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Background West Nile virus (WNV) is the leading cause of mosquito-borne illness in the continental USA. WNV occurrence has high spatiotemporal variation, and current approaches to targeted control of the virus are limited, making forecasting a public health priority. However, little research has been done to compare strengths and weaknesses of WNV disease forecasting approaches on the national scale. We used forecasts submitted to the 2020 WNV Forecasting Challenge, an open challenge organized by the Centers for Disease Control and Prevention, to assess the status of WNV neuroinvasive disease (WNND) prediction and identify avenues for improvement. Methods We performed a multi-model comparative assessment of probabilistic forecasts submitted by 15 teams for annual WNND cases in US counties for 2020 and assessed forecast accuracy, calibration, and discriminatory power. In the evaluation, we included forecasts produced by comparison models of varying complexity as benchmarks of forecast performance. We also used regression analysis to identify modeling approaches and contextual factors that were associated with forecast skill. Results Simple models based on historical WNND cases generally scored better than more complex models and combined higher discriminatory power with better calibration of uncertainty. Forecast skill improved across updated forecast submissions submitted during the 2020 season. Among models using additional data, inclusion of climate or human demographic data was associated with higher skill, while inclusion of mosquito or land use data was associated with lower skill. We also identified population size, extreme minimum winter temperature, and interannual variation in WNND cases as county-level characteristics associated with variation in forecast skill. Conclusions Historical WNND cases were strong predictors of future cases with minimal increase in skill achieved by models that included other factors. Although opportunities might exist to specifically improve predictions for areas with large populations and low or high winter temperatures, areas with high case-count variability are intrinsically more difficult to predict. Also, the prediction of outbreaks, which are outliers relative to typical case numbers, remains difficult. Further improvements to prediction could be obtained with improved calibration of forecast uncertainty and access to real-time data streams (e.g. current weather and preliminary human cases). Graphical Abstract

The disaccharide galactose-α-1,3-galactose (alpha-gal) is expressed in mammals other than humans, apes, and old-world monkeys. In humans, elevated immunoglobulin-E (IgE) antibodies specific for alpha-gal can result in allergic hypersensitivity known as alpha-gal syndrome (AGS). Case reports and series suggest that tick bites can induce alpha-gal specific IgE antibodies.Evaluate tick exposure as a risk factor for AGS and elevated alpha-gal specific IgE (sIgE).We conducted a case-control study comparing AGS patients from a North Carolina allergy clinic with controls who were patients at a nearby internal medicine clinic. Cases and controls were administered a questionnaire to obtain information about demographics, home environment, outdoor activities, and recollection of tick bite. Serum samples taken at the time of enrollment were tested for total IgE, alpha-gal sIgE, and antibodies to other tickborne pathogens.AGS patients were more likely to recall finding a tick on themselves (OR=11.20, 95% CI 4.97-25.15), live near wooded forest (OR=2.27, 95% CI 0.92-5.55), and spend 17 or more hours per week outdoors in wooded areas (OR=5.58, 95% CI 2.56-12.19). AGS patients were also more likely to report 4 or more tick bites (OR=33.05, 95% CI 9.92-155.12) and reactions at the site of tick bites (OR=7.93, 95% CI 3.74-16.80). Elevated alpha-gal sIgE was also observed in 33% of controls and was also associated with tick exposure in the controls (OR=4.25, 95% CI 2.21-8.18).The results define tick bite as a risk factor for AGS and elevated alpha-gal sIgE.

