Temporal correlations between tick abundance and prevalence of ticks infected with Borrelia burgdorferi and increasing incidence of Lyme disease

The abundance of host-seeking Ixodes scapularis nymphs, the principal vector for the Lyme disease agent, Borrelia burgdorferi, in Old Lyme, Lyme, and East Haddam, Connecticut, was compared with the incidence of reported human Lyme disease in the 12-town area around the Connecticut River and the State of Connecticut for the period 1989 to 1996. Ticks were sampled from lawns and woodlands by dragging flannel over the vegetation and examined for the presence of B. burgdorferi by indirect fluorescent antibody staining. The infection rate of the nymphal ticks by B. burgdorferi during the 9-year period was 14.3% (of 3,866), ranging from 8.6% (1993) to 24.4% (1996). The incidence of Lyme disease was positively correlated with tick abundance in the 12 town area (r = 0.828) and the State of Connecticut (r = 0.741). An entomological risk index based upon the number of I. scapularis ticks infected by B. burgdorferi was highest in 1992, 1994, and 1996 and was highly correlated with the incidence of Lyme disease in Connecticut (r = 0.944). The number of Lyme disease cases has been influenced, in part, by annual changes in population densities of I. scapularis and, presumably, a corresponding change in the risk of contact with infected ticks. Based upon tick activity and spirochetal infection rates, epidemiologically based Lyme disease case reports on a regional scale appear to reflect real trends in disease.     

Reduced abundance of Ixodes scapularis (Acari: Ixodidae) with exclusion of deer by electric fencing

To assess the effect of deer exclusion on populations of Ixodes scapularis Say (formerly I. dammini Spielman, Clifford, Piesman & Corwin) in the northeastern United States, host-seeking ticks and ticks on white-footed mice, Peromyscus leucopus (Rafinesque), were monitored inside and outside a wooded, residential deer exclosure (approximately 3.5 ha) in Lyme, CT, in 1991 and 1992. Another deer exclosure was added in Lyme (approximately 7.4 ha) during 1992. Additional sample sites at other residences served as secondary controls. A seven-wire, slanted, high-tensile electric deer fence was used at both areas. Larvae of I. scapularis were 81.5% (1991) and 97.8% (1992) less abundant within the exclosure than immediately outside the deer exclosures. Nymphs of I. scapularis were 47.4% (1991) and 55.8% (1992) less abundant within the deer fence. The effect on adult ticks was mixed. No difference in tick abundance was seen at the 3.5-ha site. However, larvae, nymphs, and adults were 100, 83.8, and 74.1% less abundant, respectively, in plots at the 7.4-ha exclosure > or = 70 m from the deer fence and isolated from woodlands outside the fence by lawns, driveways, and buildings. The recovery of larvae and nymphs of I. scapularis from mice captured within the deer exclosures indicates that infestations of nymphs and adults are probably, at least in part, a result of the movement of these rodents. Based upon the number of nymphs per 100 m2 infected with Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, the causal agent of Lyme disease, there were 73 and 82% fewer infected nymphs within the deer exclosures in 1992 in comparison with the number of infected ticks outside the fence and at the secondary control sites, respectively. The exclusion of deer in conjunction with other tick control strategies in large areas could substantially reduce populations of I. scapularis and the risk of acquiring Lyme disease.     

A method and device for measuring force transfers between the deep flexors in the musician''s hand

