Measurement of apoptotic fragments in growing hair follicles following gamma-ray irradiation in mice

Feeding ticks are generally spatially distributed in clusters on vertebrate hosts. To test the effect of clustering on transmission of a tick-borne pathogen, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner-infected Ixodes ricinus L. nymphs and uninfected I. ricinus larvae were allowed to feed together in retaining chambers on uninfected AKR/N mice. Engorged infective nymphs dropped off at days 5, 6, and 7, and the 1st infected larvae that fed in the chambers together with the infected nymphs dropped off at day 5. In contrast, ear biopsies and xenodiagnostic larvae placed on the head remained negative during that period. These results suggest that a cofeeding transmission occurred between B. burgdorferi-infected ticks and noninfected ones in the absence of a disseminated infection. Further investigations are being undertaken to determine whether the mechanism responsible for this cofeeding transmission is similar to that described previously with virus-infected ticks.     

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.     

Amblyomma variegatum (Acari: Ixodidae): mechanism and control of arbovirus secretion in tick saliva

Saliva is considered to be the conduit by which pathogens are transmitted from blood-sucking arthropod vectors to their vertebrate hosts, but supporting evidence for this is fragmentary. To determine if Thogoto (THO) virus, a tick-borne member of the influenza virus family, is transmitted via tick saliva, and whether virus replication is a prerequisite for such transmission, two experimental conditions were compared: (1) "biological transmission" and (2) "mechanical transmission." In (1), THO virus was allowed to infect and replicate in a natural vector, Amblyomma variegatum: virus was detected in saliva collected from 3/22 (14%) ticks. In (2), virus was inoculated directly into the hemocoel with the drug used to induce salivation and saliva was collected immediately to preclude the possibility of virus replication: virus was detected in saliva collected from 31/170 (18%) ticks. The results demonstrate that THO virus is secreted in tick saliva and that virus can pass from the hemolymph to the salivary glands independently of viral replication within the tick. The comparatively low numbers of ticks that yielded virus-positive saliva samples together with the results from assays of serial saliva samples suggested that virus secretion may not be a continuous process during salivation. Ticks in which THO virus had established an infection showed an impaired secretory response compared with uninfected ticks and ticks used for mechanical transmission.     

Effects of low pH and nicotine on carotid body chemoreceptor activity in the rabbit

Ixodes scapularis ticks acquired spirochetes while cofeeding with Borrelia burgdorferi-infected nymphs (donors) on uninfected naive gerbils. Overall, 19% (67 of 345) of the recipient nymphs randomly exposed to gerbils with donor nymphs acquired spirochetes by fluorescent antibody (FA) tests, 18% (62 of 345) by the polymerase chain reaction. In a second experiment, donor nymphs were placed on the left ears, recipient nymphs were placed on the left and right ears, and xenodiagnostic larvae were placed on the gerbils' backs. Only recipient nymphs and larvae removed from the left ears were infected with B. burgdorferi. Infection rates were 47% (9 of 19), 87% (13 of 15) and 88% (14 of 16) in recipient nymphs placed on gerbils 0, 3, or 5 days after the donor nymphs, respectively, and 48% (12 of 25) in the larvae by FA analysis. Spirochetes appear to be acquired by cofeeding ticks from a localized infection near the feeding site rather than from a disseminated infection in the skin or blood.     

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.     

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.     

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.     

Fatal encephalitis caused by concomitant infection with tick-borne encephalitis virus and Borrelia burgdorferi

We describe a 38-year-old farmer from the southwestern archipelago of Finland where both tick-borne encephalitis (TBE) virus and Borrelia burgdorferi are endemic. He presented with fever and headache, developed severe meningoencephalitis in 3 days, and, after 1 month, died without regaining consciousness. High titers of IgG and IgM antibodies to TBE virus were present in both serum and CSF. Serology for Borrelia was negative. Autopsy revealed necrotizing encephalitis and myelitis with involvement of the dorsal root ganglion. With use of polymerase chain reaction tests, segments of two separate genes of B. burgdorferi were amplified from the patient's CSF. This case demonstrates that the possibility of dual infection should be considered for patients residing in geographic areas where Ixodes ticks may carry both the TBE virus and B. burgdorferi. We believe that the most severe damage in this case was caused by TBE virus rather than by B. burgdorferi. Nevertheless, the coinfection might have contributed to the fatal outcome that has not been previously observed in Finnish patients with TBE.     

