Ticks feeding on humans: a review of records on human-biting Ixodoidea with special reference to pathogen transmission

Tick hazard in the South Downs National Park (UK): species, distribution, key locations for future interventions, site density, habitats

Background

South Downs National Park (SDNP) is UK's most visited National Park, and a focus of tick-borne Lyme disease. The first presumed UK autochthonous cases of tick-borne encephalitis and babesiosis were recorded in 2019-20. SDNP aims to conserve wildlife and encourage recreation, so interventions are needed that reduce hazard without negatively affecting ecosystem health. To be successful these require knowledge of site hazards.

Methods

British Deer Society members submitted ticks removed from deer. Key potential intervention sites were selected and six 50 m2 transects drag-sampled per site (mostly twice yearly for 2 years). Ticks were identified in-lab (sex, life stage, species), hazard measured as tick presence, density of ticks (all life stages, DOT), and density of nymphs (DON). Sites and habitat types were analysed for association with hazard. Distribution was mapped by combining our results with records from five other sources.

Results

A total of 87 Ixodes ricinus (all but one adults, 82% F) were removed from 14 deer (10 Dama dama; three Capreolus capreolus; one not recorded; tick burden, 1-35) at 12 locations (commonly woodland). Five key potential intervention sites were identified and drag-sampled 2015-16, collecting 623 ticks (238 on-transects): 53.8% nymphs, 42.5% larvae, 3.7% adults (13 M, 10 F). Ticks were present on-transects at all sites: I. ricinus at three (The Mens (TM); Queen Elizabeth Country Park (QECP); Cowdray Estate (CE)), Haemaphysalis punctata at two (Seven Sisters Country Park (SSCP); Ditchling Beacon Nature Reserve (DBNR)). TM had the highest DOT at 30/300 m2 (DON = 30/300 m2), followed by QECP 22/300 m2 (12/300 m2), CE 8/300 m2 (6/300 m2), and SSCP 1/300 m2 (1/300 m2). For I. ricinus, nymphs predominated in spring, larvae in the second half of summer and early autumn. The overall ranking of site hazard held for DON and DOT from both seasonal sampling periods. DBNR was sampled 2016 only (one adult H. punctata collected). Woodland had significantly greater hazard than downland, but ticks were present at all downland sites. I. ricinus has been identified in 33/37 of SDNPs 10 km2 grid squares, Ixodes hexagonus 10/37, H. punctata 7/37, Dermacentor reticulatus 1/37.

Conclusions

Mapping shows tick hazard broadly distributed across SDNP. I. ricinus was most common, but H. punctata's seeming range expansion is concerning. Recommendations: management of small heavily visited high hazard plots (QECP); post-visit precaution signage (all sites); repellent impregnated clothing for deerstalkers; flock trials to control H. punctata (SSCP, DBNR). Further research at TM may contribute to knowledge on ecological dynamics underlying infection density and predator re-introduction/protection as public health interventions. Ecological research on H. punctata would aid control. SDNP Authority is ideally placed to link and champion policies to reduce hazard, whilst avoiding or reducing conflict between public health and ecosystem health.

The complete mitochondrial genome of cattle tick clade C reveals the genetic relationship within Rhipicephalus microplus complex

Cattle ticks (Rhipicephalus microplus) are important economic ectoparasites causing direct and indirect damage to cattle and leading to severe economic losses in cattle husbandry. It is common knowledge that R. microplus is a species complex including five clades; however, the relationships within the R. microplus complex remain unresolved. In the present study, we assembled the complete mitochondrial genome of clade C by next-generation sequencing and proved its correctness based on long PCR amplification. It was 15,004 bp in length and consisted of 13 protein genes, 22 transfer genes, and two ribosomal genes located in the two strains. There were two copies of the repeat region (pseudo-nad1 and tRNA-Glu). Data revealed that cox1, cox2, and cox3 genes were conserved within R. microplus with small genetic differences. Ka/Ks ratios suggested that 12 protein genes (excluding nad6) may be neutral selection. The genetic and phylogenetic analyses indicated that clade C was greatly close to clade B. Findings in the current study provided more data for the identification and differentiation of the R. microplus complex and made up for the lack of information about R. microplus clade C.

Effects of climate change and human activities on vector-borne diseases

Vector-borne diseases are transmitted by haematophagous arthropods (for example, mosquitoes, ticks and sandflies) to humans and wild and domestic animals, with the largest burden on global public health disproportionately affecting people in tropical and subtropical areas. Because vectors are ectothermic, climate and weather alterations (for example, temperature, rainfall and humidity) can affect their reproduction, survival, geographic distribution and, consequently, ability to transmit pathogens. However, the effects of climate change on vector-borne diseases can be multifaceted and complex, sometimes with ambiguous consequences. In this Review, we discuss the potential effects of climate change, weather and other anthropogenic factors, including land use, human mobility and behaviour, as possible contributors to the redistribution of vectors and spread of vector-borne diseases worldwide.

Nationwide survey of ticks on domesticated animals in Taiwan: Revealing the hidden threat to animal and public health

Ticks are not only bloodsucking ectoparasites but also important vectors of tick-borne diseases (TBDs), posing significant threats to public and animal health. Domesticated animals serve as critical hosts for numerous ticks, highlighting the importance of understanding tick infestations in Taiwan. To address this knowledge gap, we conducted a nationwide survey to identify ticks on domesticated animals and associated environments in 2018 and 2019. A total of 6,205 ticks were collected from 1,337 host animals, revealing the presence of seven tick species, with Rhipicephalus microplus, and Rhipicephalus sanguineus being the dominant species. High infestation rates and widespread distribution of ticks were observed on domesticated animals, especially on dogs and cattle (yellow cattle and angus cattle), and the neighbouring grassland of yellow cattle. While this study has certain limitations, it provides valuable insights into the distribution and prevalence of ticks on domesticated animals in Taiwan and their implications for controlling TBDs. Further research is needed to comprehensively understand the complex interactions among ticks, hosts and pathogens.

Exotic ticks removed from German travelers

We report the finding of five nymphs and three adult ticks attached to German tourists while traveling the American continents. All eight specimens were morphologically identified and confirmed genetically using the 16S rRNA gene and screened for Rickettsia spp. infections. Five tick species were identified: one Amblyomma mixtum nymph from Ecuador, one Amblyomma varium nymph from Colombia, three Amblyomma coelebs nymphs from Costa Rica, one Amblyomma americanum male from the USA, one Dermacentor andersoni female and one D. andersoni male from Canada. Tick-borne microorganisms screening using the pan-Rickettsia-PCR resulted in two positive and six negative ticks. The A. mixtum nymph was positive for Rickettsia amblyommatis, while the D. andersoni female was positive for Rickettsia peacockii.

The hidden threat: Exploring the parasite burden and feeding habits of invasive raccoon dogs (Nyctereutes procyonoides) in central Europe

Originally from Asia, the raccoon dog Nyctereutes procyonoides is an invasive alien species in Europe, listed since 2019 on the List of invasive alien species of Union concern. The raccoon dog is considered to have negative impact on native biodiversity, as well as a crucial role in hosting and transmitting diverse parasites and pathogens of human and veterinary importance. In the present study, stomach content analyses and parasitological examinations were performed on 73 raccoon dogs from Germany. In addition, fecal samples were analyzed. The results of the study confirm the assumption that the examined raccoon dogs were infested with a various ecto- and endoparasite fauna. A total of 9 ecto- and 11 endoparasites were detected, with 6 of the endoparasites having human pathogenic potential. Trichodectes canis (P = 53.42%), Toxocara canis (P = 50.68%) and Uncinaria stenocephala (P = 68.49%) were the most abundant parasite species. The stomach contents consisted of approximately one-third vegetable and two-thirds animal components, composed of various species of amphibians, fish, insects, mammals and birds. Among them were specially protected or endangered species such as the grass frog Rana temporaria. The study shows that the raccoon dog exerts predation pressure on native species due to its omnivorous diet and, as a carrier of various parasites, poses a potential risk of infection to wild, domestic and farm animals and humans.