Alpha-gal syndrome (AGS) is an IgE-mediated allergy to galactose-alpha-1,3-galactose. Clinical presentation ranges from hives to anaphylaxis; episodes typically occur 2-6 h after exposure to alpha-gal-containing products. In the United States, lone star tick bites are associated with the development of AGS. To characterize features of AGS, we evaluated a cohort of patients presenting for care at the University of North Carolina, focusing on symptoms, severity, and identifying features unique to specific alpha-gal-containing product exposures.We performed a chart review and descriptive analysis of 100 randomly selected patients with AGS during 2010-2019.Median age at onset was 53 years, 56% were female, 95% reported White race, 86% reported a history of tick bite, and 75% met the criteria for anaphylaxis based on the involvement of ≥2 organ systems. Those reporting dairy reactions were significantly less likely to report isolated mucocutaneous symptoms (3% vs. 24%; ratio [95% CI]: 0.1 [0.1, 0.3]) than those who tolerated dairy, and were more likely to report gastrointestinal symptoms (79% vs. 59%; ratio [95% CI]: 1.3 [0.7, 2.6]), although this difference was not statistically significant. Dairy-tolerant patients demonstrated higher alpha-gal sIgE titers (as a percentage of total IgE) than dairy-reactive patients (GM 4.1 [95% CI: 2.7, 6.1] vs. GM 2.5 [95% CI: 1.3, 4.8], respectively; ratio -1.6 [95% CI: -1.0, 3.9]).While tick exposure is common in the southern United States, nearly all AGS patients reported a tick bite. Gastrointestinal symptoms were prominent among those reporting reactions to dairy. Anaphylaxis was common, underscoring the severity and need to raise awareness of AGS among patients and providers.

An amendment to this paper has been published and can be accessed via the original article.

BackgroundTriatomine bugs, the vectors of Chagas disease, associate with vertebrate hosts in highly diverse ecotopes. When these blood-sucking bugs adapt to new microhabitats, their phenotypes may change. Although understanding phenotypic variation is key to the study of adaptive evolution and central to phenotype-based taxonomy, the drivers of phenotypic change and diversity in triatomines remain poorly understood.Methods/FindingsWe combined a detailed phenotypic appraisal (including morphology and morphometrics) with mitochondrialcytband nuclear ITS2 DNA-sequence analyses to studyRhodnius ecuadoriensispopulations from across the species’ range. We found three major, naked-eye phenotypic variants. Southern-Andean bugs (SW Ecuador/NW Peru) from house and vertebrate-nest microhabitats are typical, light-colored, small bugs with short heads/wings. Northern-Andean bugs (W Ecuador wet-forest palms) are dark, large bugs with long heads/wings. Finally, northern-lowland bugs (coastal Ecuador dry-forest palms) are light-colored and medium-sized. Wing and (size-free) head shapes are similar across Ecuadorian populations, regardless of habitat or naked-eye phenotype, but distinct in Peruvian bugs. Bayesian phylogenetic and multispecies-coalescent DNA-sequence analyses strongly suggest that Ecuadorian and Peruvian populations are two independently-evolving lineages, with little within-lineage structuring/differentiation.ConclusionsWe report sharp naked-eye phenotypic divergence of genetically similar EcuadorianR. ecuadoriensis(house/nest southern-Andeanvs. palm-dwelling northern bugs; and palm-dwelling Andeanvs. lowland); and sharp naked-eye phenotypic similarity of typical, yet genetically distinct, southern-Andean bugs from house and nest (but not palm) microhabitats (SW Ecuadorvs. NW Peru). This remarkable phenotypic diversity within a single nominal species likely stems from microhabitat adaptations possibly involving predator-driven selective pressure (yielding substrate-matching camouflage coloration) and a shift from palm-crown to vertebrate-nest microhabitats (yielding smaller bodies and shorter heads and wings). These findings shed new light on the origins of phenotypic diversity in triatomines, warn against excess reliance on phenotype-based triatomine-bug taxonomy, and confirm the Triatominae as an informative model-system for the study of phenotypic change under ecological pressure.Author summaryTriatomine bugs feed on the blood of vertebrates including humans and transmit the parasite that causes Chagas disease. The bugs, of which 150+ species are known, are highly diverse in size, shape, and color. Some species look so similar that they are commonly confused, whereas a few same-species populations look so different that they were thought to be separate species. Despite the crucial role of naked-eye phenotypes in triatomine-bug identification and classification (which are essential for vector control-surveillance), the origins of this variation remain unclear. Here, we describe a striking case of phenotypic divergence, with genetically similar bugs looking very different from one another, and phenotypic convergence, with bugs from two genetically distinct populations (likely on their way to speciation) looking very similar – and all within a single nominal species,Rhodnius ecuadoriensis. Phenotypically divergent populations occupy different ecological regions (wetvs. dry) and microhabitats (palm-crownsvs. vertebrate nests), whereas convergent populations occupy man-made and nest (but not palm) microhabitats. These findings suggest that triatomines can ‘respond’ to ecological novelty by changing their external, naked-eye phenotypes as they adapt to new microhabitats. We therefore warn that phenotypic traits such as overall size or color may confound triatomine-bug species identification and classification.