Ultrastructural nucleolar alterations induced by an ametantrone--poly r(A-U) complex

Several studies have described changes in the expression of proteins, especially of OspA and OspC, of B. burgdorferi sensu stricto during tick feeding. In this study, the expression of OspA and OspC of B. afzelii in unfed and feeding I. ricinus nymphs and in the subsequent adults was followed by means of the immunofluorescence test. Spirochaetes expressing OspA and OspC were observed in 70% and 80%, respectively of the unfed nymphs. In feeding and in fully engorged ticks, spirochaetes expressed OspC, while OspA disappeared 24 hours after the beginning of the blood meal. Spirochaetes expressing OspC in salivary glands were observed in one engorged tick. After molting, in unfed adults spirochaetes again expressed OspA and OspC but did so less frequently (6% and 13%, respectively). The mouse strain (AKR/N or BALB/C) on which ticks had their infectious blood meal influenced OspC expression in the following tick stage. In the skin of AKR/N mice, at the tick feeding site, B. afzelii expressed OspC only, as was shown by immunostaining.     

Distribution and movement of infective-stage larvae of Dipetalonema viteae (Filarioidea) in the vector tick, Ornithodoros tartakowskyi (Argasidae)

To determine the behavior of Dipetalonema viteae in its tick vector, Ornithodoros tartakowskyi, the ticks were fed on jirds at successive intervals of 30 to 35 days after a single infective blood meal, and the number of larvae passing from the tick during each bite was determined by recovery of: 1) adult worms from the jirds' tissues; 2) larvae from skin snips taken at the feeding site immediately after the bite; and 3) larvae from serum and tissue after artificial feeding through a skin-membrane. All methods gave similar results. Ticks harboring few larvae released most of them (82%) during the first bite, and required only 2 bites to transmit all. Ticks with moderate or heavy infections required 3 or 4 bites to transfer all larvae. Factors which may explain this are: 1) relatively short duration of the bite of heavily infected ticks due to irritation and damage to the muscles of mouthparts and pharynx by the larvae; 2) resistance of the anterior alimentary tract to penetration by the larvae; and 3) retarding effects of crowding on development and migration of larvae. Aging of infection in the tick apparently did not influence the rate of transfer of larvae. Infection adversely affected the feeding and retarded the molting of young nymphs, but with the loss of larvae in successive bites the ability to suck blood was regained.     

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.     

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.     

An epidemiological study of the adolescent nonfatal unintentional injuries in Taiwan

Despite the observation of TBE cases after consumption of raw milk from cows or goats, so far the proof of the alimentary route of human infection has not been possible. In the regions of southwestern Germany, where TBE is known to be endemic, milk-borne TBE infections have not yet been observed. To assess the significance of raw milk consumption for viral transmission, a cross-sectional study (114 forestry workers, 177 individuals exposed during their leisure-time activities, 170 non-exposed individuals) and a case-control study (50 TBE patients, 150 controls) were carried out. The results of the study show that both the time spent in the endemic region and also the professional exposure to ticks do influence TBE seroprevalence, whereas the consumption of raw milk (milk directly from the farmer) is no major risk factor for TBE infection or disease. Among leisure-time activities, only hunting has an effect comparable to the one of the professional exposure to ticks. Besides epidemiological data obtained in humans, serological investigations of cows were performed. Here it is shown that milk-producing animals are involved in the natural transmission of TBE virus. Since former studies had shown that TBE-viremic animals excrete the virus with the milk--although over a short period and in low concentrations--the occurrence of milk-borne TBE infections cannot be excluded in the endemic regions of south-western Germany. However, from the epidemiological point of view, their significance may be neglected. Vaccination has proven the most reliable means of TBE prevention, irrespective of the route of infection.     

Frequency of replication errors in colorectal cancer and their association with family history

In the Czech Republic, the incidence of Lyme borreliosis (LB) has shown a rising trend since 1988. The goal of this study has been to find out to what extent a selected part of population is aware of ticks and of the relationship between ticks and LB. The study was based on a questionnaire survey. A total of 110 respondents were selected, including 19 secondary school students, 32 blood donors, 44 park-goers, 15 countryside people. As many as 99% of the respondents were aware of the presence of ticks, 91% knew that ticks are sucking blood of humans and animals, 1.8% thought they eat leaves. 74.5% of the respondents expect ticks to reach them from the vegetation while 22% believe that ticks fall from the trees. Furthermore, 87% and 75% of the respondents indicated to have had ticks attached to the skin or to have removed a tick from other persons' skin, respectively. Only 6.7% of them had never come into contact with ticks. 17% of the respondents use disinfectant when removing a tick, while 67% use oil for tick removal. Almost 30% remove ticks with naked hands. Over 14% destroy the ticks by squashing them with naked fingers. Finally, about 11% of the population studied had never heard about LB and 41% were not aware of the risk of tick-borne encephalitis.     

