Lyme disease and preventive behaviors in residents of Nantucket Island, Massachusetts

BACKGROUND: To determine the age-specific prevalence of Lyme disease and whether preventive behaviors on Nantucket Island correlate with Lyme disease, we surveyed island residents. METHODS: A survey with questions on Lyme disease symptoms, history, and preventive behaviors was mailed to all residents. Respondents were stratified by likelihood of having had Lyme disease. A subsample was selected for examination, and then classified according to the Lyme disease national surveillance case definition. RESULTS: The overall lifetime prevalence of Lyme disease for Nantucket residents was 15% (CI, 10%-19.8%): 19% among females, and 11% among males. The prevalence was highest among age groups 0-16 and 30-49 years. Overall, 86% of the population practiced at least one behavior. The most frequently reported preventive behavior was checking oneself for ticks (80%), followed by wearing protective clothing (53%), avoiding tick areas (34%), and using tick repellent (11%). Younger individuals practiced fewer preventive behaviors than older individuals (p=0.001). Although males reported greater tick exposure than females, females uniformly practiced preventive behaviors more frequently (p=0.001). The practice of preventive behaviors was not associated with a history of Lyme disease, but finding more than 5 ticks per year on oneself was (p=0.001). CONCLUSION: Lyme disease is highly prevalent on Nantucket Island. Young people are particularly at risk and health education should emphasize preventive behaviors less frequently practiced: using tick repellent, avoiding tick areas, and wearing protective clothing.     

Increased diversity of zoonotic pathogens and Borrelia burgdorferi strains in established versus incipient Ixodes scapularis populations across the Midwestern United States

The center of origin theory predicts that genetic diversity will be greatest near a specie’s geographic origin because of the length of time for evolution. By corollary, diversity will decrease with distance from the origin; furthermore, invasion and colonization are frequently associated with founder effects that reduce genetic variation in incipient populations. The blacklegged tick, Ixodes scapularis, harbors a suite of zoonotic pathogens, and the geographic range of the tick is expanding in the upper Midwestern United States. Therefore, we posited that diversity of I. scapularis-borne pathogens across its Midwestern range should correlate with the rate of the range expansion of this tick as well as subsequent disease emergence. Analysis of 1565 adult I. scapularis ticks from 13 sites across five Midwestern states revealed that tick infection prevalence with multiple microbial agents (Borrelia burgdorferi, Borrelia miyamotoi, Babesia odocoilei, Babesia microti, and Anaplasma phagocytophilum), coinfections, and molecular genetic diversity of B. burgdorferi all were positively correlated with the duration of establishment of tick populations, and therefore generally support the center of origin – pathogen diversity hypothesis. The observed differences across the gradient of establishment, however, were not strong and were nuanced by the high frequency of coinfections in tick populations at both established and recently-invaded tick populations. These results suggest that the invasion of ticks and their associated pathogens likely involve multiple means of pathogen introduction, rather than the conventionally presented scenario whereby infected, invading ticks are solely responsible for introducing pathogens to naïve host populations.     

The diagnostic usefulness of dermoscopy for identifying six-legged larval ticks

Ticks are vectors of a variety of diseases such as Lyme disease and Japanese spotted fever. We examined an 87-year-old female with multiple tick bites by at least 236 larval Amblyomma testudinarium infestations. Numerous tick bites are generally caused by the six-legged larvae, which were verified in this case by dermoscopy. The present case indicates the diagnostic usefulness of dermoscopy for six-legged larval tick bites.     

