Nymphal Ticks Research Articles

A Geographic Information System Approach to Map Tick Exposure Risk at a Scale for Public Health Intervention.

Tick-borne disease control and prevention have been largely ineffective compared to the control of other vector-borne diseases. Although control strategies exist, they are costly or ineffective at large spatial scales. We need tools to target these strategies to places of highest tick exposure risk. Here we present a geographic information system (GIS) method for mapping predicted tick exposure risk at a 200 m by 200 m resolution, appropriate for public health intervention. We followed the approach used to map tick habitat suitability over large areas. We used drag-cloth sampling to measure the density of nymphal blacklegged ticks (Ixodes scapularis, Say (Acari: Ixodidae)) at 24 sites in Addison and Rutland Counties, VT, United States. We used a GIS to average habitat, climatological, land-use/land-cover, and abiotic characteristics over 100 m, 400 m, 1,000 m, and 2,000 m buffers around each site to evaluate which characteristic at which buffer size best predicted density of nymphal ticks (DON). The relationships between predictor variables and DON were determined with random forest models. The 100 m buffer model performed best and explained 37.7% of the variation in DON, although was highly accurate at classifying sites as having below or above average DON. This model was applied to Addison County, VT, to predict tick exposure risk at a 200 m resolution. This GIS approach to map predicted DON over a small area with fine resolution, could be used to target public health campaigns and land management practices to reduce human exposure to ticks.

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

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. 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. 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. 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.

Isolation of Metarhizium guizhouense and Metarhizium robertsii Strains from Soil-Exposed Amblyomma americanum (Acarina: Ixodidae) from Northwest Arkansas, USA

The lone star tick, Amblyomma americanum (L.) (Acarina: Ixodidae), is the most abundant tick species found in Arkansas and is involved in the transmission of pathogens of medical and veterinary importance. When not feeding, most non-nidicolous tick species shelter in the soil and leaf litter where they may be exposed to and potentially infected with entomopathogenic fungi that reside naturally in the soil. Entomopathogenic fungi in the genus Metarhizium Sorokīn (Hypocreales: Clavicipitaceae) have shown promise as biological control agents of ticks. Here, the first study to isolate and identify Arkansas-derived isolates of Metarhizium from A. americanum ticks is presented. We exposed 320 ticks artificially to native soil from Savoy. Of these soil exposed ticks, 2.5% of adults and 1.5% of nymphs displayed signs of infection with Metarhizium. Of the infected Savoy adults, 3.3% were females and 1.7% were males. Similarly exposed ticks from West Fork resulted in only 2.4% of nymphal ticks being infected with this fungus. Eight isolates of Metarhizium were cultured from infected ticks exposed to soil from these locations. Four of these Metarhizium isolates (3 from Savoy and 1 from West Fork) were identified to species by sequencing of the ITS locus and the EF1-α genes. Three Savoy strains (P10N1, P10AF1, and P2AM1) had identical sequences and were identified as Metarhizium robertsii (Bischoff, Rehner & Humber) (Hypocreales: Clavicipitaceae). The strain from West Fork (P9N2) was identified as Metarhizium guizhouense (Chen & Guo) (Hypocreales: Clavicipitaceae). The ITS and the EF1-α sequences of the Savoy strains showed 100% similarity to M. robertsii strains ARSEF 2575 and ART 500, respectively. The ITS and EF1-α sequences of the West Fork strain showed 99% similarity to M. guizhouense strains ARSEF 977 and CBS 258.90, respectively. This study demonstrates that entomopathogenic fungi M. guizhouense and M. robertsii are pathogenic to and can be isolated from A. americanum. Furthermore, the EF1-α genetic marker was shown to be a very effective tool for distinguishing different species of Metarhizium from ticks when used in conjunction with ITS sequence data. Standardizing the use of ticks in soil exposure methods for isolating entomopathogenic fungi could be useful for obtaining isolates that are highly virulent to A. americanum. The isolation and identification of Metarhizium spp. from A. americanum in Arkansas indicates that further exploration of entomopathogenic fungi as biological agents to control A. americanum is warranted.

Transovarial Transmission of Borrelia hermsii by Its Tick Vector and Reservoir Host Ornithodoros hermsi.

