Importance of localized skin infection in tick-borne encephalitis virus transmission

Arboviruses are transmitted to vertebrates by the "bite" of infected arthropods. Events at the site of virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) virus transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus). Virus transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels > or = 2.0 log10 ic mouse LD50/0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE virus transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne virus transmission.     

Aetiology of skeletal muscle ''cramps'' during exercise: a novel hypothesis

Secretions of the tick salivary glands are essential to the successful completion of the prolonged feeding of these ectoparasites as well as the conduit by which most tick-borne pathogens are transmitted to the host. In ixodid ticks the salivary glands are the organs of osmoregulation, and excess water from the bloodmeal is returned via saliva into the host. Host blood must continue to flow into the feeding lesion as well as remain fluid in the tick mouthparts and gut. The host's haemostatic mechanisms are thwarted by various anti-platelet aggregatory, anticoagulatory and anti-vasoconstrictory factors in tick saliva. Saliva components suppress the immune and inflammatory response of the host permitting the ticks to remain on the host for an extended period of time and, adventitiously, enhancing the transmission and establishment of tick-borne pathogens. Over the years much work has been done on the numerous enzyme and pharmacological activities found in the tick saliva. The present article reviews the most recent work on salivary gland secretions with special emphasis on how they favour pathogen transmission.     

Mx1-based resistance to thogoto virus in A2G mice is bypassed in tick-mediated virus delivery

The interferon-induced mouse Mx1 protein has intrinsic antiviral activity against orthomyxoviruses, including Thogoto virus. Thus, Mx1(+) A2G mice are apparently resistant to infection following needle- or tick-borne virus challenge. However, tick-borne challenge and, to a lesser degree, injection of virus mixed with tick salivary gland extract resulted in virus transmission to uninfected ticks feeding on the A2G mice. The data indicate that immunomodulatory components in tick saliva can overcome a natural antiviral mechanism.     

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.     

Impact of pharmaceutical underutilization: a study of insurance drug claims data

From 1989 to 1992, a longitudinal study of the relationships between different tick species and domestic ungulates in the transmission and amplification of Crimean-Congo hemorrhagic fever (CCHF) virus was undertaken in the Bandia area in Senegal where the presence of the virus had been reported previously. An epizootic occurred in 1991-1992 and 22 strains of CCHF virus were isolated from Hyalomma marginatum rufipes Koch, Amblyomma variegatum (F.), Rhipicephalus guilhoni Morel & Vassiliades, and R. evertsi evertsi Neumann ticks collected from cattle and goats. No human cases were reported. Transmission of CCHF virus in the area involves a complicated pattern including many tick species and hosts. Amplicons of the S fragment (536 bp) of the CCHF genome of 12 isolates from the study were obtained by polymerase chain reaction and analyzed by restriction-length fragment polymorphism. Three different genotypes of CCHF virus were identified and present during the epizootic. One genotype was recovered from A. variegatum, R. guilhoni, and R. e. evertsi and 2 genotypes were isolated from H. m. rufipes.     

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.     

Effects of cattle tick (Boophilus microplus) infestation on the bovine immune system

The immunosuppressive effect of experimental Boophilus microplus infestation on bovine peripheral blood lymphocytes (PBL) and on host antibody production to a protein antigen (ovalbumin) was examined. Boophilus microplus infestation caused a marginal decrease in the percentage of T lymphocytes in PBL, which was observed in both lightly (5000 larvae) and heavily (40,000 larvae) infested cattle, and began at the second infestation and continued until the end of the fourth infestation. The percentage of B lymphocytes in heavily tick-infested cattle was less than that in non-infested control cattle after the fourth infestation. The response of PBL from tick-infested cattle to phytohemagglutinin (PHA) was always less than that of tick-free cattle after the second infestation. No noteworthy differences were detected between the three stages of tick infestation, that is, 1 week before the peak of adult engorgement, the middle of the peak and 1 week after all ticks had dropped. Boophilus microplus saliva (100 microliters ml-1) suppressed 47% of the response of bovine PBL to PHA in vitro. This suppressive effect of saliva may contribute to the lower responsiveness of PBL from tick-infested cattle. Antibody production by tick-infested cattle was examined during the third and fourth heavy tick infestation. Tick-infested cattle showed a diminished response against ovalbumin after the second immunization. The immunosuppressive effects of tick infestation may play an important role in tick survival or in the transmission of tick-borne diseases in the field.     

