B. burgdorferi s.s. during the key third day of nymphal I. scapularis feeding, when the risk of transmission rapidly increases. The cumulative probability that 50% of infected ticks transmitted B. burgdorferi s.s. occurred at 68 h of tick attachment and our overall estimate that a human tick bite would result in transmission of B. burgdorferi s.s. was 2.4%.

Ability of 4-poster Passive Topical Treatment Devices for Deer to Sustain Low Population Levels of Ixodes Scapularis (Acari: Ixodidae) After Integrated Tick Management in a Residential Landscape

Journal of Medical Entomology. Sep, 2008  |  Pubmed ID: 18826033

In a recent study, the combined use of 4-Posters and Maxforce TMS bait boxes along with a barrier application of deltamethrin resulted in accelerated control of Ixodes scapularis Say by sequentially attacking each postembryonic life stage. We report the results of a follow-up study to test the ability of 4-Posters used alone to sustain the high levels of control achieved through the integrated tick management (ITM) approach after withdrawal of the bait boxes. In the first year after withdrawal, we observed declines in the level of control of larvae on small mammals, as well as of numbers of host-seeking larvae in the treatment area. There was no difference in the level of control of host-seeking adults in the treatment area after 2 yr. Within 2 yr, we observed a decline in control of subadult ticks infesting small mammals, but continued to see significant control of both host-seeking nymphs (85.9%) and larvae (89.0%) in the treatment area. The inconsistency that we observed between the apparent ability of 4-Posters to sustain high levels of control of host-seeking ticks, although having less effect on tick burdens on small mammal hosts, may be explained by the host-seeking ecology of immature I. scapularis.

Increased Recognition of Powassan Encephalitis in the United States, 1999-2005

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). Dec, 2008  |  Pubmed ID: 18959500

Powassan virus (POWV) disease is a rare human disease caused by a tick-borne encephalitis group flavivirus maintained in a transmission cycle between Ixodes cookei and other ixodid ticks and small and medium-sized mammals. During 1958-1998, only 27 POWV disease cases (mostly Powassan encephalitis) were reported from eastern Canada and the northeastern United States (average, 0.7 cases per year). During 1999-2005, nine cases (described herein) of serologically confirmed POWV disease were reported in the United States (average, 1.3 cases per year): four from Maine, two from New York, and one each from Michigan, Vermont, and Wisconsin. The Michigan and Wisconsin cases are the first ever reported from the north-central United States. Of these nine patients, 5 (56%) were men, the median age was 69 years (range: 25-91 years), and 6 (67%) had onset during May-July. All but one patient developed encephalitis with acute onset of profound muscle weakness, confusion, and other severe neurologic signs. In one case, no neurologic symptoms were present but the presence of pleocytosis, an elevated cerebrospinal fluid (CSF) protein concentration, and POWV-specific immunoglobulin M in CSF suggested neuroinvasion. All patients recovered from their acute disease, but most had long-term neurologic sequelae. Periresidential ecologic investigations were performed in three cases, including tests of local mammals and ticks for evidence of POWV infection. Woodchucks (Marmota monax), striped skunks (Mephitis mephitis), and a raccoon (Procyon lotor) collected at two of the Maine case-patients' residences had neutralizing antibody titers to POWV. I. cookei were found on woodchucks and skunks and questing in grassy areas of one of these residences; all were negative for POWV. Although POWV disease is rare, it is probably under-recognized, and it causes significant morbidity, and thus is an additional tick-borne emerging infectious disease entity. Because no vaccine or specific therapy is available, the basis of prevention is personal protection from ticks (or "tick hygiene") and reduced exposure to peridomestic wild mammals.