Individual heterogeneity in ixodid tick infestation and prevalence of Borrelia burgdorferi sensu lato in a northern community of small mammalian hosts

Heterogeneous aggregation of parasites between individual hosts is common and regarded as an important factor in understanding transmission dynamics of vector-borne diseases. Lyme disease is vectored by generalist tick species, yet we have a limited understanding of how individual heterogeneities within small mammal host populations affect the aggregation of ticks and likelihood of infection. Male hosts often have higher parasite and infection levels than females, but whether this is linked to sexual body size dimorphism remains uncertain. Here, we analysed how host species, sex, and body mass influenced Ixodes ricinus tick infestations and the infection prevalence of Borrelia burgdorferi sensu lato (s.l.) in three species of small mammals involved in the enzootic transmission cycle of Lyme disease in Norway from 2018 to 2022. Larval and nymphal ticks were found on 98% and 34% of all individual hosts, respectively. In bank voles and wood mice, both larval and nymphal tick infestation and infection probability increased with body mass, and it increased more with mass for males than for females. Tick infestation in the common shrew increased with body mass and was higher in males, while pathogen infection was higher in females. Sex-biases in infestation did not correspond with level of sexual body mass dimorphism across species. This study contributes to our understanding of how individual heterogeneity among small mammalian hosts influences I. ricinus tick aggregation and prevalence of B. burgdorferi s.l. at northern latitudes.

Efficacy of the Vaccine Candidate Based on the P0 Peptide against Dermacentor nitens and Ixodes ricinus Ticks

The control of ticks through vaccination offers a sustainable alternative to the use of chemicals that cause contamination and the selection of resistant tick strains. However, only a limited number of anti-tick vaccines have reached commercial realization. In this sense, an antigen effective against different tick species is a desirable target for developing such vaccines. A peptide derived from the tick P0 protein (pP0) conjugated to a carrier protein has been demonstrated to be effective against the Rhipicephalus microplus, Rhipicephalus sanguineus, and Amblyomma mixtum tick species. The aim of this work was to assess the efficacy of this peptide when conjugated to the Bm86 protein against Dermacentor nitens and Ixodes ricinus ticks. An RNAi experiment using P0 dsRNA from I. ricinus showed a dramatic reduction in the feeding of injected female ticks on guinea pigs. In the follow-up vaccination experiments, rabbits were immunized with the pP0-Bm86 conjugate and challenged simultaneously with larvae, nymphs, and the adults of I. ricinus ticks. In the same way, horses were immunized with the pP0-Bm86 conjugate and challenged with D. nitens larva. The pP0-Bm86 conjugate showed efficacies of 63% and 55% against I. ricinus and D. nitens ticks, respectively. These results, combined with previous reports of efficacy for this conjugate, show the promising potential for its development as a broad-spectrum anti-tick vaccine.

Anti-tick vaccine candidate subolesin is important for blood feeding and innate immune gene expression in soft ticks

Subolesin is a conserved molecule in both hard and soft ticks and is considered as an effective candidate molecule for the development of anti-tick vaccine. Previous studies have reported the role of subolesin in blood feeding, reproduction, development, and gene expression in hard ticks. However, studies addressing the role of subolesin in soft ticks are limited. In this study, we report that subolesin is not only important in soft tick Ornithodoros turicata americanus blood feeding but also in the regulation of innate immune gene expression in these ticks. We identified and characterized several putative innate immune genes including Toll, Lysozyme precursor (Lp), fibrinogen-domain containing protein (FDP), cystatin and ML-domain containing protein (MLD) in O. turicata americanus ticks. Quantitative real-time polymerase chain reaction analysis revealed the expression of these genes in both O. turicata americanus salivary glands and midgut and in all developmental stages of these soft ticks. Significantly increased expression of fdp was noted in salivary glands and midgut upon O. turicata americanus blood feeding. Furthermore, RNAi-mediated knockdown of O. turicata americanus subolesin expression affected blood feeding and innate immune gene expression in these ticks. Significant downregulation of toll, lp, fdp, cystatin, and mld transcripts was evident in sub-dsRNA-treated ticks when compared to the levels noted in mock-dsRNA-treated control. Collectively, our study not only reports identification and characterization of various innate immune genes in O. turicata americanus ticks but also provides evidence on the role of subolesin in blood feeding and innate immune gene expression in these medically important ticks.

Survival of adult Amblyomma americanum, Amblyomma maculatum, and Dermacentor variabilis (Acari: Ixodidae) in four habitats in southeastern Virginia

Adult, unfed Amblyomma americanum (Linnaeus), Amblyomma maculatum Koch, and Dermacentor variabilis (Say) ticks were housed inside environmental containers in situ from May through August 2015. The environmental containers were placed in 4 habitats in southeastern Virginia, United States. Two of the habitats were located in low ground and were prone to flooding; the other two consisted of a drier landscape located in a more upland habitat. A Cox Regression survival analysis indicated there was a significant difference in survival among species across all field sites. There was a 50.5-times higher risk of mortality for A. maculatum compared to A. americanum, a 4.3-times higher risk of mortality for A. maculatum compared to D. variabilis, and an 11.9-times higher risk of mortality for D. variabilis compared to A. americanum. There was also significantly higher mortality in field sites prone to flooding than in drier, upland field sites. We concluded that A. americanum was not negatively affected by increased flooding or the variable environmental conditions in southeastern Virginia. Dermacentor variabilis also was successful at remaining in the environment off-host, although increased flooding reduced survival over time. Amblyomma maculatum was more susceptible to mortality during long periods of time off-host in both environments, with high mortality rates in both dry upland and low-ground, flood-prone habitats.

Morphological and molecular identification of the brown dog tick in Mexico

Ticks of the Rhipicephalus sanguineus complex are known as the brown dog ticks. This complex groups at least 12 species of ticks that are distributed worldwide. On the American continents, R. sanguineus sensu stricto (s.s.), is distributed in temperate areas, while Rhipicephalus sanguineus sensu lato (s.l.), also called "tropical lineage" is distributed in tropical regions. Previous analyses of brown dog ticks from Mexico have identified the so-called tropical lineage and the country generally has a climate more favorable for these ticks (> 20o C in average). In addition, some pathogens thought to be transmitted by this lineage (such as Ehrlichia canis, and Rickettsia rickettsii) are prevalent in Mexico. Herein we aim to contribute to the study of brown dog ticks by providing morphological identification and molecular analysis of mt 12S rDNA and 16S rDNA sequences from ticks collected from 12 states in Mexico. Our results indicate that the tropical lineage of R. sanguineus s.l., recently redescribed as R. linnaei is widely distributed in Mexico.

Distribution of the soft tick Carios vespertilionis in lowlands and low mountain regions of Germany

In Germany, the knowledge about ticks infesting bats is limited, and is restricted only to a few studies, most of them dating back decades. To further improve our knowledge on ticks parasitising bats, healthy and sick bats in central Germany were examined for ticks. In total 519 larvae and one nymph of Carios vespertilionis were collected from nine bat species: Eptesicus nilssonii, Eptesicus serotinus, Myotis daubentonii, Myotis myotis, Nyctalus leisleri, Pipistrellus nathusii, Pipistrellus pygmaeus, Pipistrellus pipistrellus, and Vespertilio murinus. Either the presence of C. vespertilionis was new for some areas or it was confirmed in some federal states in central Germany. The infestation rate was mostly low (n = 1-5 larvae/bat). However, in two cases a high number of ticks was observed. The highest infestation of 97 C. vespertilionis larvae was recorded on one Parti-coloured bat (V. murinus).

