Nymphal Ticks Research Articles

Transovarial and transstadial transmission of Borrelia valaisiana, the pathogen of Lyme borreliosis, in the sheep tick, Ixodes ricinus L.

In this study, molecular analysis was used to show the possibility of transovarial and transstadial transmission of Borrelia valaisiana in Ixodes ricinus ticks in the natural biotopes of North-Western Russia. Female ticks collected in nature were fed on rabbits; larvae obtained from these females were fed on white mice. Eggs, female ticks after the egg deposition, larvae and nymphs of ticks after overwintering were studied for Borrelia burgdorferi s.l. within the natural inserts. The identification of Borrelia burgdorferi in ticks was carried out using the PCR method with real-time hybridization-fluorescence detection. The genotyping was performed by sequencing fragments of the intergenic region rrf-rrl. Spirochetes of only one genospecies B. valaisiana, previously not detected in North-Western Russia, were identified in ticks I. ricinus. The isolates of B. burgdorferi were obtained by inoculation of the gut contents of ticks into a prepared nutrient medium BSK-H with 6% rabbit serum (Sigma, USA). The positive reaction for B. valaisiana was observed in six out of 13 I. ricinus females (46.2%), which were successfully fed and laid eggs. Of the six infected female ticks, four (66.7%) (30.8% of the total four out of 13) were able to transmit B. valaisiana to eggs and then to larvae. 50.0% of the infected female ticks (23.1% of the total number) could transmit B. valaisiana to nymphs. In addition, the overwintered larvae and nymphs did not retain B. valaisiana. The subsequent transmission can occur as a result of feeding the overwintered larvae and nymphs on the infected overwintered hosts.

Individual variation underlies large-scale patterns: Host conditions and behavior affect parasitism.

Identifying the factors that affect host-parasite interactions is essential for understanding the ecology and dynamics of vector-borne diseases and may be an important component of predicting human disease risk. Characteristics of hosts themselves (e.g., body condition, host behavior, immune defenses) may affect the likelihood of parasitism. However, despite highly variable rates of parasitism and infection in wild populations, identifying widespread links between individual characteristics and heterogeneity in parasite acquisition has proven challenging because many zoonoses exist over wide geographic extents and exhibit both spatial and temporal heterogeneity in prevalence and individual and population-level effects. Using seven years of data collected by the National Ecological Observatory Network (NEON), we examined relationships among individual host condition, behavior, and parasitism by Ixodid ticks in a keystone host species, the white-footed mouse, Peromyscus leucopus. We found that individual condition, specifically sex, body mass, and reproductive condition, had both direct and indirect effects on parasitism by ticks, but the nature of these effects differed for parasitism by larval versus nymphal ticks. We also found that condition differences influenced rodent behavior, and behavior directly affected the rates of parasitism, with individual mice that moved farther being more likely to carry ticks. This study illustrates how individual-level data can be examined using large-scale datasets to draw inference and uncover broad patterns in host-parasite encounters at unprecedented spatial scales. Our results suggest that intraspecific variation in the movement ecology of hosts may affect host-parasite encounter rates and, ultimately, alter zoonotic disease risk through anthropogenic modifications and natural environmental conditions that alter host space use.

Is dragging a drag or is trapping a trap? A comparison of two methods for collecting Amblyomma americanum ticks in sites near the species range boundary

The incidence of tick-borne diseases in the United States has more than doubled since the early 2000s. Research on ticks is a priority to mitigate the spread of tick-borne diseases. Thus, it is important to understand how to efficiently collect large numbers of ticks for studies of genetics, behavior, physiology, vector competence, tick repellants, and acaricides. In this study, we compared the efficiency of two methods—dragging and CO2-baited trapping—for collecting lone star ticks (Amblyomma americanum) across two distinct regions of its expanding range. We performed simultaneous dragging and trapping collections at six sites, three in Oklahoma and three in New York and New Jersey, USA. Our results demonstrate that dragging was more efficient than trapping for collecting lone star tick nymphs. However, dragging and trapping were similar in efficiency for collecting adult males and females. There were no regional differences in trapping or dragging efficiency. Additionally, we discuss material and labor costs of each method to inform researchers who need to rapidly collect as many ticks as possible with the most efficient and cost-effective method.