Transovarial passage of relapsing fever spirochetes (Borrelia species) by infected female argasid ticks to their progeny is a widespread phenomenon. Yet this form of vertical inheritance has been considered rare for the North American tick Ornithodoros hermsi infected with Borrelia hermsii. A laboratory colony of O. hermsi was established from a single infected female and two infected males that produced a population of ticks with a high prevalence of transovarial transmission based on infection assays of single and pooled ticks feeding on mice and immunofluorescence microscopy of eggs and larvae. Thirty-eight of forty-five (84.4%) larval cohorts (groups of larvae originating from the same egg clutch) transmitted B. hermsii to mice over four and a half years, and one hundred and three single and one hundred and fifty-three pooled nymphal and adult ticks transmitted spirochetes during two hundred and fourteen of two hundred and fifty-six (83.6%) feedings on mice over seven and a half years. The perpetuation of B. hermsii for many years by infected ticks only (without acquisition of spirochetes from vertebrate hosts) demonstrates the reservoir competence of O. hermsi. B. hermsii produced the variable tick protein in eggs and unfed larvae infected by transovarial transmission, leading to speculation of the possible steps in the evolution of borreliae from a tick-borne symbiont to a tick-transmitted parasite of vertebrates.

'Candidatus Mycoplasma haematohydrochoerus', a novel hemoplasma species in capybaras (Hydrochoerus hydrochaeris) from Brazil.

Three different species of hemoplasmas have been described in rodents, Mycoplasma coccoides, 'Candidatus Mycoplasma haemomuris' and 'Candidatus Mycoplasma haemosphiggurus'. Additionally, potentially novel hemoplasma species have been detected in wild rodents from Brazil, including capybaras (Hydrochoerus hydrochaeris). Capybaras are the largest rodent in the world and are well adapted to live within close proximity to humans, which increases the risk to spread of zoonotic pathogens. Herein, we investigate the occurrence and genetic diversity of hemoplasmas infecting free-ranging capybaras from southern Brazil. Blood samples and ticks from 17 capybaras were collected. Packed cell volume and total plasma protein were measured, DNA was extracted, and further screened by species-specific and pan-hemoplasma PCR assays targeting the 16S rRNA gene of hemoplasmas. Sixteen out of 17 (94.12%; 95% CI: 73.02-98.95%) were anemic. Only one young female was hypoproteinemic. All capybaras were infested by adults and nymphs of Amblyomma dubitatum ticks. Using the PCR assay targeting the 16S rRNA gene of M. coccoides, 13/17 (76.47%; 95% CI: 52.74-90.44%) capybaras were positive for hemoplasmas. When DNA samples were tested by the pan-hemoplasma PCR, 16/17 (94.12%; 95% CI: 73.02-98.95%) animals were positive. One out of 11 (9.09%) adult ticks salivary glands tested positive for hemoplasma by the pan-hemoplasma PCR assay. Sequencing and phylogenetic analysis of the 16S and 23S rRNA gene fragments confirmed that animals were infected by a novel hemotropic Mycoplasma sp. previously reported in capybaras from Brazil. Additionally, sequencing and phylogenetic analysis of the 23S rRNA gene from three hemoplasma-positive capybaras samples from a previous study performed in midwestern Brazil also confirm our findings. Based on phylogenetic and Neighbor-Net network analysis of the 16S rRNA and 23S rRNA genes, the name 'Candidatus Mycoplasma haematohydrochoerus' is proposed for this novel organism.

Ixodes ricinus Salivary Serpin Iripin-8 Inhibits the Intrinsic Pathway of Coagulation and Complement.