Rickettsia species in Dermacentor reticulatus ticks feeding on human skin and clinical manifestations of tick-borne infections after tick bite

Dermacentor reticulatus ticks are sporadically removed from human skin and therefore the medical consequences of their feeding are neglected compared to Ixodes ricinus. We investigated the prevalence of pathogens in D. reticulatus removed from human skin and possible clinical manifestations suggestive of tick-borne diseases after a tick bite. A total of 2153 ticks were studied and of these only 34 were D. reticulatus. The mean prevalence of Rickettsia in D. reticulatus was 50.0% and R. raoultii was identified in 82.4% of infected D. reticulatus ticks. We confirmed the first case of R. aeschlimannii infection in D. reticulatus ticks. Among participants bitten by D. reticulatus, 13.3% reported reddening around the tick bite site and flu-like symptoms, including lymphadenopathy and 3.3% reported eschar on the tick site bite. All of the participants with flu-like symptoms after tick removal were bitten by ticks infected with R. raoultii. The results of this study indicate that even though D. reticulatus ticks bite humans sporadically, pathogenic Rickettsia have a remarkably high prevalence in this tick species. We can expect that the incidence of tick-borne lymphadenopathy might increase with the reported expansion of the D. reticulatus into new areas and its growing abundance in Central Europe.

Molecular Detection of Anaplasma, Ehrlichia and Rickettsia Pathogens in Ticks Collected from Humans in the Republic of Korea, 2021

Tick-borne pathogens (TBPs), transmitted by the bites of ticks, are of great medical and veterinary importance. They include bacteria, viruses, and protozoan parasites. To provide fundamental data on the risk of tick contact and public health strategies, we aimed to perform a molecular investigation on four tick-borne bacterial pathogens in ticks collected from humans across the Republic of Korea (ROK) in 2021. In total, 117 ticks were collected, including Haemaphysalis longicornis (56.4%), Amblyomma testudinarium (26.5%), Ixodes nipponensis (8.5%), H. flava (5.1%), and I. persulcatus (0.9%). Among the ticks, 20.5% (24/117) contained tick-borne bacterial pathogens, with infection rates of 17.9% for Rickettsia (Candidatus Rickettsia jingxinensis, R. tamurae, R. monacensis, and Candidatus Rickettsia tarasevichiae), 2.5% for Anaplasma (A. phagocytophilum, A. capra, and A. bovis), and 0.9% for Ehrlichia (Ehrlichia sp.). Additionally, the co-detection rate for R. monacensis and A. phagocytophilum was 0.9%. To our knowledge, this is the first report of A. capra and A. bovis detection in ticks collected from humans in the ROK. This study contributes to the understanding of the potential risk of tick contact and provides fundamental data for establishing a public health strategy for tick-borne disease management in the ROK.

Monitoring of hard tick parasitism in domestic ruminants: A scale evidence for policymakers

Domestic ruminants such as camels, cattle, goats, and sheep represent a substantial part of the global world economy. Hard ticks are well-known as obligatory bloodsucking ectoparasites of domestic ruminants. Policymakers need to get results that show the global distribution of tick genera and species, their parasitic levels, and their roles as disease vectors in camels, cattle, goats, and sheep. Iran is endemic to a broad range of hard tick-borne diseases. A study that reviews the tick genera and species, life stage, seasonal and attachment site parasitism levels, the global mean ranks of tick species parasitism rates and records, and their distribution in target animals would be of particular importance. Accordingly, this review aims to summarize the above objectives. After evaluating the identified articles, 147 were selected to be part of the survey based on the study objectives. Globally, tick parasitism levels were 28.7, 29.9, 36.0 and 47.6% for goats, cattle, sheep, and camels, respectively. The tick parasitism trends have exhibited an increasing trend for camels and sheep over the years while remaining constant for cattle and goats, indicating that current tick control measures are not being properly followed. Ticks tend to parasitize females more than males because males are more resistant to certain pests than females. The distribution of tick genera and species, their parasitism levels, and their roles as disease vectors provided. This information addresses the needs of decision-makers to make decisions.

Human-biting ticks and zoonotic tick-borne pathogens in North Africa: diversity, distribution, and trans-Mediterranean public health challenges

North Africa is home to more than 200 million people living across five developing economies (Egypt, Libya, Tunisia, Algeria, and Morocco) and two Spanish exclaves (Ceuta and Melilla), many of whom are impacted by ticks and tick-borne zoonoses. Populations in Europe are also increasingly vulnerable to North African ticks and tick-borne zoonoses due to a combination of climate change and the movement of ticks across the Mediterranean on migratory birds, human travellers, and trafficked wildlife. The human-biting ticks and tick-borne zoonoses in North Africa are reviewed along with their distribution in the region. We also assess present and future challenges associated with ticks and tick-borne zoonoses in North African and highlight opportunities for collaboration and coordination between governments in Europe and North Africa to address public health challenges posed by North African ticks and tick-borne zoonoses.

A new host record of Haemaphysalis semermis (Acari: Ixodidae) from the domestic cat (Felis catus) (Carnivora: Felidae) in Orang Asli village, Pahang National Park Malaysia

We report the presence of a male Haemaphysalis semermis collected from the domestic cat, Felis catus in an aboriginal village located in Pahang, Malaysia. This paper constitutes a new host record of this tick species, and also the first documentation of the infestation of companion animals other than domestic dogs (Canis lupus) by H. semermis in Malaysia. Additionally, we have included an updated host index of the tick species in Southeast Asia.

Putative target sites in synganglion for novel ixodid tick control strategies

Acaricide resistance is a global problem that has impacts worldwide. Tick populations with broad resistance to all commercially available acaricides have been reported. Since resistance selection in ticks and their role in pathogen transmission to animals and humans result in important economic and public health burden, it is essential to develop new strategies for their control (i.e., novel chemical compounds, vaccines, biological control). The synganglion is the tick central nervous system and it is responsible for synthesizing and releasing signaling molecules with different physiological functions. Synganglion proteins are the targets of the majority of available acaricides. In this review we provide an overview of the mode-of-action and resistance mechanisms against neurotoxic acaricides in ticks, as well as putative target sites in synganglion, as a supporting tool to identify new target proteins and to develop new strategies for tick control.

Knowledge, Attitudes, and Practices of Pastoralists Towards Tick Bites, and Tick Control in Plateau State, Nigeria

PURPOSE

Pastoralists regularly come in contact with ticks as they herd their animals and are exposed to pathogens that cause zoonotic diseases. No study has been conducted in Nigeria to evaluate the knowledge, attitudes, and practices (KAP) of these Pastoralists towards ticks, tick bite, and tick control, and thus this research.

METHODS

A KAP survey of pastoralists (n = 119) was conducted in Plateau State, Nigeria. Data generated were analysed using Statistical Package for Social Sciences (SPSS).

RESULTS

The majority of the pastoralists (99.2%) had knowledge of ticks, with 79% of them being aware that ticks attach and bite humans, whereas only 30.3% believed that ticks transmit diseases to humans. Eighty-four per cent of the pastoralists do not wear protective clothing while herding their animals and 81.5% indicated to having been bitten by ticks, whereas hospital visit after tick bite was low (7.6%). Statistically significant variables were observed when knowledge of the respondents were compared in relation to the ability of ticks to cause diseases (Χ² = 9.980, P = 0.007); hospital visit after a bite (Χ² = 11.453, P = 0.003); and the use of protective clothing for herding (Χ² = 22.596, P = 0). The main tick control measure was hand picking (58.8%).

CONCLUSIONS

The pastoralists were unaware of the ability of ticks to transmit zoonotic pathogens. Preventive practices were insufficient to reduce tick bites, and thus were constantly exposed to tick-borne diseases. This study hopes to provide important insights for the development of educational awareness programmes for the pastoralists and serve as a guide for the health workers in designing future preventive programmes against tick-borne zoonoses in Nigeria.