回归热流行病学研究进展及防控措施

回归热是一种由回归热螺旋体引起的人感染性疾病。感染回归热一般会造成患者螺旋体血症和反复高热。为了全面了解该病的分类、分布及影响因素等相关内容,本文梳理了全球回归热流行病学研究进展,并提出了防制措施及建议。回归热的类型较为复杂,普遍认为有蜱传回归热、虱传回归热和禽回归热。蜱传回归热又分为软蜱传播和硬蜱传播两种,软蜱传播的回归热有明显的地域特点,而硬蜱传播的回归热在全球广泛分布;虱传回归热的传播媒介为体虱,发病一般与战乱、饥荒、难民、贫困和卫生条件差有关。防控措施的制定应根据当地情况而定。     

Virus meningo-encephalitis in Slovenia

The authors describe the main epidemiological features of the meningo-encephalitis observed in Slovenia since 1946. It is endemic there with occasional epidemic outbreaks; close study has been made of the epidemic which occurred in 1953. The disease is markedly seasonal, 95% of all cases in 1953 occurring from May to September. Another characteristic feature is the mention of tick bites in a very large number of case-histories; although the Slovenian tick fauna has not yet been systematically investigated, the generally incriminated vector is the tick Ixodes ricinus. In close association with this feature, the disease appears primarily among persons whose work lies in the woods where the ticks are found. This consequently affects the age distribution of patients, 56.2% of whom in 1953 were 11-30 years old. No spread of infection from person to person has been noted.     

Lyme disease: basis for treatment strategy, primary preventive care and secondary preventive care

Lyme disease is the most common tick borne disease and is caused by Borrelia burgdorferi sensu lato. Ticks of the genus Ixodes are the vectors that transmit the infection to host mammals in endemic foci. Ixodes is infected by Borrelia at larval stage when it feeds on infected mammals. Man is an occasional host. The infection risk is linked to interaction between human and the natural environment. Strategies for prevention are closely related to the enzootic cycle of the Ixodes tick. Environmental measures to reduced tick density or host mammals are expensive, need to be repeated annually and cannot be applied to large areas. The primary prevention could be reduced to personal preventive measures such as reducing the amount of exposed skin and frequent checking for ticks. The risk of Lyme disease transmission after a tick bite is relatively low, and remains under 4%. The transmission rate depends on the duration of feeding. A rapide tick removal with fine tweezers or preferably special forceps and disinfection of the bite site appear to be the best technique. The absence of scientific evidence, and the risk of adverse events does not lead to recommending antimicrobial prophylaxis. Follow-up and educating the patients on the disease, clinical manifestation, and later primary prevention should be undertaken.     

Diversity of tick species biting humans in an emerging area for Lyme disease.

BACKGROUND. Although most tick bites in humans in areas of the northeastern United States in which Lyme disease is highly endemic are due to Ixodes dammini, no study documents the frequency of I. dammini bites in low-prevalence or emerging areas for Lyme disease. Data on the proportion of tick bites in humans that are due to I. dammini in a region may have implications for public health policy and clinical management. METHODS. A statewide survey of the tick species that parasitized humans in Maine was conducted during 1989 and 1990. Tick submissions from throughout the state were elicited through media announcements. All ticks that had been removed from humans were identified, and data were collected that included bite seasonality and geography and demographics of tick bite victims. RESULTS. Of 709 ticks submitted, only 17% were I. dammini. Ixodes cookei, a vector for Powassan encephalitis, accounted for 34% of bites, and Dermacentor variabilis accounted for 45%. Other tick species were occasionally implicated. CONCLUSIONS. The likelihood that a tick bite was due to I. dammini was lower in Maine than in areas in the northeastern United States in which Lyme disease is highly endemic. Other tick vectors, associated with diseases other than Lyme disease, were more frequently implicated. Regional tick bite surveys may prove useful in assessing the risk of Lyme disease following a tick bite.     

Effectiveness of permethrin-treated clothing to prevent tick exposure in foresters in the central Appalachian region of the USA

Outdoor workers are at risk from mosquito and tick bites and the extent to which exposures are linked to vector-borne disease is not understood. This pilot study characterizes for ester exposure to mosquitoes and ticks, and assesses effectiveness of permethrin-treated clothing for prevention of tick bites. Foresters (N = 34) from Kentucky, North Carolina, Ohio, Tennessee, Virginia, and West Virginia were placed into treatment (permethrin-treated clothing) or control (untreated clothing) groups. Foresters completed questionnaires about work-related tick/mosquito exposure and 454 ticks were collected/identified from May to June 2013. A time-weighted analysis based on information submitted by foresters about time working outdoors showed that control participants received a lower rate of tick exposure (0.15 tick bites/hour; 13 bites/person) compared to treatment participants (0.27 bites/hour; 21 bites/person). However, more control participants (85?%) received at least one tick bite compared to treatment participants (52?%). Outdoor workers should be aware of available protective measures, such as permethrin-treated clothing, that may mitigate occupational risks.     

