Bourbon Virus Transmission, New York, USA.

In July 2019, Bourbon virus RNA was detected in an Amblyomma americanum tick removed from a resident of Long Island, New York, USA. Tick infection and white-tailed deer (Odocoileus virginianus) serosurvey results demonstrate active transmission in New York, especially Suffolk County, emphasizing a need for surveillance anywhere A. americanum ticks are reported.

Isolation of Heartland Virus from Lone Star Ticks, Georgia, USA, 2019.

Report of a human death and exposure of white-tailed deer to Heartland virus (HRTV) in Georgia, USA, prompted the sampling of questing ticks during 2018-2019 in 26 sites near where seropositive deer were captured and the residence of the human case-patient. We processed 9,294 Amblyomma americanum ticks in pools by virus isolation in Vero E6 cells and reverse transcription PCR. Positive pools underwent whole-genome sequencing. Three pools were positive for HRTV (minimum infection rate 0.46/1,000 ticks) and none for Bourbon virus. Cell cultures confirmed HRTV presence in 2 pools. Genome sequencing, achieved for the 3 HRTV isolates, showed high similarity among samples but marked differences with previously sequenced HRTV isolates. The isolation and genomic characterization of HRTV from A. americanum ticks in Georgia confirm virus presence in the state. Clinicians and public health professionals should be aware of this emerging tickborne pathogen.

Repellency and toxicity of a CO2-derived cedarwood oil on hard tick species (Ixodidae).

The repellency and toxicity of a CO2-derived cedarwood oil (CWO) was evaluated against actively questing unfed nymphs of four species of hard ticks: Amblyomma americanum (L.), Dermacentor variabilis (Say), Ixodes scapularis Say, and Rhipicephalus sanguineus (Latreille). Using a vertical climb bioassay for repellency, nymphs of these species avoided a CWO-treated filter paper in proportional responses to treatment concentrations. At 60 min of exposure, I. scapularis nymphs were most sensitive with 50% repellency concentration (RC50) of 19.8 µg cm-2, compared with RC50 of 30.8, 83.8 and 89.6 µg cm-2 for R. sanguineus, D. variabilis and A. americanum, respectively. Bioassays determined the lethal concentration for 50% (LC50) and 90% (LC90) mortality of nymphs exposed to CWO in treated vials after 24- and 48-h exposure. After 24 h exposure, the LC50 values were 1.25, 3.45 and 1.42 µg cm-2 and LC90 values were 2.39, 7.59 and 4.14 µg cm-2 for D. variabilis, I. scapularis and R. sanguineus, respectively, but had minimal effect on A. americanum. After 48 h exposure, the LC50 values were 4.14, 0.78, 0.79 and 0.52 µg cm-2, and LC90 values were 8.06, 1.48, 1.54 and 1.22 µg cm-2 for A. americanum, D. variabilis, I. scapularis and R. sanguineus, respectively. The repellency of CWO on tick species decreased with time. The repellency and toxicity bioassays demonstrated concentration-dependent responses of tick nymphs to the oil, indicating the potential of the CO2-derived cedarwood oil be developed as an eco-friendly repellent and/or acaricide.

Heartland Virus Transmission, Suffolk County, New York, USA.

During 2018, Heartland virus RNA was detected in an Amblyomma americanum tick removed from a resident of Suffolk County, New York, USA. The person showed seroconversion. Tick surveillance and white-tailed deer (Odocoileus virginianus) serosurveys showed widespread distribution in Suffolk County, emphasizing a need for disease surveillance anywhere A. americanum ticks are established or emerging.

Active surveillance of ticks in peri-domestic areas of Indiana, Midwest United States.