Use of diatomaceous earth to control nymphal American dog ticks,Dermacentor variabilis Say (Acari: Ixodidae): laboratory to simulated field experiments.

Diatomaceous earth (DE) recently was shown to rapidly kill ticks. Proof of concept for use of DE to kill the American dog tick, Dermacentor variabilis, the most widely distributed native three-host tick in North America, has not been investigated. Unfed D. variabilis nymphs dipped into DE and incubated at 30 °C and 50 versus 70% relative humidity (RH) had an estimated median survival time of 5h and 4h, respectively, with mortality starting within 1h. There was no difference in survival time at the 50 and 70% RH. In a two-choice assay at 30 °C and 50% RH, ticks walked freely onto DE treated surfaces; the estimated median survival time was 3h, indicating that DE is not a repellent. There was no difference in locomotor activity between DE-treated nymphs and untreated controls. In simulated-field experiments, pine straw infested with nymphs and then treated with DE at 5.00, 2.50, 1.25, 0.63 and 0.31g DE/m2 resulted in 100% mortality and 81.40% (± 4.13%) mortality at 0.15g DE/m2 after 24h. Scanning electron microscopy of the dead ticks in the 0.15g DE/m2 treatments showed most of the cuticle surface was devoid of DE except for the hypostome. The rapid time to first death by dipping, the no effect of RH on survival time, the small amounts of mineral on the tick body and no visible scarring on the tick cuticle questions the generally accepted mode of action for DE, that is, cuticle damage and dehydration.

Minor Hosts Have a Major Impact on the Enzootic Transmission of Borrelia burgdorferi.

In the northeast United States, subadult deer ticks feeding on white-footed mice are thought to drive the force of transmission of Borrelia burgdorferi (B. burgdorferi), the agent of Lyme disease. However, control measures targeting mice have produced inconsistent results, suggesting that other animals are significant contributors to enzootic transmission. Such contributions have previously been difficult to quantify. We used a retrotransposon-based host blood meal assay to measure the relative contribution of hosts to enzootic B. burgdorferi transmission at two insular sites in Massachusetts. Over 6 years, we identified mice and deer as the most common larval hosts at our Nantucket Island site. Infected nymphal ticks were derived mainly from mice (35%) and shrews (31%), despite shrews having fed only 12% of larvae. Deer were identified in 19% of the infected nymphs, despite their known reservoir incompetence. Shrews were consistently the most important host in our Martha's Vineyard site and were identified as the source of 41% of nymphs overall and 39% of the infected nymphs. Sciurids were variable contributors, feeding from 4% to 42% of the larval ticks each year, and contributed no infected nymphs in 2020 and as many as 83% in 2023. We conclude that host contributions to feeding larval ticks change over time and within sites and that shrews may be more influential than mice at some sites. Shrews, sciurids, and even deer may contribute to B. burgdorferi maintenance. Hosts that apparently feed a minor proportion of ticks can have a major impact on the force of B. burgdorferi transmission.

Climate‐associated variation in the within‐season dynamics of juvenile ticks in California