Plague, a fleaborne rodent-associated zoonosis, is a neglected disease with most recent cases reported from east and central Africa and Madagascar. Because of its low incidence and sporadic occurrence, most of our knowledge of plague ecology, prevention, and control derives from investigations conducted in response to human cases. Long-term studies (which are uncommon) are required to generate data to support plague surveillance, prevention, and control recommendations. Here we describe a 15-year, multidisciplinary commitment to plague in the West Nile region of Uganda that led to significant advances in our understanding of where and when persons are at risk for plague infection and how to reduce morbidity and mortality. These findings provide data-driven support for several existing recommendations on plague surveillance and prevention and may be generalizable to other plague foci.

Reported cases of vector-borne diseases in the United States have more than tripled since 2004, characterized by steadily increasing incidence of tick-borne diseases and sporadic outbreaks of domestic and invasive mosquito-borne diseases. An effective public health response to these trends relies on public health surveillance and laboratory systems, proven prevention and mitigation measures, scalable capacity to implement these measures, sensitive and specific diagnostics, and effective therapeutics. However, significant obstacles hinder successful implementation of these public health strategies. The recent emergence of Haemaphysalis longicornis, the first invasive tick to emerge in the United States in approximately 80 years, serves as the most recent example of the need for a coordinated public health response. Addressing the dual needs for innovation and discovery and for building state and local capacities may overcome current challenges in vector-borne disease prevention and control, but will require coordination across a national network of collaborators operating under a national strategy. Such an effort should reduce the impact of emerging vectors and could reverse the increasing trend of vector-borne disease incidence and associated morbidity and mortality.

Introduction Vectorborne diseases are major causes of death and illness worldwide. In the United States, the most common vectorborne pathogens are transmitted by ticks or mosquitoes, including those causing Lyme disease; Rocky Mountain spotted fever; and West Nile, dengue, and Zika virus diseases. This report examines trends in occurrence of nationally reportable vectorborne diseases during 2004-2016. Methods Data reported to the National Notifiable Diseases Surveillance System for 16 notifiable vectorborne diseases during 2004-2016 were analyzed; findings were tabulated by disease, vector type, location, and year. Results A total 642,602 cases were reported. The number of annual reports of tickborne bacterial and protozoan diseases more than doubled during this period, from >22,000 in 2004 to >48,000 in 2016. Lyme disease accounted for 82% of all tickborne disease reports during 2004-2016. The occurrence of mosquitoborne diseases was marked by virus epidemics. Transmission in Puerto Rico, the U.S. Virgin Islands, and American Samoa accounted for most reports of dengue, chikungunya, and Zika virus diseases; West Nile virus was endemic, and periodically epidemic, in the continental United States. Conclusions and implications for public health practice Vectorborne diseases are a large and growing public health problem in the United States, characterized by geographic specificity and frequent pathogen emergence and introduction. Differences in distribution and transmission dynamics of tickborne and mosquitoborne diseases are often rooted in biologic differences of the vectors. To effectively reduce transmission and respond to outbreaks will require major national improvement of surveillance, diagnostics, reporting, and vector control, as well as new tools, including vaccines.

Vector-borne diseases (VBDs) cause significant morbidity and mortality each year in the United States. Over the last 14 yr, over 700,000 cases of diseases carried by ticks, mosquitoes, and fleas have been reported from U.S. states and territories to the Centers for Disease Control and Prevention. The number of reported cases has been increasing annually with two major trends: a steady increase in tick-borne diseases and increasing intermittent outbreaks of mosquito-borne arboviruses. The factors that are driving VBD introduction and emergence vary among diseases but are not likely to disappear, indicating that current trends will continue and probably worsen in the absence of effective prevention and control tools and implementation capacity. There are a number of challenges to preventing VBDs, including the lack of vaccines and effective vector control tools, insecticide resistance, and eroding technical capacities in public health entomology at federal, state, and local levels. For these reasons, a national strategy is needed to address VBD threats and to reverse the alarming trend in morbidity and mortality associated with these diseases.