BACKGROUND & OBJECTIVES: The incidence of Borreliosis, Anaplasmosis, Babesiosis and other tick-borne diseases acquired from private residential/peri-domestic areas has increased over the decades. However, tick activity and proportion of private residential properties with established tick populations remain unknown. The purpose of the current study was to determine the predictors of tick activity in peri-domestic areas. METHODS: In a cross-sectional study design, we used snowball-sampling with cold-calling techniques to collect free-living ticks, sociodemographic, and microclimatic data from June to November 2018 from a total of 96 private residential areas in south-central Indiana, USA. RESULTS: Thirty-eight percent of peri-domestic areas sampled had tick activity, and of these, 50% had established tick populations. Nymphal ticks were the most abundant life stage. Self-reported TBD diagnosis was 16%. Amblyomma americanum [Linnaeus (lone star tick)] was the most abundant tick species collected. Other tick species identified include: Ixodes scapularis [Say (black-legged/deer tick)] and Dermacentor variabilis [Say (American dog tick)]. Increasing temperature was positively associated with tick activity, while elevation was negatively associated with tick abundance. INTERPRETATION & CONCLUSION: Our study results reveal that the proportion of peri-domestic areas in Indiana with established tick populations is high. Amblyomma americanum tick is the most predominant tick species in peri-domestic areas of south-central Indiana. Active surveillance of ticks in peri-domestic areas is necessary for informing decisions by households and communities about where to target tick exposure and tick-borne disease prevention efforts.

Using convolutional neural networks for tick image recognition - a preliminary exploration.

Smartphone cameras and digital devices are increasingly used in the capture of tick images by the public as citizen scientists, and rapid advances in deep learning and computer vision has enabled brand new image recognition models to be trained. However, there is currently no web-based or mobile application that supports automated classification of tick images. The purpose of this study was to compare the accuracy of a deep learning model pre-trained with millions of annotated images in Imagenet, against a shallow custom-build convolutional neural network (CNN) model for the classification of common hard ticks present in anthropic areas from northeastern USA. We created a dataset of approximately 2000 images of four tick species (Ixodes scapularis, Dermacentor variabilis, Amblyomma americanum and Haemaphysalis sp.), two sexes (male, female) and two life stages (adult, nymph). We used these tick images to train two separate CNN models - ResNet-50 and a simple shallow custom-built. We evaluated our models' performance on an independent subset of tick images not seen during training. Compared to the ResNet-50 model, the small shallow custom-built model had higher training (99.7%) and validation (99.1%) accuracies. When tested with new tick image data, the shallow custom-built model yielded higher mean prediction accuracy (80%), greater confidence of true detection (88.7%) and lower mean response time (3.64 s). These results demonstrate that, with limited data size for model training, a simple shallow custom-built CNN model has great prospects for use in the classification of common hard ticks present in anthropic areas from northeastern USA.

Antibody Titers Reactive With Rickettsia rickettsii in Blood Donors and Implications for Surveillance of Spotted Fever Rickettsiosis in the United States.

BACKGROUND: Since 2000, the reported prevalence of tick-borne spotted fever rickettsiosis has increased considerably. We compared the level of antibody reactivity among healthy blood donors from 2 widely separated regions of the United States and evaluated the impact of antibody prevalence on public health surveillance in one of these regions. METHODS: Donor serum samples were evaluated by indirect immunofluorescence antibody assay to identify immunoglobulin G (IgG) antibodies reactive with Rickettsia rickettsii. The Georgia Department of Public Health (GDPH) analyzed characteristics of cases from 2016 surveillance data to evaluate the utility of laboratory surveillance for case assessment. RESULTS: Of the Georgia donors (n = 1493), 11.1% demonstrated antibody titers reactive with R. rickettsii at titers ≥64, whereas 6.3% of donors from Oregon and Washington (n = 1511) were seropositive. Most seropositive donors had a titer of 64; only 3.1% (n = 93) of all donors had titers ≥128. During 2016, GDPH interviewed 243 seropositive case patients; only 28% (n = 69) met inclusion criteria in the national case definition for spotted fever rickettsiosis. CONCLUSIONS: These findings suggest that a single IgG antibody titer is an unreliable measure of diagnosis and could inaccurately affect surveillance estimates that define magnitude and clinical characteristics of Rocky Mountain spotted fever and other spotted fever rickettsioses.

Heartland Virus in Lone Star Ticks, Alabama, USA.

We detected Heartland virus (HRTV) in lone star nymphs collected in 2018 in northern Alabama, USA. Real-time reverse transcription PCR selective for the small segment of the HRTV genome and confirmatory sequencing of positive samples showed high identity with HRTV strains sequenced from Tennessee and Missouri.

Heartland Virus in Humans and Ticks, Illinois, USA, 2018-2019.

In 2018, Heartland disease virus infected 2 persons in Illinois, USA. In 2019, ticks were collected at potential tick bite exposure locations and tested for Heartland and Bourbon viruses. A Heartland virus-positive pool of adult male Amblyomma americanum ticks was found at 2 locations, 439 km apart, suggesting widespread distribution in Illinois.