Tick saliva is a rich source of antihemostatic, anti-inflammatory, and immunomodulatory molecules that actively help the tick to finish its blood meal. Moreover, these molecules facilitate the transmission of tick-borne pathogens. Here we present the functional and structural characterization of Iripin-8, a salivary serpin from the tick Ixodes ricinus, a European vector of tick-borne encephalitis and Lyme disease. Iripin-8 displayed blood-meal-induced mRNA expression that peaked in nymphs and the salivary glands of adult females. Iripin-8 inhibited multiple proteases involved in blood coagulation and blocked the intrinsic and common pathways of the coagulation cascade in vitro. Moreover, Iripin-8 inhibited erythrocyte lysis by complement, and Iripin-8 knockdown by RNA interference in tick nymphs delayed the feeding time. Finally, we resolved the crystal structure of Iripin-8 at 1.89 Å resolution to reveal an unusually long and rigid reactive center loop that is conserved in several tick species. The P1 Arg residue is held in place distant from the serpin body by a conserved poly-Pro element on the P′ side. Several PEG molecules bind to Iripin-8, including one in a deep cavity, perhaps indicating the presence of a small-molecule binding site. This is the first crystal structure of a tick serpin in the native state, and Iripin-8 is a tick serpin with a conserved reactive center loop that possesses antihemostatic activity that may mediate interference with host innate immunity.

Observation of Tick Parasitism on Scincella lateralis in Texas

Cases of Ixodes scapularis (Blacklegged Tick or Deer Tick) are known to infest a variety of lizard species including Scincella lateralis (Ground Skink). We report the finding of 1 Ground Skink with an attached immature tick, later identified as an engorged Blacklegged Tick nymph, in a population with a low rate of tick infestation. Of the 151 Ground Skinks we collected at the Piney Woods Environmental Laboratory, only 1 was parasitized by any tick species. We extracted whole-body tick DNA and tested for various bacterial pathogens, including Anaplasma phagocytophilum, Ehrlichia spp., Borrelia spp., and Rickettsia spp. PCR tests for these pathogens were negative except for Rickettsia spp. Within our sampling region of Walker County, TX, in the East Texas Piney Woods, we estimated the infestation prevalence of Blacklegged Ticks utilizing Ground Skinks as a host at 0.66%, much lower than previous estimations in Oklahoma.

The Tick Microbiota Dysbiosis Promote Tick-Borne Pathogen Transstadial Transmission in a Babesia microti-Infected Mouse Model.

Ticks are obligate hematophagous ectoparasites. They are important vectors for many pathogens, of both medical and veterinary importance. Antibiotic residues in animal food are known, but very little is known about the effects of antibiotic residues in animals on the microbiome diversity of ticks and tick-borne pathogen transmission. We used a Haemaphysalis longicornis–infested mouse model to evaluate the effect of antibiotic usage on tick microbiome. Nymphal ticks were fed on an antibiotic cocktail-treated or water control mice. Adult ticks molted from nymphs fed on the antibiotic cocktail-treated mouse had a dysbiosed microbiota. Nymphal ticks were also fed on a B. microti–infected mice that had been treated with antibiotic cocktail or water. We found that the B. microti infection in adult ticks with a dysbiosed microbiota (44.7%) was increased compared with the control adult ticks (24.2%) by using qPCR targeting 18S rRNA gene. This may increase the risk of tick-borne pathogens (TBPs) transmission from adult ticks to a vertebrate host. These results show that an antibiotic-treated mouse can induce tick microbiota dysbiosis. Antibiotic treatment of B. microti-infected mouse poses the possibility of increasing transstadial transmission of B. microti from the nymph to the adult H. longicornis. These findings suggest that B. microti transmission may be exacerbated in high antibiotic usage areas.

A Pilot Study on the Microbiome of Amblyomma hebraeum Tick Stages Infected and Non-Infected with Rickettsia africae.

Variation in tick microbiota may affect pathogen acquisition and transmission but for many vector species, including Amblyomma hebraeum, components and determinants of the microbiome are unidentified. This pilot study aimed to determine baseline microbial community within A. hebraeum nymphs infected- and non-infected with Rickettsia africae from the environment, and within adult ticks infected- and non-infected with R. africae collected from cattle sampled from two locations in the Eastern Cape province of South Africa. Adult A. hebraeum ticks (N = 13) and A. hebraeum nymph (N = 15) preliminary screened for R. africae were randomly selected and subjected to Illumina sequencing targeting the v3–v4 hypervariable regions of the 16S rRNA gene. No significant difference in microbial community composition, as well as rarefied OTU richness and diversity were detected between adults and nymphs. Nymphs showed a higher richness of bacterial taxa indicating blood-feeding could have resulted in loss of microbial diversity during the moulting stage from nymph to adult. Core OTUs that were in at least 50% of nymphs and adults negative and positive for Rickettsia at 1% minimum relative abundance were Rickettsia, Coxiella and Ruminococcaceae UCG-005 with a single genus Arsenophonus occurring only in nymphs negative for Rickettsia. Ehrlichia spp. was present in only four nymphal ticks positive for Rickettsia. Interestingly, Rickettsia aeschlimannii was found in one nymph and one adult, indicating the first ever detection of the species in A. hebraeum. Furthermore, A. hebraeum harboured a Coxiella-like endosymbiont, which should be investigated further as Coxiella may affect the viability and transmission of other organisms.