Use of a whole blood assay to monitor the immune response to mycobacterial antigens in leprosy patients: a predictor for type 1 reaction onset?

In this study, we investigated tick saliva effects on T cell proliferation, antigen presentation and IFN-gamma-induced macrophage activation, events which are associated with host immune defense mechanisms. Mice repeatedly infested with Rhipicephalus sanguineus ticks, similarly to dogs, did not develop resistance to further infestations. We determined that R. sanguineus tick saliva inhibited, in a dose-dependent manner, both Con-A and specific antigen-induced splenic T cell proliferation. Tick saliva diluted twenty times (64 microg/ml) inhibited Con-A-induced and antigen-specific T cell proliferation in 83% and 69%, respectively. In addition, the inhibition of cell proliferation correlated with a decrease in IL-2 production. Microconcentrator fractionated saliva was tested on a Con-A-induced cell proliferation assay, and showed that one fraction between 3 and 10 kDa and another smaller than 3 kDa can be responsible for the inhibition of T cell proliferation. Although saliva inhibited cell proliferation, it did not impair antigen presentation. Tick saliva further abrogated the killing of intracellular forms of Trypanosoma cruzi by IFN-gamma-activated macrophages. Moreover, saliva-induced macrophage inhibition of IFN-gamma-induced-trypanocidal activity was paralleled with 69% less nitric oxide (NO) production. Finally, tick saliva doubled the production of IL-10 and reduced 84.6% production of IFN-gamma by splenocytes cultured with T. cruzi, suggesting that decreased macrophage NO production may be due to a saliva-induced cytokine imbalance, leading to decreased NO synthase activity. Together, these data indicate that tick saliva can modulate host immune response, thus, contributing to its feeding success and favoring the transmission of tick-borne pathogens.     

Lizards as hosts for immature Ixodes scapularis (Acari: Ixodidae) in North Carolina

Previously archived museum specimens of lizards collected throughout North Carolina were examined for Ixodes scapularis (Say). Lizards (n = 1,349) collected in 80 of North Carolina's 100 counties were examined. Lizards with ticks were collected in 23 (29%) of the 80 counties from which lizards were examined. I. scapularis was detected on 8.7% (n = 117) of the lizards and was the sole species of tick obtained from lizards. Immature ticks were most frequently found on the southeastern five-lined skink, Eumeces inexpectatus, and the eastern glass lizard, Ophisaurus ventralis. Larvae were most frequently found on the six-lined racerunner, Cnemidophorus sexlineatus. One C. sexlineatus harbored 177 larvae and 2 nymphs. Nymphs were most frequently observed on E. inexpectatus. The majority of counties (chi 2, P < 0.01) where ticks were found on lizards were in the Coastal Plain.     

Erythema migrans-like rash illness at a camp in North Carolina: a new tick-borne disease?

BACKGROUND: Borrelia burgdorferi, the causative agent of Lyme disease, has never been isolated from a patient thought to have acquired Lyme disease in any southeastern state. OBJECTIVE: To investigate 14 cases of an erythema migrans (EM)-like rash illness that occurred during 2 summers at an outdoor camp in central North Carolina in an effort to determine the etiologic, epidemiological, and clinical aspects of this illness. METHODS: Using active surveillance, we identified cases of clinically diagnosed EM in residents and staff of the camp. We collected clinical and demographic information; history of exposure to ticks; acute and convalescent serum antibodies to B. burgdorferi, Rickettsia rickettsii, and Ehrlichia chaffeensis; and cultures for spirochetes from biopsy specimens of skin lesions. Serum samples from a group of residents and staff who did not develop rashes were tested for the same antibodies. We speciated ticks removed from people and collected from vegetation. RESULTS: We identified 14 cases of EM-like rash illness during the 2 summers. Of the 14 case-patients, 10 had associated mild systemic symptoms and 1 had documented fever. All 14 case-patients had removed attached ticks, and 8 remembered having removed a tick from the site where the rash developed a median of 12 days earlier (range, 2-21 days). One tick removed from the site where a rash later developed was identified as Amblyomma americanum, the Lone Star tick; 97% of ticks collected from vegetation and 95% of ticks removed from people were A. americanum. No spirochetes were isolated from skin biopsy specimens. Paired serum samples from 13 case-patients did not show diagnostic antibody responses to B. burgdorferi or other tick-borne pathogens. CONCLUSIONS: This investigation suggests the existence of a new tick-associated rash illness. We suspect that the disease agent is carried by A. americanum ticks. In the southern United States, EM-like rash illness should no longer be considered definitive evidence of early Lyme disease.     