A case of morphological anomalies in Amblyomma americanum (Acari: Ixodidae) collected from nature.

We describe a case of morphological anomalies in Amblyomma americanum, a medically important species associated with several human diseases and medical conditions. Based on morphological characters using dichotomous morphological keys, high-resolution light microscopy, and scanning electron microscopy imaging, the tick was identified as Am. americanum nymph exhibiting various morphological anomalies including ectromely associate with asymmetry, olygomely (lack) of the fourth left leg, and schizomely (bifurcation of palpus) on the right side. We believe this is the first report of the presence of several spontaneous anomalies in one Am. americanum specimen. Morphological identity of the specimen was corroborated by DNA sequencing of the mitochondrial 16S region. We discuss recent reports of morphological anomalies in ixodid ticks and emphasize the significance of additional studies of teratology in medically important tick species and its potential implications.

Predicting the potential distribution of Amblyomma americanum (Acari: Ixodidae) infestation in New Zealand, using maximum entropy-based ecological niche modelling.

Although currently exotic to New Zealand, the potential geographic distribution of Amblyomma americanum (L.), the lone star tick, was modelled using maximum entropy (MaxEnt). The MaxEnt model was calibrated across the native range of A. americanum in North America using present-day climatic conditions and occurrence data from museum collections. The resulting model was then projected onto New Zealand using both present-day and future climates modelled under two greenhouse gas emission scenarios, representative concentration pathways (RCP) 4.5 (low) and RCP 8.5 (high). Three sets of WorldClim bioclimatic variables were chosen using the jackknife method and tested in MaxEnt using different combinations of model feature class functions and regularization multiplier values. The preferred model was selected based on partial receiver operating characteristic tests, the omission rate and the lowest Akaike information criterion. The final model had four bioclimatic variables, Annual Mean Temperature (BIO1), Annual Precipitation (BIO12), Precipitation Seasonality (BIO15) and Precipitation of Driest Quarter (BIO17), and the projected New Zealand distribution was broadly similar to that of Haemaphysalis longicornis Neumann, New Zealand's only livestock tick, but with a more extensive predicted suitability. The climate change predictions for the year 2050 under both low and high RCP scenarios projected only moderate increases in habitat suitability along the mountain valleys in the South Island. In conclusion, this analysis shows that given the opportunity and license A. americanum could and would successfully establish in New Zealand and could provide another vector for theileriosis organisms.

Ehrlichia Isolate from a Minnesota Tick: Characterization and Genetic Transformation.

Ehrlichia muris subsp. eauclairensis is recognized as the etiological agent of human ehrlichiosis in Minnesota and Wisconsin. We describe the culture isolation of this organism from a field-collected tick and detail its relationship to other species of Ehrlichia The isolate could be grown in a variety of cultured cell lines and was effectively transmitted between Ixodes scapularis ticks and rodents, with PCR and microscopy demonstrating a broad pattern of dissemination in arthropod and mammalian tissues. Conversely, Amblyomma americanum ticks were not susceptible to infection by the Ehrlichia Histologic sections further revealed that the wild-type isolate was highly virulent for mice and hamsters, causing severe systemic disease that was frequently lethal. A Himar1 transposase system was used to create mCherry- and mKate-expressing EmCRT mutants, which retained the ability to infect rodents and ticks.IMPORTANCE Ehrlichioses are zoonotic diseases caused by intracellular bacteria that are transmitted by ixodid ticks. Here we report the culture isolation of bacteria which are closely related to, or the same as the Ehrlichia muris subsp. eauclairensis, a recently recognized human pathogen. EmCRT, obtained from a tick removed from deer at Camp Ripley, MN, is the second isolate of this subspecies described and is distinctive in that it was cultured directly from a field-collected tick. The isolate's cellular tropism, pathogenic changes caused in rodent tissues, and tick transmission to and from rodents are detailed in this study. We also describe the genetic mutants created from the EmCRT isolate, which are valuable tools for the further study of this intracellular pathogen.

Fatal attraction: lone star ticks (Amblyomma americanum) exhibit preference for human female breath over male breath.