Prevention of Tick-borne Diseases

Annual Review of Entomology. 2008  |  Pubmed ID: 17877457

Tick-borne diseases are on the rise. Lyme borreliosis is prevalent throughout the Northern Hemisphere, and the same Ixodes tick species transmitting the etiologic agents of this disease also serve as vectors of pathogens causing human babesiosis, human granulocytic anaplasmosis, and tick-borne encephalitis. Recently, several novel agents of rickettsial diseases have been described. Despite an explosion of knowledge in the fields of tick biology, genetics, molecular biology, and immunology, transitional research leading to widely applied public health measures to combat tick-borne diseases has not been successful. Except for the vaccine against tick-borne encephalitis virus, and a brief campaign to reduce this disease in the former Soviet Union through widespread application of DDT, success stories in the fight against tick-borne diseases are lacking. Both new approaches to tick and pathogen control and novel ways of translating research findings into practical control measures are needed to prevent tick-borne diseases in the twenty-first century.

Short Report: Time Course of Hematogenous Dissemination of Francisella Tularensis A1, A2, and Type B in Laboratory Mice

The American Journal of Tropical Medicine and Hygiene. Feb, 2009  |  Pubmed ID: 19190224

Tularemia is a tick-borne zoonotic bacterial disease. In the United States, human tularemia infections are caused by Francisella tularensis subspecies tularensis (Type A, clades A1 and A2) or F. tularensis subspecies holarctica (Type B). We developed a mouse model that can be used to study the ability of ticks to acquire and transmit fully virulent strains of F. tularensis (A1, A2, and Type B). We showed that 1) bacteremia was evident by 2 days post-infection (dpi) for A1, A2, and B, 2) bacteremia was expected to reach levels of > 10(8) cfu/mL by 3 dpi for A1 and A2 but not until 4 dpi for Type B, and 3) illness onset was delayed for mice exposed to Type B compared with A1 and A2. To maximize the likelihood of ticks acquiring infection from laboratory-infected mice before they become moribund and must be euthanized, ticks should be placed on mice so that periods of rapid engorgement occur 3-4 dpi for A1 and A2 and 4-5 dpi for Type B. Rigorous experimental studies of tick vector competence and efficiency conducted under standardized conditions are required to address several significant public health issues related to preventing and controlling tularemia. Our study provides the basis for a mouse model needed as the starting point to address these questions.

A Borreliacidal Factor in Amblyomma Americanum Saliva is Associated with Phospholipase A2 Activity

Experimental Parasitology. Apr, 2009  |  Pubmed ID: 19271281

Previous work in our laboratory described the in vitro killing of Borrelia burgdorferi when co-cultured with saliva from adult Amblyomma americanum. Borreliacidal activity was not evident using Ixodes scapularis saliva. Mixing trypsin with saliva eliminated the borreliacidal activity of A. americanum saliva, while incorporating a trypsin inhibitor restored all borreliacidal activity, indicating this factor was of protein or peptide origin. One-dimensional PAGE indicated at least 7 major protein differences between I. scapularis and A. americanum saliva. To determine the borreliacidal factor, A. americanum saliva was fractionated by gel filtration and subsequent killing of B. burgdorferi was associated with a single fraction. Two-dimensional gel analysis indicated protein and/or peptide(s) in borreliacidal fractions running between 38 and 64 kDa. Finally, admixing saliva with the phospholipase A2 inhibitor oleyloxyethyl phosphorylcholine completely eliminated the ability of A. americanum saliva to kill B. burgdorferi. These studies indicate the borreliacidal activity found in A. americanum saliva is likely due to phospholipase A2 enzymatic activity.

Characterization of a Novel Relapsing Fever Spirochete in the Midgut, Coxal Fluid, and Salivary Glands of the Bat Tick Carios Kelleyi

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). Dec, 2009  |  Pubmed ID: 19281412

Bat ticks, Carios kelleyi, from Iowa were examined for the presence of relapsing fever group borreliae. A novel spirochete was characterized by DNA sequence analysis of polymerase chain reaction amplicons for the 16S rRNA, flaB, and glpQ genes in either triturated tick pools or single ticks. All loci and the concatenated DNA sequence of 3,289 bases identified the Carios bacterium as a relapsing fever spirochete most closely related to, but distinct from, Borrelia turicatae. Spirochetes reactive with a Borrelia-specific monoclonal antibody were observed microscopically in the coxal fluid and salivary glands from one tick. These data confirm the presence of a novel species of relapsing fever spirochete in bat ticks and the potential for new enzootic foci for endemic relapsing fever that warrants further investigation. The name Borrelia johnsonii is proposed for this novel spirochete in honor of Dr. Russell C. Johnson.