Background Vector-borne diseases are an important cause of morbidity and mortality in the USA. Effective, convenient prevention methods are needed. Long-lasting permethrin-impregnated (LLPI) clothing can prevent tick bites, however, additional information is needed on the real-world effectiveness and safety of this preventative measure. Methods In this pilot study, we recruited state and county park employees from North Carolina to wear LLPI uniforms for three months during the summer of 2016. We collected spot urine samples for biomonitoring of permethrin metabolites at one week, one month and three months after first use of the LLPI uniform. Following three months of wear, we collected pants and socks and analyzed them for permethrin content and mortality to ticks and mosquitoes. Results Thirteen park employees were included in the analysis. Bioactive amounts of permethrin remained in all clothing swatches tested, although there was great variability. Tick mortality was high, with 78% of pant and 88% of sock swatches having mean knockdown percentages ≥ 85%. In contrast, mosquito mortality was low. Over the study period, the absorbed dosage of permethrin averaged < 4 μg/kg/d of body weight based on measurements of three metabolites. Conclusions LLPI clothing retained permethrin and bioactivity against ticks after three months of use in real-world conditions. The estimated absorbed dosage of permethrin was well below the U.S. EPA level of concern, suggesting that LLPI clothing can be used safely by outdoor workers for tick bite prevention. Electronic supplementary material The online version of this article (10.1186/s13071-019-3314-1) contains supplementary material, which is available to authorized users.

Background Alpha-gal syndrome (AGS) is an emerging immunoglobulin E (IgE)–mediated allergy to galactose-alpha-1,3-galactose (alpha-gal). The geographic distribution and burden of AGS in the United States are unknown. Objective To characterize alpha-gal IgE testing patterns and describe the trends and distribution from 2010 to 2018 in the United States. Methods This retrospective analysis included all persons tested for alpha-gal IgE antibodies by Viracor-IBT Laboratories (Lee’s Summit, Missouri), the primary site of testing in the United States. Data included age and sex of person tested, specimen state of origin, collection date, and result value; persons with at least 1 positive test result (≥0.1 kU/L) were compared with negatives. Proportions tested and with positive test results were calculated using the US Census population estimates. Results Overall, 122,068 specimens from 105,674 persons were tested for alpha-gal IgE during July 1, 2010, to December 31, 2018. Nearly one-third (34,256, 32.4%) had at least 1 positive result. The number of persons receiving positive test results increased 6-fold from 1110 in 2011 to 7798 in 2018. Of those receiving positive test results, mean [SD] age was 46.9 (19.8) years; men were more likely to test positive than women (43.3% vs 26.0%). Arkansas, Virginia, Kentucky, Oklahoma, and Missouri had the highest number of persons who were tested and had a positive result per 100,000 population. Conclusion More than 34,000 persons, most presumably symptomatic, have received positive test results for IgE antibodies to alpha-gal, suggesting AGS is an increasingly recognized public health problem. The geographic distribution of persons who tested positive is consistent with exposure to Amblyomma americanum ticks.

CDC has updated its interim guidance for U.S. health care providers caring for pregnant women with possible Zika virus exposure, to include the emerging data indicating that Zika virus RNA can be detected for prolonged periods in some pregnant women. To increase the proportion of pregnant women with Zika virus infection who receive a definitive diagnosis, CDC recommends expanding real-time reverse transcription-polymerase chain reaction (rRT-PCR) testing. Possible exposures to Zika virus include travel to or residence in an area with active Zika virus transmission, or sex* with a partner who has traveled to or resides in an area with active Zika virus transmission without using condoms or other barrier methods to prevent infection.(†) Testing recommendations for pregnant women with possible Zika virus exposure who report clinical illness consistent with Zika virus disease(§) (symptomatic pregnant women) are the same, regardless of their level of exposure (i.e., women with ongoing risk for possible exposure, including residence in or frequent travel to an area with active Zika virus transmission, as well as women living in areas without Zika virus transmission who travel to an area with active Zika virus transmission, or have unprotected sex with a partner who traveled to or resides in an area with active Zika virus transmission). Symptomatic pregnant women who are evaluated