Isolation of aerobic microbes from Ixodes scapularis (Acari: Ixodidae), the vector of Lyme disease in the eastern United States

The spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Benner is transmitted by Ixodes scapularis Say, a vector of Lyme disease. As a 1st step into investigating the possibility of biocontrol of the tick, we identified the microbiota associated with the ticks. We collected, identified, and determined the sex of ticks from foliage and deer. Seventy-three initial bacterial isolates were recovered from 43 ticks (27 adults and 16 nymphs). The bacteria isolated from nymphs were qualitatively different (mainly gram-negative cocci) from the bacteria isolated from adult ticks (gram-negative and gram-positive rods). To determine long-term viability, these isolates were stored for 6 mo under laboratory conditions. After storage, 63 surviving bacterial isolates were characterized using the Biology System of identification by substrate utilization. Forty-four isolates were identified to the species level. Our characterization efforts focused on the 40 spore-forming bacteria, which could prove useful in the biocontrol of ticks. Eleven species of Bacillus were identified. Bacillus thuringiensis-B. cereus was the predominant species group isolated. Six isolates from this group formed crystals.     

Characterization of Borrelia burgdorferi isolated from different organs of Ixodes ricinus ticks collected in nature

Borrelia burgdorferi was isolated from 22 out of 133 adult Ixodes ricinus ticks collected from vegetation at two sites in Switzerland. From 17 ticks, spirochetes could be isolated from more than one organ. When the different isolates obtained from one tick were compared by SDS-PAGE analysis, differences in the protein profiles were observed in 8 cases. The isolates were further compared by immunological methods using mono- and polyclonal antibodies. Differences were observed in the proteins of 31-35 kDa and 18-25 kDa. Genetic divergence among isolates was evaluated by use of a B. burgdorferi specific gene probe for ospA. Correlation could be observed between immunological differences in OspA defined by monoclonal antibody LA31 and genetic variation of ospA as judged by restriction fragment length polymorphism (RFLP). Our findings indicate that systemic infection in unfed I. ricinus adults, as reflected by isolation of B. burgdorferi from multiple organs of one tick, is more frequent (8/22, 36%) than previously described (5%). Moreover, the presence of different B. burgdorferi phenotypes/genotypes in one tick is described for the first time. The findings may have bearings (i) on the time of tick attachment required for spirochete transmission since borreliae are already present in the salivary glands of systemically infected ticks at the beginning of the blood meal and (ii) perhaps also on the diversity of B. burgdorferi phenotypes inoculated by these ticks.     

Why is HIV rarely transmitted by oral secretions? Saliva can disrupt orally shed, infected leukocytes

BACKGROUND: Oral transmission of human immunodeficiency virus (HIV) by the millions of HIV-infected individuals is a rare event, even when infected blood and exudate is present. Saliva of viremic individuals usually contains only noninfectious components of HIV indicating virus breakdown. OBJECTIVE: To determine whether unknown HIV inhibitory mechanisms may explain the almost complete absence of infectious HIV in the saliva. METHODS: Since most of the infectious HIV that is shed mucosally by asymptomatic individuals is found in, produced by, and transmitted by infected mononuclear leukocytes, we determined whether saliva, which is hypotonic, may disrupt these infected cells, thereby preventing virus multiplication and cell-to-cell transmission of HIV. Specifically, we measured (1) whether mononuclear leukocytes were lysed by saliva and (2) whether the lysis by saliva inhibits the multiplication of HIV and other viruses in infected leukocytes and other cells. RESULTS: Saliva rapidly disrupted 90% or more of blood mononuclear leukocytes and other cultured cells. Concomitantly, there was a 10000-fold or higher inhibition of the multiplication of HIV and surrogate viruses. Further experiments indicated that the cell disruption is due to the hypotonicity of saliva: CONCLUSIONS: Hypotonic disruption may be a major mechanism by which saliva kills infected mononuclear leukocytes and prevents their attachment to mucosal epithelial cells and production of infectious HIV, thereby preventing transmission. Implications for the known oral HIV transmission by milk and seminal fluid, as well as potential oral transmission to contacts and health care workers, are considered. This effective salivary defense may be applicable medically to interdict vaginal, rectal, and oral transmission of HIV by infected cells in seminal fluid or milk by the use of anticellular substances.     