Francisella-like Endosymbiont DNA and Francisella Tularensis Virulence-related Genes in Brazilian Ticks (Acari: Ixodidae)

Journal of Medical Entomology. Mar, 2009  |  Pubmed ID: 19351090

Ticks are vectors of a variety of pathogens, including Francisella tularensis. Bacteria in the genus Francisella have been identified mostly in the Northern Hemisphere and include tick endosymbionts. Francisella has never been described in Brazil, where Amblyomma spp. ticks are known as the vector of many bacterial zoonotic pathogens. In the present work, we have identified bacterial DNA sequences with identity to Francisella genes in Amblyomma dubitatum Neumann Dermacentor nitens (Neumann), and Rhipicephalus microplus (Canestrini) in Brazil. DNA fragments with homology to Francisella spp. 16S rDNA and the tul4 gene were polymerase chain reaction amplified from tick DNA samples collected in Minas Gerais and Mato Grosso states. These sequences were 96-99% identical to the reported sequences for Francisella-like tick endosymbionts (FLEs). Sequences similar to the tularemia agent F. tularensis pathogenicity island gene iglC and its regulatory gene mglA also were identified in FLEs.

A Borreliacidal Factor in Amblyomma Americanum Saliva is Associated with Phospholipase A(2) Activity

Experimental Parasitology. Jan, 2009  |  Pubmed ID: 19545533

Previous work in our laboratory described the in vitro killing of Borrelia burgdorferi when co-cultured with saliva from adult Amblyomma americanum. Borreliacidal activity was not evident using Ixodes scapularis saliva. Mixing trypsin with saliva eliminated the borreliacidal activity of A. americanum saliva, while incorporating a trypsin inhibitor restored all borreliacidal activity, indicating this factor was of protein or peptide origin. One dimensional PAGE indicated at least 7 major protein differences between Ixodes scapularis and A. americanum saliva. To determine the borreliacidal factor, A. americanum saliva was fractionated by gel filtration and subsequent killing of B. burgdorferi was associated with a single fraction. Two dimensional gel analysis indicated protein and/or peptide(s) in borreliacidal fractions running between 38-64kDa. Finally, admixing saliva with the phospholipase A(2) inhibitor oleyloxyethyl phosphorlycholine completely eliminated the ability of A. americanum saliva to kill B. burgdorferi. These studies indicate the borreliacidal activity found in A. americanum saliva is likely due to phospholipase A(2) enzymatic activity.

Molecular Identification of Salp15, a Key Salivary Gland Protein in the Transmission of Lyme Disease Spirochetes, from Ixodes Persulcatus and Ixodes Pacificus (Acari: Ixodidae)

Journal of Medical Entomology. Nov, 2009  |  Pubmed ID: 19960697

Salp15 is a multifunctional protein, vital to the tick in its need to obtain vertebrate host blood without stimulating a host inflammatory and immune response. The Salpl5 protein from both Ixodes scapularis Say and Ixodes ricinus (L.), the principal vectors of the Lyme disease spirochete in eastern North America and Europe, respectively, have been well characterized and found to bind the murine CD4 receptor, DC-SIGN, and the OspC protein of Borrelia burgdorferi. In the current study, we characterized the full salp15 gene in Ixodes pacificus Cooley & Kohls and Ixodes persulcatus Schulze, the principal vectors of Lyme disease spirochetes in western North America and Asia, respectively. In comparing the Salp15 protein of all four principal vector ticks of public health importance for the transmission of Lyme disease spirochetes, we find the 53 C-terminal amino acids to have a high degree of similarity. There are at least three clades in the tree of Salp15 and its homologues, probably representing a multigene family.