AbstractChanging climate has driven shifts in species phenology, influencing a range of ecological interactions from plant–pollinator to consumer–resource. Phenological changes in host–parasite systems have implications for pathogen transmission dynamics. The seasonal timing, or phenology, of peak larval and nymphal tick abundance is an important driver of tick‐borne pathogen prevalence through its effect on cohort‐to‐cohort transmission. Tick phenology is tightly linked to climatic factors such as temperature and humidity. Thus, variation in climate within and across regions could lead to differences in phenological patterns. These differences may explain regional variation in tick‐borne pathogen prevalence of the Lyme disease‐causing Borrelia bacteria in vector populations in the United States. For example, one factor thought to contribute to high Lyme disease prevalence in ticks in the eastern United States is the asynchronous phenology of ticks there, where potentially infected nymphal ticks emerge earlier in the season than uninfected larval ticks. This allows the infected nymphal ticks to transmit the pathogen to hosts that are subsequently fed upon by the next generation of larval ticks. In contrast, in the western United States where Lyme disease prevalence is generally much lower, tick phenology is thought to be more synchronous with uninfected larvae emerging slightly before, or at the same time as, potentially infected nymphs, reducing horizontal transmission potential. Sampling larval and nymphal ticks, and their host‐feeding phenology, both across large spatial gradients and through time, is challenging, which hampers attempts to conduct detailed studies of phenology to link it with pathogen prevalence. In this study, we demonstrate through intensive within‐season sampling that the relative abundance and seasonality of larval and nymphal ticks are highly variable along a latitudinal gradient and likely reflect the variable climate in the far western United States with potential consequences for pathogen transmission. We find that feeding patterns were variable and synchronous feeding of juvenile ticks on key blood meal hosts was associated with mean temperature. By characterizing within‐season phenological patterns of the Lyme disease vector throughout a climatically heterogeneous region, we can begin to identify areas with high potential for tick‐borne disease risk and underlying mechanisms at a finer scale.

Ixodes ricinus ticks survive flooding.

Climate-change induced weather extremes like floods are increasing in frequency and intensity, with potential consequences for disease vector ecology. We report on a flooding event during the winter of 2023/2024 in Hanover city, Germany. Our observations demonstrate that I. ricinus, the most important vector of tick-borne diseases in Europe, can survive prolonged periods under water and quickly resume host-seeking activity once conditions normalize. Despite being submerged for a total of 25 days, nymphal and adult ticks were observed questing four weeks of the water receding, with densities comparable to pre-flood levels. These findings underscore the resilience of I. ricinus and highlight the potential of ticks to pose infection risks even after extreme weather events.

Prevalence of Babesia microti Co-Infection with Other Tick-Borne Pathogens in Pennsylvania.

Babesia microti is a protozoan that infects red blood cells, causing hemolytic anemia and flu-like symptoms in humans. Understanding co-infections is crucial for the better diagnosis, treatment, and management of tick-borne diseases. This study examined the prevalence of Babesia microti co-infection with other prevalent tick-borne pathogens in Pennsylvania. The dataset acquired from the Dr. Jane Huffman Wildlife Genetics Institute included passive surveillance data from Ixodes spp. from 2021 to 2023. Submitted ticks were screened for tick-borne pathogens using species-specific TaqMan qPCR. Of the 793 B. microti-positive ticks pulled for analysis, 65.0% were co-infected with other pathogens (n = 516). Notably, 60.9% of the B. microti-positive ticks were co-infected with Borrelia burgdorferi, 10.2% with Anaplasma phagocytophilum Ap-ha, and 7.5% carried a triple co-infection with B. burgdorferi and A. phagocytophilum Ap-ha. The rates of B. microti infection and its co-infections are on the rise, with patterns observed in Pennsylvania and other regions of the USA. While other studies have collected both nymphal and adult ticks to screen for co-infections in Pennsylvania, our study stood out as a unique contribution to the field by focusing exclusively on B. microti-positive ticks. The continued monitoring of tick-borne co-infections is vital to prevent misdiagnosis and ensure effective treatment regimens.

Maximizing and sustaining the efficacy of tick tubes for management of Ixodes scapularis through optimized deployment strategies.

The number of tick-borne disease cases continues to rise in the United States, with Lyme disease the most frequently reported vector-borne disease nationally. Practical and effective tick control tools and strategies are needed to reduce tick encounters and tick-borne disease risk. Tick management tubes have shown varying efficacy when used as part of a tick management plan. To evaluate factors contributing to the efficacy of tick management tubes, this study assessed changes in tick tube deployment on tick burden on wild-caught Peromyscus mice, a primary reservoir for the bacterium causing Lyme disease, in Pennsylvania from 2021 to 2023. Over 2 years, tick tubes were deployed starting at different times of the year, with cotton removal from the tubes assessed every 2 weeks from April to November and tick burden on wild-caught mice assessed every 2 months from April to October of each year. The effect of distance between tick management tubes was assessed in year 3 of this study, with mouse tick burden assessed pre- and post-treatment with tick tubes at varying intervals in a field setting. There was a significant reduction in mouse tick burden between treated and control transects, and pre- and post-treatment transects. Tick tube distance did not affect cotton removal or tick burden on mice. Still, cotton removal was highest in September-October, and amount removed increased the longer tick tubes were deployed in the field, highlighting the long-term benefits of using tick tubes as part of an integrated tick management plan. Future investigations to evaluate the impact of tick management tubes on tick nymph density and infection would be valuable for assessing the effectiveness of tick management tubes in reducing tick bite risk.