A transwell assay method to evaluate Borrelia burgdorferi sensu stricto migratory chemoattraction toward tick saliva proteins

We developed a transwell assay to quantify migration of the Lyme disease agent, Borrelia burgdorferi sensu stricto (s.s.), toward Ixodes scapularis salivary gland proteins. The assay was designed to assess B. burgdorferi s.s. migration upward against gravity through a transwell polycarbonate membrane overlaid with 6% gelatin. Borreliae that channeled into the upper transwell chamber in response to test proteins were enumerated by flow cytometry. The transwell assay measured chemoattractant activity for B. burgdorferi s.s. from salivary gland extract (SGE) harvested from nymphal ticks during bloodmeal engorgement on mice 42 h post-attachment and saliva collected from adult ticks. Additionally, SGE protein fractions separated by size exclusion chromatography demonstrated various levels of chemoattractant activity in the transwell assay. Sialostatin L, and Salp-like proteins 9 and 11 were identified by mass spectrometry in SGE fractions that exhibited elevated activity. Recombinant forms of these proteins were tested in the transwell assay and showed positive chemoattractant properties compared to controls and another tick protein, S15A. These results were reproducible providing evidence that the transwell assay is a useful method for continuing investigations to find tick saliva components instrumental in driving B. burgdorferi s.s. chemotaxis.

A multi-seasonal study investigating the phenology, host and habitat associations, and pathogens of Haemaphysalis longicornis in Virginia, U.S.A

Understanding the abiotic and biotic variables affecting tick populations is essential for studying the biology and health risks associated with vector species. We conducted a study on the phenology of exotic Haemaphysalis longicornis (Asian longhorned tick) at a site in Albemarle County, Virginia, United States. We also assessed the importance of wildlife hosts, habitats, and microclimate variables such as temperature, relative humidity, and wind speed on this exotic tick's presence and abundance. In addition, we determined the prevalence of infection with selected tick-borne pathogens in host-seeking H. longicornis. We determined that the seasonal activity of H. longicornis in Virginia was slightly different from previous studies in the northeastern United States. We observed nymphal ticks persist year-round but were most active in the spring, followed by a peak in adult activity in the summer and larval activity in the fall. We also observed a lower probability of collecting host-seeking H. longicornis in field habitats and the summer months. In addition, we detected H. longicornis on several wildlife hosts, including coyote (Canis latrans), eastern cottontail (Sylvilagus floridanus), raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), white-tailed deer (Odocoileus virginianus), woodchuck (Marmota monax), and a Peromyscus sp. mouse. This latter record is the first detection of a larval H. longicornis on a North American rodent host important to the enzootic maintenance of tick-borne pathogens of humans and animals. Finally, we continued to detect the exotic piroplasm parasite, Theileria orientalis Ikeda, in H. longicornis as well as other pathogens, including Rickettsia felis, Anaplasma phagocytophilum (AP-1), and a Hepatozoon sp. previously characterized in Amblyomma americanum. These represent some of the first detections of arthropod-borne pathogens native to the United States in host-seeking H. longicornis. These data increase our understanding of H. longicornis biology in the United States and provide valuable information into the future health risks associated with this tick and pathogens.