Ability of Two Natural Products, Nootkatone and Carvacrol, to Suppress Ixodes Scapularis and Amblyomma Americanum (Acari: Ixodidae) in a Lyme Disease Endemic Area of New Jersey

Journal of Economic Entomology. Dec, 2009  |  Pubmed ID: 20069863

We evaluated the ability of the natural, plant-derived acaricides nootkatone and carvacrol to suppress Ixodes scapularis Say and Amblyomma americanum (L.) (Acari: Ixodidae). Aqueous formulations of 1 and 5% nootkatone applied by backpack sprayer to the forest litter layer completely suppressed I. scapularis nymphs through 2 d. Thereafter, the level of reduction gradually declined to < or =50% at 28 d postapplication. Against A. americanum nymphs, 1% nootkatone was less effective, but at a 5% concentration, the level of control was similar or greater to that observed with I. scapularis through 21 d postapplication. Initial applications of 0.05% carvacrol were ineffective, but a 5% carvacrol formulation completely suppressed nymphs of both species through 2 d and resulted in significant reduction in I. scapularis and A. americanum nymphs through 28 and 14 d postapplication, respectively. Backpack sprayer applications of 5% nootkatone to the shrub and litter layers resulted in 100% control of I. scapularis adults through 6 d, but the level of reduction declined to 71.5% at 28 d postapplication. By contrast, high-pressure applications of 2% nootkatone to the litter layer resulted in 96.2-100% suppression of both I. scapularis and A. americanum nymphs through 42 d, whereas much lower control was obtained from the same formulation applied by backpack sprayer. Backpack sprayer application of a 3.1% nootkatone nanoemulsion resulted in 97.5-98.9 and 99.3-100% reduction in I. scapularis and A. americanum nymphs, respectively, at 1 d postapplication. Between 7 d and 35 d postapplication, the level of control varied between 57.1% and 92.5% for I. scapularis and between 78.5 and 97.1% for A. americanum nymphs. The ability of natural products to quickly suppress and maintain significant control of populations of these medically important ticks at relatively low concentrations may represent a future alternative to the use of conventional synthetic acaricides.

Transmission Dynamics of Francisella Tularensis Subspecies and Clades by Nymphal Dermacentor Variabilis (Acari: Ixodidae)

The American Journal of Tropical Medicine and Hygiene. Sep, 2010  |  Pubmed ID: 20810833

In the United States, the American dog tick, Dermacentor variabilis (Say) is considered an important biological vector of Francisella tularensis, the etiologic agent of tularemia. In this study, we evaluated the vector efficiency of nymphal D. variabilis infected as larvae with differing clades and subspecies (A1b, A2, and type B) of F. tularensis. In all cases, D. variabilis larvae were able to acquire, maintain, and transstadially transmit F. tularensis. Significant replication of the bacteria also occurred in infected nymphs. Transmission of F. tularensis to Swiss Webster mice was not observed with A1b, and low rates were observed with A2 (8.0%) and type B (13.5%). Negative effects on tick survivorship were also observed for A1b, A2, and type B infections. Our results provide evidence of a high fitness cost and low transmission rates during the immature stages, suggesting that D. variabilis may play a limited role in enzootic maintenance of F. tularensis.

Multilocus Sequence Analysis of Borrelia Bissettii Strains from North America Reveals a New Borrelia Species, Borrelia Kurtenbachii

Ticks and Tick-borne Diseases. Dec, 2010  |  Pubmed ID: 21157575

Using multilocus sequence analyses (MLSA), we investigated the phylogenetic relationship of spirochaete strains from North America previously assigned to the genospecies Borrelia bissettii. We amplified internal fragments of 8 housekeeping genes (clpA, clpX, nifS, pepX, pyrG, recG, rplB, and uvrA) located on the main linear chromosome by polymerase chain reaction. Phylogenetic analysis of concatenated sequences of the 8 loci showed that the B. bissettii clade consisted of 4 closely related clusters which included strains from California (including the type strain DN127-Cl9-2/p7) and Colorado that were isolated from Ixodes pacificus, I. spinipalpis, or infected reservoir hosts. Several strains isolated from I. scapularis clustered distantly from B. bissettii. Genetic distance analyses confirmed that these strains are more distant to B. bissettii than they are to B. carolinensis, a recently described Borrelia species, which suggests that they constitute a new Borrelia genospecies. We propose that it be named Borrelia kurtenbachii sp. nov. in honour of the late Klaus Kurtenbach. The data suggest that ecological differences between B. bissettii and the new Borrelia genospecies reflect different transmission cycles. In view of these findings, the distinct vertebrate host-tick vector associations and the distributions of B. bissettii and B. kurtenbachii require further investigation.

