Phenology of five tick species in the central Great Plains.

The states of Kansas and Oklahoma, in the central Great Plains, lie at the western periphery of the geographic distributions of several tick species. As the focus of most research on ticks and tick-borne diseases has been on Lyme disease which commonly occurs in areas to the north and east, the ticks of this region have seen little research attention. Here, we report on the phenology and activity patterns shown by tick species observed at 10 sites across the two states and explore factors associated with abundance of all and life specific individuals of the dominant species. Ticks were collected in 2020-2022 using dragging, flagging and carbon-dioxide trapping techniques, designed to detect questing ticks. The dominant species was A. americanum (24098, 97%) followed by Dermacentor variabilis (370, 2%), D. albipictus (271, 1%), Ixodes scapularis (91, <1%) and A. maculatum (38, <1%). Amblyomma americanum, A. maculatum and D. variabilis were active in Spring and Summer, while D. albipictus and I. scapularis were active in Fall and Winter. Factors associated with numbers of individuals of A. americanum included day of year, habitat, and latitude. Similar associations were observed when abundance was examined by life-stage. Overall, the picture is one of broadly distributed tick species that shows seasonal limitations in the timing of their questing activity.

Analysis of gaps in feline ectoparasiticide purchases from veterinary clinics in the United States.

BACKGROUND: The study objective was to examine cat owner ectoparasiticide purchases in the United States and estimate the impact of purchase gaps on timely ectoparasite protection administration. These purchase gaps lead to periods of time when cats are unprotected from ectoparasites. METHODS: Ectoparasiticide purchase transactions for individual cats from 671 U.S. veterinary clinics from January 1, 2017 through June 30, 2019 were evaluated to determine time "gaps" between doses of ectoparasiticides purchased in a defined 12-month period. Ectoparasiticides examined were topically applied products that contained fluralaner, fipronil/(S)-methoprene/pyriproxyfen, imidacloprid/pyriproxyfen or selamectin as active ingredients. The duration of protection following administration of one dose was 8-12 weeks for the fluralaner-containing product and one month for the other products. RESULTS: Ectoparasiticide purchase records were obtained from 114,853 cat owners and analysis found that most owners bought ≤ 6 months of protection during the year, with 61-75% (depending on the product) purchasing just 1-3 months of protection. The size of the average purchase gap was determined for all dose combinations out to 12 months of protection (5-7 doses for fluralaner and 12 doses for the other three products dosed monthly. The largest gaps occurred between the first and second doses and the second and third doses. Average purchase gaps for the four different products between doses 1 and 2 ranged from 11.2 to 13.9 weeks and between doses 2 and 3 ranged from 7.7 to 12.2 weeks. The fraction of purchases separated by gaps and the average length of the gap tended to decrease with increasing number of doses purchased. Owners purchasing the 8 to 12-week duration product containing fluralaner provided ectoparasite protection ("doses plus gap period") for a larger proportion of each 2-dose period compared with owners purchasing products administered monthly. CONCLUSIONS: When cat owners purchase flea and tick medication, gaps between subsequent purchases reduces the proportion of time ectoparasite protection can be provided. The duration of the gap between doses has an impact on the effectiveness of flea/tick medication because it inserts a period without flea and tick protection between doses of flea and tick medication. The gaps between purchases were shorter and the period of ectoparasite protection was larger for owners purchasing a 12-week product than for owners purchasing a monthly product.

Molecular detection of Rickettsia raoultii, Rickettsia tamurae, and associated pathogens from ticks parasitizing water deer (Hydropotes inermis argyropus) in South Korea.