Ticks on the turf: investigating the presence of ixodid ticks on and around football fields in Germany

Ixodes ricinus is the most abundant tick species and an important vector of pathogens in Germany and in large parts of Europe. A few other ixodid tick species, e.g., Dermacentor reticulatus, may also be of eco-epidemiological relevance. As ticks are not only found in natural but also in suburban areas (parks, gardens), the present study investigated whether ticks occur on and near football grounds thus posing a potential risk to players and visitors. Thirty-two football grounds from all 16 German federal states were selected, mainly situated adjacent to a green area (forest, park). Ticks were collected by the conventional flagging method in spring 2018, and nymphs and adults were counted and morphologically determined. Altogether 807 nymphal and adult ticks were collected from 29 football grounds: 714 I. ricinus, 64 Ixodes inopinatus, 2 Ixodes frontalis, 24 Ixodes sp. ticks, and 3 D. reticulatus. Ixodes inopinatus was found in 13 out of 16 German states. Three ticks were even found on the turf of two football fields. It can be concluded that ticks occur quite frequently and sometimes in high abundance near football grounds situated close or adjacent to a forest or a park.

Lake Michigan insights from island studies: the roles of chipmunks and coyotes in maintaining Ixodes scapularis and Borrelia burgdorferi in the absence of white-tailed deer

Deer management (e.g., reduction) has been proposed as a tool to reduce the acarological risk of Lyme disease. There have been few opportunities to investigate Ixodes scapularis (blacklegged tick) and Borrelia burgdorferi sensu stricto dynamics in the absence of white-tailed deer (Odocoileus virginianus) in midwestern North America. A pair of islands in Lake Michigan presented a unique opportunity to study the role of alternative hosts for the adult stage of the blacklegged tick for maintaining a tick population as a deer herd exists on North Manitou Island but not on South Manitou Island, where coyotes (Canis latrans) and hares (Lepus americanus) are the dominant medium mammals. Additionally, we were able to investigate the maintenance of I. scapularis and B. burgdorferi in small mammal communities on both islands, which were dominated by eastern chipmunks (Tamias striatus). From 2011 to 2015, we surveyed both islands for blacklegged ticks by drag cloth sampling, bird mist netting, and small and medium-sized mammal trapping. We assayed questing ticks, on-host ticks, and mammal biopsies for the Lyme disease pathogen, B. burgdorferi. We detected all three life stages of the blacklegged tick on both islands. Of the medium mammals sampled, no snowshoe hares (Lepus americanus, 0/23) were parasitized by adult blacklegged ticks, but 2/2 coyotes (Canis latrans) sampled on South Manitou Island in 2014 were parasitized by adult blacklegged ticks, suggesting that coyotes played a role in maintaining the tick population in the absence of deer. We also detected I. scapularis ticks on passerine birds from both islands, providing support that birds contribute to maintaining as well as introducing blacklegged ticks and B. burgdorferi to the islands. We observed higher questing adult and nymphal tick densities, and higher B. burgdorferi infection prevalence in small mammals and in adult ticks on the island with deer as compared to the deer-free island. On the islands, we also found that 25% more chipmunks were tick-infested than mice, fed more larvae and nymphs relative to their proportional abundance compared to mice, and thus may play a larger role compared to mice in the maintenance of B. burgdorferi. Our investigation demonstrated that alternative hosts could maintain a local population of blacklegged ticks and an enzootic cycle of the Lyme disease bacterium in the absence of white-tailed deer. Thus, alternative adult blacklegged tick hosts should be considered when investigating deer-targeted management tools for reducing tick-borne disease risk, especially when the alternative host community may be abundant and diverse.

Prevention of Lyme and other tickborne diseases using a rodent-targeted approach: A randomized controlled trial in Connecticut.

Tickborne diseases are an increasing public health problem in the northeastern USA. Bait boxes that apply acaricide to rodents have been shown in small field studies to significantly reduce abundance of Ixodes scapularis ticks as well as their pathogen infection rates in treated areas. The effectiveness of this intervention for preventing human tickborne diseases (TBDs) has not been demonstrated. During 2012-2016, TickNET collaborators conducted a randomized, blinded, placebo-controlled trial among 622 Connecticut households. Each household received active (containing fipronil wick) or placebo (empty) bait boxes in their yards over two consecutive years. Information on tick encounters and TBDs among household members was collected through biannual surveys. Nymphal ticks were collected from a subset of 100 properties during spring at baseline, during treatment, and in the year post-intervention. Demographic and property characteristics did not differ between treatment groups. There were no significant differences post-intervention between treatment groups with respect to tick density or pathogen infection rates, nor for tick encounters or TBDs among household members. We found no evidence that rodent-targeted bait boxes disrupt pathogen transmission cycles or significantly reduce household risk of tick exposure or TBDs. The effectiveness of this intervention may depend on scale of use or local enzootic cycles.