Coinfections of Rickettsia Slovaca and Rickettsia Helvetica with Borrelia Lusitaniae in Ticks Collected in a Safari Park, Portugal

Ticks and Tick-borne Diseases. Dec, 2010  |  Pubmed ID: 21771525

Borrelia and Rickettsia bacteria are the most important tick-borne agents causing disease in Portugal. Identification and characterization of these circulating agents, mainly in recreational areas, is crucial for the development of preventive measures in response to the gradually increasing exposure of humans to tick vectors. A total of 677 questing ticks including Dermacentor marginatus, Rhipicephalus sanguineus, Ixodes ricinus, Hyalomma lusitanicum, H. marginatum, and Haemaphysalis punctata were collected in a Safari Park in Alentejo, Portugal, to investigate the prevalences of infection and characterize Borrelia and Rickettsia species. From a total of 371 ticks tested by PCR for Borrelia burgdorferi sensu lato (s.l.), of which 247 were tested for Rickettsia, an infection prevalence of 18.3% was found for B. lusitaniae and 55.1% for Rickettsia spp. Sequence analysis of positive amplicons identified the presence of B. lusitaniae (18.3%), R. monacensis strain IRS3 (51.7%), and R. helvetica (48.3%) in I. ricinus. R. slovaca (41.5%), R. raoultii (58.5%), and also B. lusitaniae (21%) were identified in D. marginatus ticks. One (5.9%) H. lusitanicum was infected with B. lusitaniae, and R. massiliae was found in one Rhipicephalus sanguineus. Coinfection was found in 7 (20%) I. ricinus and 34 (23.3%) D. marginatus ticks. We report, for the first time, simultaneous infection with R. helvetica and B. lusitaniae and also R. slovaca, the agent of TIBOLA/DEBONEL, with B. lusitaniae. Additionally, 6 isolates of B. lusitaniae were established, and isolates of Rickettsia were also obtained for the detected species using tick macerates cultured in mammalian and mosquito cell lines. This report describes the detection and isolation of tick-borne agents from a Portuguese Safari Park, highlighting the increased likelihood of infection with multiple agents to potential visitors or staff.

Molecular Characterization of a New Isolate of Borrelia Lusitaniae Derived from Apodemus Sylvaticus in Portugal

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). Jun, 2010  |  Pubmed ID: 19725761

A total of 196 small mammals were collected in Portugal and tested for Borrelia burgdorferi sensu lato. Tissue samples were taken from each animal and cultured in Barbour-Stoenner-Kelly (BSK)-II medium. The single strain of spirochete isolated was confirmed as Borrelia lusitaniae by genetic analyses. This is the first report of B. lusitaniae isolated from Apodemus sylvaticus.

Characterization of the Highly Regulated Antigen BBA05 in the Enzootic Cycle of Borrelia Burgdorferi

Infection and Immunity. Jan, 2010  |  Pubmed ID: 19822648

Dramatic alteration of surface lipoprotein profiles is a key strategy that Borrelia burgdorferi, the Lyme disease pathogen, has evolved for adapting to the diverse environments of arthropod and mammalian hosts. Several of these differentially expressed lipoproteins have been shown to play important roles in the enzootic cycle of B. burgdorferi. The BBA05 protein is a previously identified putative lipoprotein (P55 or S1 antigen) that elicits antibody responses in mammals. Recent microarray analyses indicate that the BBA05 gene is differentially expressed by many environmental factors, including temperature. However, the role of the BBA05 protein in the life cycle of B. burgdorferi has not been elucidated. Here we show that expression of the BBA05 gene was exclusively induced in feeding nymphal ticks during the spirochetal transmission from ticks to mammals. Upon generating a BBA05 mutant in an infectious strain of B. burgdorferi, we showed that the BBA05 mutant remained capable of establishing infection in mice, being acquired by ticks, persisting through tick molting, and reinfecting new mammalian hosts. These results indicate that, despite being a highly conserved and regulated antigen, the BBA05 protein has a nonessential role in the transmission cycle of B. burgdorferi, at least in the animal model.