Most defined Rickettsiales, which can be transmitted by ticks, are known to be important zoonotic pathogens. Some of these pathogens can cause severe diseases in humans, including anaplasmosis, rickettsioses, and ehrlichiosis. Previous studies in South Korea have investigated tick-borne pathogens (TBPs) residing in ticks found on grassy vegetation and animals. However, there is limited phylogenetic information on TBPs in ticks parasitizing Korean water deer (KWD; Hydropotes inermis argyropus). This study evaluated the prevalence, risk factors (regions, tick stages, and tick species), and coinfections of TBPs in ticks parasitizing KWD. Were collected a total of 283 hard ticks, including Haemaphysalis longicornis, Haemaphysalis flava, and Ixodes nipponensis from KWD in South Korea from 2013 to 2017. In 173 tested tick pools, genes for seven TBPs, namely Rickettsia raoultii (20 %), Rickettsia tamurae (1 %), Candidatus Rickettsia longicornii (31 %), Ehrlichia canis (3 %), Anaplasma capra (3 %), Anaplasma bovis (2 %), and Anaplasma sp. (1 %), were detected. The unidentified Anaplasma sp. isolates revealed a 98.4 %-99.3 % sequence identity with Anaplasma sp. in GenBank sequences obtained from ticks. To the best of our knowledge, this is the first study to report the presence of the emerging human pathogen R. tamurae in South Korea. These results should increase awareness about the need for continued development of epidemiological control measures, and medical and veterinary communities must be informed of their high infection potential and clinical complexity in humans.

Mapping ticks and tick-borne pathogens in China.

Understanding ecological niches of major tick species and prevalent tick-borne pathogens is crucial for efficient surveillance and control of tick-borne diseases. Here we provide an up-to-date review on the spatial distributions of ticks and tick-borne pathogens in China. We map at the county level 124 tick species, 103 tick-borne agents, and human cases infected with 29 species (subspecies) of tick-borne pathogens that were reported in China during 1950-2018. Haemaphysalis longicornis is found to harbor the highest variety of tick-borne agents, followed by Ixodes persulcatus, Dermacentor nutalli and Rhipicephalus microplus. Using a machine learning algorithm, we assess ecoclimatic and socioenvironmental drivers for the distributions of 19 predominant vector ticks and two tick-borne pathogens associated with the highest disease burden. The model-predicted suitable habitats for the 19 tick species are 14‒476% larger in size than the geographic areas where these species were detected, indicating severe under-detection. Tick species harboring pathogens of imminent threats to public health should be prioritized for more active field surveillance.

Tick Microbiomes in Neotropical Forest Fragments Are Best Explained by Tick-Associated and Environmental Factors Rather than Host Blood Source.

The composition of tick microbiomes varies both within and among tick species. Whether this variation is intrinsic (related to tick characteristics) or extrinsic (related to vertebrate host and habitat) is poorly understood but important, as microbiota can influence the reproductive success and vector competence of ticks. We aimed to uncover what intrinsic and extrinsic factors best explain the microbial composition and taxon richness of 11 species of neotropical ticks collected from eight species of small mammals in 18 forest fragments across central Panama. Microbial richness varied among tick species, life stages, and collection sites but was not related to host blood source. Microbiome composition was best explained by tick life stage, with bacterial assemblages of larvae being a subset of those of nymphs. Collection site explained most of the bacterial taxa with differential abundance across intrinsic and extrinsic factors. Francisella and Rickettsia were highly prevalent, but their proportional abundance differed greatly among tick species, and we found both positive and negative cooccurrence between members of these two genera. Other tick endosymbionts (e.g., Coxiella and Rickettsiella) were associated with specific tick species. In addition, we detected Anaplasma and Bartonella in several tick species. Our results indicate that the microbial composition and richness of neotropical ticks are principally related to intrinsic factors (tick species and life stage) and collection site. Taken together, our analysis informs how tick microbiomes are structured and can help anchor our understanding of tick microbiomes from tropical environments more broadly.IMPORTANCE Blood-feeding arthropod microbiomes often play important roles in disease transmission, yet the factors that structure tick microbial communities in the Neotropics are unknown. Utilizing ticks collected from live animals in neotropical forest fragments, this study teases apart the contributions of intrinsic and extrinsic tick-associated factors on tick microbial composition as well as which specific microbes contribute to differences across tick species, tick life stages, the mammals they fed on, and the locations from where they were sampled. Furthermore, this study provides revelations of how notable tick-associated bacterial genera are interacting with other tick-associated microbes as well as the forest animals they encounter.

Interactions Between Ticks and Lyme Disease Spirochetes.