Introduction Chagas disease, a neglected tropical disease that affects millions of Latin Americans, has been effectively controlled in Guatemala after multiple rounds of indoor residual insecticide spraying (IRS). However, a few foci remain with persistent Triatoma dimidiata infestation. One such area is the municipality of Comapa, Department of Jutiapa, in the southeastern region of Guatemala, where control interventions appear less effective. We carried out three cross sectional entomological and serological surveys in Comapa to evaluate a decade of vector control activities. Baseline serological (1999) and entomological (2001–2) surveys were followed by three rounds of insecticide applications (2003–2005) and intermittent focal spraying of infested houses, until approximately 2012. Household inspections to determine entomological indices and construction materials were conducted in 2001, 2007 and 2011. Seroprevalence surveys were conducted in school-age children in 1999, 2007 and 2015, and in women of child bearing age (15–44 years) only in 2015. After multiple rounds of indoor residual sprayings (IRS), the infestation index decreased significantly from 39% (2001–2) to 27% (2011). Household construction materials alone predicted 10%. Conclusion After a decade of vector control activities in Comapa, there is evidence of significantly reduced transmission. However, the continued risk for vector-borne and congenital transmission pose a threat to the 2022 Chagas disease elimination goal. Systematic integrated vector control and improved Chagas disease screening and treatment programs for congenital and vector-borne disease are needed to reach the elimination goal in regions with persistent vector infestation., Author summary Despite the success of the Chagas disease vector control program in Guatemala, there are still regions with persistent T. dimidiata infestation. The municipality of Comapa, Jutiapa, is one of such areas. After several rounds of residual insecticide sprayings, infestation of some communities remained >15%. We evaluated the impact of a decade of vector control activities through three cross-sectional seroprevalence and entomological surveys (1999 through 2015). We found that transmission to children has decreased ten-fold. However, new infections persist in women and children. To reach the Chagas disease elimination goal, integrated vector control strategies should include community-wide insecticide applications, education to change exposure to risk factors and increased access to diagnostics and treatment for women and children.

This is a photograph of Raymond Edward Ryckman, PhD, (Figure) a medical entomologist. His studies of triatomine bugs, Trypanosoma cruzi, and Chagas disease formed a rich library of information about vectors and hosts of T. cruzi, including the behavioral ecology of the vectors and the role of pack rats for sustaining T. cruzi in natural habitats. Figure Raymond Edward Ryckman Ryckman was born June 19, 1917, on a farm in southern Wisconsin, USA; fascinated at an early age by insects, he built an observation beehive and was eager to show the colony to visitors. He was drafted during World War II and served 4 years at the Presidio Army Base hospital in San Francisco, California, USA. After receiving a bachelor of science degree in zoology at the University of California, Berkeley, in 1950, Ryckman was recruited to teach at Loma Linda University in Loma Linda, California. Soon after arriving at Loma Linda, he was approached by the Army Surgeon General’s office and asked to research the dynamics of plague transmission, with regard to the Army’s interest in troop health and safety in Southeast Asia. Ryckman used the natural plague system in southern California to study squirrel and flea population dynamics and potential insecticides. The innovative methods he used included electric-fence enclosures, ferrets trained to place devices within squirrel burrows, and crucible tongs used to gently handle unmanageable squirrels (1–3). His research played a major role in the understanding of the dynamics of plague transmission and control. After the Army Surgeon General’s plague grant ended, Ryckman returned to the University of California, Berkeley, where he completed his master’s thesis on Cimicidae (bed bugs) and forged ahead with PhD studies under Dr. Robert Usinger. His research explored the systematics, hybridization, and reproduction of the triatomine Triatoma protracta—vector of T. cruzi, the agent of Chagas disease (4). He completed his PhD research while fulfilling teaching requirements at Loma Linda University. He educated hundreds of medical and graduate students at the School of Medicine at Loma Linda University until his retirement in 1987. In addition to being a triatomine researcher, he was a naturalist eager to investigate organisms that captured his interest, generally incidental to studies of triatomines. During his career he published articles about cactiphilic flies (5) and lizard mites (6). After his retirement, he continued to write, co-authoring a book about Edmund C. Jaeger, a naturalist who studied the desert ecology of the southwestern United States (7). Ryckman traveled throughout Central and South America, generally returning with field-collected triatomines to start new colonies. His family frequently traveled with him, and he published several articles with his sons (8–10). Ryckman credits his wife with careful and patient review of his manuscripts before submission. He authored or co-authored ≈115 publications, most of which were 1- or 2-author publications. Later in Ryckman’s career, his focus turned to the publication of bibliographies. Before Internet and electronic searching were available, bibliographies were valuable sources of information for researchers, and their collation was a time-intensive, although perhaps underappreciated, achievement. In Ryckman’s words, “A bibliographic monograph is the summation of our historical, cultural, and scientific heritage in a given field of endeavor” (11). His career capstone was the publication of bibliographies “concerned with the world literature to the Triatominae and Triatominae-borne pathogens and clinical Chagas’ disease” (12). Careful curation was achieved with the help of assistants, requests via reprint request cards, use of a shopping cart to transport journals between the university library and copy shop, and use of a punch card system to organize articles. Compiled over 16 years and containing >23,000 publications, these bibliographies are a unique contribution to the field of Chagas disease research (11–13). The hard copy (print) collection resides at the Centers for Disease Control and Prevention in Atlanta, Georgia, USA. In addition to a legacy of bibliographies and publications, Ryckman’s collection of >25,000 insects is available for study at the Bohart Museum of Entomology, University of California, Davis. This collection includes the triatomine specimens that resulted from Ryckman’s many colonies of triatomines and other insects. In honor of his contributions to the study of Chagas disease vectors, Ryckman was honored with an eponym in 1972: Triatoma ryckmani, a rare species from Central America (14). As an authority on triatomine ecology and Chagas disease, a patient teacher and mentor, an international scholar, and a family man, Raymond E. Ryckman is an admirably well-rounded scientist.

