Ixodes scapularis (Acari: Ixodidae) distribution surveys in the Chicago metropolitan region

Assessing knowledge gaps and empowering Extension workers in Illinois with information on ticks and tickborne diseases through KAP surveys

Tickborne diseases (TBDs) are increasingly prevalent in Illinois and the Upper Midwest region. People who work in occupations that require time outdoors in agricultural or natural settings, such as some Extension workers, are at risk of tick bites and TBDs. Additionally, Extension workers are often a primary source of information about ticks and TBDs in rural communities. However, there is limited information on the level of awareness about ticks and TBDs in the Extension community. The goals of this study were to sequentially i) determine the baseline awareness of Extension workers in Illinois about ticks and TBDs using a knowledge, attitudes, and practices (KAP) survey tool, ii) provide comprehensive training on ticks and TBDs to this demographic, and iii) measure the uptake of knowledge after the training intervention through a post-training survey. The study period was from June 2022 until May 2023. We received 233 pre-training and 93 paired post-training survey responses. Most survey respondents were Extension volunteers, identified as women, and were over 50 years old. Knowledge about ticks and TBDs varied. We identified several gaps in their current tick awareness, most importantly, in tick prevention measures, tick identification, and TBDs in general. TBD knowledge, attitude, and practice scores all significantly improved after training (p < 0.001), with a mean difference of 10.47, 1.49, and 2.64 points, respectively. Additionally, both Extension professionals (79.2 %) and Extension volunteers (66.7 %) were more likely to feel confident in engaging with their stakeholders on ticks and TBDs after participating in training. Poisson models revealed that higher attitude and practice scores and greater self-reported knowledge were the factors most significantly associated with higher TBD knowledge. We found that greater concern for ticks and TBD (attitudes) and adherence to science-based prevention and management methods (practices) were also associated with higher knowledge scores. To our knowledge, this is the first study in Illinois to capture Extension workers' awareness of ticks and TBDs. The results highlight Extension workers' interest in filling knowledge gaps through learning, and the importance of training Extension workers to disseminate reliable and updated information on ticks and TBDs to their constituents, a critical step in preventing TBDs.

Current and Future Habitat Suitability Models for Four Ticks of Medical Concern in Illinois, USA

The greater U.S. Midwest is on the leading edge of tick and tick-borne disease (TBD) expansion, with tick and TBD encroachment into Illinois occurring from both the northern and the southern regions. To assess the historical and future habitat suitability of four ticks of medical concern within the state, we fit individual and mean-weighted ensemble species distribution models for Ixodes scapularis, Amblyomma americanum, Dermacentor variabilis, and a newly invading species, Amblyomma maculatum using a variety of landscape and mean climate variables for the periods of 1970-2000, 2041-2060, and 2061-2080. Ensemble model projections for the historical climate were consistent with known distributions of each species but predicted the habitat suitability of A. maculatum to be much greater throughout Illinois than what known distributions demonstrate. The presence of forests and wetlands were the most important landcover classes predicting the occurrence of all tick species. As the climate warmed, the expected distribution of all species became strongly responsive to precipitation and temperature variables, particularly precipitation of the warmest quarter and mean diurnal range, as well as proximity to forest cover and water sources. The suitable habitat for I. scapularis, A. americanum, and A. maculatum was predicted to significantly narrow in the 2050 climate scenario and then increase more broadly statewide in the 2070 scenario but at reduced likelihoods. Predicting where ticks may invade and concentrate as the climate changes will be important to anticipate, prevent, and treat TBD in Illinois.

A Scoping Review of Species Distribution Modeling Methods for Tick Vectors

Background

Globally, tick-borne disease is a pervasive and worsening problem that impacts human and domestic animal health, livelihoods, and numerous economies. Species distribution models are useful tools to help address these issues, but many different modeling approaches and environmental data sources exist.

Objective

We conducted a scoping review that examined all available research employing species distribution models to predict occurrence and map tick species to understand the diversity of model strategies, environmental predictors, tick data sources, frequency of climate projects of tick ranges, and types of model validation methods.

Design

Following the PRISMA-ScR checklist, we searched scientific databases for eligible articles, their references, and explored related publications through a graphical tool (www.connectedpapers.com). Two independent reviewers performed article selection and characterization using a priori criteria.