Borrelia burgdorferi sensu lato causes Lyme borreliosis in a variety of animals and humans. These atypical bacterial pathogens are maintained in a complex enzootic life cycle that primarily involves a vertebrate host and Ixodes spp. ticks. In the Northeastern United States, I. scapularis is the main vector, while wild rodents serve as the mammalian reservoir host. As B. burgdorferi is transmitted only by I. scapularis and closely related ticks, the spirochete-tick interactions are thought to be highly specific. Various borrelial and arthropod proteins that directly or indirectly contribute to the natural cycle of B. burgdorferi infection have been identified. Discrete molecular interactions between spirochetes and tick components also have been discovered, which often play critical roles in pathogen persistence and transmission by the arthropod vector. This review will focus on the past discoveries and future challenges that are relevant to our understanding of the molecular interactions between B. burgdorferi and Ixodes ticks. This information will not only impact scientific advancements in the research of tick- transmitted infections but will also contribute to the development of novel preventive measures that interfere with the B. burgdorferi life cycle.

Records of ticks (Acari: Ixodidae) on humans and distribution of spotted-fever cases and its tick vectors in Paraná State, southern Brazil.

Brazilian spotted fever (BSF) is the deadliest rickettsiosis in the world. Although the epidemiology of the disease has been established in Brazil, there are still limited data available on distribution of tick vectors and tick species parasitizing humans in the country, particularly in Paraná State. The State of Paraná is located in the southern region of the country and is covered by two biomes: Atlantic rainforest and Cerrado. Thus, the aims of this study were i) to map the distribution of SF tick vectors, ii) to describe and map the distribution of human parasitism by ticks, and iii) to map the distribution of fatal and non-fatal spotted fever (SF) cases in Paraná State, southern Brazil. Data were reviewed and compiled from previous published reports, and also from two scientific collections of Paraná State. SF cases were retrieved from the Brazilian Notifiable Diseases Information System. A total of 50 cases of human parasitism by ticks were recorded, with a total of 64 (22 males, 12 females, 30 nymphs) ticks collected. The following 12 tick species were identified: Amblyomma aureolatum, Amblyomma brasiliense, Amblyomma calcaratum, Amblyomma dubitatum, Amblyomma incisum, Amblyomma longirostre, Amblyomma ovale, Amblyomma parkeri, Amblyomma scalpturatum, Amblyomma sculptum, Haemaphysalis juxtakochi and Rhipicephalus sanguineus sensu lato (s.l.). The most prevalent tick species associated to cases of human parasitism were A. sculptum (13/50; 26 %), A. aureolatum (10/50; 20 %), A. brasiliense (5/50; 10 %), A. ovale (5/50; 10 %) and A. parkeri (4/50; 8%). A total of 51 non-fatal and five fatal SF cases were recorded. Data from this study highlights the need for monitoring ticks parasitizing humans aiming early detection of tick-borne diseases cases, particularly BSF in Paraná State, southern Brazil.

Karyotype changes in long-term cultured tick cell lines.

Tick cell lines are an easy-to-handle system for the study of viral and bacterial infections and other aspects of tick cellular processes. Tick cell cultures are often continuously cultivated, as freezing can affect their viability. However, the long-term cultivation of tick cells can influence their genome stability. In the present study, we investigated karyotype and genome size of tick cell lines. Though 16S rDNA sequencing showed the similarity between Ixodes spp. cell lines at different passages, their karyotypes differed from 2n = 28 chromosomes for parental Ixodes spp. ticks, and both increase and decrease in chromosome numbers were observed. For example, the highly passaged Ixodes scapularis cell line ISE18 and Ixodes ricinus cell lines IRE/CTVM19 and IRE/CTVM20 had modal chromosome numbers 48, 23 and 48, respectively. Also, the Ornithodoros moubata cell line OME/CTVM22 had the modal chromosome number 33 instead of 2n = 20 chromosomes for Ornithodoros spp. ticks. All studied tick cell lines had a larger genome size in comparison to the genomes of the parental ticks. Thus, highly passaged tick cell lines can be used for research purposes, but possible differences in encoded genetic information and downstream cellular processes, between different cell populations, should be taken into account.

RNA virome analysis of questing ticks from Hokuriku District, Japan, and the evolutionary dynamics of tick-borne phleboviruses.