Bio-efficacy of permethrin/tetramethrin and lambda-cyhalothrin treatments in habitats of hard ticks (Acari, Ixodidae) populations with confirmed Borrelia spp. infection

The aim of the study was to evaluate the bio-efficacy of two different acaricides against mobile stages of hard ticks Ixodes ricinus, Dermacentor marginatus, and Haemaphysalis punctata in their natural habitats. The study was conducted during 2020 and 2021 at localities populated by I. ricinus as the predominant species, at which the presence of Borrelia afzelii, Borrelia garinii, and Borrelia lusitaniae was confirmed. During the first investigation year, a combination of two pyrethroids, permethrin, and tetramethrin, with an insecticide synergist piperonyl butoxide (trade name: Perme Plus®) was tested. At the first evaluation, 24 h after the treatment with Perme Plus®, the efficacy expressed as a reduction rate of the population density was within the interval of satisfying performance (70-90%) at all localities, while the highest efficacy (97.8%) was recorded on the 14th post-treatment day. In the second investigation year, the formulation based on lambda-cyhalothrin (trade name: Icon® 10CS) was used. On the first post-treatment evaluation day, satisfying effects were also demonstrated. The highest recorded efficacy rate of lambda-cyhalothrin (94.7%) was recorded on the 14th post-treatment day. Both tested acaricides manifested satisfying initial acaricidal effects against mobile stages of ticks and provided long-term effects. Comparison of the regression trend lines of population reduction revealed that satisfying effects of treatment with Perme Plus® lasted until the 17th post-treatment day, while in the case of Icon® 10CS, the residual effects were significantly prolonged (30 days).

The Biological and Ecological Features of Northbound Migratory Birds, Ticks, and Tick-Borne Microorganisms in the African-Western Palearctic

Identifying the species that act as hosts, vectors, and vehicles of vector-borne pathogens is vital for revealing the transmission cycles, dispersal mechanisms, and establishment of vector-borne pathogens in nature. Ticks are common vectors for pathogens causing human and animal diseases, and they transmit a greater variety of pathogenic agents than any other arthropod vector group. Ticks depend on the movements by their vertebrate hosts for their dispersal, and tick species with long feeding periods are more likely to be transported over long distances. Wild birds are commonly parasitized by ticks, and their migration patterns enable the long-distance range expansion of ticks. The African-Palearctic migration system is one of the world's largest migrations systems. African-Western Palearctic birds create natural links between the African, European, and Asian continents when they migrate biannually between breeding grounds in the Palearctic and wintering grounds in Africa and thereby connect different biomes. Climate is an important geographical determinant of ticks, and with global warming, the distribution range and abundance of ticks in the Western Palearctic may increase. The introduction of exotic ticks and their microorganisms into the Western Palearctic via avian vehicles might therefore pose a greater risk for the public and animal health in the future.

Rickettsia africae and Rickettsia massiliae in ixodid ticks infesting small ruminants in agro-pastoral settlements in Plateau State, Nigeria

Arthropods, especially ixodid ticks, have been incriminated in the epidemiology of Spotted Fever Group rickettsioses globally leading to an increasing spectrum of emerging and re-emerging zoonoses with attendant consequences on trade and tourism. The objective of this study was to determine the role of ixodid ticks infesting small ruminants in Plateau State, Nigeria, in the epidemiology of Spotted Fever Group Rickettsiae (SFGR) in the study area. DNA from 130 out of 323 ixodid ticks collected from 179 goats and 121 sheep owned by agro-pastoralists in Plateau State were screened for the evidence of SFGR by molecular methods. Six tick species from four genera were identified: Amblyomma, Hyalomma, Rhipicephalus (Boophilus) and Rhipicephalus. Rhipicephalus sanguineus sensu lato (s.l.) was the predominant (54.5%) species among collected ticks. Tick infestation was significantly associated with the species of small ruminants, the sex of the animals and the sampling locations except for Jos South. Conventional PCR targeting the 381 bp of the citrate synthase (gltA) and 820 bp of the outer membrane protein B (ompB) genes detected DNA of SFGR in nine and eight samples, respectively. Sequence analysis revealed that five sequences obtained from Amblyomma variegatum were 99-100% identical to Rickettsia africae and three sequences from Rh. sanguineus (s.l.) were 100% identical to Rickettsia massiliae reported from Spain. To our knowledge, this is the first report of the detection of R. africae DNA in Am. variegatum collected from small ruminants in Plateau State. Ixodid ticks infesting small ruminants in Plateau state harbor DNA of SFGR with potential veterinary and public health implications.

Identification of a rickettsial endosymbiont in a soft tick Ornithodoros turicata americanus

Bacterial endosymbionts are abundantly found in both hard and soft ticks. Occidentia massiliensis, a rickettsial endosymbiont, was first identified in the soft tick Ornithodoros sonrai collected from Senegal and later was identified in a hard tick Africaniella transversale. In this study, we noted the presence of Occidentia species, designated as Occidentia-like species, in a soft tick O. turicata americanus. Sequencing and phylogenetic analyses of the two genetic markers, 16S rRNA and groEL confirmed the presence of Occidentia-like species in O. turicata americanus ticks. The Occidentia-like species was noted to be present in all developmental stages of O. turicata americanus and in different tick tissues including ovaries, synganglion, guts and salivary gland. The levels of Occidentia-like species 16S rRNA transcripts were noted to be significantly higher in ovaries than in a gut tissue. In addition, Occidentia-like species groEL expression was noted to be significantly higher in tick synganglion than in ovaries and gut tissues. Furthermore, levels of Occidentia-like species 16S rRNA transcripts increased significantly upon O. turicata americanus blood feeding. Taken together, our study not only shows that Occidentia-like species is present in O. turicata americanus but also suggests that this bacterium may play a role in tick-bacteria interactions.

Tick-Borne Rickettsioses in the Iberian Peninsula

Tick-borne rickettsioses (TBR) are caused by obligate, intracellular bacteria of the spotted-fever group (SFG) of the genus Rickettsia (Order Rickettsiales), transmitted by hard ticks. TBR are one of the oldest known vector-borne zoonoses and pose a threat to both human and animal health, as over the years, new SFG Rickettsia spp. have been reported worldwide with the potential to be human pathogens. In Portugal and Spain, the countries that constitute the Iberian Peninsula, reported TB rickettsiae causing human disease include Rickettsia conorii conorii, Rickettsia conorii israelensis, Rickettsia slovaca, Rickettsia raoultii, Candidatus Rickettsia rioja, Rickettsia sibirica mongolitimonae, and Rickettsia monacensis. An allochthonous case of TBR caused by Rickettsia massiliae, described in Spain, points to the need to monitor disease epidemiology, to predict risks of exposure and spread of disease, and taking into account globalization and climate changes. This review aims to provide up-to-date information on the status of TBR in the Iberian Peninsula, as well as to show the importance of a national and international collaborative epidemiology surveillance network, towards monitoring Rickettsia spp. circulation in both Portugal and Spain.

The control of Hyalomma ticks, vectors of the Crimean–Congo hemorrhagic fever virus: Where are we now and where are we going?

At a time of major global, societal, and environmental changes, the shifting distribution of pathogen vectors represents a real danger in certain regions of the world as generating opportunities for emergency. For example, the recent arrival of the Hyalomma marginatum ticks in southern France and the concurrent appearance of cases of Crimean–Congo hemorrhagic fever (CCHF)—a disease vectored by this tick species—in neighboring Spain raises many concerns about the associated risks for the European continent. This context has created an urgent need for effective methods for control, surveillance, and risk assessment for ticks and tick-borne diseases with a particular concern regarding Hyalomma sp. Here, we then review the current body of knowledge on different methods of tick control—including chemical, biological, genetical, immunological, and ecological methods—and the latest developments in the field, with a focus on those that have been tested against ticks from the genus Hyalomma. In the absence of a fully and unique efficient approach, we demonstrated that integrated pest management combining several approaches adapted to the local context and species is currently the best strategy for tick control together with a rational use of acaricide. Continued efforts are needed to develop and implement new and innovative methods of tick control.

Disease-bearing Hyalomma ticks are an increasingly emerging threat to humans and livestock worldwide. Various chemical, biological, genetic, and ecological methods for tick control have been developed, with variable efficiencies. Today, the best tick control strategy involves an integrated pest management approach.

