-
Clinical Microbiology Reviews Mar 2020Increases in tick-borne disease prevalence and transmission are important public health issues. Efforts to control these emerging diseases are frustrated by the struggle... (Review)
Review
Increases in tick-borne disease prevalence and transmission are important public health issues. Efforts to control these emerging diseases are frustrated by the struggle to control tick populations and to detect and treat infections caused by the pathogens that they transmit. This review covers tick-borne infectious diseases of nonrickettsial bacterial, parasitic, and viral origins. While tick surveillance and tracking inform our understanding of the importance of the spread and ecology of ticks and help identify areas of risk for disease transmission, the vectors are not the focus of this document. Here, we emphasize the most significant pathogens that infect humans as well as the epidemiology, clinical features, diagnosis, and treatment of diseases that they cause. Although detection via molecular or immunological methods has improved, tick-borne diseases continue to remain underdiagnosed, making the scope of the problem difficult to assess. Our current understanding of the incidence of tick-borne diseases is discussed in this review. An awareness of the diseases that can be transmitted by ticks in specific locations is key to detection and selection of appropriate treatment. As tick-transmitted pathogens are discovered and emerge in new geographic regions, our ability to detect, describe, and understand the growing public health threat must also grow to meet the challenge.
Topics: Animals; Clinical Laboratory Techniques; Humans; Tick-Borne Diseases; Ticks
PubMed: 31896541
DOI: 10.1128/CMR.00083-18 -
Current Opinion in Insect Science Apr 2024As obligate blood-feeders, ticks serve as vectors for a variety of pathogens that pose threats on both human and livestock health. The microbiota that ticks harbor play... (Review)
Review
As obligate blood-feeders, ticks serve as vectors for a variety of pathogens that pose threats on both human and livestock health. The microbiota that ticks harbor play important roles in influencing tick nutrition, development, reproduction, and vector. These microbes also affect the capacity of ticks to transmit pathogens (vector competence). Therefore, comprehending the functions of tick microbiota will help in developing novel and effective tick control strategies. Here, we summarize the effects of main tick symbiotic bacteria on tick physiology and vector competency.
Topics: Animals; Humans; Ticks; Symbiosis; Tick-Borne Diseases; Bacteria
PubMed: 38244689
DOI: 10.1016/j.cois.2024.101163 -
Nature Communications Feb 2021Understanding ecological niches of major tick species and prevalent tick-borne pathogens is crucial for efficient surveillance and control of tick-borne diseases. Here...
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.
Topics: Animals; China; Cluster Analysis; Geography; Incidence; Species Specificity; Tick Infestations; Tick-Borne Diseases; Ticks
PubMed: 33597544
DOI: 10.1038/s41467-021-21375-1 -
Parasite Immunology May 2021'Omics' technologies have facilitated the identification of hundreds to thousands of tick molecules that mediate tick feeding and play a role in the transmission of... (Review)
Review
'Omics' technologies have facilitated the identification of hundreds to thousands of tick molecules that mediate tick feeding and play a role in the transmission of tick-borne diseases. Deep sequencing methodologies have played a key role in this knowledge accumulation, profoundly facilitating the study of the biology of disease vectors lacking reference genomes. For example, the nucleotide sequences of the entire set of tick salivary effectors, the so-called tick 'sialome', now contain at least one order of magnitude more transcript sequences compared to similar projects based on Sanger sequencing. Tick feeding is a complex and dynamic process, and while the dynamic 'sialome' is thought to mediate tick feeding success, exactly how transcriptome dynamics relate to tick-host-pathogen interactions is still largely unknown. The identification and, importantly, the functional analysis of the tick 'sialome' is expected to shed light on this 'black box'. This information will be crucial for developing strategies to block pathogen transmission, not only for anti-tick vaccine development but also the discovery and development of new, pharmacologically active compounds for human diseases.
Topics: Animals; Genome; Host-Pathogen Interactions; Humans; Proteomics; Salivary Glands; Ticks; Transcriptome
PubMed: 33135186
DOI: 10.1111/pim.12807 -
Ticks and Tick-borne Diseases Nov 2022The 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... (Review)
Review
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.
Topics: Dogs; Animals; Humans; United States; Dermacentor; Rhipicephalus sanguineus; Ixodes; Ornithodoros; Bites and Stings; Amblyomma; Tick Infestations
PubMed: 35973261
DOI: 10.1016/j.ttbdis.2022.102025 -
Parasite Immunology May 2021Ticks are the primary vector of arboviruses in temperate climates worldwide. They are both the vector of these pathogens to humans and an integral component of the viral... (Review)
Review
Ticks are the primary vector of arboviruses in temperate climates worldwide. They are both the vector of these pathogens to humans and an integral component of the viral sylvatic cycle. Understanding the tick-pathogen interaction provides information about the natural maintenance of these pathogens and informs the development of countermeasures against human infection. In this review, we discuss currently available information on tick-viral interactions within the broader scope of general tick immunology. While the tick immune response to several pathogens has been studied extensively, minimal work centres on responses to viral infection. This is largely due to the high pathogenicity of tick-borne viruses; this necessitates high-containment laboratories or low-pathogenicity substitute viruses. This has biased most research towards tick-borne flaviviruses. More work is required to fully understand the role of tick-virus interaction in sylvatic cycling and transmission of diverse tick-borne viruses.