Tick-borne viruses have emerged recently in many parts of the world, and the discoveries of novel tick-borne viruses have been accelerated by the development of high-throughput sequencing technology. In this study, a cost-efficient small benchtop next-generation sequencer, the Illumina MiniSeq, was used for the RNA virome analysis of questing ticks collected from Hokuriku District, Japan, and assessed for their potential utility in a tick-borne virus surveillance system. We detected two phleboviruses [Kabuto Mountain virus (KAMV) and Okutama tick virus (OKTV)], a coltivirus [Tarumizu tick virus (TarTV)], and a novel iflavirus [Hamaphysalis flava iflavirus (HfIFV)] from tick homogenates and/or cell culture supernatants after virus isolation processes. The number of sequence reads from KAMV and TarTV markedly increased when cell culture supernatants were used, indicating a successful isolation of these viruses. In contrast, OKTV and HfIFV were detected only in tick homogenates but not from cell culture supernatants, suggesting a failure to isolate these viruses. Furthermore, we performed genomic and phylogenetic analyzes of these detected viruses. OKTV and some phleboviruses discovered recently by NGS-based methods were probably deficient in the M genome segment, which are herein proposed as M segment-deficient phlebovirus (MdPV). A phylogenetic analysis of phleboviruses, including MdPV, suggested that Uukuniemi and Kaisodi group viruses and kabutoviruses evolved from an ancestral MdPV, which provides insights into the evolutionary dynamics of phleboviruses as emerging pathogens.

The scale affects our view on the identification and distribution of microbial communities in ticks.

Ticks transmit the highest variety of pathogens impacting human and animal health worldwide. It is now well established that ticks also harbour a microbial complex of coexisting symbionts, commensals and pathogens. With the development of high throughput sequencing technologies, studies dealing with such diverse bacterial composition in tick considerably increased in the past years and revealed an unexpected microbial diversity. These data on diversity and composition of the tick microbes are increasingly available, giving crucial details on microbial communities in ticks and improving our knowledge on the tick microbial community. However, consensus is currently lacking as to which scales (tick organs, individual specimens or species, communities of ticks, populations adapted to particular environmental conditions, spatial and temporal scales) best facilitate characterizing microbial community composition of ticks and understanding the diverse relationships among tick-borne bacteria. Temporal or spatial scales have a clear influence on how we conduct ecological studies, interpret results, and understand interactions between organisms that build the microbiome. We consider that patterns apparent at one scale can collapse into noise when viewed from other scales, indicating that processes shaping tick microbiome have a continuum of variability that has not yet been captured. Based on available reports, this review demonstrates how much the concept of scale is crucial to be considered in tick microbial community studies to improve our knowledge on tick microbe ecology and pathogen/microbiota interactions.

Modelling tick bite risk by combining random forests and count data regression models.

The socio-economic and demographic changes that occurred over the past 50 years have dramatically expanded urban areas around the globe, thus bringing urban settlers in closer contact with nature. Ticks have trespassed the limits of forests and grasslands to start inhabiting green spaces within metropolitan areas. Hence, the transmission of pathogens causing tick-borne diseases is an important threat to public health. Using volunteered tick bite reports collected by two Dutch initiatives, here we present a method to model tick bite risk using human exposure and tick hazard predictors. Our method represents a step forward in risk modelling, since we combine a well-known ensemble learning method, Random Forest, with four count data models of the (zero-inflated) Poisson family. This combination allows us to better model the disproportions inherent in the volunteered tick bite reports. Unlike canonical machine learning models, our method can capture the overdispersion or zero-inflation inherent in data, thus yielding tick bite risk predictions that resemble the original signal captured by volunteers. Mapping model predictions enables a visual inspection of the spatial patterns of tick bite risk in the Netherlands. The Veluwe national park and the Utrechtse Heuvelrug forest, which are large forest-urban interfaces with several cities, are areas with high tick bite risk. This is expected, since these are popular places for recreation and tick activity is high in forests. However, our model can also predict high risk in less-intensively visited recreational areas, such as the patchy forests in the northeast of the country, the natural areas along the coastline, or some of the Frisian Islands. Our model could help public health specialists to design mitigation strategies for tick-borne diseases, and to target risky areas with awareness and prevention campaigns.

A comprehensive survey of the prevalence and spatial distribution of ticks infesting cattle in different agro-ecological zones of Cameroon.