Fine-scale determinants of the spatiotemporal distribution of Ixodes scapularis in Quebec (Canada)

The tick vector of Lyme disease, Ixodes scapularis, is currently expanding its geographical distribution northward into southern Canada driving emergence of Lyme disease in the region. Despite large-scale studies that attributed different factors such as climate change and changes in land use to the geographical expansion of the tick, a comprehensive understanding of local patterns of tick abundance is still lacking in that region. Using a newly endemic periurban nature park located in Quebec (Canada) as a model, we explored intra-habitat patterns in tick distribution and their relationship with biotic and abiotic factors. We verified the hypotheses that (1) there is spatial heterogeneity in tick densities at the scale of the park and (2) these patterns can be explained by host availability, habitat characteristics and microclimatic conditions. During tick activity season in three consecutive years, tick, deer, rodent and bird abundance, as well as habitat characteristics and microclimatic conditions, were estimated at thirty-two sites. Patterns of tick distribution and abundance were investigated by spatial analysis. Generalised additive mixed models were constructed for each developmental stage of the tick and the relative importance of significant drivers on tick abundance were derived from final models. We found fine-scale spatial heterogeneity in densities of all tick stages across the park, with interannual variability in the location of hotspots. For all stages, the local density was related to the density of the previous stage in the previous season, in keeping with the tick's life cycle. Adult tick density was highest where drainage was moderate (neither waterlogged nor dry). Microclimatic conditions influenced the densities of immature ticks, through the effects of weather at the time of tick sampling (ambient temperature and relative humidity) and of the seasonal microclimate at the site level (degree-days and number of tick adverse moisture events). Seasonal phenology patterns were generally consistent with expected curves for the region, with exceptions in some years that may be attributable to founder events. This study highlights fine scale patterns of tick population dynamics thus providing fundamental knowledge in Lyme disease ecology and information applicable to the development of well-targeted prevention and control strategies for public natural areas affected by this growing problem in southern Canada.     

Tick prevention in a population living in a highly endemic area

AIMS: To describe environmental and personal tick-preventive measures and their predictors, taken by a population living in a highly tick-endemic area. METHODS: Owing to the recent confirmation of human tick-borne encephalitis cases, vaccination against tick-borne encephalitis was offered to the population living in the endemic area through the use of leaflets and media campaigns. At the time of the initial dose, information and enrollment to this cohort study was carried out. Participants' characteristics, frequency of tick-bites and preventive measures were included in questionnaires. Logistic analysis was used to determine behavioural differences in activities taken in order to prevent tick bites. CONCLUSION: In total, 70% of the permanent residents had themselves vaccinated before the next tick season. Of the studied participants 356/517 (69%) regularly took preventive measures in their environment and/or personally. Women in particular, and those previously treated for a tick-borne disease, took significantly more preventive measures. When analysing all variables together, spending less time in a tick-endemic area and being tick-bitten during the latest tick season significantly increased the probability of taking preventive measures. After being tick-bitten, men were more inclined to start taking preventive measures than women. Awareness of the risks caused by living in a high tick-endemic area influenced the participant's daily life through preventive activities. Public health action should be considered, thus encouraging out-of-door activities for the population without anxiety as to the risks of contracting tick-borne disease after being tick-bitten.     

Vector interactions and molecular adaptations of lyme disease and relapsing fever spirochetes associated with transmission by ticks

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.     