In the United States, ticks transmit the greatest diversity of arthropod-borne pathogens and are responsible for the most cases of all vector-borne diseases. In recent decades, the number of reported cases of notifiable tick-borne diseases has steadily increased, geographic distributions of many ticks and tick-borne diseases have expanded, and new tick-borne disease agents have been recognized. In this review, we (1) describe the known disease agents associated with the most commonly human-biting ixodid ticks, (2) review the natural histories of these ticks and their associated pathogens, (3) highlight spatial and temporal changes in vector tick distributions and tick-borne disease occurrence in recent decades, and (4) identify knowledge gaps and barriers to more effective prevention of tick-borne diseases. We describe 12 major tick-borne diseases caused by 15 distinct disease agents that are transmitted by the 8 most commonly human-biting ixodid ticks in the United States. Notably, 40% of these pathogens were described within the last two decades. Our assessment highlights the importance of animal studies to elucidate how tick-borne pathogens are maintained in nature, as well as advances in molecular detection of pathogens which has led to the discovery of several new tick-borne disease agents.

The blacklegged tick, Ixodes scapularis Say, is the primary vector to humans in the eastern United States of the Lyme disease spirochete Borrelia burgdorferi, as well as causative agents of anaplasmosis and babesiosis. Its close relative in the far western United States, the western blacklegged tick Ixodes pacificus Cooley and Kohls, is the primary vector to humans in that region of the Lyme disease and anaplasmosis agents. Since 1991, when standardized surveillance and reporting began, Lyme disease case counts have increased steadily in number and in geographical distribution in the eastern United States. Similar trends have been observed for anaplasmosis and babesiosis. To better understand the changing landscape of risk of human exposure to disease agents transmitted by I. scapularis and I. pacificus, and to document changes in their recorded distribution over the past two decades, we updated the distribution of these species from a map published in 1998. The presence of I. scapularis has now been documented from 1,420 (45.7%) of the 3,110 continental United States counties, as compared with 111 (3.6%) counties for I. pacificus. Combined, these vectors of B. burgdorferi and other disease agents now have been identified in a total of 1,531 (49.2%) counties spread across 43 states. This marks a 44.7% increase in the number of counties that have recorded the presence of these ticks since the previous map was presented in 1998, when 1,058 counties in 41 states reported the ticks to be present. Notably, the number of counties in which I. scapularis is considered established (six or more individuals or one or more life stages identified in a single year) has more than doubled since the previous national distribution map was published nearly two decades ago. The majority of county status changes occurred in the North-Central and Northeastern states, whereas the distribution in the South remained fairly stable. Two previously distinct foci for I. scapularis in the Northeast and North-Central states appear to be merging in the Ohio River Valley to form a single contiguous focus. Here we document a shifting landscape of risk for human exposure to medically important ticks and point to areas of re-emergence where enhanced vector surveillance and control may be warranted.