BACKGROUND: Ticks and tick-borne diseases are a major impediment to livestock production worldwide. Cattle trade and transnational transhumance create risks for the spread of ticks and tick-borne diseases and threaten cattle production in the absence of an effective tick control program. Few studies have been undertaken on cattle ticks in the Central African region; therefore, the need to assess the occurrence and the spatial distribution of tick vectors with the aim of establishing a baseline for monitoring future spread of tick borne-diseases in the region is urgent. RESULTS: A total of 7091 ixodid ticks were collected during a countrywide cross-sectional field survey and identified using morphological criteria. Of these, 4210 (59.4%) ticks were Amblyomma variegatum, 1112 (15.6%) Rhipicephalus (Boophilus) microplus, 708 (10.0%) Rhipicephalus (Boophilus) decoloratus, 28 (0.4%) Rhipicephalus (Boophilus) annulatus, 210 (3.0%) Hyalomma rufipes, 768 (10.8%) Hyalomma truncatum, and 19 (0.3%) Rhipicephalus sanguineus. Three ticks of the genus Hyalomma spp. and 33 of the genus Rhipicephalus spp. were not identified to the species level. Cytochrome c oxidase subunit 1 (cox1) gene sequencing supported the data from morphological examination and led to identification of three additional species, namely Hyalomma dromedarii, Rhipicephalus sulcatus and Rhipicephalus pusillus. The finding of the invasive tick species R. microplus in such large numbers and the apparent displacement of the indigenous R. decoloratus is highly significant since R. microplus is a highly efficient vector of Babesia bovis. CONCLUSIONS: This study reports the occurrence and current geographical distribution of important tick vectors associated with cattle in Cameroon. It appears that R. microplus is now well established and may be displacing native Rhipicephalus (Boophilus) species, such as R. decoloratus. This calls for an urgent response to safeguard the livestock sector in western central Africa.

Genome-wide screen identifies novel genes required for Borrelia burgdorferi survival in its Ixodes tick vector.

Borrelia burgdorferi, the causative agent of Lyme disease in humans, is maintained in a complex biphasic life cycle, which alternates between tick and vertebrate hosts. To successfully survive and complete its enzootic cycle, B. burgdorferi adapts to diverse hosts by regulating genes required for survival in specific environments. Here we describe the first ever use of transposon insertion sequencing (Tn-seq) to identify genes required for B. burgdorferi survival in its tick host. We found that insertions into 46 genes resulted in a complete loss of recovery of mutants from larval Ixodes ticks. Insertions in an additional 56 genes resulted in a >90% decrease in fitness. The screen identified both previously known and new genes important for larval tick survival. Almost half of the genes required for survival in the tick encode proteins of unknown function, while a significant portion (over 20%) encode membrane-associated proteins or lipoproteins. We validated the results of the screen for five Tn mutants by performing individual competition assays using mutant and complemented strains. To better understand the role of one of these genes in tick survival, we conducted mechanistic studies of bb0017, a gene previously shown to be required for resistance against oxidative stress. In this study we show that BB0017 affects the regulation of key borrelial virulence determinants. The application of Tn-seq to in vivo screening of B. burgdorferi in its natural vector is a powerful tool that can be used to address many different aspects of the host pathogen interaction.

Future Lyme disease risk in the south-eastern United States based on projected land cover.

Lyme disease is the most significant vector-borne disease in the United States, and its southward advance over several decades has been quantified. Previous research has examined the potential role of climate change on the disease's expansion, but no studies have considered the role of future land cover upon its distribution. This research examines Lyme disease risk in the south-eastern U.S. based on projected land cover developed under four Intergovernmental Panel on Climate Change Scenarios: A1B, A2, B1, and B2. Land cover types and edge indices significantly associated with Lyme disease in Virginia were incorporated into a spatial Poisson regression model to quantify potential land cover suitability for Lyme disease in the south-eastern U.S. under each scenario. Our results indicate an intensification of potential land cover suitability for Lyme disease under the A scenarios and a decrease of potential land cover suitability under the B scenarios. The decrease under the B scenarios is a critical result, indicating that Lyme disease risk can be decreased by making different land cover choices. Additionally, health officials can focus efforts in projected high incidence areas.

Ticks (Acari: Ixodida) on birds (Aves) migrating through the Polish Baltic coast.