Low-density Microarrays for the Detection of Borrelia Burgdorferi S.s. (the Lyme Disease Spirochete) in Nymphal Ixodes Scapularis

Ticks and Tick-borne Diseases. Mar, 2011  |  Pubmed ID: 21771534

Lyme disease is the most common tick-borne disease in Europe and North America. In the hyperendemic Lyme disease regions of the eastern United States, nymphal Ixodes scapularis are the principal ticks transmitting the Lyme disease spirochete, Borrelia burgdorferi sensu stricto (s.s.). Approximately 25% of questing nymphs in endemic regions are infected with spirochetes. High throughput-sensitive and specific methods for testing nymphal I. scapularis for infection with B. burgdorferi are clearly needed. In the current study, we evaluated whether low-density microarrays could be adapted for the rapid and accurate detection and characterization of spirochetes in nymphal I. scapularis. Three different microarray platforms were developed and tested for the detection of spirochetes in ticks. They could both detect and differentiate different Borrelia genospecies, in one case detecting as few as a single copy of Borrelia DNA.

Transmission Efficiency of Francisella Tularensis by Adult American Dog Ticks (Acari: Ixodidae)

Journal of Medical Entomology. Jul, 2011  |  Pubmed ID: 21845949

The American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae), has been implicated as a potential bridging vector to humans of Francisella tularensis, the etiological agent of tularemia. Since the initial studies evaluating vector competency of D. variabilis were conducted, F. tularensis has been subdivided into subspecies and clades that differ in their geographical distribution in the United States and in the severity of infections caused in humans. Here, we demonstrate that D. variabilis nymphs efficiently acquire, transtadially maintain, and transmit each of the strains tested (clades A1b and A2, and type B). Transmission efficiency by adult females was similarly high among infection groups and ranged from 58% for type B to 89% for A2 infections. In addition, we demonstrated that transmission can occur shortly after tick attachment. These findings support the concept that D. variabilis adults may play a significant role in epizootic transmission of F. tularensis, and as a bridging vector to humans.

Elimination of Borrelia Burgdorferi and Anaplasma Phagocytophilum in Rodent Reservoirs and Ixodes Scapularis Ticks Using a Doxycycline Hyclate-laden Bait

The American Journal of Tropical Medicine and Hygiene. Dec, 2011  |  Pubmed ID: 22144454

A field trial was conducted in a Lyme disease-endemic area of New Jersey to determine the efficacy of a doxycyline hyclate rodent bait to prophylactically protect and cure small-mammal reservoirs and reduce infection rates in questing Ixodes scapularis ticks for Borrelia burgdorferi and Anaplasma phagocytophilum. The doxycycline-laden bait was formulated at a concentration of 500 mg/kg and delivered during the immature tick feeding season in rodent-targeted bait boxes. The percentage of infected small mammals recovered from treated areas after 2 years of treatment was reduced by 86.9% for B. burgdorferi and 74% for A. phagocytophilum. Infection rates in questing nymphal ticks for both B. burgdorferi and A. phagocytophilum were reduced by 94.3% and 92%, respectively. Results from this study indicate that doxycycline-impregnated bait is an effective means of reducing infection rates for B. burgdorferi and A. phagocytophilum in both rodent reservoirs and questing I. scapularis ticks.

Suppression of Host-seeking Ixodes Scapularis and Amblyomma Americanum (Acari: Ixodidae) Nymphs After Dual Applications of Plant-derived Acaricides in New Jersey