Repellency of Veratraldehyde (3,4-Dimethoxy Benzaldehyde) against Mosquito Females and Tick Nymphs

Arthropod-borne infectious diseases cause many deaths and a major economic burden worldwide. Repellents play an important role in protecting people from infectious biting arthropods. The repellency of veratraldehyde, a known food additive, and the WJ-1041 formulation containing 10% veratraldehyde was tested against Aedes albopictus and Culex pipiens pallens females and Haemaphysalis longicornis nymphs using arm-in-cage, indoor or filter paper tests. Veratraldehyde exhibited repellency similar to or lower than that of n,n-diethyl-meta-toluamide (DEET) against A. albopictus, but in H. longicornis, the activity of veratraldehyde was better than that of DEET. The repellency of the 10% veratraldehyde solution was comparable to that of 20% DEET against the two mosquitoes. When comparing repellency between the WJ-1041 formulation (10% veratraldehyde) and 10% DEET against C. pipiens pallens, A. Albopictus and H. longicornis, the two showed similar repellency and complete protection time (CPT) values. However, there was a small difference depending on the tested insects. The absorption of veratraldehyde via skin was minimal, if at all. The pharmacokinetic parameters (Cmax and Tmax) of veratraldehyde in blood samples of rats were not different from those of the control group. Based on these results, veratraldehyde has high potential to be commercialized as a repellent agent against infectious disease-borne pests in the near future.

Migration and season explain tick prevalence in Brazilian birds.

Neotropical birds are mostly parasitized by immature ticks and act as reservoir hosts of tick-borne pathogens of medical and veterinary interest. Hence, determining the factors that enable ticks to encounter these highly mobile hosts and increase the potential for tick dispersal throughout migratory flyways are important for understanding tick-borne disease transmission. We used 9682 individual birds from 572 species surveyed across Brazil and Bayesian models to disentangle possible avian host traits and climatic drivers of infestation probabilities, accounting for avian host phylogenetic relationships and spatiotemporal factors that may influence tick prevalence. Our models revealed that the probability of an individual bird being infested with tick larvae and nymphs was lower in partial migrant hosts and during the wet season. Notably, infestation probability increased in areas with a higher proportion of partial migrant birds. Other avian ecological traits known to influence tick prevalence (foraging habitat and body mass) and environmental condition that might constrain tick abundance (annual precipitation and minimum temperature) did not explain infestation probability. Our findings suggest that migratory flyways harbouring a greater abundance of migrant bird hosts also harbour a higher prevalence of immature ticks with potential to enhance the local transmission of tick-borne pathogens and spread across regions.

Interactive Gene Expression Between Metarhizium anisopliae JEF-290 and Longhorned Tick Haemaphysalis longicornis at Early Stage of Infection.

The longhorned tick, Haemaphysalis longicornis (Acari: Ixodidae), is a hard tick and a vector for severe fever with thrombocytopenia syndrome (SFTS) virus. The number of patients infected with SFTS is rapidly increasing. Recently, the invertebrate pathogen Metarhizium anisopliae JEF-290 was reported to be useful to control the tick as an alternative to chemical acaricides, which are not easily applicable in human living areas where the tick is widely spread. In this study, we analyzed how the tick and the fungal pathogen interact at the transcriptional level. Field-collected tick nymphs were treated with JEF-290 conidia at 1 × 108 conidia/ml. In the early stage of infection with 2.5% mortality, the infected ticks were subjected to RNA sequencing, and non-infected ticks and fungal masses served as controls. Fungus and tick genes were mostly up-regulated at the early stage of infection. In the gene set enrichment analysis of the infecting fungus, catabolic processes that included lipids, phospholipids, and detoxification processes, the response to oxidative stress, and toxic substances were significantly up-regulated. In this fungal up-regulation, various lipase, antioxidant enzyme, and hydrolase genes were highly transcribed. The gene set enrichment analysis of the infected tick showed that many peptide synthesis processes including translation, peptide metabolism, ribonucleotide metabolism, and energy production processes that included ATP generation and ADP metabolism were significantly up-regulated. Structurally, mitochondria and ribosome subunit genes in ticks were highly transcribed to upregulate these processes. Together these results indicate that JEF-290 initiates process that infects the tick while the tick actively defends against the fungal attack. This work provides background to improve our understanding of the early stage of fungal infection in longhorned tick.