The efficacy of passive immunisation against tick-transmitted Lyme disease spirochaetal infection was determined in relation to the duration of previous feeding of infected vector ticks. Thus, mice challenged with spirochaete-infected unfed or partially fed nymphal ticks were passively immunised with monoclonal and polyclonal antibodies against the Lyme disease spirochaete (Borrelia burgdorferi) at various intervals after tick attachment. Spirochaetal infection in challenged mice and engorged ticks was verified by xenodiagnosis and indirect immunofluorescent antibody assay, respectively. Although tick-transmitted spirochaetal infection could be aborted by anti-OspA antibodies and hyperimmune antiserum, nearly all immunised mice challenged with infected ticks that had previous 36-h attachment became infected. More than 72% of the nymphal ticks used in this challenge retained their B. burgdorferi infection after engorgement on mice immunised with anti-spirochaete antibodies, and their subsequent infectivity to mice remained effective. It is concluded that a higher efficiency of transmission by partially fed infected nymphs and a lower efficacy of passive immunisation against infection result from an effect of previous feeding of infected ticks that activates antigenic change and enables the spirochaetes to circumvent OspA-based humoral immunity.     

Geographic risk for lyme disease and human granulocytic ehrlichiosis in southern New York state

Ixodes scapularis, the tick vector of Lyme disease and human granulocytic ehrlichiosis (HGE), is prevalent in much of southern New York state. The distribution of this species has increased, as have reported cases of both Lyme disease and HGE. The unreliability of case reports, however, demonstrates the need for tick and pathogen surveillance in order to accurately define areas of high risk. In this study, a total of 89,550 m2 at 34 study sites was drag sampled in 1995 and a total of 51,540 m2 at 40 sites was sampled in 1996 to determine tick and pathogen distribution in southern New York state. I. scapularis was collected from 90% of the sites sampled, and regionally, a 2.5-fold increase in nymphal abundance occurred from 1995 to 1996. I. scapularis individuals from all sites were infected with Borrelia burgdorferi in 1995, while an examination of ticks for both B. burgdorferi and the agent of HGE in 1996 confirmed that these organisms were present in all counties; the average coinfection rate was 1.9%. No correlation was found between estimated risk and reported cases of Lyme disease. The geographic disparity of risk observed among sites in this study underscores the need for vector and pathogen surveillance on a regional level. An entomologic risk index can help identify sites for targeted tick control efforts.     

Impact of controlled burns on the abundance of Ixodes scapularis (Acari: Ixodidae)

Information on the effect of vegetative destruction by controlled burns in reducing the abundance of the blacklegged tick, Ixodes scapularis Say, the vector for the agents of Lyme disease, human babesiosis, and human granulocytic ehrlichiosis, is limited. Therefore, the abundance of nymphal, larval, and adult I. scapularis was monitored by dragging the vegetation at 2 separate 4-ha tracts in Cockaponset State Forest in Connecticut following a single controlled burn on 15 April or 21 May 1992. The burn at the April burn site was rated as light to moderate with a flame height of 0.3 m and consumed approximately 67% of the surface leaf litter. The burn at the May burn site was rated moderate to severe with a flame height of 0.6-0.9 m., which consumed vegetation < 5 cm in diameter and approximately 100% of the surface leaf litter. The impact of the burn was strongly influenced by the intensity and timing of the burn. Burning of the vegetation resulted in a reduction of the abundance of nymphal I. scapularis by 74% at the moderately burned site and 97% at the severely burned site, compared with adjacent unburned woodland. No larvae were recovered later in the summer from the severely burned tract. However, judging by the comparable abundance of adult I. scapularis in the fall at the burned and unburned woodlands, the effect of the burns was temporary. Burning the vegetation for the control of I. scapularis appears limited in effect and could be applied only on a large scale in areas with little or no human habitations.     

Determining the duration of Ixodes scapularis (Acari: Ixodidae) attachment to tick-bite victims