Journal of Economic Entomology. Apr, 2011  |  Pubmed ID: 21510219

We evaluated the ability of dual applications of natural, plant-derived acaricides to suppress nymphal Ixodes scapularis Say and Amblyomma americanum (L.) (Acari: Ixodidae) in a Lyme disease endemic area of New Jersey. An aqueous formulation of 2% nootkatone provided >90% control of I. scapularis through 7 d. Control declined to 80.9% at 14 d, and a second application was made that provided >95% control through the remaining 4 wk of the nymphal season. Nootkatone provided >90% control of A. americanum through 35 d postapplication. Applications of 2% carvacrol and EcoTrol T&O resulted in rapid knockdown of both tick species, but control declined significantly to 76.7 and 73.7%, respectively, after 14 d when a second application was made that extended control of both tick species to between 86.2 and 94.8% at 21 d. Subsequently, control declined steadily in all plots by 42 d postapplication except for I. scapularis in carvacrol-treated plots, where levels of control >90% were observed through 35 d. Of the three compounds tested, 2% nootkatone provided the most consistent results, with 96.5 and 91.9% control of I. scapularis and A. americanum through 42 and 35 d, respectively. The ability of plant-derived natural products to quickly suppress and maintain significant control of populations of these medically important ticks may represent a future alternative to the use of conventional synthetic acaricides. In addition, the demonstrated efficacy of properly-timed backpack sprayer application may enable homeowner access to these minimal-risk acaricides.

Functional Analysis of the Borrelia Burgdorferi Bba64 Gene Product in Murine Infection Via Tick Infestation

PloS One. 2011  |  Pubmed ID: 21559293

Borrelia burgdorferi, the causative agent of Lyme borreliosis, is transmitted to humans from the bite of Ixodes spp. ticks. During the borrelial tick-to-mammal life cycle, B. burgdorferi must adapt to many environmental changes by regulating several genes, including bba64. Our laboratory recently demonstrated that the bba64 gene product is necessary for mouse infectivity when B. burgdorferi is transmitted by an infected tick bite, but not via needle inoculation. In this study we investigated the phenotypic properties of a bba64 mutant strain, including 1) replication during tick engorgement, 2) migration into the nymphal salivary glands, 3) host transmission, and 4) susceptibility to the MyD88-dependent innate immune response. Results revealed that the bba64 mutant's attenuated infectivity by tick bite was not due to a growth defect inside an actively feeding nymphal tick, or failure to invade the salivary glands. These findings suggested there was either a lack of spirochete transmission to the host dermis or increased susceptibility to the host's innate immune response. Further experiments showed the bba64 mutant was not culturable from mouse skin taken at the nymphal bite site and was unable to establish infection in MyD88-deficient mice via tick infestation. Collectively, the results of this study indicate that BBA64 functions at the salivary gland-to-host delivery interface of vector transmission and is not involved in resistance to MyD88-mediated innate immunity.

Coxiella Symbionts in the Cayenne Tick Amblyomma Cajennense

Microbial Ecology. Jul, 2011  |  Pubmed ID: 21611689

Members of the Coxiella genus are intracellular bacteria that can infect a variety of animals including humans. A symbiotic Coxiella was recently described in Amblyomma americanum ticks in the Northern Hemisphere with no further investigations of other Amblyomma species in other geographic regions. These ixodid ticks represent a group of important vectors for human infectious agents. In the present work, we have demonstrated that symbiotic Coxiella (SCox) are widespread, occurring in South America and infecting 100% of all life stages and eggs of the Cayenne ticks Amblyomma cajennense from Brazil and the USA. Using light microscopy, in situ hybridization, and PCR, we demonstrated SCox in salivary glands, ovaries, and the intestines of A. cajennense. These symbionts are vertically and transtadially transmitted in laboratory reared A. cajennense, and quantitative PCR analyses indicate that SCox are more abundant in adult female ticks, reaching values corresponding to an 11×, 38×, and 200× increase in SCox 16S rRNA gene copy number in unfed females, compared to unfed nymphs, larvae, and eggs, respectively. Phylogenetic analyses showed distinct SCox subpopulations in the USA and Brazil and demonstrated that SCox bacteria do not group with pathogenic Coxiella burnetii.