Lyme disease has increased both in incidence and geographic extent in the United States and Canada over the past two decades. One of the underlying causes is changes during the same time period in the distribution and abundance of the primary vectors: Ixodes scapularis Say and Ixodes pacificus Cooley and Kohls in eastern and western North America, respectively. Aside from short periods of time when they are feeding on hosts, these ticks exist in the environment where temperature and relative humidity directly affect their development, survival, and host-seeking behavior. Other important factors that strongly influence tick abundance as well as the proportion of ticks infected with the Lyme disease spirochete, Borrelia burgdorferi, include the abundance of hosts for the ticks and the capacity of tick hosts to serve as B. burgdorferi reservoirs. Here, we explore the linkages between climate variation and: 1) duration of the seasonal period and the timing of peak activity; 2) geographic tick distributions and local abundance; 3) enzootic B. burgdorferi transmission cycles; and 4) Lyme disease cases. We conclude that meteorological variables are most influential in determining host-seeking phenology and development, but, while remaining important cofactors, additional variables become critical when exploring geographic distribution and local abundance of ticks, enzootic transmission of B. burgdorferi, and Lyme disease case occurrence. Finally, we review climate change-driven projections for future impact on vector ticks and Lyme disease and discuss knowledge gaps and research needs.

Serological assays and a two-tiered test algorithm are recommended for laboratory confirmation of Lyme disease. In the United States, the sensitivity of two-tiered testing using commercially available serology-based assays is dependent on the stage of infection and ranges from 30% in the early localized disease stage to near 100% in late-stage disease. Other variables, including subjectivity in reading Western blots, compliance with two-tiered recommendations, use of different first- and second-tier test combinations, and use of different test samples, all contribute to variation in two-tiered test performance. The availability and use of sample sets from well-characterized Lyme disease patients and controls are needed to better assess the performance of existing tests and for development of improved assays. To address this need, the Centers for Disease Control and Prevention and the National Institutes of Health prospectively collected sera from patients at all stages of Lyme disease, as well as healthy donors and patients with look-alike diseases. Patients and healthy controls were recruited using strict inclusion and exclusion criteria. Samples from all included patients were retrospectively characterized by two-tiered testing. The results from two-tiered testing corroborated the need for novel and improved diagnostics, particularly for laboratory diagnosis of earlier stages of infection. Furthermore, the two-tiered results provide a baseline with samples from well-characterized patients that can be used in comparing the sensitivity and specificity of novel diagnostics. Panels of sera and accompanying clinical and laboratory testing results are now available to Lyme disease serological test users and researchers developing novel tests.

Local knowledge of when humans are at elevated risk for exposure to tick vectors of human disease agents is required both for the effective use of personal protection measures to avoid tick bites and for implementation of control measures to suppress host-seeking ticks. Here, we used previously published data on the seasonal density of host-seeking Ixodes pacificus Cooley and Kohls nymphs, the primary vectors of Lyme disease spirochetes in the far western USA, collected across a broad habitat and climate gradient in northwestern California to identify predictors of periods of time within the year when questing nymphal density is elevated. Models based on calendar week alone performed similarly to models based on calendar week and woodland type, or meteorological variables. The most suitable model for a given application will depend on user objectives, timescale of interest, and the geographic extent of predictions. Our models sought not only to identify when seasonal host-seeking activity commences, but also when it diminishes to low levels. Overall, we report a roughly 5–7 month period in Mendocino County during which host-seeking nymphal densities exceed a low threshold value.

International audience; Parasites and pathogens are increasingly recognized as significant drivers of ecological and evolutionary change in natural ecosystems. Concurrently, transmission of infectious agents among human, livestock, and wildlife populations represents a growing threat to veterinary and human health. In light of these trends and the scarcity of long‐term time series data on infection rates among vectors and reservoirs, the National Ecological Observatory Network (NEON) will collect measurements and samples of a suite of tick‐, mosquito‐, and rodent‐borne parasites through a continental‐scale surveillance program. Here, we describe the sampling designs for these efforts, highlighting sampling priorities, field and analytical methods, and the data as well as archived samples to be made available to the research community. Insights generated by this sampling will advance current understanding of and ability to predict changes in infection and disease dynamics in novel, interdisciplinary, and collaborative ways.