Physician-diagnosed erythema migrans and erythema migrans-like rashes following Lone Star tick bites

OBJECTIVE: To differentiate cases of physician-diagnosed erythema migrans and erythema migrans-like rashes associated with Lone Star tick (Amblyomma americanum) bites. DESIGN: Retrospective case series. SETTING: Private primary care clinic in rural Missouri. PATIENTS: Seventeen patients with physician-diagnosed erythema migrans following a definite Lone Star tick bite at the rash site. INTERVENTIONS: A biopsy was performed on all rash sites. All patients were treated with oral antibiotics. MAIN OUTCOME MEASURES: Rash appearance, size, body location, multiple lesions, incubation times, associated symptoms, seasonal occurrence, histopathological features, tick stage and sex, patient age and sex, treatment response, growth in BSK II culture media, and serologic evaluation. RESULTS: Rashes associated with Lone Star ticks were similar to erythema migrans vectored by other Ixodes ticks. Differences were noted in Lyme disease serology results, especially flagellin-based enzyme immunoassays, and failure to yield spirochetes in BSK II cultures. Lyme serology results were often negative, but were also frequently inconsistent with results of controls without Lyme disease. CONCLUSIONS: Lone Star ticks are associated with rashes that are similar, if not identical, to erythema migrans associated with borrelial infection. The recent isolation and cultivation of Borrelia burgdorferi from ticks (including 1 Lone Star tick) from the farm of a patient included in this report has raised the possibility that Lone Star ticks are "bridge vectors" for human borrelial infection. Although further investigation is needed, these rashes may be secondary to spirochetal infection.     

Present state of research on ticks (Ixodoidea) in the Czech Republic

Tick research in the Czech Republic started developing rapidly after World War II and was directed to the faunistics and taxonomy, biology, ecology and behaviour, physiology and genetics, disease transmission, host-parasite relationships and control. Altogether 15 tick species were reported from the territory of the Czech Republic. Most studies in biology, ecology and virus transmission were dedicated to Ixodes ricinus, but biology and ecology of Dermacentor reticulatus, I. laguri and I. hexagonus were also studied. Many studies were done on argasid ticks, mostly on pheromonal communication of Argas persicus and immunology of feeding of A. polonicus. Population variability of both these species was also studied. The present research on ticks is mostly directed to study of interaction among hosts, ticks and pathogens on the humoral, cellular and molecular level.     

The biological basis of grooming in moose: programmed versus stimulus-driven grooming

In domestic and wild mammals, tick infestation can be a significant fitness cost. Grooming behaviour has been shown to be effective in removing ticks. We studied grooming by moose, Alces alces, infested with winter ticks, Dermacentor albipictus, to determine which of two nonexclusive models for the regulation of tick-removal grooming, programmed or stimulus driven, best fit this host-parasite relationship. The programmed grooming model states that most grooming is driven by an internal timing mechanism which periodically evokes a bout a grooming independent of peripheral stimulation from tick bites. Because programmed grooming is preventive, the model predicts that those animals that groom the most will carry the fewest ticks, and a baseline level of programmed grooming is predicted even in a tick-sparse or tick-free environment. The stimulus-driven grooming model, on the other hand, states that grooming is a direct response to cutaneous irritation caused by tick bites and other sources of irritation. This stimulus-driven model predicts that (1) animals showing the highest rate of grooming will carry the most ticks and (2) animals will groom little when tick challenge is low. Both predictions of the stimulus-driven model were supported for moose: (1) calves oral-groomed three times more than cows, and tick densities on calves were three times higher than on cows; and (2) although all moose carried high densities of immature winter ticks (larvae, nymphs) from October through to February, grooming rate was very low until adult ticks started feeding in March-April. Peak grooming rates occurred during adult tick engorgement in March-April. Because an engorging adult female tick produces far more irritation than an engorging nymphal or larval tick, moose appeared to groom in direct proportion to the degree of cutaneous irritation and did not show a baseline level of grooming. The predominance of stimulus-driven grooming and apparent absence of programmed grooming may be the result of relaxed selection pressure for grooming in the evolutionary history of moose. Because the winter tick appears to have been introduced to moose from deer relatively recently, moose may not have had the time to adapt to winter ticks. The coevolutionary relationship between moose and winter ticks may be of insufficient duration for the evolution and/or maintenance of programmed grooming. (c) 1998 The Association for the Study of Animal Behaviour.     