Topics: Animals; Bunyaviridae; Flaviviridae; Humans; Immunity, Innate; Orthomyxoviridae; RNA Interference; Reoviridae; Ticks; Virus Physiological Phenomena; Viruses
PubMed: 33368375
DOI: 10.1111/pim.12815 -
Ticks and Tick-borne Diseases Jan 2021Over recent years, a multitude of pathogens have been reported to be tick-borne. Given this, it is unsurprising that these might co-exist within the same tick, however... (Review)
Review
Over recent years, a multitude of pathogens have been reported to be tick-borne. Given this, it is unsurprising that these might co-exist within the same tick, however our understanding of the interactions of these agents both within the tick and vertebrate host remains poorly defined. Despite the rich diversity of ticks, relatively few regularly feed on humans, 12 belonging to argasid and 20 ixodid species, and literature on co-infection is only available for a few of these species. The interplay of various pathogen combinations upon the vertebrate host and tick vector represents a current knowledge gap. The impact of co-infection in humans further extends into diagnostic challenges arising when multiple pathogens are encountered and we have little current data upon which to make therapeutic recommendations for those with multiple infections. Despite these short-comings, there is now increasing recognition of co-infections and current research efforts are providing valuable insights into dynamics of pathogen interactions whether they facilitate or antagonise each other. Much of this existing data is focussed upon simultaneous infection, however the consequences of sequential infection also need to be addressed. To this end, it is timely to review current understanding and highlight those areas still to address.
Topics: Animals; Coinfection; Humans; Prevalence; Tick-Borne Diseases; Ticks
PubMed: 33220628
DOI: 10.1016/j.ttbdis.2020.101607 -
Trends in Parasitology Sep 2019Recently, our knowledge of the composition and complexity of tick microbial communities has increased and supports microbial impact on tick biology. Results support a... (Review)
Review
Recently, our knowledge of the composition and complexity of tick microbial communities has increased and supports microbial impact on tick biology. Results support a phylogenetic association between ticks and their microbiota across evolution; this is known as phylosymbiosis. Herein, using published datasets, we confirm the existence of phylosymbiosis between Ixodes ticks and their microbial communities. The strong phylosymbiotic signal and the phylogenetic structure of microbial communities associated with Ixodid ticks revealed that phylosymbiosis may be a widespread phenomenon in tick-microbiota evolution. This finding supports the existence of a species-specific tick hologenome with a largely unexplored influence on tick biology and pathogen transmission. These results may provide potential targets for the construction of paratransgenic ticks to control tick infestations and tick-borne diseases.
Topics: Animals; Biological Evolution; Genome; Host Microbial Interactions; Microbiota; Symbiosis; Ticks
PubMed: 31331734
DOI: 10.1016/j.pt.2019.06.014 -
Advances in Experimental Medicine and... 2010Ticks are blood feeding parasites transmitting a wide variety of pathogens to their vertebrate hosts. The vector competence of ticks is tightly linked with their immune... (Review)
Review
Ticks are blood feeding parasites transmitting a wide variety of pathogens to their vertebrate hosts. The vector competence of ticks is tightly linked with their immune system. Despite its importance, our knowledge of tick innate immunity is still inadequate and the limited number of sufficiently characterized immune molecules and cellular reactions are dispersed across numerous tick species. The phagocytosis of microbes by tick hemocytes seems to be coupled with a primitive complement-like system, which possibly involves self/nonself recognition by fibrinogen-related lectins and the action of thioester-containing proteins. Ticks do not seem to possess a pro-phenoloxidase system leading to melanization and also coagulation of tick hemolymph has not been experimentally proven. They are capable of defending themselves against microbial infection with a variety of antimicrobial peptides comprising lysozymes, defensins and molecules not found in other invertebrates. Virtually nothing is known about the signaling cascades involved in the regulation of tick antimicrobial immune responses. Midgut immunity is apparently the decisive factor of tick vector competence. The gut content is a hostile environment for ingested microbes, which is mainly due to the antimicrobial activity of hemoglobin fragments generated by the digestion of the host blood as well as other antimicrobial peptides. Reactive oxygen species possibly also play an important role in the tick-pathogen interaction. The recent release of the Ixodes scapularis genome and the feasibility of RNA interference in ticks promise imminent and substantial progress in tick innate immunity research.
Topics: Animals; Hemocytes; Host-Pathogen Interactions; Immunity, Innate; Ticks
PubMed: 21528697
DOI: No ID Found -
Frontiers in Cellular and Infection... 2018
Topics: Animals; Host-Pathogen Interactions; Humans; Immunity, Innate; Tick-Borne Diseases; Ticks; Transcriptome; Vaccines
PubMed: 29963500
DOI: 10.3389/fcimb.2018.00194