Higher probability of tick infestation reveals a hidden cost of army ant‐following in Amazonian birds

The foraging specialization of army ant‐following birds has long intrigued ecologists and provided numerous questions such as why, how and when did this foraging guild specialization arise and evolve. Many of the answers to these questions have focused on ecological interactions such as predation and competition, whereas little has been done to study the potential effects of host–parasite interactions among members of this foraging guild. Using 1177 Amazonian birds from 187 species, we studied the probability of tick infestation in relation to attendance of birds at army ant swarms. We demonstrate that the probability of tick infestation was higher among professional and occasional ant‐followers than in bird species that do not follow army ants to prey upon leaf‐litter flushed arthropods. Moreover, occasional ant‐followers harbored a greater diversity of nymphal ticks. We argue that although the evolutionary transition toward specialized ant‐following behavior has a genetic basis, a trade‐off between the cost of evolution of this trait and its fitness benefits might exist. In this case, the cost is in the form of higher parasite pressure. Therefore, parasites may impose a selective pressure not only during foraging but also through the allocation of resources for an immunological response. Our results of an analysis of tick parasitism on Amazonian birds emphasizes the importance of parasitic organisms on ecology and evolution of behavioural traits of their hosts. Considering the effects imposed by parasite pressure is essential for understanding the evolution and maintenance of behavioral and life‐history traits.

Real-time PCR biochip for on-site detection of Coxiella burnetii in ticks

BackgroundQ fever, a zoonosis caused by Coxiella burnetii, has adverse effects on public health. Ticks are vectors of C. burnetii and they contribute to the transmission of the pathogen. A tool for rapid, sensitive, and accurate detection of C. burnetii from ticks is important for the prevention of Q fever.MethodsUltra-rapid real-time PCR (UR-qPCR) as a chip-based real-time PCR system was developed for the detection of C. burnetii from ticks. The UR-qPCR system was established and evaluated for the rapidity, sensitivity, and specificity of C. burnetii detection.ResultsC. burnetii was detected using UR-qPCR from 5644 larval, nymphal, and adult ticks from 408 pools collected from livestock and epidemiologically linked environments in two provinces, Gangwon and Jeju, in Korea. Ticks from three species were identified; Haemaphysalis longicornis accounted for the highest number, present in 333 of 408 pools (81.62%), followed by Haemaphysalis flava in 62 pools (15.19%) and Ixodes nipponensis in 13 pools (3.19%). The rapidity and sensitivity of PCR detection was demonstrated with the sufficient amplification and detection of approximately 56 copies of C. burnetii DNA with only 20 min of PCR amplification. The kappa value for the diagnostic agreement between UR-qPCR and stationary qPCR was in perfect agreement (κ = 1). PCR detection and sequencing indicated that C. burnetii was present in 5 of the 408 pools (1.23%), in which four pools contained H. longicornis and one pool contained H. flava. The infection rates of C. burnetii in the tick pools collected from Gangwon and Jeju Provinces were 1.70% and 0.58%, respectively. Phylogenetic analysis indicated a close relationship between the detected C. burnetii and those originating from goats, humans, and ticks in different countries, such as the USA, France, Germany, and Serbia.ConclusionsThe methods described in this study could be important for the prevention and control of Q fever in the two provinces. The UR-qPCR, with its features of mobility, sensitivity, and rapidity, is helpful for constructing early alert systems in the field for C. burnetii in ticks and could help alleviate the transmission of and economic damage due to Q fever.Graphical

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.