Cyclic Di-GMP is Essential for the Survival of the Lyme Disease Spirochete in Ticks

PLoS Pathogens. Jun, 2011  |  Pubmed ID: 21738477

Cyclic dimeric GMP (c-di-GMP) is a bacterial second messenger that modulates many biological processes. Although its role in bacterial pathogenesis during mammalian infection has been documented, the role of c-di-GMP in a pathogen's life cycle within a vector host is less understood. The enzootic cycle of the Lyme disease pathogen Borrelia burgdorferi involves both a mammalian host and an Ixodes tick vector. The B. burgdorferi genome encodes a single copy of the diguanylate cyclase gene (rrp1), which is responsible for c-di-GMP synthesis. To determine the role of c-di-GMP in the life cycle of B. burgdorferi, an Rrp1-deficient B. burgdorferi strain was generated. The rrp1 mutant remains infectious in the mammalian host but cannot survive in the tick vector. Microarray analyses revealed that expression of a four-gene operon involved in glycerol transport and metabolism, bb0240-bb0243, was significantly downregulated by abrogation of Rrp1. In vitro, the rrp1 mutant is impaired in growth in the media containing glycerol as the carbon source (BSK-glycerol). To determine the contribution of the glycerol metabolic pathway to the rrp1 mutant phenotype, a glp mutant, in which the entire bb0240-bb0243 operon is not expressed, was generated. Similar to the rrp1 mutant, the glp mutant has a growth defect in BSK-glycerol medium. In vivo, the glp mutant is also infectious in mice but has reduced survival in ticks. Constitutive expression of the bb0240-bb0243 operon in the rrp1 mutant fully rescues the growth defect in BSK-glycerol medium and partially restores survival of the rrp1 mutant in ticks. Thus, c-di-GMP appears to govern a catabolic switch in B. burgdorferi and plays a vital role in the tick part of the spirochetal enzootic cycle. This work provides the first evidence that c-di-GMP is essential for a pathogen's survival in its vector host.

Human Risk of Infection with Borrelia Burgdorferi, the Lyme Disease Agent, in Eastern United States

The American Journal of Tropical Medicine and Hygiene. Feb, 2012  |  Pubmed ID: 22302869

Abstract. The geographic pattern of human risk for infection with Borrelia burgdorferi sensu stricto, the tick-borne pathogen that causes Lyme disease, was mapped for the eastern United States. The map is based on standardized field sampling in 304 sites of the density of Ixodes scapularis host-seeking nymphs infected with B. burgdorferi, which is closely associated with human infection risk. Risk factors for the presence and density of infected nymphs were used to model a continuous 8 km×8 km resolution predictive surface of human risk, including confidence intervals for each pixel. Discontinuous Lyme disease risk foci were identified in the Northeast and upper Midwest, with a transitional zone including sites with uninfected I. scapularis populations. Given frequent under- and over-diagnoses of Lyme disease, this map could act as a tool to guide surveillance, control, and prevention efforts and act as a baseline for studies tracking the spread of infection.

What Do We Need to Know About Disease Ecology to Prevent Lyme Disease in the Northeastern United States?

Journal of Medical Entomology. Jan, 2012  |  Pubmed ID: 22308766

Lyme disease is the most commonly reported vector-borne disease in the United States, with the majority of cases occurring in the Northeast. It has now been three decades since the etiological agent of the disease in North America, the spirochete Borrelia burgdorferi, and its primary North American vectors, the ticks Ixodes scapularis Say and I. pacificus Cooley & Kohls, were identified. Great strides have been made in our understanding of the ecology of the vectors and disease agent, and this knowledge has been used to design a wide range of prevention and control strategies. However, despite these advances, the number of Lyme disease cases have steadily increased. In this article, we assess potential reasons for the continued lack of success in prevention and control of Lyme disease in the northeastern United States, and identify conceptual areas where additional knowledge could be used to improve Lyme disease prevention and control strategies. Some of these areas include: 1) identifying critical host infestation rates required to maintain enzootic transmission of B. burgdorferi, 2) understanding how habitat diversity and forest fragmentation impacts acarological risk of exposure to B. burgdorferi and the ability of interventions to reduce risk, 3) quantifying the epidemiological outcomes of interventions focusing on ticks or vertebrate reservoirs, and 4) refining knowledge of how human behavior influences Lyme disease risk and identifying barriers to the adoption of personal protective measures and environmental tick management.