Molecular Identification of Spotted Fever Group Rickettsiae in Ticks in the Republic of Korea.

The Rickettsia species transmitted by ticks are mostly classified within the spotted fever group rickettsiae (SFGR), which causes tick-borne rickettsiosis. Although efforts have been made to investigate their prevalence in the Republic of Korea (ROK), research has been limited to certain areas. Furthermore, the pooling method for ticks does not fully reflect the exact infection rate. Therefore, we aimed to perform molecular identification of SFGR in ticks to elucidate the current prevalence of tick-borne rickettsiosis in the ROK. The SFGR of ticks was identified using polymerase chain reaction targeting the 17 kDa antigen, ompA, and gltA, followed by sequencing for species identification and phylogenetic analysis. In total, 302 ticks belonging to four species (Haemaphysalis flava, H. longicornis, Ixodes nipponensis, and Amblyomma testudinarium) were collected between April and November 2022. The overall SFGR infection rate was 26.8% (81/302 patients). Both adult and nymphal ticks and the SFGR infection rate increased during April-May, reaching their peaks in June, followed by a marked decline in August and July, respectively. Phylogenetic analysis revealed three species (R. monacensis, R. heilongjiangensis, and Candidatus R. jingxinensis) of SFGR. Thus, our results emphasize the importance of tick surveys for the prevention and management of tick-borne rickettsiosis.

Parasitic system Ixodes persulcatus (Ixodinae) – Borrelia garinii – small mammals in the northwest of Russia

Relationships between members of the parasitic system formed by the taiga tick Ixodes persulcatus (Schulze, 1930) at the preimaginal developmental stages, Borrelia garinii and small mammals were studied. Transovarial transmission of B. garinii in the taiga tick was not found. In natural biotopes of northwestern Russia, small mammals that were hosts of the preimaginal stages of Ixodes persulcatus included Myodes glareolus (Schreber, 1780) (52–53%), Sorex araneus Linnaeus, 1758 (33–34%), and Apodemus uralensis (Pallas, 1811) (14%). Larvae and nymphs were most numerous on hosts at the beginning of the season, in May and June. Subsequently, their number decreased by 5–10 times and slightly increased in September. In populations, up to 31.9% of M. glareolus individuals and 20.5% of A. uralensis individuals were infected with B. garinii. The aggregated type of distribution of taiga tick larvae and nymphs on hosts has been revealed. Infection of the main part of hungry larvae and nymphs occurred at the beginning of the activity season after wintering when feeding on overwintered infected hosts. This period is the key in circulation (exchange between vectors and reservoir hosts) and the preservation of B. garinii in the natural focus of borreliosis in northwestern Russia. Vertical transmission of B. garinii is possible from larvae and nymphs fed at the beginning of the season to nymphs and adult ticks that had molted in August-September, respectively. Horizontal transmission of the pathogen from small mammals, especially the bank vole, to larvae and nymphs, and vice versa, ensures the circulation and persistence of B. garinii in natural foci. The question of the preservation of the pathogen in overwintering preimaginal stages of ticks requires further research.