Lyme Disease,Virginia, USA, 2000–2011

Lyme disease, caused by the bacterium Borrelia burgdorferi and transmitted in the eastern United States by the black-legged tick (Ixodes scapularis), is increasing in incidence and expanding geographically. Recent environmental modeling based on extensive field collections of host-seeking I. scapularis ticks predicted a coastal distribution of ticks in mid-Atlantic states and an elevational limit of 510 m. However, human Lyme disease cases are increasing most dramatically at higher elevations in Virginia, a state where Lyme disease is rapidly emerging. Our goal was to explore the apparent incongruity, during 2000–2011, between human Lyme disease data and predicted and observed I. scapularis distribution. We found significantly higher densities of infected ticks at our highest elevation site than at lower elevation sites. We also found that I. scapularis ticks in Virginia are more closely related to northern than to southern tick populations. Clinicians and epidemiologists should be vigilant in light of the changing spatial distributions of risk.     

Lyme disease: prophylaxis after tick bite

Lyme disease is a bacterial infection caused by Borrelia burgdorferi, which is transmitted by infected ticks. The transmission depends on several factors, especially on the duration of the tick's presence in the host body (the nymph which is smaller than the adults and thus less visible, is in this case the most frequently involved) and on whether the tick is infected or not. The interpretation of results in the few available studies is made difficult by the lack of information obtained (due to difficulty to collect information and examination costs). The comparison is made even more difficult by the difference between Borrelia ticks species in various regions. Today, the best methods are preventive: protective clothing, tick repellents, checking and removal of ticks after a journey in an endemic zone, and in case of tick bite, regular examination of the bite site during the following weeks in order to initiate an early curative treatment if ECM is diagnosed. The currently available data seems to be insufficient to suggest systematic antimicrobial prophylaxis in case of tick bite.     

A practical protocol to prepare paraffin-embedded whole tick histology sections

Ticks are important ectoparasites that are capable of transmitting multiple classes of pathogens and are currently linked with many emerging tick-borne diseases worldwide. With increasing occurrences of tick-borne diseases in both humans and veterinary species, there is a continuous need to further our understanding of ticks and the pathogens they transmit. Whole tick histology provides a full scope of the tick internal anatomy, allowing researchers to examine multiple organs of interest in a single section. This is in contrast to other techniques that are more commonly utilized in tick-borne disease research, such as electron microscopy and light microscopy of individual organs. There is a lack of literature describing a practical technique to process whole tick histologic sections. Therefore, the current study aims to provide researchers with a workable protocol to prepare high quality paraffin-embedded whole tick histology sections. Amblyomma americanum adults were used as an example species for this study. After a series of pilot experiments using a combination of various fixatives, softening agents and processing techniques, we elected to compare two common fixatives, 10% neutral-buffered formalin (NBF) and Bouin's solution for whole ticks. Equal numbers of A. americanum unfed adults (n = 10/fixative) were processed identically and their whole tick histology coronal sections were individually scored. Higher scores were assigned to whole tick sections that contained more internal organs that are crucial for tick-borne disease research (e.g. salivary glands and midgut), high integrity of tissues and exoskeleton on the section, and good fixation and staining quality of the tissues. The mean total scores for Bouin's-fixed ticks were significantly higher compared to NBF-fixed ticks (p = 0.001). To further assess our preferred technique, we also demonstrated the feasibility of producing high quality whole tick sections for three other common tick species of medical importance (Rhipicephalus sanguineus, Ixodes scapularis, and Dermacentor variabilis) using Bouin's solution. While this technique may require further optimization for other tick species, we described a feasible protocol that uses commonly available tools, reagents and standard histologic equipment. This should allow any investigator to easily make adjustments to this protocol as needed based on their experimental goals.     

Relationships between the Rhipicephalus sanguineus complex ecology and mediterranean spotted fever epidemiology in France

The authors examine the epidemiologic features of Meditteranean spotted fever in France in light of the bioecological pecularities of each of the three known member of the Rhipicephalus sanguineus tick group (R. sanguineus, R. turanicus, R. pusillus). The results show that R. sanguineus is the main vector. Certain aspects of this tick species are of interest: affinity for man, close contact with humans for a long periods, peak of tick population (preimaginal stages) at the same time as the peak of the disease. The largest populations of R. sanguineus are noted in the endemic zone of human rickettsiosis. The fact that immature stages are more prevalent during the hot season and these forms' ability to bite humans is important and may suggest a role for them in the epidemiology of the disease. The sporadic isolation of this species outside the endemic zone may explain the occurrence of isolated cases of the disease in these areas. We cannot currently exclude vector roles for the two other species, which can parasitize humans, though none of our data supports this hypothesis.     