Seasonal bird (Aves) migration between breeding and wintering areas, often located on different continents, can facilitate the spreading of tick species (Acari: Ixodida) and of tick-borne pathogens. The aim of the study was to analyse the occurrence of ticks dispersed by birds migrating along the Polish Baltic coast during spring and autumn migration. Field research was conducted at the bird ringing station in Wicie, located on the middle of the Polish Baltic coast, in 2011 and 2012 during spring and autumn migration. A total of 2657 birds from 45 species was examined. The most common species inspected were European robin (Erithacus rubecula) (63.3%), song thrush (Turdus philomelos) (5.13%), and goldcrest (Regulus regulus) (4.5%). Overall, 3129 ticks belonging to six species were collected: Ixodes ricinus (1650 larvae, 1390 nymphs and 1 male), Ixodes frontalis (20 larvae, 20 nymphs), Ixodes arboricola (35 larvae), Dermacentor reticulatus (1 larva), and Haemaphysalis punctata (1 nymph). Ten larvae and one nymph could only be identified to the genus level Ixodes. Ticks were located on various parts of the head: on the corner of the beak (75.0%), near the eyes (14.6%), on the chin (4.4%), near the ears (4.4%), on the neck (1.1%), and in the beak (0.5%). The overall tick prevalence was 40.5%. The highest prevalence was for bird species feeding on the ground, covering a medium distance to wintering grounds and migrating at night. Statistically significant differences between the number of ticks and the sex of the host species were detected in blackbirds: males carried more parasites than females, both, during spring and autumn migration. The fact that I. ricinus and other ticks parasitize birds migrating through Poland extends the possibility of the spread of tick-borne diseases.

Local host-tick coextinction in neotropical forest fragments.

Ticks are obligatory parasites with complex life cycles that often depend on larger bodied vertebrates as final hosts. These traits make them particularly sensitive to local coextinction with their host. Loss of wildlife abundance and diversity should thus lead to loss of tick abundance and diversity to the point where only generalist tick species remain. However, direct empirical tests of these hypotheses are lacking, despite their relevance to our understanding of tick-borne disease emergence in disturbed environments. Here, we compare vertebrate and tick communities across 12 forest islands and peninsulas in the Panama Canal that ranged 1000-fold in size (2.6-2811.3 ha). We used drag sampling and camera trapping to directly assess the abundance and diversity of communities of questing ticks and vertebrate hosts. We found that the abundance and species richness of ticks were positively related to those of wildlife. Specialist tick species were only present in fragments where their final hosts were found. Further, less diverse tick communities had a higher relative abundance of the generalist tick species Amblyomma oblongoguttatum, a potential vector of spotted fever group rickettsiosis. These findings support the host-parasite coextinction hypothesis, and indicate that loss of wildlife can indeed have cascading effects on tick communities. Our results also imply that opportunities for pathogen transmission via generalist ticks may be higher in habitats with degraded tick communities. If these patterns are general, then tick identities and abundances serve as useful bioindicators of ecosystem health, with low tick diversity reflecting low wildlife diversity and a potentially elevated risk of interspecific disease transmission via remaining host species and generalist ticks.

How ticks keep ticking in the adversity of host immune reactions.

Ixodid ticks are acknowledged as one of the most important hematophagous arthropods because of their ability in transmitting a variety of tick-borne diseases. Mathematical models have been developed, based on emerging knowledge about tick ecology, pathogen epidemiology and their interface, to understand tick population dynamics and tick-borne diseases spread patterns. However, no serious effort has been made to model and assess the impact of host immunity triggered by tick feeding on the distribution of the tick population according to tick stages and on tick population extinction and persistence. Here, we construct a novel mathematical model taking into account the effect of host immunity status on tick population dynamics, and analyze the long-term behaviours of the model solutions. Two threshold values, [Formula: see text] and [Formula: see text], are introduced to measure the reproduction ratios for the tick-host interaction in the absence and presence of host immunity. We then show that these two thresholds (sometimes under additional conditions) can be used to predict whether the tick population goes extinct ([Formula: see text]) and the tick population grows without bound ([Formula: see text]). We also prove tick permanence (persistence and boundedness of the tick population) and the existence of a tick persistence equilibrium if [Formula: see text]. As the host species adjust their immunity to tick infestation levels, they form for the tick population an environment with a carrying capacity very much like that in logistic growth. Numerical results show that the host immune reactions decrease the size of the tick population at equilibrium and apparently reduce the tick-borne infection risk.