Amblyomma multipunctum Neuman, 1899 (Acari: Ixodidae): new locality record and new association with Pudu (Pudella) mephistophiles (Artiodactyla: Cervidae) in the Central Andes of Colombia</p >

Amblyomma multipunctum is a poorly known Neotropical tick (Acari, Ixodidae) described in 1899. It has been found associated with large mammals such as tapirs (Tapirus), and the Andean bear (Tremarctos ornatus). Males, females and nymphs have been described; however, the larvae of the species remain unknown. Valid records for A. multipunctum are few and limited to three countries in northwestern South America: Colombia, Ecuador, and Venezuela. In the present work, two partially engorged nymphs of A. multipunctum parasitizing the northern pudu, Pudu (Pudella) mephistophiles, were collected near to the Puracé National Natural Park, Department of Cauca, Colombia. Ticks were identified by morphology, with diagnostic characters such as scutum with multiple punctuations, two separate spurs in coxa I (the external being longer than the internal), a small triangular spur in coxae II–IV, spiracular plate triangular with rounded angles and a vestigial prolongation in article I of the palps. In addition, the taxonomical identity was validated using molecular evidence by PCR amplification of a fragment of the 16S rDNA gene, showing an identity percentage of 100% comparing with sequences in GenBank for A. multipunctum. This study reports the first association of A. multipunctum with P. mephistophiles, the extension of geographical distribution in Colombia, extending its elevational range by 644 m in the country, and contributing to the knowledge of the intraspecific variation of the tick nymph.

Comparative analysis of essential oil efficacy against the Asian longhorned tick Haemaphysalis longicornis (Acari: Ixodidae).

This study evaluated the potential repellent and acaricidal effects of 4 essential oils (clove, eucalyptus, lavender, and mint) against the Asian longhorned tick Haemaphysalis longicornis, a vector of various tick-borne diseases in medical and veterinary contexts. Selected for their potential repellent and acaricidal properties, the 4 essential oils were tested on adult and nymph H. longicornis ticks at different concentrations. The experiment assessed mortality rates and repellency, particularly during tick attachment to host skin. There was a significant increase (p<0.05) in tick mortality and repellency scores across all groups. At a 1% concentration, adult tick mortality ranged from 36% to 86%, while nymph mortality ranged from 6% to 97%. Clove oil exhibited notable efficacy, demonstrating high mortality rates of nymphs and adults. Clove oil also displayed strong repellency properties, with a repellency index of 0.05, surpassing those of mint, eucalyptus, and lavender oils. Clove oil showed the highest effectiveness in deterring nonattached adult ticks (90%) and nymphs (95%) when applied to skin. Clove oil was the most effective against adult and nymph ticks, achieving mortality rates of 86% and 97%, respectively, and led to the highest nonattachment rates when applied to skin. In conclusion, essential oils such as clove, eucalyptus, lavender, and mint oils present promising results for tick population control.

Sequences Related to Chimay Rhabdovirus Are Widely Distributed in Ixodes ricinus Ticks across England and Wales.

Ticks are the main arthropod vector of pathogens to humans and livestock in the British Isles. Despite their role as a vector of disease, many aspects of tick biology, ecology, and microbial association are poorly understood. To address this, we investigated the composition of the microbiome of adult and nymphal Ixodes ricinus ticks. The ticks were collected on a dairy farm in Southwest England and RNA extracted for whole genome sequencing. Sequences were detected from a range of microorganisms, particularly tick-associated viruses, bacteria, and nematodes. A majority of the viruses were attributed to phlebo-like and nairo-like virus groups, demonstrating a high degree of homology with the sequences present in I. ricinus from mainland Europe. A virus sharing a high sequence identity with Chimay rhabdovirus, previously identified in ticks from Belgium, was detected. Further investigations of I. ricinus ticks collected from additional sites in England and Wales also identified Chimay rhabdovirus viral RNA with varying prevalence in all tick populations. This suggests that Chimay rhabdovirus has a wide distribution and highlights the need for an extended exploration of the tick microbiome in the United Kingdom (UK).