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.     

Effects of the feeding process of Ixodes scapularis (Acari: Ixodidae) on embryonic development of its parasitoid, Ixodiphagus hookeri (Hymenoptera: Encyrtidae)

The chalcid wasp Ixodiphagus hookeri (Howard) is a parasitoid of several ixodid ticks including the blacklegged tick, Ixodes scapularis Say. We evaluated effects of the feeding process of nymphal I. scapularis on the embryonic development of I. hookeri. Potentially wasp-parasitized nymphal I. scapularis were collected on Prudence Island, RI. Subsamples of the questing nymph cohort were allowed to feed on laboratory white mice. Both the body length and the scutal length of ticks were measured individually for questing nymphs and for feeding nymphs that were removed from hosts at time intervals of 12, 24, 36, 48, and 72 h after attachment. The diameters of wasp eggs they contained were also measured for each designated time interval. There was a positive relationship between the mean scutal index (ratio between body length and scutal length) of ticks and the mean diameter of wasp eggs during 72 h of tick feeding (P < 0.05). Moreover, it appeared that within 24 h of tick attachment, the scutal index of ticks remained unchanged. However, after that period, the scutal index increased significantly (P < 0.05). Diameters of wasp eggs increased continuously during tick feeding and at 72 h after attachment, enclosed eggs and completely formed larvae were found in several ticks. We conclude that factors related to the feeding process of nymphal I. scapularis are necessary to initiate the embryonic development of wasps.     

Human granulocytic ehrlichiosis in southern Germany: increased seroprevalence in high-risk groups

To date, human granulocytic ehrlichiosis (HGE), the causative agent of which is likely transmitted by ticks in the Ixodes ricinus-Ixodes persulcatus complex, has not been diagnosed with certainty in patients outside the United States. The presence of a closely related vector tick, I. ricinus, as well as the occurrence of similar Ehrlichia spp. of veterinary importance, suggests that this disease is likely to be present in Europe. The aim of the present study was to compare the prevalence of antibodies against the HGE agent in sera collected from patients in groups at high risk for exposure to I. ricinus with that of a control population. Risk groups consisted of 150 forestry workers and 105 patients with an established diagnosis of Lyme disease. The control group was 103 healthy blood donors without a history of tick bites. We used a patient isolate of the HGE agent from Minnesota (J. L. Goodman, C. Nelson, B. Vitale, J. E. Madigan, J. S. Dumler, T. J. Kurtti, and U. G. Munderloh, N. Engl. J. Med. 334:209-215, 1996) propagated in HL60 cells as the source of antigen for a specific immunofluorescence assay (IFA). Elevated IFA titers (> or = 1:80) were present in 21 of 150 (14%) serum samples from forestry workers and in 12 of 105 (11.4%) serum samples from Lyme disease patients, but in only 2 of 103 (1.9%) serum samples from blood donors (P < or = 0.01 for either of the at-risk groups versus blood donors). The results of this study suggest that the HGE agent or a closely related organism exists in southern Germany and that seroconversion to it is common among groups exposed to Ixodes ticks. Final proof that HGE occurs in Germany will require the isolation of the causative agent from patients. HGE should be considered in the differential diagnosis of febrile illnesses in individuals exposed to Ixodes ticks in Europe as well as in North America.     

Detection of human herpesvirus 8 DNA sequences in tissues and bodily fluids

Human herpesvirus 8 (HHV-8) has been proposed as a sexually transmitted etiologic agent of Kaposi's sarcoma (KS). In this study, by use of a sensitive polymerase chain reaction assay, HHV-8 DNA was detected in the skin lesions (92%), normal skin (23%), peripheral blood mononuclear cells (PBMC) (46%), plasma (7%), saliva (37%), and semen (12%) but not stool samples from KS patients. The average number of HHV-8 copies per microgram of positive target DNA was 64, 000, 9000, 40, 33,000, and 300 for skin, PBMC, plasma, saliva, and semen samples, respectively. Only 1 non-KS donor sample, of saliva, was positive for HHV-8. Sequencing showed 5% divergence among HHV-8 strains. The data suggest that saliva may be more important than semen or stool in the sexual transmission of HHV-8. The relatively high prevalence of HHV-8 in PBMC raises the question as to why there is no evidence for bloodborne virus transmission.