Ticks use a variety of chemical cues to locate hosts, the main cue being carbon dioxide, which is exhaled by hosts. This study sought to experimentally determine whether ticks exhibit preference among human hosts based on host sex, as the chemical components of human male and female breath have been shown to differ. We focused on the lone star tick, Amblyomma americanum, due to its importance as a disease vector in the United States and its active host-seeking behavior. To test the hypothesis that ticks exhibit preference based upon host sex, we conducted a binary choice behavioral bioassay. Male and female human volunteers (n = 20 pairs) breathed into opposite sides of a secured polycarbonate tube containing 10 adult A. americanum and the proportion of ticks that exhibited a host preference was recorded. We found that under controlled conditions, human females attract a significantly larger proportion of ticks than males. Possible mechanisms to explain these results include that (1) female breath contains components that ticks find attractive, and/or (2) male breath contains a repellent chemical component.

Mosquito and tick repellency of two Anthemis essential oils from Saudi Arabia.

The essential oils (EOs) of Anthemis melampodina (Am) and Anthemis scrobicularis (As) (Asteraceae) were extracted from the aerial parts of the plants by hydrodistillation, and their chemical compositions were analyzed using GC-FID and GC-MS. Fifty-six components representing 85.5% of the oil composition of Anthemis melampdina were identified, and the major components were α-pinene (17.1%) and ß-eudesmol (13.8%). Forty-one components representing 86% of the oil composition of Anthemis scrobicularis were identified, and the major component was ß-eudesmol (12.8%). Laboratory bioassays were conducted to determine repellency of Am and As EOs against the yellow fever mosquito Aedes aegypti L. and the lone star tick Amblyomma americanum L. The minimum effective doses (MEDs) of the Am and As EOs against mosquitoes were 0.187 ±â€¯0.000 and 0.312 ±â€¯0.063 mg/cm2 respectively, which were significantly higher than that of DEET (0.023 ±â€¯0.000 mg/cm2) in human-based repellent bioassays. The As EO was more repellent than Am EO against nymphal ticks but was less effective than DEET in vertical paper bioassays.

Bourbon Virus in Field-Collected Ticks, Missouri, USA.

Bourbon virus (BRBV) was first isolated in 2014 from a resident of Bourbon County, Kansas, USA, who died of the infection. In 2015, an ill Payne County, Oklahoma, resident tested positive for antibodies to BRBV, before fully recovering. We retrospectively tested for BRBV in 39,096 ticks from northwestern Missouri, located 240 km from Bourbon County, Kansas. We detected BRBV in 3 pools of Amblyomma americanum (L.) ticks: 1 pool of male adults and 2 pools of nymphs. Detection of BRBV in A. americanum, a species that is aggressive, feeds on humans, and is abundant in Kansas and Oklahoma, supports the premise that A. americanum is a vector of BRBV to humans. BRBV has not been detected in nonhuman vertebrates, and its natural history remains largely unknown.

Ability of Three General-Use Pesticides To Suppress Nymphal Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae).

We evaluated 3 over-the-counter pesticides for their ability to suppress host-seeking Ixodes scapularis and Amblyomma americanum nymphs. We applied liquid concentrate and granular formulations of Bayer Advanced Complete Insect Killer, Spectracide Triazicide Insect Killer, and Ortho Bug-B-Gon to forest plots using equipment available for purchase at retail home improvement outlets. All 3 liquid formulations provided rapid knockdown (≥98% control) of both species 1 day after application. Liquid Ortho Bug-B-Gone provided 100% suppression of I. scapularis throughout the 28-day postapplication period, while the other 2 liquid materials provided >95% control after 28 days. All liquid products also provided ≥95% control of A. americanum nymphs after 28 days. Granular formulations provided less consistent results, including lower 1-day knockdown rates for both species, due to very dry conditions, which prevented adequate release of the active ingredient from the carrier materials. After it rained in the study area, 7 and 14 days after application, we observed ≥99% suppression of both species. At 28 days posttreatment, control ranged between 87.5% and 95.6% for I. scapularis and between 89.3% and 94.4% for A. americanum . We show that these over-the-counter acaricides effectively suppressed 2 medically important tick vectors for at least 4 wk, and they provide a cost-effective tick control option for homeowners. In general, liquid formulations provided more rapid and greater and more consistent suppression than granular formulations, which may have implications for homeowner use of these products.

Frequency and Distribution of Rickettsiae, Borreliae, and Ehrlichiae Detected in Human-Parasitizing Ticks, Texas, USA.