Results

We describe data collected from 107 peer-reviewed articles that met our inclusion criteria. The literature reflects that tick species distributions have been modeled predominantly in North America and Europe and have mostly modeled the habitat suitability for Ixodes ricinus (n = 23; 21.5%). A wide range of bioclimatic databases and other environmental correlates were utilized among models, but the WorldClim database and its bioclimatic variables 1–19 appeared in 60 (56%) papers. The most frequently chosen modeling approach was MaxEnt, which also appeared in 60 (56%) of papers. Despite the importance of ensemble modeling to reduce bias, only 23 papers (21.5%) employed more than one algorithm, and just six (5.6%) used an ensemble approach that incorporated at least five different modeling methods for comparison. Area under the curve/receiver operating characteristic was the most frequently reported model validation method, utilized in nearly all (98.9%) included studies. Only 21% of papers used future climate scenarios to predict tick range expansion or contraction. Regardless of the representative concentration pathway, six of seven genera were expected to both expand and retract depending on location, while Ornithodoros was predicted to only expand beyond its current range.

Conclusion

Species distribution modeling techniques are useful and widely employed tools for predicting tick habitat suitability and range movement. However, the vast array of methods, data sources, and validation strategies within the SDM literature support the need for standardized protocols for species distribution and ecological niche modeling for tick vectors.

Knowledge, attitudes, and practices of veterinary professionals towards ticks and tick-borne diseases in Illinois

Objective

A lack of standardized surveillance or reporting of tick-borne diseases (TBDs) in Illinois creates uncertainty for veterinarians regarding TBDs occurring within their practice geography or which TBDs may be encroaching on their area from neighboring territories. Therefore, the objective of this study was to gauge the knowledge, attitudes, and practices of veterinary professionals in Southern and Central Illinois to establish a foundation for targeting educational and outreach programs that address knowledge gaps.

Sample

72 veterinary professionals in Central and Southern Illinois.

Procedures

An online knowledge, attitudes, and practices survey was distributed to veterinary professionals in Southern and Central Illinois. Poisson regression analyses were conducted to determine factors associated with knowledge scores and the estimated number of TBD cases diagnosed.

Results

Knowledge scores were significantly higher among veterinary practitioners with recent (within the last 5 years) training on TBD. The number of cases of TBD diagnosed was higher among those reporting concern about TBD, and among those who routinely test for TBDs. The types of diseases diagnosed were heavily influenced by the diagnostic method used.

Clinical relevance

This study paints a cohesive picture of human factors associated with diagnosing veterinary diseases and TBD prevalence in Southern and Central Illinois. Our results highlight the importance and practical value of veterinary continuing education on ticks and TBDs for both companion animals and public health. Building capacity for training veterinarians in parasitology using partnerships between academia and industry may strengthen the knowledge and understanding of ticks and tick-borne pathogens in the veterinary community.

Comparing Contributions of Passive and Active Tick Collection Methods to Determine Establishment of Ticks of Public Health Concern Within Illinois

In Illinois, between 1990 and 2017, tick-borne diseases in humans increased 10-fold, yet we have insufficient information on when and where people are exposed to vector ticks (Ixodida: Ixodidae). The aims of our research were to compare contributions of passive and active tick collection methods in determining establishment of ticks of public health concern and obtain information on tick distributions within Illinois. We used three surveillance strategies within the Illinois Tick Inventory Collaboration Network to gather information about the ticks of public health concern: 1) passive collection (voluntary submission by the public); 2) systematic collection (biweekly active surveillance); and 3) special collections (active collections in locations of special interest). Of collected adult and nymphal ticks, 436 were from passive collections, 142 from systematic collections, and 1,270 from special collections. Tick species distribution status changed in 36 counties. Our data provide noteworthy updates to distribution maps for use by public health agencies to develop prevention and control strategies. Additionally, the program built a network of collaborations and partnerships to support future tick surveillance efforts within Illinois and highlighted how the combination of the three surveillance strategies can be used to determine geographic spread of ticks, pinpoint locations in need of more surveillance, and help with long-term efforts that support phenology studies.