Tick species infesting humans in the United States

The data for human tick encounters in the United States (US) presented in this paper were compiled with the goals of: (i) presenting quantitative data across the full range of native or recently established human biting ixodid (hard) and argasid (soft) tick species with regards to their frequency of infesting humans, based on published records of ticks collected while biting humans or crawling on clothing or skin; and (ii) providing a guide to publications on human tick encounters. Summary data are presented in table format, and the detailed data these summaries were based on are included in a set of Supplementary Tables. To date, totals of 36 ixodid species (234,722 specimens) and 13 argasid species (230 specimens) have been recorded in the published literature to infest humans in the US. Nationally, the top five ixodid species recorded from humans were the blacklegged tick, Ixodes scapularis (n=158,008 specimens); the lone star tick, Amblyomma americanum (n=36,004); the American dog tick, Dermacentor variabilis (n=26,624); the western blacklegged tick, Ixodes pacificus (n=4,158); and the Rocky Mountain wood tick, Dermacentor andersoni (n=3,518). Additional species with more than 250 ticks recorded from humans included Ixodes cookei (n=2,494); the Pacific Coast tick, Dermacentor occidentalis (n=809); the brown dog tick, Rhipicephalus sanguineus sensu lato (n=714); the winter tick, Dermacentor albipictus (n=465); and the Gulf Coast tick, Amblyomma maculatum (n=335). The spinose ear tick, Otobius megnini (n=69), and the pajaroello tick, Ornithodoros coriaceus (n=55) were the argasid species most commonly recorded from humans. Additional information presented for each of the 49 tick species include a breakdown of life stages recorded from humans, broad geographical distribution in the US, host preference, and associated human pathogens or medical conditions. The paper also provides a history of publications on human tick encounters in the US, with tables outlining publications containing quantitative data on human tick encounters as well as other notable publications on human-tick interactions. Data limitations are discussed. Researchers and public health professionals in possession of unpublished human tick encounter data are strongly encouraged to publish this information in peer-reviewed scientific journals. In future papers, it would be beneficial if data consistently were broken down by tick species and life stage as well as host species and ticks found biting versus crawling on clothing or skin.

Ticks (Acari: Ixodidae) and Associated Pathoge Collected From Domestic Animals and Vegetation in Stann Creek District, Southeastern Belize, Central America

Data on the prevalence and distribution of ticks and tick-borne diseases in Belize are lacking. Ticks (n = 564) collected from dogs, horses, and vegetation in two villages in Stann Creek District in southeastern Belize in 2018, were molecularly identified and screened for tick-borne nonviral human pathogens. The identity of 417 ticks was molecularly confirmed by DNA barcoding as Rhipicephalus sanguineus (Latreille) (66.43%), Amblyomma ovale Koch (15.59%), Dermacentor nitens Neumann (11.51%), Amblyomma sp. ADB0528 (3.6%), and the remainder being small records (2.87%) of Amblyomma coelebs Neumann, Amblyomma imitator Kohls, Amblyomma tapirellum Dunn, Amblyomma auricularium Conil, and Amblyomma maculatum Koch. Individual tick extracts were screened for the presence of Rickettsia spp., Babesia spp., Babesia microti, Borrelia spp., Ehrlichia spp., and Anaplasma spp. using available conventional polymerase chain reaction (PCR) assays. Rickettsia parkeri strain Atlantic Rainforest was identified in five specimens of A. ovale, and one other unidentified tick, all collected from dogs. Another unidentified tick-also collected from a dog-tested positive for an undefined but previously detected Ehrlichia sp. With the exception of D. nitens, all eight other tick species identified in this study were collected on dogs, suggesting that dogs could be usefully employed as sentinel animals for tick surveillance in Belize.

Molecular Prevalence of Selected Tick-Borne Pathogens in Dermacentor reticulatus Collected in a Natural Park in Italy

Dermacentor reticulatus is one of the most important vectors of tick-borne pathogens (TBPs) in Europe causing diseases in animals and humans. A longitudinal study was planned, aimed to detect the molecular prevalence of tick-borne pathogens, i.e., Babesia spp. and the spotted fever group Rickettsiae, and its seasonal variation in D. reticulatus questing ticks to define the temporal infection risk. Ticks were collected monthly over a period of 15 months in a peri-urban park in Lombardy, Italy. DNA extraction and molecular analyses were performed. Statistical analysis was carried out. Out of 488, 53 (P = 10.9%) adult questing ticks were positive for Babesia DNA. A higher prevalence was revealed in male (32/241, P = 13.3%) than in female (21/247, P = 8.5%) ticks. Positive ticks were mostly collected in winter months (P = 13.3%) compared to early (P = 7.9) and late (P = 12.8) spring months. A similar percentage of positive ticks was evidenced in transects 1 and 3 (5.8% and 6.5%, respectively); instead, a significant higher prevalence was recorded in transect 2 (P = 16.0%). Obtained sequences confirmed a homology of 100% with B. canis sequences deposited in GenBank. No ticks tested positive for Rickettsia spp. DNA (0/488, P = 0%). The conspicuous circulation of B. canis infection in D. reticulatus adult questing ticks confirms their role in the epidemiology of canine babesiosis and requires preventive measures for dogs in this recreational area. Even if no tick was positive for the spotted fever group Rickettsia, its capacity as a vector of zoonotic pathogens should not be neglected.

Geographical distribution of hard ticks (Acari:Ixodidae) and tick-host associations in Benin, Burkina-Faso, Ivory-Coast and Togo

Knowledge of ticks and associated pathogens is crucial to assess the risk of exposure of humans and animals to pathogens. For this review, we collected relevant data from published articles and field collections to provide an update on the biodiversity of ticks, and tick-host associations in four countries of West Africa: Benin, Burkina-Faso, Ivory-Coast, and Togo. The literature review was done according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The search was limited to literature published from 1953 to 2021 in English and French sources. Out of 104 articles retrieved, only 41 studies met the eligibility criteria and were included in the review. The final database included a total of 53,619 adults, nymphs and larval ticks belonging to 24 species and five genera (Amblyomma, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus) that were collected from 23 different species of wild and domestic animals. This is the first record of Ixodes aulacodi and Rhipicephalus simpsoni in Benin, together with two new host records for A. latum. This checklist allows an update on tick-host associations and provides information on the diversity of ticks in West Africa.

A review of argasid ticks and associated pathogens of China

It has been recorded 221 species of soft ticks in the world. However, the classification system of Argasidae is still unclear with nearly two-third controversial species in genus level. Therefore, comprehensive research is still necessary. In 2016, Wen and Chen overviewed the valid species of soft ticks in China for the first time. Up to now, the soft tick fauna of China remains poorly known. Although several studies have been undertaken, the information regarding soft ticks and associated diseases are fragmentary. To facilitate the future study of this group, the scattered information on soft ticks of China is herein synthesized. Toward the end of 2021, 15 valid species of argasid ticks have been reported, of these, 9 species (60%) including Argas beijingensis, A. japonicus, A. persicus, A. sinensis, A. vespertilionis, A. vulgaris, Ornithodoros lahorensis, O. tartakovskyi, and O. papillipes have been recorded biting humans. Argas persicus is the most common species, and its borne pathogens are widely investigated, while most other argasid ticks are not sufficiently studied in China. Here, we summarize detailed information regarding hosts, geographical distribution, molecular data, and vector roles of argasid ticks in China.