The duration of tick attachment is one factor associated with risk for human infection caused by several tick-borne pathogens. We measured tick engorgement indices at known time intervals after tick attachment and used these indices to determine the length of time that ticks were attached to tick-bite victims in selected Rhode Island and Pennsylvania communities where the agents of Lyme disease and human babesiosis occur. The total body length and width as well as the length and width of the scutum were measured on nymphal and adult female Ixodes scapularis Say removed from laboratory animals at 0, 12, 24, 36, 48, 60, and 72 h after their attachment. Three engorgement indices were calculated at each time interval. In addition, engorgement indices measurements were recorded for 504 ticks submitted to a commercial laboratory for pathogen detection testing between 1990 and 1992. No detectable change was observed in the average engorgement indices for either nymphal or adult ticks between 0 and 24 h of attachment using any of the engorgement indices. After 24 h of tick attachment, all engorgement indices continuously increased: average indices for nymphs attached 36, 48, and 60 h were significantly different from those attached < or = 24 h and from each other. Similarly, average engorgement indices for adult ticks attached < or = 36 h were significantly different from those attached for 48 h or more. More than 60% of tick-bite victims removed adult ticks by 36 h of attachment, but only 10% found and removed the smaller nymphal ticks within the first 24 h of tick feeding. The duration of tick attachment may serve as a useful predictor of risk for acquiring various infections, such as Lyme disease and babesiosis, transmitted by I. scapularis. Regression equations developed herein correlate tick engorgement indices with duration of feeding. A table containing specific engorgement index prediction intervals calculated for both nymphs and adults will allow the practitioner or clinical laboratory to use easily measured tick engorgement indices to predict transmission risk by determining the duration of feeding by individual ticks.     

Transmission of Borrelia burgdorferi s.l. from mammal reservoirs to the primary vector of Lyme borreliosis, Ixodes ricinus (Acari: Ixodidae), in Sweden

Factors regulating prevalence of Borrelia burgdorferi s.l. Johnson, Schmid, Hyde, Steigerwalt & Brenner in Ixodes ricinus (L.) were examined during 1991-1992 at Bogesund, near Stockholm in south-central Sweden. Nine species of small and medium-sized mammals (Sorex araneus L., S. minutus L., Neomys fodiens Pennant, Clethrionomys glareolus [Schreber], Microtus agrestis [L.], Apodemus sylvaticus [L.], A. flavicollis [Melchior], Lepus europaeus Pallas, L. timidus L.) were found to infect feeding tick larvae with B. burgdorferi s.l., whereas two species of large mammals (Capreolus capreolus L., Alces alces L.) failed to infect feeding tick larvae with this spirochete. The most important mammalian reservoirs at the study locality were S. araneus and rodents, accounting for 91% of all I. ricinus larvae infected. In view of the great number of potentially effective reservoirs for B. burgdorferi s.l. in Sweden, control of Lyme disease by reduction of abundance of reservoir hosts will be difficult to achieve. We also found that infectivity of a rodent species is related to the number of infesting, potentially infective nymphal I. ricinus. Insectivores and rodents were the most important hosts of larval I. ricinus, whereas most nymphal ticks fed on hares and cervids. Adult I. ricinus were frequently found on all species of hares and cervids examined but never on insectivores and rodents. No single species seemed to be of paramount importance as a source of blood for female ticks. Therefore, control of Lyme disease by reduction of abundance of mammal hosts available for female tick engorgement will probably require massive reductions of numbers of both C. capreolus and L. timidus.     

Lyme disease: self-regulation and pathogen invasion

Ecological interactions underlying the epidemic of Lyme disease involve a spirochete, a tick (with larval, nymph and adult stages), and two (or more) vertebrate hosts. Juvenile ticks ordinarily feed on mice; adult ticks feed on deer. Mice acquire the spirochete from infected nymphs and then pass the infection to larvae of the next tick generation. Lyme disease may result when a human is inadvertently bitten by an infectious nymph. Our model of the Lyme phenomenon counts the total number of ticks in each stage, the numbers of infected ticks by stage, and the number of infected mice. We fix the total population sizes of deer and mice, assume the ticks self-regulate, and solve the homogeneous-mixing case for equilibrium abundances. A local stability analysis identifies a condition where extinction of the spirochete is stable. Reversing this condition implies that the spirochete can invade the system of ticks and vertebrate hosts. When the spirochete can invade, a positive equilibrium number of infected organisms is locally stable. Spirochete invasion is promoted by a sufficient density of mice suffering low mortality, high susceptibility to infection in both mice and ticks, a high attack rate of ticks on mice, a high density of larval ticks, and low mortality among tick nymphs. Low mouse mortality allows the frequency of infection among nymphs to approach an individual tick's susceptibility when feeding on an infected mouse.     