Impact of Unexplored Data Sources on the Historical Distribution of Three Vector Tick Species in Illinois

We updated the Illinois historical (1905-December 2017) distribution and status (not reported, reported or established) maps for Amblyomma americanum (L.) (Acari: Ixodidae), Dermacentor variabilis (Say) (Acari: Ixodidae), and Ixodes scapularis (Say) (Acari: Ixodidae) by compiling publicly available, previously unexplored or newly identified published and unpublished data (untapped data). Primary data sources offered specific tick-level information, followed by secondary and tertiary data sources. For A. americanum, D. variabilis, and I. scapularis, primary data contributed to 90% (4,045/4,482), 80% (2,124/2,640), and 32% (3,490/10,898) tick records vs 10%, 20%, and 68%, respectively from secondary data; primary data updated status in 95% (62/65), 94% (51/54) and in 90% (9/10) of the updated counties for each of these tick species; by 1985 there were tick records in 6%, 68%, and 0% of the counties, compared to 20%, 72%, and 58% by 2004, and 77%, 96%, and 75% of the counties by 2017, respectively for A. americanum, D. variabilis, and I. scapularis. We document the loss of tick records due to unidentified, not cataloged tick collections, unidentified ticks in tick collections, unpublished data or manuscripts without specific county location, and tick-level information, to determine distribution and status. In light of the increase in tick-borne illnesses, updates in historical distributions and status maps help researchers and health officials to identify risk areas for a tick encounter and suggest targeted areas for public outreach and surveillance efforts for ticks and tick-borne diseases. There is a need for a systematic, national vector surveillance program to support research and public health responses to tick expansions and tick-borne diseases.

Reported County-Level Distribution of the American Dog Tick (Acari: Ixodidae) in the Contiguous United States

In the United States, tick-borne diseases are increasing in incidence and cases are reported over an expanding geographical area. Avoiding tick bites is a key strategy in tick-borne disease prevention, and this requires current and accurate information on where humans are at risk for exposure to ticks. Based on a review of published literature and records in the U.S. National Tick Collection and National Ecological Observatory Network databases, we compiled an updated county-level map showing the reported distribution of the American dog tick, Dermacentor variabilis (Say). We show that this vector of the bacterial agents causing Rocky Mountain spotted fever and tularemia is widely distributed, with records derived from 45 states across the contiguous United States. However, within these states, county-level records of established tick populations are limited. Relative to the range of suitable habitat for this tick, our data imply that D. variabilis is currently underreported in the peer-reviewed literature, highlighting a need for improved surveillance and documentation of existing tick records.

Rickettsia parkeri and "Candidatus Rickettsia andeanae" in Amblyomma maculatum (Acari: Ixodidae) collected from the Atlanta metropolitan area, Georgia, United States

Rickettsia parkeri is a recently recognized human pathogen transmitted in the southeastern United States by Amblyomma maculatum, the Gulf Coast tick. Since R. parkeri was conclusively identified as a human pathogen in 2004, over 40 cases of R. parkeri rickettsiosis have been identified in the United States, most of which occur in the southeastern states. During 2012-2014, five of these cases were identified by a single urgent care practice in Coweta County, a Georgia county within the Atlanta metropolitan area. To investigate the occurrence of R. parkeri-infected A. maculatum in the Atlanta metropolitan area, ticks were collected from 6 counties around the city of Atlanta and evaluated for infection with a Rickettsia species. A total of 263 questing adult A. maculatum were collected during 2015 and 2016. Of these, 93 (35%) were PCR-positive for DNA of R. parkeri and an additional 46 (17%) were PCR-positive for DNA of "Candidatus Rickettsia andeanae," a spotted fever group Rickettsia species of unknown pathogenicity. No co-infections of these two rickettsiae were detected; however four of the six counties sampled showed presence of both rickettsial organisms. The high frequency of R. parkeri in these tick populations indicates a potential risk for those living, working, or recreating in A. maculatum-infested habitats within these six counties in the Atlanta metropolitan area.

Active surveillance to update county scale distribution of four tick species of medical and veterinary importance in Oklahoma

The incidence of tick-borne disease continues to increase in humans and companion animals in the United States, yet distribution maps for several tick vectors in Oklahoma, including Dermacentor variabilis, Dermacentor albipictus, Ixodes scapularis, and Amblyomma maculatum, are not available or are outdated. To address this issue, county-scale tick records from peer-reviewed literature and passive collections were reviewed for Oklahoma. Additionally, dry ice traps, tick drags, and harvested deer were utilized to actively collect adult ticks throughout the state. Through these methods, D. variabilis, D. albipictus, I. scapularis, and A. maculatum were identified in 88% (68/77), 45.4% (35/77), 66.2% (51/77), and 64.9% (50/77) of the counties in Oklahoma, respectively. Baseline maps were developed for the distribution of D. variabilis and D. albipictus and distribution maps were updated for I. scapularis and A. maculatum. This data confirms that these four species of ticks continue to be widespread within Oklahoma with a western expansion of the range of I. scapularis within the state. These results assist efforts to better understand the epidemiology of the different diseases caused by pathogens transmitted by these tick species within the Great Plains region.