The Distribution, Seasonal Abundance, and Environmental Factors Contributing to the Presence of the Asian Longhorned Tick (Haemaphysalis longicornis, Acari: Ixodidae) in Central Appalachian Virginia

Over the past decade, Haemaphysalis longicornis, the Asian longhorned tick, has undergone a geographic range expansion in the United States, from its historical range in east Asia. This tick has been characterized by its frequent parasitism of livestock, an ability to reproduce through parthenogenesis, and its ability to transmit a variety of vector-borne pathogens to livestock, wildlife, and human hosts in its native geographic range. Thus far in the United States, 17 states have reported H. longicornis populations, including 38 counties in Virginia. These numbers come from presence-absence reports provided to the U.S. Department of Agriculture, but little has been reported about this ticks' seasonality in Virginia or its habitat preferences. Our current study detected H. longicornis populations in seven of the nine surveyed counties in Virginia. Haemaphysalis longicornis were observed in multiple habitat types including mixed hardwood forests and pastures, with abundant H. longicornis populations detected at one particular pasture site in Wythe County. This study also attempted to investigate environmental conditions that may be of importance in predicting tick presence likelihood. While sample size limited the scope of these efforts, habitat type and climatic metrics were found to be important indicators of H. longicornis collection success and abundance for both the nymphal and larval life stages. This current study reports useful surveillance data for monitoring these tick populations as they become established in the western half of Virginia and provides insight into their current distribution and maintenance over a large study region.

Interaction between Old World fruit bats and humans: From large scale ecosystem services to zoonotic diseases

The Old World tropical and subtropical frugivorous bat genus Rousettus (Pteropodidae) contains species with broad distributions, as well as those occurring in restricted geographical areas, particularly islands. Herein we review the role of Rousettus as a keystone species from a global "One Health" approach and related to ecosystem functioning, zoonotic disease and public health. Rousettus are efficient at dispersing seeds and pollinating flowers; their role in forest regeneration is related to their ability to fly considerable distances during nightly foraging bouts and their relatively small body size, which allows them to access fruits in forested areas with closed vegetation. Rousettus are also reservoirs for various groups of pathogens (viruses, bacteria, fungi, protozoa), which, by definition, are infectious agents causing disease. The study of day roosts of different species of Rousettus and the successful establishment of captive breeding colonies have provided important details related to the infection dynamics of their associated pathogens. Large-scale conversion of forested areas into agricultural landscapes has increased contact between humans and Rousettus, therefore augmenting the chances of infectious agent spillover. Many crucial scientific details are still lacking related to members of this genus, which have direct bearing on the prevention of emerging disease outbreaks, as well as the conservation of these bats. The public should be better informed on the capacity of fruit bats as keystone species for large scale forest regeneration and in spreading pathogens. Precise details on the transmission of zoonotic diseases of public health importance associated with Rousettus should be given high priority.

Knowledge, attitudes, and practices regarding tick-borne diseases among an at-risk population living in Niigata prefecture, Japan

Objective

This study examined the knowledge, attitudes, and practices (KAP) of an at-risk population living in Niigata prefecture regarding tick-borne diseases (TBDs) and preventive strategies.

Methods

A cross-sectional questionnaire-based study was conducted to assess the KAP of the community.

Results

In total, 186 responses were received. Among the respondents, 130 (69·9%) were men, and the mean age was 51.1 (14·3). Nine (4·8%) respondents reported having experienced tick bites. Of the respondents, 44 (23.7%) knew about both scrub typhus and severe fever with thrombocytopenia syndrome, while 156 (83·9%) and 71 (38·2%) recognized limiting skin exposure and use of insect repellents as preventive measures, respectively. The attitudes towards TBDs: being worried about tick bites (p = 0·018) and interested in preventing TBDs (p = 0·001), were significantly higher among women than men. About 75% of the respondents reported taking preventive measures against tick bites, and limiting skin exposure was the most frequently applied method (69·9%). Insect repellents were used by 58 (31·2%) respondents. Age (p = 0·049), being worried about tick bites (p = 0·046), and knowledge of ticks score (p = 0·024) were the significant independent predictors of practicing countermeasures.

Conclusion

We identified gaps in knowledge and practices regarding TBDs. Public health interventions should be implemented to improve public awareness of TBDs.

Identification and Distribution of Human-Biting Ticks in Northwestern Spain

Simple Summary

We conducted a tick surveillance study in northwestern Spain. Nymphs of Ixodes ricinus were the most frequently collected. Rhipicephalus bursa, Rhipicephalus sanguineus sensu lato (s.l.), Hyalomma marginatum, Hy. lusitanicum, Dermacentor marginatus, D. reticulatus and Haemaphysalis punctata were also found, with adults as the main stage. The number of collected Hyalomma spp. and R. bursa has been progressively increasing over time. Although bites occurred throughout the year, the highest number of incidents was reported from April to July. The distribution patterns of the tick species were different between the north and the south of the region, which was related to cases detected in humans of the pathogens they carried. Adult men were more likely to be bitten by ticks than women. Ticks were most frequently removed from adults from the lower limbs, while for children, they were mainly attached to the head. Epidemiological surveillance is essential given the increase in tick populations in recent years.

Abstract

Ticks transmit a wide diversity of pathogens to a great variety of hosts, including humans. We conducted a tick surveillance study in northwestern Spain between 2014 and 2019. Ticks were removed from people and identified. Tick numbers, species, development stages, the timeline, seasonal and geographical distribution and epidemiological characteristics of people bitten by ticks were studied. We collected ticks from 8143 people. Nymphs of I. ricinus were the most frequently collected. Rhipicephalus bursa, R. sanguineus s.l., Hy. marginatum, Hy. lusitanicum, D. marginatus, D. reticulatus and H. punctata were also found, with adults as the main stage. The number of collected Hyalomma spp. and R. bursa has been progressively increasing over time. Although bites occurred throughout the year, the highest number of incidents was reported from April to July. The distribution patterns of the tick species were different between the north and the south of the region, which was related to cases detected in humans of the pathogens they carried. Adult men were more likely to be bitten by ticks than women. Ticks were most frequently removed from adults from the lower limbs, while for children, they were mainly attached to the head. Epidemiological surveillance is essential given the increase in tick populations in recent years, mainly of species potentially carrying pathogens causing emerging diseases in Spain, such as Crimean–Congo hemorrhagic fever (CCFH).

Protozoan and Rickettsial Pathogens in Ticks Collected from Infested Cattle from Turkey

Diseases caused by tick-transmitted pathogens including bacteria, viruses, and protozoa are of veterinary and medical importance, especially in tropical and subtropical regions including Turkey. Hence, molecular surveillance of tick-borne diseases will improve the understanding of their distribution towards effective control. This study aimed to investigate the presence and perform molecular characterization of Babesia sp., Theileria sp., Anaplasma sp., Ehrlichia sp., and Rickettsia sp. in tick species collected from cattle in five provinces of Turkey. A total of 277 adult ticks (males and females) were collected. After microscopic identification, tick pools were generated according to tick species, host animal, and sampling sites prior to DNA extraction. Molecular identification of the tick species was conducted through PCR assays. Out of 90 DNA pools, 57.8% (52/90) were detected to harbor at least 1 pathogen. The most frequently-detected pathogens were Babesia bovis, with a minimum detection rate of 7.9%, followed by Ehrlichia sp. (7.2%), Theileria annulata (5.8%), Coxiella sp. (3.3%), Anaplasma marginale (2.5%), Rickettsia sp. (2.5%), and B. occultans (0.7%). Rickettsia sp. identified in this study include Candidatus Rickettsia barbariae, R. aeschlimannii, and Rickettsia sp. Chad. All sequences obtained from this study showed 99.05−100% nucleotide identity with those deposited in GenBank (query cover range: 89−100%). This is the first molecular detection of Rickettsia sp. Chad, a variant of Astrakhan fever rickettsia, in Turkey. Results from this survey provide a reference for the distribution of ticks and tick-borne pathogens in cattle and expand the knowledge of tick-borne diseases in Turkey.