Reservoir competence of the meadow vole (Rodentia: Cricetidae) for the Lyme disease spirochete Borrelia burgdorferi

The reservoir competence of the meadow vole, Microtus pennsylvanicus Ord, for the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner was established on Patience Island, RI. Meadow voles were collected from 5 locations throughout Rhode Island. At 4 of the field sites, M. pennsylvanicus represented only 4.0% (n = 141) of the animals captured. However, on Patience Island, M. pennsylvanicus was the sole small mammal collected (n = 48). Of the larval Ixodes scapularis Say obtained from the meadow voles on Patience Island, 62% (n = 78) was infected with B. burgdorferi. Meadow voles from all 5 locations were successfully infected with B. burgdorferi in the laboratory and were capable of passing the infection to xenodiagnostic I. scapularis larvae for 9 wk. We concluded that M. pennsylvanicus was physiologically capable of maintaining B. burgdorferi infection. However, in locations where Peromyscus leucopus (Rafinesque) is abundant, the role of M. pennsylvanicus as a primary reservoir for B. burgdorferi was reduced.     

Accelerated infectivity of tick-transmitted Lyme disease spirochetes to vector ticks

We determined whether the span of infectivity of Lyme disease spirochetes (Borrelia burgdorferi) to vector ticks varies with the mode of infection in laboratory mice. Noninfected larval deer ticks were permitted to feed on two strains of spirochete-infected mice that had been naturally (via tick bite) and parenterally (via needle injection) infected with B. burgdorferi 2, 4, or 8 weeks earlier, and engorged ticks were dissected and examined for spirochetes by direct immunofluorescence microscopy. After initial infection, spirochetal infectivity to ticks was less efficient in needle-infected mice than in mice infected via tick bites. Tick-transmitted spirochetes develop more rapidly from the skin of infected mice and do not induce a strong antispirochete antibody response during the early stage of infection.     

Temporal pattern of Borrelia burgdorferi p21 expression in ticks and the mammalian host

The temporal synthesis of the P21 protein of Borrelia burgdorferi and the development of the humoral response to this antigen was assessed in infected mice. p21 is a member of the ospE-F gene family and its protein, P21, has been shown to be expressed by B. burgdorferi within infected mice but not by spirochetes cultured in vitro. P21 was not detected on B. burgdorferi in unfed or engorged Ixodes dammini (also known as I. scapularis) ticks, further supporting the postulate that P21 synthesis is specific for the mammalian host. In B. burgdorferi-infected mice, ospE mRNA and OspE antibodies were observed at 7 d, whereas p21 mRNA and P21-specific antibodies were detected at 21-28 d, suggesting that p21 is expressed later than ospE. Moreover, ospA mRNA was not discernible until day 14, indicating that ospA, like p21, is not expressed in the early stages of tick-transmitted murine Lyme borreliosis. Because p21 is expressed during infection in mice, we assessed the human humoral response to P21. 28% (34 of 122) of the patients with either early- or late-stage Lyme disease, and 33% (11 of 33) of the individuals with Lyme arthritis had P21 antibodies, suggesting that a P21 response may serve, at least partially, as a marker of infection. Active immunization with recombinant P21 did not protect C3H mice from tick-borne B. burgdorferi infection, and passive transfer of P21 antiserum to infected mice did not alter the course of disease. These data suggest that the antigenic structure of B. burgdorferi changes during the early stages of murine infection.     