Risk of encountering ticks and tick-borne pathogens in a rapidly growing metropolitan area in the U.S. Great Plains

The prevalence of tick-borne diseases has increased dramatically in many urban areas of the U.S., yet little is known about the ecology of ticks and tick-borne pathogens in relation to characteristics of North American urban and suburban landscapes. This study aimed to begin identification of the risk of encountering ticks and tick-borne pathogens within a rapidly expanding metropolitan area in the U.S. Great Plains region. Ten sites across Oklahoma City, Oklahoma were selected for tick sampling based on presence of tick habitat and level of urbanization intensity. Sampling was conducted using CO₂ traps and flagging in June, July and October 2015. A total of 552 ticks were collected from eight of the ten sampled greenspaces. The majority of ticks collected in summer were Amblyomma americanum (N=534 (97.8%)), followed by Dermacentor variabilis (N=10 (1.8%)) and Amblyomma maculatum (N=2 (0.3%)). Ixodes scapularis adult females (N=4) and nymphal A. americanum (N=2) were also collected in October 2015. Tick species diversity was highest in sites with >15% of the surrounding landscape composed of undeveloped land. Rickettsia sp. (including R. amblyommii and 'Candidatus R. andeanae'), Ehrlichia chaffeensis and/or E. ewingii were detected in tick pools from all eight sites where ticks were found. Our data suggest that the risk of encountering ticks and tick-borne pathogens exists throughout the Oklahoma City metropolitan area and that tick populations are likely influenced by urbanization intensity. Continued research is needed to clarify the full range of abiotic and biotic features of urban landscapes that influence the risk of encountering ticks and transmitting tick-borne diseases.

County-Scale Distribution of Ixodes scapularis and Ixodes pacificus (Acari: Ixodidae) in the Continental United States

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.

Are ticks venomous animals?

INTRODUCTION

As an ecological adaptation venoms have evolved independently in several species of Metazoa. As haematophagous arthropods ticks are mainly considered as ectoparasites due to directly feeding on the skin of animal hosts. Ticks are of major importance since they serve as vectors for several diseases affecting humans and livestock animals. Ticks are rarely considered as venomous animals despite that tick saliva contains several protein families present in venomous taxa and that many Ixodida genera can induce paralysis and other types of toxicoses. Tick saliva was previously proposed as a special kind of venom since tick venom is used for blood feeding that counteracts host defense mechanisms. As a result, the present study provides evidence to reconsider the venomous properties of tick saliva.

RESULTS

Based on our extensive literature mining and in silico research, we demonstrate that ticks share several similarities with other venomous taxa. Many tick salivary protein families and their previously described functions are homologous to proteins found in scorpion, spider, snake, platypus and bee venoms. This infers that there is a structural and functional convergence between several molecular components in tick saliva and the venoms from other recognized venomous taxa. We also highlight the fact that the immune response against tick saliva and venoms (from recognized venomous taxa) are both dominated by an allergic immunity background. Furthermore, by comparing the major molecular components of human saliva, as an example of a non-venomous animal, with that of ticks we find evidence that ticks resemble more venomous than non-venomous animals. Finally, we introduce our considerations regarding the evolution of venoms in Arachnida.

CONCLUSIONS

Taking into account the composition of tick saliva, the venomous functions that ticks have while interacting with their hosts, and the distinguishable differences between human (non-venomous) and tick salivary proteins, we consider that ticks should be referred to as venomous ectoparasites.

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.

Occurrence and county-level distribution of ticks (Acari: Ixodoidea) in Nebraska using passive surveillance

A 100 yr (1911-2011) examination of tick submissions was compiled from the U.S. National Tick Collection and three state databases to determine tick species occurrence in Nebraska Sixteen tick species were identified including Amblyomma americanum (L.), Dermacentor variabilis (Say), Dermacentor albipictus (Packard), Dermacentor andersoni Stiles, Haemaphysalis leporispalustris (Packard), Rhipicephalus sanguineus (Latreille), and Otobius megrini (Dughs). Amblyomma maculatum Koch and Ixodes scapularis Say were identified in only two and four submissions, respectively, but all identifications have occurred after 1990. County submissions were associated with county population, forested area, and number of recreation areas.