Role of ixodid ticks in tick-borne pathogen spread and circulation in the Belarusian Lakeland

Results of ixodid tick analysis for their ecological, epizootological and epidemiological significance for tick-borne pathogen spread across the Belarusian Lakeland are presented. The ticks were collected in publicly accessible areas of the Vitebsk Raion in April – November 2022: 8 routes were tracked, 18 flag-km were passed, 529 tick specimens were collected, including 350 imago ticks and 179 nymph ticks. The ixodid tick genus and species were determined using N. A. Filippova’s ixodid tick determinator. All caught ticks were tested for Borrelia spp., Anaplasma spp. (Ehrlichia spp.), Babesia spp. and Tick-borne encephalitis virus genetic materials with real-time polymerase chain reaction using the reagent kit for nucleic acid extraction from environmental samples in accordance with the manufacturer’s instruc­tions. The specimens were grouped in accordance with the MG 3.1.1027-01 “Collection, recording and preparation for laboratory tests of blood-sucking arthropods being vectors of natural focal infections”; therewith, one specimen includes only one tick. Differences in the numbers of ixodid ticks and the occurrence of genetic markers of tick-borne pathogens in them were found to be associated with ecological characteristics of the examined territories. The following epidemically and epizootically significant ticks contributing to transmissible infection and invasion spread were found in the Belarusian Lakeland: ticks of Ixodes and Dermacentor genera; their frequency index was 70.1 and 29.9%, respectively. Tick-transmitted pathogen prevalence rate in the examined territories of the Vitebsk Raion was as follows: 61.7% for Borrelia spp., 25.8% for Anaplasma spp. (Ehrlichia spp.) and 25% for Babesia spp., mixed infections were found in 10.8% of the ticks. No tick-borne encephalitis virus genetic materials were found in the specimens. Total infection rate for ixodid ticks was 22.7%.

Co-feeding transmission leads to bi-stability of tick-borne disease spread dynamics

Considering that co-feeding transmission depends on the loads of infected ticks on each host, we develop a tick-borne disease dynamics model with co-feeding transmission probability peaking at an intermediate level of infected tick loads. We stratify tick and host population by their infection status and divide the vector population in terms of infection status and post-egg stages (larvae, nymphs and adults). We use the tick population dynamics and disease spread basic reproduction numbers and co-feeding transmission characteristics to describe the disease endemic structure, and show, for the first time, that density-dependent co-feeding transmission provides a novel mechanism for bi-stability. Numerical simulations based on parameters from laboratory and fields data confirm the possibility of bi-stability in biologically realistic settings, and sensitivity analyses show that the nymphal tick load value at which the co-feeding transmission probability reaches the maximum impacts most significantly on the stable endemic equilibrium value.

Tick bite-induced alpha-gal syndrome and immunologic responses in an alpha-gal deficient murine model.

Alpha-Gal Syndrome (AGS) is a delayed allergic reaction due to specific IgE antibodies targeting galactose-α-1,3-galactose (α-gal), a carbohydrate found in red meat. This condition has gained significant attention globally due to its increasing prevalence, with more than 450,000 cases estimated just in the United States alone. Previous research has established a connection between AGS and tick bites, which sensitize individuals to α-gal antigens and elevate the levels of specific IgE. However, the precise mechanism by which tick bites influence the host's immune system and contribute to the development of AGS remains poorly understood. This study investigates various factors related to ticks and the host associated with the development of AGS following a tick bite, using mice with a targeted disruption of alpha-1,3-galactosyltransferase (AGKO) as a model organism. Lone-star tick (Amblyomma americanum) and gulf-coast tick (Amblyomma maculatum) nymphs were used to sensitize AGKO mice, followed by pork meat challenge. Tick bite site biopsies from sensitized and non-sensitized mice were subjected to mRNA gene expression analysis to assess the host immune response. Antibody responses in sensitized mice were also determined. Our results showed a significant increase in the total IgE, IgG1, and α-gal IgG1 antibodies titers in the lone-star tick-sensitized AGKO mice compared to the gulf-coast tick-sensitized mice. Pork challenge in Am. americanum -sensitized mice led to a decline in body temperature after the meat challenge. Gene expression analysis revealed that Am. americanum bites direct mouse immunity toward Th2 and facilitate host sensitization to the α-gal antigen. This study supports the hypothesis that specific tick species may increase the risk of developing α-gal-specific IgE and hypersensitivity reactions or AGS, thereby providing opportunities for future research on the mechanistic role of tick and host-related factors in AGS development.