Temporal relation between Ixodes scapularis abundance and risk for Lyme disease associated with erythema migrans

Understanding the role that nymphal and female ticks, Ixodes scapularis, have in the epidemiology of Lyme disease is essential to the development of successful prevention programs. In this study, the authors sought to evaluate the seasonal and annual relations between tick densities and patients > or = 16 years of age diagnosed with erythema migrans (EM), the rash associated with early Lyme disease. Ticks were collected weekly by drag sampling throughout most of the year from 1991 to 1996 in Westchester County, New York. The number of EM cases was based on patients diagnosed at the Westchester County Medical Center using Centers for Disease Control and Prevention (CDC) criteria. No patients with EM were diagnosed from January through April, when only adult ticks were active. Correlation analysis between monthly tick densities and EM incidence was significant for nymphs (r = 0.87, p < 0.01), but not for adult ticks (r = -0.57, p > 0.05). There was a strong, although not significant, correlation between peak annual number of patients with EM and peak nymphal tick abundance (r = 0.76, p = 0.08). These data indicate that bites from adult I. scapularis only rarely result in Lyme disease, and that annual nymphal tick abundance determines exposure. This suggests that annual fluctuations in Lyme disease case numbers are largely due to natural changes in tick abundance and, therefore, that control of nymphal I. scapularis should be a major component of Lyme disease prevention efforts.     

Lyme borreliosis

Lyme borreliosis is a complex infectious process that primarily involves the skin, heart, joints, and nervous systems. The infectious agent is the spirochete B burgdorferi, which is transmitted by the Ixodes genus of ticks. The clinical presentations of Lyme disease are protean because of the overlap of stages and varied organ system involvement. Furthermore, as previously mentioned, approximately one-third of Lyme patients are unable to recall a tick bite. Lyme borreliosis should be suspected in anyone with a tick bite. The findings of an EM lesion and flu-like symptoms strongly favor the diagnosis of stage 1 disease. Stage 2 evolves weeks to months after a tick bite, with cardiac and neurological findings as well as musculoskeletal pain. Stage 3 primarily manifests itself as arthritis associated with continuing or additional neurologic complications. Serologic studies are currently the most practical laboratory aid in diagnosis, because almost all infected individuals have a positive antibody response to the spirochete. Treatment with antibiotics usually proves successful, although longer courses of therapy may be needed in later stages of the disease, and some patients may not respond.     

宁波市动物染蜱情况调查结果分析

目的:初步了解宁波市动物染蜱现状,为进一步建立蜱媒传染病综合监测系统。方法:采用现状调查方法,摸清宁波市家养和野外动物染蜱情况。结果:家养动物蜱感染率为29.94%,以狗染蜱最高;野外动物染蜱阳性率为6.67%;动物染蜱部位以肩背、耳廓和颈部等前半身最常见。结论:宁波市动物染蜱情况不容乐观,应引起公共卫生部门的重视。     

Risk factors for tick exposure and suboptimal adherence to preventive recommendations

BACKGROUND: Tickborne diseases are the most common vectorborne illnesses in the United States. Understanding risk factors for tick bites and adherence to preventive measures are important in preventing morbidity associated with tickborne disease. METHODS: A random-digit-dialing telephone survey was administered to 1820 residents of 11 counties in Tennessee. RESULTS: Of respondents, 16.4% reported a tick bite within the previous year. Only 29% consistently used insect repellant in high-risk situations, and only 54% always checked their bodies for ticks after leaving potentially infested areas. Nearly one fourth of dog owners removed ticks from their pets with bare hands. Dog ownership, rural residence, and exposure to a farm were associated with increased risk of tick bites. CONCLUSIONS: We identified several groups that were at increased risk of tick bites and might benefit from targeted prevention messages.