Risk of contamination by Borrelia burgdorferi S. lato in a forest environment. Survey during 13 months of abundance of the tick Ixodes ricinus and its level of infestation by the Lyme borreliosis agent in Brittany

The authors, in a forest in Brittany previously studied for several years, caught by flagging, each month from April 1992 to May 1993, nymphs of I. ricinus tick, and looked by indirect immunofluorescence, for B. burgdorferi infestation. An amount of 1,506 ticks was thus studied. Infestation frequency was varying from 0 per cent in January and February to 14.4 per cent in August. Standarding of tick collecting method allowed to establish, for each month, a tick, "availability" index, and, according to the spirochete infestation frequency, to do estimation of the risk level, for human visiting the concerned forest, of being infected by B. burgdorferi. Obtained results show that this risk is the highest in August, and quite non-existent in January and February.     

The timing of color and location processing in the motor context

The contribution of migratory and resident birds to the introduction of Lyme disease will vary with the degree to which various species expose themselves to, and are infested by, juvenile vector ticks, and their ability to support and transmit the infectious agent. To examine the relative contribution of various passerine species during the emergence of this disease, we compared the abundance and infection rates of the blacklegged tick, Ixodes scapularis Say, removed from mist-netted birds with those from live-trapped mice at a coastal study site in southern Maine, collected during an 8-yr period in which the range of this tick and the incidence of Lyme disease increased in the state. Weekly bird-banding sessions using six 12-m Japanese mist nets were carried out from May through August 1989-1996. In 1989, 1991 and 1993, mice were live-trapped in a Sherman trap grid (7 by 7 m) during five 3-night sessions, June through August; in 1994-1996, 2 such grids were similarly trapped. Annual adult tick abundance was estimated by flagging vegetation. We removed 2,633 juvenile deer ticks from 1,713 of 1,972 birds examined. Twenty-five of 64 bird species were infested. The percentages of birds infested and the rate of infection among removed larvae and nymphs increased over the years, but species varied markedly in their ability to infect ticks. No infected larvae were removed from catbirds or towhees. The larval to nymphal ratio was higher in mice than in birds. Infection rates among bird-derived larvae were less than among mice-derived larvae, but increased with time. Because of the different ways in which individual species of passerine birds contribute to the availability of vector ticks and respond to the agent of Lyme disease in emerging areas, further research into host competency and borreliacidal mechanisms is needed.     

Infusion methods for determination of peripheral resistance: influence of infused medium and back pressure

Many isolates of Borrelia burgdorferi have been obtained from ticks and vertebrate tissues collected in North America and continental Europe but only one established culture of United Kingdom Borrelia burgdorferi has been recorded. In this paper we report the isolation of B. burgdorferi from one of 108 tick pools representing 733 ticks and eight-four tissue samples from twenty-six rodents collected in the U.K, and the subsequent failure to establish the isolate (from ticks collected in Fordingbridge) in culture. In contrast, using identical techniques and culture medium, B. burgdorferi was isolated from one of seven tick pools collected in Switzerland, and from a single pool of ticks collected in Slovakia, and both isolates were successfully passaged. Analysis of questing I. ricinus collected from Fordingbridge by direct immunofluorescence showed 6/32 (19%) of adults and 8/108 (7%) of nymphs were positive for B. burgdorferi, although only one nymph contained > or = 1000 spirochaetes. To examine further the problem of isolating U.K. B. burgdorferi, twelve Ixodes ricinus tick samples from Fordingbridge, a recognized focus of Lyme disease, were subjected to isolation and culturing techniques, and the procedures monitored by use of the polymerase chain reaction (PCR). Whereas 11/12 samples were PCR positive after 2 weeks in culture, only one was PCR positive after 4 weeks. Motile spirochaetes were not visible by dark-field microscopy in any of the cultures. The results indicate that the standard BSK II medium routinely used to isolate and culture B. burgdorferi does not readily support the replication of the Borrelia species endemic to the U.K.     