Detection of Phenuiviridae, Chuviridae Members, and a Novel Quaranjavirus in Hard Ticks From Danube Delta

Ticks are involved in the transmission of various pathogens and several tick-borne diseases cause significant problems for the health of humans and livestock. The members of the Quaranjavirus genus are mainly associated with argas ticks but recent studies demonstrated the presence of novel quaranjaviruses-like in ixodid ticks. In 2020, 169 Rhipicephalus sanguineus ticks were collected in Southern Romania from small ruminants and analyzed by high-throughput transcriptome sequencing. Among the viral families that infect Romanian ticks, we have identified sequences from Phenuiviridae (Brown dog tick phlebovirus 1 [BDTPV1] and Brown dog tick phlebovirus 2 [BDTPV2]) and Chuviridae families (Cataloi mivirus [CTMV]), and numerous sequences from a new quaranjavirus-like, tentatively named Cataloi tick quaranjavirus (CTQV). Phylogenetic analyses performed on the five segments show that CTQV is phylogenetically positioned within a clade that encompasses Ixodidae-borne viruses associated with iguanas, small ruminants, seabirds, and penguins distributed across different geographical areas. Furthermore, CTQV is positioned differently depending on the segment considered. This is the first report on the detection of a quaranjavirus-like in Eastern Europe. Further investigations are needed to discern its infectivity and pathogenicity against vertebrates.

Host in reserve: The role of common shrews ( Sorex araneus ) as a supplementary source of tick hosts in small mammal communities influenced by rodent population cycles

Rodents often act as important hosts for ticks and as pathogen reservoirs. At northern latitudes, rodents often undergo multi‐annual population cycles, and the periodic absence of certain hosts may inhibit the survival and recruitment of ticks. We investigated the potential role of common shrews (Sorex araneus) to serve as a supplementary host source to immature life stages (larvae and nymphs) of a generalist tick Ixodes ricinus and a small mammal specialist tick I. trianguliceps, during decreasing abundances of bank voles (Myodes glareolus). We used generalized mixed models to test whether ticks would have a propensity to parasitize a certain host species dependent on host population size and host population composition across two high‐latitude gradients in southern Norway, by comparing tick burdens on trapped animals. Host population size was defined as the total number of captured animals and host population composition as the proportion of voles to shrews. We found that a larger proportion of voles in the host population favored the parasitism of voles by I. ricinus larvae (estimate = −1.923, p = .039) but not by nymphs (estimate = −0.307, p = .772). I. trianguliceps larvae did not show a lower propensity to parasitize voles, regardless of host population composition (estimate = 0.875, p = .180), while nymphs parasitized shrews significantly more as vole abundance increased (estimate = 2.106, p = .002). These results indicate that common shrews may have the potential to act as a replacement host during periods of low rodent availability, but long‐term observations encompassing complete rodent cycles may determine whether shrews are able to maintain tick range expansion despite low rodent availability.

The Symbiotic Continuum Within Ticks: Opportunities for Disease Control

Among blood-sucking arthropods, ticks are recognized as being of prime global importance because of their role as vectors of pathogens affecting human and animal health. Ticks carry a variety of pathogenic, commensal, and symbiotic microorganisms. For the latter, studies are available concerning the detection of endosymbionts, but their role in the physiology and ecology of ticks remains largely unexplored. This review paper focuses on tick endosymbionts of the genera Coxiella, Rickettsia, Francisella, Midichloria, and Wolbachia, and their impact on ticks and tick-pathogen interactions that drive disease risk. Tick endosymbionts can affect tick physiology by influencing nutritional adaptation, fitness, and immunity. Further, symbionts may influence disease ecology, as they interact with tick-borne pathogens and can facilitate or compete with pathogen development within the vector tissues. Rickettsial symbionts are frequently found in ticks of the genera of Ixodes, Amblyomma, and Dermacentor with relatively lower occurrence in Rhipicephalus, Haemaphysalis, and Hyalomma ticks, while Coxiella-like endosymbionts (CLEs) were reported infecting almost all tick species tested. Francisella-like endosymbionts (FLEs) have been identified in tick genera such as Dermacentor, Amblyomma, Ornithodoros, Ixodes, and Hyalomma, whereas Wolbachia sp. has been detected in Ixodes, Amblyomma, Hyalomma, and Rhipicephalus tick genera. Notably, CLEs and FLEs are obligate endosymbionts essential for tick survival and development through the life cycle. American dog ticks showed greater motility when infected with Rickettsia, indirectly influencing infection risk, providing evidence of a relationship between tick endosymbionts and tick-vectored pathogens. The widespread occurrence of endosymbionts across the tick phylogeny and evidence of their functional roles in ticks and interference with tick-borne pathogens suggests a significant contribution to tick evolution and/or vector competence. We currently understand relatively little on how these endosymbionts influence tick parasitism, vector capacity, pathogen transmission and colonization, and ultimately on how they influence tick-borne disease dynamics. Filling this knowledge gap represents a major challenge for future research.

Babesia and Theileria Identification in Adult Ixodid Ticks from Tapada Nature Reserve, Portugal

This study, conducted in a nature reserve in southern Portugal, investigated the frequency and diversity of tick-borne piroplasms in six species of adult ixodid ticks removed from 71 fallow deer (Dama dama) and 12 red deer (Cervus elaphus), collected over the period 2012–2019. The majority of 520 ticks were Ixodes ricinus (78.5%), followed by Rhipicephalus sanguineus sensu lato, Hyalomma lusitanicum, Haemaphysalis punctata, Dermacentor marginatus, and Ixodes hexagonus. The R. sanguineus ticks collected from the deer were clearly exophilic, in contrast to the endophilic species usually associated with dogs. Four tick-borne piroplasms, including Theileria spp., and the zoonotic species, Babesia divergens and Babesia microti, were detected. B. divergens 18S rDNA, identical to that of the bovine reference strain U16370 and to certain strains from red deer, was detected in I. ricinus ticks removed from fallow deer. The sporadic detection of infections in ticks removed from the same individual hosts suggests that the piroplasms were present in the ticks rather than the hosts. Theileria sp OT3 was found in I. ricinus and, along with T. capreoli, was also detected in some of the other tick species. The natural vector and pathogenic significance of this piroplasm are unknown.

Human parasitism by the exotic tick Dermacentor variabilis (Parasitiformes: Ixodida) in Brazil: report of an imported case

In June 2012, a tick was found parasitizing a man in the city of São Paulo, who had recently returned from a visit to Pennsylvania, in the northeast of the United States. The tick was removed and sent to the São Paulo State Department of Health, where it was identified as a male of the species Dermacentor variabilis (Say, 1821), according to the literature and taxonomic keys. The tick was subjected to a PCR test to search for rickettsiae, but the result was negative. The fact that a human entered Brazilian territory unaware that he was parasitized by a hard tick not belonging to the national tick fauna is significant because of the possibility that an exotic species could be introduced and take hold in this country. Another major risk to public health is that this arthropod could be infected with the bacterium Rickettsia rickettsii, as this ectoparasite is the main vector of Spotted Fever on the East Coast of North America.

Tick immunity using mRNA, DNA and protein-based Salp14 delivery strategies

Guinea pigs exposed to multiple infestations with Ixodes scapularis ticks develop acquired resistance to ticks, which is also known as tick immunity. The I. scapularis salivary components that contribute to tick immunity are likely multifactorial. An anticoagulant that inhibits factor Xa, named Salp14, is present in tick saliva and is associated with partial tick immunity. A tick bite naturally releases tick saliva proteins into the vertebrate host for several days, which suggests that the mode of antigen delivery may influence the genesis of tick immunity. We therefore utilized Salp14 as a model antigen to examine tick immunity using mRNA lipid nanoparticles (LNPs), plasmid DNA, or recombinant protein platforms. salp14 containing mRNA-LNPs vaccination elicited erythema at the tick bite site after tick challenge that occurred earlier, and that was more pronounced, compared with DNA or protein immunizations. Humoral and cellular responses associated with tick immunity were directed towards a 25 amino acid region of Salp14 at the carboxy terminus of the protein, as determined by antibody responses and skin-testing assays. This study demonstrates that the model of antigen delivery, also known as the vaccine platform, can influence the genesis of tick immunity in guinea pigs. mRNA-LNPs may be useful in helping to elicit erythema at the tick bite site, one of the most important early hallmarks of acquired tick resistance. mRNA-LNPs containing tick genes is a useful platform for the development of vaccines that can potentially prevent selected tick-borne diseases.