Density of host-seeking Ixodes scapularis nymphs by region, state, and county in the contiguous United States generated through national tick surveillance

The majority of vector-borne disease cases reported annually in the United States are caused by pathogens spread by the blacklegged tick, Ixodes scapularis. The number and geographic distribution of cases have increased as the geographic range and abundance of the tick have expanded in recent decades. A large proportion of Lyme disease and other I. scapularis-borne diseases are associated with nymphal tick bites; likelihood of such bites generally increases with increasing nymphal densities. National tick surveillance was initiated in 2018 to track changes in the distribution and abundance of medically important ticks at the county spatial scale throughout the United States. Tick surveillance records, including historical data collected prior to the initiation of the national program, are collated in the ArboNET Tick Module database. Through exploration of ArboNET Tick Module data, we found that efforts to quantify the density of host-seeking I. scapularis nymphs (DON) were unevenly distributed among geographic regions with the greatest proportion of counties sampled in the Northeast and Upper Midwest. Submissions covering tick collections from 2004 through 2022 revealed extensive variation in DON estimates at collection site, county, state, and regional spatial scales. Throughout the entire study period, county DON estimates ranged from 0.0 to 488.5 nymphs/1,000 m2 . Although substantial variation was recorded within regions, DON estimates were greatest in the Northeast, Upper Midwest, and northern states within the Southeast regions (Virginia and North Carolina); densities were intermediate in the Ohio Valley and very low in the South and Northern Rockies and Plains regions. The proportion of counties classified as moderate or high DON was lower in the Northeast, Ohio Valley, and Southeast regions during the 2004 through 2017 time period (prior to initiation of the national tick surveillance program) compared to 2018 through 2022; DON estimates remained similarly low between these time periods in the South and the Northern Rockies and Plains regions. Despite the limitations described herein, the ArboNET Tick Module provides useful data for tracking changes in acarological risk across multiple geographic scales and long periods of time.

Species identification of adult ixodid ticks by Raman spectroscopy of their feces

BackgroundTicks and tick-borne diseases pose significant challenges to cattle production, thus the species identification of ticks and knowledge on their presence, abundance, and dispersal are necessary for the development of effective control measures. The standard method of inspection for the presence of ticks is the visual and physical examination of restrained animals, but the limitations of human sight and touch can allow larval, nymphal, and unfed adult ticks to remain undetected due to their small size and site of attachment. However, Raman spectroscopy, an analytical tool widely used in agriculture and other sectors, shows promise for the identification of tick species in infested cattle. Raman spectroscopy is a non-invasive and efficient method that employs the interaction between molecules and light for the identification of the molecular constituents of specimens.MethodsRaman spectroscopy was employed to analyze the structure and composition of tick feces deposited on host skin and hair during blood-feeding. Feces of 12 species from a total of five genera and one subgenus of ixodid ticks were examined. Spectral data were subjected to partial least squares discriminant analysis, a machine-learning model. We also used Raman spectroscopy and the same analytical procedures to compare and evaluate feces of the horn fly Haematobia irritans after it fed on cattle.ResultsFive genera and one sub-genus at overall true prediction rates ranging from 92.3 to 100% were identified from the Raman spectroscopy data of the tick feces. At the species level, Dermacentor albipictus, Dermacentor andersoni and Dermacentor variabilis at overall true prediction rates of 100, 99.3 and 100%, respectively, were identified. There were distinct differences between horn fly and tick feces with respect to blood and guanine vibrational frequencies. The overall true prediction rate for the separation of tick and horn fly feces was 98%.ConclusionsOur findings highlight the utility of Raman spectroscopy for the reliable identification of tick species from their feces, and its potential application for the identification of ticks from infested cattle in the field.Graphical

Microbiome compositions of nymphal blacklegged ticks (Ixodes scapularis) infected and uninfected with Borrelia burgdorferi in Delaware

Microbiome compositions of nymphal blacklegged ticks (Ixodes scapularis) infected and uninfected with Borrelia burgdorferi in Delaware