To describe the presence and distribution of tickborne bacteria and their vectors in Texas, USA, we screened ticks collected from humans during 2008-2014 for Rickettsia, Borrelia, and Ehrlichia spp. Thirteen tick species were identified, and 23% of ticks carried bacterial DNA from at least 1 of the 3 genera tested.

A Dynamic Population Model to Investigate Effects of Climate and Climate-Independent Factors on the Lifecycle of Amblyomma americanum (Acari: Ixodidae).

The lone star tick, Amblyomma americanum, is a disease vector of significance for human and animal health throughout much of the eastern United States. To model the potential effects of climate change on this tick, a better understanding is needed of the relative roles of temperature-dependent and temperature-independent (day-length-dependent behavioral or morphogenetic diapause) processes acting on the tick lifecycle. In this study, we explored the roles of these processes by simulating seasonal activity patterns using models with site-specific temperature and day-length-dependent processes. We first modeled the transitions from engorged larvae to feeding nymphs, engorged nymphs to feeding adults, and engorged adult females to feeding larvae. The simulated seasonal patterns were compared against field observations at three locations in United States. Simulations suggested that 1) during the larva-to-nymph transition, some larvae undergo no diapause while others undergo morphogenetic diapause of engorged larvae; 2) molted adults undergo behavioral diapause during the transition from nymph-to-adult; and 3) there is no diapause during the adult-to-larva transition. A model constructed to simulate the full lifecycle of A. americanum successfully predicted observed tick activity at the three U.S. study locations. Some differences between observed and simulated seasonality patterns were observed, however, identifying the need for research to refine some model parameters. In simulations run using temperature data for Montreal, deterministic die-out of A. americanum populations did not occur, suggesting the possibility that current climate in parts of southern Canada is suitable for survival and reproduction of this tick.

Sustained efficacy of the novel topical repellent TT-4302 against mosquitoes and ticks.

Mosquitoes and ticks are blood-feeding pests of humans and animals that can vector many important aetiological agents of disease. Previous research demonstrated that TT-4302 (Guardian(®) Wilderness) containing 5% geraniol applied to human subjects gave 5-6 h of repellency against mosquitoes (depending on species) and was repellent to ticks in vitro. This study was conducted to obtain an independent third-party evaluation of TT-4302 against Stegomyia aegypti (= Aedes aegypti) (Diptera: Culicidae) mosquitoes and to test the efficacy of the product in the field against ticks. TT-4302 provided an average of 6.5 h of repellency of ≥ 95% [Weibull mean protection time: 7.4 h, 95% confidence interval (CI) 5.8-11.3 h] for St. aegypti, whereas a 15% DEET formulation provided 4.7 h of repellency (Weibull mean protection time: 5.2 h, 95% CI 3.7-6.9 h). In tick field trials, the efficacy of TT-4302 did not differ significantly from that of a 25% DEET formulation against Amblyomma americanum (Ixodida: Ixodidae). TT-4302 was 81.3% repellent at 2.5 h after application, whereas DEET was 77.2% repellent at the same time-point. Results at 3.5 h after application were 71.4% for TT-4302 and 72.9% for DEET.

Comparison of novel and conventional methods of trapping ixodid ticks in the southeastern U.S.A.

Tick-borne disease surveillance and research rely on resource-effective methods for tick collection. This study compared the respective performances of several trapping methods in a mixed grassland-forest habitat in western Tennessee. To test for temporal differences in effectiveness, sites were sampled monthly (April-August 2013) using dry ice, dragging, flagging, sweep netting, carbon dioxide (CO2 ) dragging and CO2 flagging methods. To evaluate the effect of habitat on method effectiveness, four methods (dragging, CO2 dragging, CO2 flagging and dry ice) were compared in four habitat types (bottomland deciduous, upland deciduous, coniferous and grassland) in June 2014. In the temporal comparison, ticks were found to be most abundant in April and May, and there was a significant sampling period and method interaction, such that method effectiveness varied across sampling period. Sweep netting was significantly less effective than the other methods. In the habitat comparison, dry ice trap collections represented the most effective method in upland deciduous and coniferous habitats. Flagging using CO2 was significantly less effective than CO2 dragging and dragging in bottomland deciduous habitats. The success of the various collection methods did not differ significantly within grassland habitats. Overall, dry ice trapping and dragging were the most effective methods for tick collection across time and habitat.