Ticks infesting humans in Central America: A review of their relevance in public health

Ticks are blood-sucking arthropods that parasitize most groups of terrestrial or semiaquatic vertebrates. Humans are accidental hosts to the ticks; however, in humans the ticks can cause damages varying from simple irritation to severe allergies, toxicosis, paralysis, and the transmission of pathogens, some of which can be fatal. Central America represents a narrow isthmus between North and South America and is considered a biodiversity hotspot. The importance of tick-borne diseases in this region is manifested by fatal outbreaks caused by Rickettsia rickettsii, severe and mild cases of other rickettsioses, ehrlichiosis, and tick-borne relapsing fevers, in addition to cases paralysis and strong allergic reactions. Even so, this information is scarce in most countries of this region, and there are no epidemiological data. In this article we present a review of the ticks that parasitize humans in Central America, covering data from the 19th Century to the present day. Of nearly 80 tick species reported in Central America, 28 species are reported on humans. This list includes species that thrive within homes, grazing areas and, to a lesser extent, in wild environments, both in lowland and high mountain forests. The most important genus in this region is Amblyomma, followed by Rhipicephalus and Ornithodoros, and to a lesser extent Haemaphysalis, Ixodes and Dermacentor. These data provide information on the tick species most commonly associated with humans in Central America, and highlight the potential for tick-borne diseases in wild, rural and urban regions.

Human Otoacariasis in Two Climatically Diverse Districts in Sri Lanka: Seasonality, Risk Factors, and Case Notes

PURPOSE

Otoacariasis is a parasitic otopathy reported in many parts of the world. This study presents the seasonal pattern, risk factors, and case notes on human otoacariasis in two climatically different districts: Anuradhapura and Kandy in the Dry and Wet/Intermediate zone of Sri Lanka, respectively.

METHODS

Ticks removed from the ear canal of patients were collected. Risk factors of otoacarisis were determined by a case/control follow-up study.

RESULTS

Nymphal Dermacentor auratus (90.8%) was the main tick species associated otoacariasis. In the Kandy District, infestation was year-round, while in the Anuradhapura District, it was seasonal with a peak in December-February. Children < 10 years were a risk group in both districts. Females were a risk group in the Kandy District. Engagement in outdoor activities was a risk factor in both districts. In addition, the presence of wildlife and domesticated animals were risk factors in the Kandy and Anuradhapura districts, respectively. The treatment protocols in the two hospitals were different. An infant with otoacariasis from the Anuradhapura District developed rickettsia.

CONCLUSIONS

Although the tick species was the same, seasonality, risk groups, and risk factors in the two districts were different which could be due to the establishment and persistence of tick populations influenced by biotic and abiotic factors.

Microbiome analysis of the midguts of different developmental stages of Argas persicus in China

Argas persicus is an ectoparasite of poultry. The bacterial community structure and the pathogenic bacteria associated with different developmental stages of A. persicus have implications for control. Argas persicus were collected from chickens in the city of Jiuquan in Gansu, China. Bacterial DNA was extracted from the midgut contents of blood engorged larvae, nymphs and adult females. The V3-V4 hypervariable regions of 16S rRNA genes were sequenced using the IonS5™XL platform. Identification of Rickettsia spp. and detection of Coxiella burnetii were performed using PCR on target genes. The bacterial diversity within larvae was the highest and the bacterial diversity within nymphs was greater than that of adults. At different classification levels, seven bacterial phyla were common phyla, 27 genera were common genera, and 18 species were common species in the three samples. At the phylum level, Proteobacteria showed a marked predominance in all samples. Rickettsia, Stenotrophomonas, Spiroplasma, and Coxiella were the dominant bacteria at the genus level. The Rickettsia species in A. persicus was identified as Rickettsia hoogstraalii and the Coxiella species was identified as a Coxiella-like endosymbiont. Additionally, some bacterial species such as Pseudomonas geniculata, Sphingomonas koreensis, and Acinetobacter haemolyticus were reported here for the first time in A. persicus.

The Lyme disease agent co-opts adiponectin receptor-mediated signaling in its arthropod vector

Adiponectin-mediated pathways contribute to mammalian homeostasis; however, little is known about adiponectin and adiponectin receptor signaling in arthropods. In this study, we demonstrate that Ixodes scapularis ticks have an adiponectin receptor-like protein (ISARL) but lack adiponectin, suggesting activation by alternative pathways. ISARL expression is significantly upregulated in the tick gut after Borrelia burgdorferi infection, suggesting that ISARL signaling may be co-opted by the Lyme disease agent. Consistent with this, RNA interference (RNAi)-mediated silencing of ISARL significantly reduced the B. burgdorferi burden in the tick. RNA-seq-based transcriptomics and RNAi assays demonstrate that ISARL-mediated phospholipid metabolism by phosphatidylserine synthase I is associated with B. burgdorferi survival. Furthermore, the tick complement C1q-like protein 3 interacts with ISARL, and B. burgdorferi facilitates this process. This study identifies a new tick metabolic pathway that is connected to the life cycle of the Lyme disease spirochete.

Urban woodland habitat is important for tick presence and density in a city in England

Urban green spaces provide an opportunity for contact between members of the public and ticks infected with pathogens. Understanding tick distribution within these areas and the drivers for increased tick density or Borrelia infection are important from a risk management perspective. This study aimed to generate data on tick presence, nymph density and Borrelia infection across a range of urban green space habitats, in order to identify those that may potentially present a higher risk of Lyme borreliosis to members of the public. Several sites were visited across the English city of Bath during 2015 and 2016. Tick presence was confirmed in all habitats surveyed, with increased likelihood in woodland and woodland edge. Highest nymph densities were also reported in these habitats, along with grassland during one of the sampling years. Adult ticks were more likely to be infected compared to nymphs, and the highest densities of infected nymphs were associated with woodland edge habitat. In addition to Lyme borreliosis causing Borrelia genospecies, Borrelia miyamotoi was also detected at several sites. This study adds to the growing evidence that urban green space habitats present a public health risk from tick bites, and this has implications for many policy areas including health and wellbeing, climate adaptation and urban green space planning.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Immunomic Investigation of Holocyclotoxins to Produce the First Protective Anti-Venom Vaccine Against the Australian Paralysis Tick, Ixodes holocyclus

Venom producing animals are ubiquitously disseminated among vertebrates and invertebrates such as fish, snakes, scorpions, spiders, and ticks. Of the ~890 tick species worldwide, 27 have been confirmed to cause paralysis in mammalian hosts. The Australian paralysis tick (Ixodes holocyclus) is the most potent paralyzing tick species known. It is an indigenous three host tick species that secretes potent neurotoxins known as holocyclotoxins (HTs). Holocyclotoxins cause a severe and harmful toxicosis leading to a rapid flaccid paralysis which can result in death of susceptible hosts such as dogs. Antivenins are generally polyclonal antibody treatments developed in sheep, horses or camels to administer following bites from venomous creatures. Currently, the methods to prevent or treat tick paralysis relies upon chemical acaricide preventative treatments or prompt removal of all ticks attached to the host followed by the administration of a commercial tick-antiserum (TAS) respectively. However, these methods have several drawbacks such as poor efficacies, non-standardized dosages, adverse effects and are expensive to administer. Recently the I. holocyclus tick transcriptome from salivary glands and viscera reported a large family of 19 holocyclotoxins at 38-99% peptide sequence identities. A pilot trial demonstrated that correct folding of holocyclotoxins is needed to induce protection from paralysis. The immunogenicity of the holocyclotoxins were measured using commercial tick antiserum selecting HT2, HT4, HT8 and HT11 for inclusion into the novel cocktail vaccine. A further 4 HTs (HT1, HT12, HT14 and HT17) were added to the cocktail vaccine to ensure that the sequence variation among the HT protein family was encompassed in the formulation. A second trial comparing the cocktail of 8 HTs to a placebo group demonstrated complete protection from tick challenge. Here we report the first successful anti-venom vaccine protecting dogs from tick paralysis.