Detection of Rickettsia spp. in ticks associated to wild mammals in Northeastern Brazil, with notes on an undetermined Ornithodoros sp. collected from marsupials.

We report tick infestations and rickettsial detection in ticks infesting free-living wild mammals (Monodelphis domestica, Tolypeutes tricinctus, Thrichomys inermis and Kerodon rupestris) captured in the Caatinga ecoregion of Bahia state, northeastern Brazil, during September to December 2016. Overall, 117 ticks (61 larvae, 25 nymphs, 25 males, 6 females) belonging to two genera, and at least three species were collected: Amblyomma auricularium, Amblyomma parvum, Amblyomma sp., Ornithodoros rietcorreai and an unidentified Ornithodoros sp. We provide new host records to the rodent T. inermis parasitized by larva and nymphs of A. auricularium and to the marsupial M. domestica infested by larvae of A. auricularium. Furthermore, we describe new tick-host association for larvae of O. rietcorreai on the rodents K. rupestris and T. inermis. Concerning tick-Rickettsia associations, we detected Rickettsia amblyommatis and an uncharacterized species of Rickettsia belonging to the spotted fever group (SFG) in both A. auricularium and A. parvum. Additionally, 'Candidatus Rickettsia andeanae' was detected in A. parvum as well.

Detection of Rickettsia monacensis and Rickettsia amblyommatis in ticks collected from dogs in Costa Rica and Nicaragua.

The neotropical climate of Central America provides ideal conditions for ticks, which may transmit several human pathogens, including spotted-fever group Rickettsia. Dogs may act as sentinels or reservoirs for human tick-borne diseases due to shared tick species. Here, ticks were collected from 680 client-owned dogs in Nicaragua and Costa Rica, and a total of 316 tick pools were investigated for Rickettsia infection by quantitative real-time PCR (qPCR) targeting the gltA gene. Subsequently, up to six further genomic targets (16S rDNA, gltA, sca4, ompA, ompB and the 23S-5S intergenic spacer) were investigated for Rickettsia species determination. The predominant tick species was Rhipicephalus sanguineus sensu lato (s.l.) (19.9% of dogs infested in Costa Rica, 48.0% in Nicaragua), followed by Ixodes boliviensis (3.1% in Costa Rica / none in Nicaragua) and Amblyomma ovale (4.8% in Costa Rica, 0.9% in Nicaragua). In total, 22 of 316 tick pools containing 60 of 1023 individual ticks were Rickettsia-positive as determined by qPCR, resulting in a minimum infection rate (MIR) of 2.2%. In detail, MIR in Rh. sanguineus s.l. was 0.7% (7/281 pools), in I. boliviensis 33.3% (12/13 pools) and in A. ovale 9.7% (3/22 pools). For 11 of 12 positive I. boliviensis pools and one of six positive Rh. sanguineus s.l. pools, the species could be determined as R. monacensis. R. amblyommatis was identified in one Rh. sanguineus s.l. pool from Costa Rica and one A. ovale pool from Nicaragua. Nine of 12 R. monacensis-positive tick pools were collected in San Rafael de Heredia, Costa Rica, indicating a high local occurrence in this area. This study supports recent evidence that R. monacensis is present on the American continent. Its high local occurrence among dog-associated I. boliviensis, which may also parasitize humans, in Costa Rica gives cause for concern, as R. monacensis is also pathogenic to humans.

Neglected aspects of tick-borne rickettsioses.

Rickettsioses are among the oldest known infectious diseases. In spite of this, and of the extensive research carried out, many aspects of the biology and epidemiology of tick-borne rickettsiae are far from being completely understood. Their association with arthropod vectors, the importance of vertebrates as reservoirs, the rarity of clinical signs in animals, or the interactions of pathogenic species with rickettsial endosymbionts and with the host intracellular environment, are only some examples. Moreover, new rickettsiae are continuously being discovered. In this review, we focus on the 'neglected' aspects of tick-borne rickettsioses and on the gaps in knowledge, which could help to explain why these infections are still emerging and re-emerging threats worldwide.