Ear dominance and telephone sales

BACKGROUND: Lyme disease is caused by Borrelia burgdorferi which is transmitted in Europe by the tick ixodes ricinus. Erythema migrans is a skin lesion which is pathognomonic of Lyme disease. A retrospective study was carried out to determine the geographical distribution of the occurrence of tick bites and erythema migrans in the Netherlands and to identify ecological risk factors. METHODS: In April 1995, all general practitioners (GPs) in the Netherlands were asked to complete a postal questionnaire on the number of tick bites and erythema migrans case-patients seen in 1994 and the size of the practice. Reminders were sent to non-responders. Information on ecological risk factors by local government area was obtained from a geographical information system. RESULTS: The response rate was 79.9%. In 1994, GPs reported seeing approximately 33,000 patients with tick bites and 6500 with erythema migrans. The incidence rate of erythema migrans was estimated at 4.3 per 10,000 population. Ecological risk factors for both tick bites and erythema migrans were the proportion of the area covered by woods, sandy soil, dry uncultivated land, the number of tourist-nights per inhabitant and sheep population density. The cattle population density was a risk factor for erythema migrans. CONCLUSIONS: Using simple methods, a crude estimate of the incidence rate of erythema migrans was obtained rapidly, and high risk areas were identified. Lyme disease appears to be an important problem in the Netherlands.     

Lyme disease in children and adolescents

148 children and adolescents with Lyme borreliosis and tick bite or suspection on tick bite were examined. The examined patients were aged from 14 months to 24 years and divided into four age groups. Skin lesions were discovered in 25 percent of patients with tick bite. Erythema migrans occurred in 91 percent, Lymphocytoma in 3 percent and sclerodermatous lesions (Lichen sclerosus et atrophicus and Morphea) in 6 percent of patients with Lyme disease. Serologic tests on the presence of antibodies to Borreliae burgdorferi were performed in 96 percent of cases with tick bite. Antibody titer 1:80 or higher in 8 percent of patients with tick bite, was discovered. We found positive serologic test results in 5 (29 percent) of 29 persons with Erythema migrans, in 4 (4 percent) of 110 patients with tick bite (without skin lesions), as well as, in 1 patient with Lymphocytoma. Antibiotic therapy was applied in all cases with Erythema migrans, in person with Lymphocytoma, as well as, in patients with asymptomatic infections (patients without skin lesion recalling a tick bite and with antibodies against Borrelia burgdorferi). A general sensitivity, to infection with Borrelia burgdorferi, is stressed, a fact based on appearance by Lyme borreliosis in all age groups even in the newborn children.     

Rheumatic manifestations in Lyme borreliosis: personal experience in patients with oligoarthritis of "unknown" origin

Lyme borreliosis is an infectious illness caused by the spirochete Borrelia burgdorferi and is transmitted by tick vectors. A prospective study was performed from January 1990, to investigate whether Lyme arthritis might have been undetected among patients with (unclassified arthritis) oligoarthritis of "unknown" aetiology. 210 patients were tested for antibodies to Borrelia burgdorferi: 82 patients with oligoarthritis of "unknown" aetiology; 52 patients with Reiter's syndrome; 20 patients with seronegative, B-27 positive oligoarthritis and 56 controls. Serological testing for Borrelia burgdorferi was performed by indirect immunofluorescence assay. The occurrence of positive antibodies (1:80) in 11 (13.4%) patients with arthritis of "unknown" aetiology was significantly different from the combined control group (1.6%) (p < 0.05). Four out of 11 patients remembered a tick bite, two out of 11 patients developed erythema migrans after 3 to 10 days. Six weeks later 2 patients developed oligoarthritis and one patient after a month. In the remaining 8 patients arthritis was the first sign of the disease. Knees were most commonly affected (90%). Radiographic abnormalities (osteoporosis, soft tissue swelling) were noted in 3 patients. The synovial fluid findings were typical for inflammatory arthritides in 6 patients. The diagnosis of Lyme borreliosis was made according to following data: origin from an area endemic for Lyme borreliosis, tick bite, erythema migrans, significant levels of the antibodies to the Borrelia burgdorferi and oligoarthritis. It can be concluded that arthritis may be the main manifestation of Borrelia burgdorferi infection.     