Lethal effect of Rickettsia rickettsii on its tick vector (Dermacentor andersoni)

Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, was lethal for the majority of experimentally and transovarially infected Rocky Mountain wood ticks (Dermacentor andersoni). Overall, 94.1% of nymphs infected as larvae by feeding on rickettsemic guinea pigs died during the molt into adults and 88. 3% of adult female ticks infected as nymphs died prior to feeding. In contrast, only 2.8% of uninfected larvae failed to develop into adults over two generations. Infected female ticks incubated at 4 degreesC had a lower mortality (80.9%) than did those held at 21 degreesC (96.8%). Rickettsiae were vertically transmitted to 39.0% of offspring, and significantly fewer larvae developed from infected ticks. The lethal effect of R. rickettsii may explain the low prevalence of infected ticks in nature and affect its enzootic maintenance.     

Development of early-summer meningoencephalitis (FSME) in the Thurgau region 1990-1995--a new endemic area?

Tick-borne encephalitis (TBE) is a viral infection transmitted by bites of infected ticks. The clinical course is mostly mild, but death occurs in 1-2% of TBE infections and nearly half of patients with meningitis/meningoencephalitis show residual disease, above all chronic headache. TBE-infected ticks occur only in endemic areas. A knowledge of the endemic areas is very important for immunoprophylaxis of TBE. In recent years between 26 and 97 cases of TBE have occurred in Switzerland. The largest endemic areas are in Canton Schaffhausen, the northern part of Canton Zurich and the north-west of Canton Thurgau. Another endemic area is known in the region of Thun in Canton Berne. Another possible endemic area is known in the Zurich Oberland around Elgg, only 7 km from Aadorf in Thurgau. Up to now, Diessenhofen in the north-west of Thurgau was the only known possible endemic area. In 1994 and 1995 we observed an accumulation of TBE infections in western Thurgau. The question was whether there are other endemic areas in Thurgau. In this retrospective analysis we studied the TBE cases in Thurgau between 1990 and 1995 with data derived from the cantonal health authorities reports. Clinical data were taken from case histories of the two cantonal hospitals in Frauenfeld and Münsterlingen, completed by data from family doctors and patients. Between 1990 and 1995 30 TBE infections (1990; 1, 1991: 4, 1992: 3, 1993: 1, 1994: 4 certain, 3 uncertain, 1995: 14) were observed. TBE infections appeared between May and October (maximum in May). 14 patients remembered a bite by a tick several weeks before onset of the illness. 7 bites occurred in the area of Frauenfeld/Aadorf. Only one bite occurred in Diessenhofen. 2 patients were infected in well-known endemic areas in Canton Zurich, a vicinal region in the west of Thurgau. In 1995 the incidence of TBE in Thurgau was 5.4/100000 population. In 9 of the 14 patients recalling a bite by a tick (64.4%), the bites occurred near their domicile. No bite was seen east of a line between Steckborn and Weinfelden. The incidence of TBE in Thurgau in 1995 was clearly higher than the average in Switzerland in recent years (0.46/100000), and higher than in the well-known endemic areas in the vicinity (Schaffhausen 3.95, Zurich 1.31). Based on our data, the region Frauenfeld/Aadorf must be declared a new endemic area for TBE. Probably the well-known endemic area in the Zurich Oberland in the vicinity of Elgg has spread eastward. Persons who are often in the forests of this region should be advised to be vaccinated.     

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.     

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.     

Competence of urban rats as reservoir hosts for Lyme disease spirochetes

To determine whether urban rats serve efficiently as reservoir hosts for the agent of Lyme disease, we recorded the frequency of infection in nymphal Ixodes ricinus (L.) ticks that had fed as larvae on experimentally infected Norway rats, Rattus norvegicus (Berkenhout), or on black rats, R. rattus (L.), and evaluated the nidicolous venue of transmission. Subadult vector ticks attached readily to Norway rats as well as black rats and virtually all became infected in the course of feeding. Larval ticks detached when these nocturnally active hosts were at rest. Rats appeared to be competent reservoir hosts of Lyme disease spirochetes in a transmission cycle in urban sites.     

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.