Lyme disease, which is caused by the spirochetal agent Borrelia burgdoferi, is the most common vector-borne illness in the United States. In 1998, the US Food and Drug Administration approved a recombinant Lyme disease vaccine that was later voluntarily withdrawn from the market by the manufacturer. Current Lyme disease prevention efforts focus on a combination of methods and approaches, including area acaricides, landscape management, host-targeted interventions, management of deer populations, and personal protective measures, such as the use of insect repellant and tick checks. Although these methods are generally safe and relatively inexpensive, the primary limitations of these methods are that their effectiveness has been difficult to demonstrate conclusively and that rates of compliance are generally poor. An effective human Lyme disease vaccine that has been adequately evaluated in the highest-risk population groups could be very beneficial in preventing Lyme disease; however, it would need to meet high standards regarding safety, efficacy, cost, and public acceptance.

Background: When Pneumocystis DNA is recovered from respiratory specimens of patients without Pneumocystis pneumonia (PCP), patients are said to be colonised with Pneumocystis , although the significance of this state is unknown. Understanding risk factors for and outcomes of colonisation may provide insights into the life cycle and transmission dynamics of Pneumocystis jirovecii . Methods: We performed a cross sectional study of the prevalence and clinical predictors of Pneumocystis colonisation in 172 HIV infected, PCP negative inpatients undergoing diagnostic evaluation of 183 episodes of pneumonia at either the Medical Center of Louisiana at New Orleans between 2003 and 2005 or San Francisco General Hospital between 2000 and 2005. DNA was extracted from sputum and bronchoalveolar lavage specimens and amplified using a nested PCR assay at the mitochondrial large subunit (18S) ribosomal RNA locus. Colonisation was deemed present if Pneumocystis DNA was identified by both gel electrophoresis and direct DNA sequencing. Results: 68% (117/172) of all patients were colonised with Pneumocystis . No strong associations with colonisation were identified for any demographic factors. Among clinical factors, having a CD4+ T cell count ⩽50 cells/μl (unadjusted OR 2.4, 95% CI 1.09 to 5.48; p = 0.031) and using PCP prophylaxis (unadjusted OR 0.55, 95% CI 0.29 to 1.07; p = 0.077) were associated with Pneumocystis colonisation, although the latter association may have been due to chance. After adjustment for CD4+ T cell count, use of PCP prophylaxis was associated with a decreased odds of colonisation (adjusted OR 0.45, 95% CI 0.21 to 0.98; p = 0.045). 11 patients who were colonised were subsequently readmitted for evaluation of a second episode of pneumonia; three were found to be colonised again, but none had PCP. Conclusions: The majority of hospitalised HIV infected patients with non-PCP pneumonia are colonised with Pneumocystis . Failure to use co-trimoxazole prophylaxis and severe immunosuppression are associated with an increase in the odds of colonisation. Pneumocystis colonisation among hospitalised patients does not commonly lead to PCP.

Pneumocystis pneumonia (PCP), caused by infection with Pneumocystis jirovecii, remains an important opportunistic infection in humans. A reverse transcriptase polymerase chain reaction assay has been shown to specifically detect viable P. jirovecii organisms. In the current study, we evaluated this assay on different types of respiratory samples. The assay had a diagnostic sensitivity of 100% and a specificity of 86% when applied to bronchoalveolar lavage samples. The assay's performance declined when applied to less invasive induced sputum and oropharyngeal wash (OPW) samples. The sensitivity, when applied to OPWs, was improved by examining multiple sequential OPW samples and was affected by clinical sampling parameters that could increase or decrease the number of potential organisms in the oropharynx. When used in conjunction with an optimized clinical sampling protocol, this assay may become a useful tool for detecting and monitoring P. jirovecii in minimally invasive clinical samples.

Lyme disease is the most commonly reported vector-borne illness in the United States. Lyme disease occurrence is highly seasonal and the annual springtime onset of cases is modulated by meteorological conditions in preceding months. A meteorological-based empirical model for Lyme disease onset week in the United States is driven with downscaled simulations from five global climate models and four greenhouse gas emissions scenarios to project the impacts of 21st century climate change on the annual onset week of Lyme disease. Projections are made individually and collectively for the 12 eastern States where >90% of cases occur. The national average annual onset week of Lyme disease is projected to become 0.4–0.5 weeks earlier for 2025–2040 (p