Effect of reduced bronchial circulation on lung fluid flux after smoke inhalation in sheep

Murine monoclonal antibodies directed against proteins of Borrelia burgdorferi B31 (low passage) were generated by the administration of antigen via the bite of borrelia-infected ticks. This strategy was employed as a mechanism to create antibodies against antigens presented by the natural route of tick transmission versus those presented by inoculation with cultured borreliae. One of the resultant antibodies reacted with a 17-kDa antigen from cultured B. burgdorferi, as seen by immunoblot analysis. This antibody was used to screen a B. burgdorferi genomic DNA lambda vector expression library, and an immunoreactive clone was isolated. DNA sequence analysis of this clone, containing a 2.7-kb insert, revealed several open reading frames. These open reading frames were found to be homologs of genes discovered as a multicopy gene family in the 297 strain of B. burgdorferi by Porcella et al. (S. F. Porcella, T. G. Popova, D. R. Akins, M. Li, J. D. Radolf, and M. V. Norgard, J. Bacteriol. 178:3293-3307, 1996). By selectively subcloning genes found in this insert into an Escherichia coli plasmid expression vector, the observation was made that the rev gene product was the protein reactive with the 17-kDa-specific monoclonal antibody. The rev gene product was found to be expressed in low-passage, but not in high-passage, B. burgdorferi B31. Correspondingly, the rev gene was not present in strain B31 genomic DNA from cultures that had been passaged >50 times. Serum samples from Lyme disease patients demonstrated an antibody response against the Rev protein. The generation of an anti-Rev response in Lyme disease patients, and in mice by tick bite inoculation, provides evidence that the Rev protein is expressed and immunogenic during the course of natural transmission and infection.     

Plasminogen is required for efficient dissemination of B. burgdorferi in ticks and for enhancement of spirochetemia in mice

The role of the host plasminogen activation system in transmission of and invasion by Borrelia burgdorferi, the tick-borne spirochetal agent of Lyme disease, was investigated using plasminogen (Plg)-knockout mice. PLG was not detected in spirochetes from unfed ticks, but binding occurred as ticks fed on the host's blood. Plasminogen activators were derived from the host blood meal. PLG was required for efficient dissemination of B. burgdorferi within the tick and for enhancement of spirochetemia in mice but was not critical for transmission and infection. These results provide evidence for a bacterium using a vertebrate protease to disseminate in an invertebrate vector and underscores the interplay among vector, pathogen, and host in promoting the life cycle and disease.     

Borrelia burgdorferi erp proteins are immunogenic in mammals infected by tick bite, and their synthesis is inducible in cultured bacteria

Borrelia burgdorferi, the causative agent of Lyme disease, can contain multiple genes encoding different members of the Erp lipoprotein family. Some arthropod-borne bacteria increase the synthesis of proteins required for transmission or mammalian infection when cultures are shifted from cool, ambient air temperature to a warmer, blood temperature. We found that all of the erp genes known to be encoded by infectious isolate B31 were differentially expressed in culture after a change in temperature, with greater amounts of message being produced by bacteria shifted from 23 to 35 degrees C than in those maintained at 23 degrees C. Mice infected with B31 by tick bite produced antibodies that recognized each of the Erp proteins within 4 weeks of infection, suggesting that the Erp proteins are produced by the bacteria during the early stages of mammalian infection and may play roles in transmission from ticks to mammals. Several of the B31 Erp proteins were also recognized by antibodies from patients with Lyme disease and may prove to be useful antigens for diagnostic testing or as components of a protective vaccine.