Tick Host Pathogen Interactions

Besides causing direct damage associated with blood feeding and in some cases through the excretion of toxins with their saliva, the main relevance of ticks lies in the wide variety of pathogens that they can transmit, including viruses, bacteria, protozoa and helminths. Owing to socioeconomic and environmental changes, tick distribution is changing with incursions of ticks and tick-borne diseases occurring in different regions of the world when the widespread deployment of chemical acaricides and repellents has led to the selection of resistance in multiple populations of ticks. New approaches that are environmentally sustainable and that provide broad protection against current and future tick-borne pathogen (TBP) are thus urgently needed. Such development, however, requires improved understanding of factors resulting in vector competence and tick-host-pathogen interactions. This Research Topic provides an overview of known molecular tick-host-pathogen interactions for a number of TBPs and highlights how this knowledge can contribute to novel control and prevention strategies for tick-borne diseases.

Besides causing direct damage associated with blood feeding and in some cases through the excretion of toxins with their saliva, the main relevance of ticks lies in the wide variety of pathogens that they can transmit, including viruses, bacteria, protozoa and helminths. Owing to socioeconomic and environmental changes, tick distribution is changing with incursions of ticks and tick-borne diseases occurring in different regions of the world when the widespread deployment of chemical acaricides and repellents has led to the selection of resistance in multiple populations of ticks. New approaches that are environmentally sustainable and that provide broad protection against current and future tick-borne pathogen (TBP) are thus urgently needed. Such development, however, requires improved understanding of factors resulting in vector competence and tick-host-pathogen interactions. This Research Topic provides an overview of known molecular tick-host-pathogen interactions for a number of TBPs and highlights how this knowledge can contribute to novel control and prevention strategies for tick-borne diseases.

This volume contains the Proceedings of the 4th International Conference on Ticks and Tick-borne Pathogens (TTP-4), held in Banff, Alberta, Canada, from 21 to 26 July 2002. TTP-4 continues an important tradition established in 1992 at the first Conference in St. Paul, Minnesota, USA, and developed subsequently at the Kruger National Park, South Africa (1995) and the High Tatra Mountains, Slovakia (1999). The 31 papers published in this special issue are divided between six sessions, with a keynote address as an introduction. The first session, which deals with biosystematics, genomics and proteomics of ticks, contains the most recent world list of valid tick names. The papers deal with a broad range of tick-host-pathogen interactions, including remote sensing and mapping of ticks and tick-borne pathogens as well as practical aspects of tick control. It is recommended reading for anyone working on ticks and tick-borne pathogens, which are of increasing medical and veterinary importance worldwide.

A single tick bite can have debilitating consequences. Lyme disease is the most common disease carried by ticks in the United States, and the number of those afflicted is growing steadily. If left untreated, the diseases carried by ticks-known as tick-borne diseases-can cause severe pain, fatigue, neurological problems, and other serious health problems. The Institute of Medicine held a workshop October 11-12, 2010, to examine the state of the science in Lyme disease and other tick-borne diseases.

This book is a collection of 77 expert opinions arranged in three sections. Section 1 on "Climate" sets the scene, including predictions of future climate change, how climate change affects ecosystems, and how to model projections of the spatial distribution of ticks and tick-borne infections under different climate change scenarios. Section 2 on "Ticks" focuses on ticks (although tick-borne pathogens creep in) and whether or not changes in climate affect the tick biosphere, from physiology to ecology. Section 3 on "Disease" focuses on the tick-host-pathogen biosphere, ranging from the triangle of tick-host-pathogen molecular interactions to disease ecology in various regions and ecosystems of the world. Each of these three sections ends with a synopsis that aims to give a brief overview of all the expert opinions within the section. The book concludes with Section 4 (Final Synopsis and Future Predictions). This synopsis attempts to summarize evidence provided by the experts of tangible impacts of climate change on ticks and tick-borne infections. In constructing their expert opinions, contributors give their views on what the future might hold. The final synopsis provides a snapshot of their expert thoughts on the future.

Ticks are noticeable by the high diversity of pathogens they can transmit, most of them with implications in human and animal health. Ticks are arachnids, meaning that they do not share the biological and ecological features of the mosquitoes and other parasitic Diptera. The natural foci of tick-borne pathogens may be as large as a continent, or be restricted to small portions of a country, without apparently too many similar features. The life cycle of the ticks involved three developing instars. The precise relationships of ticks and their hosts, the specific seasonal pattern of activity of ticks, and the still poorly known molecular relationships between ticks and the pathogens they can transmit, make these vectors a specially fecund field of research. Importantly, extensive studies on the biological and ecological relationships of ticks and abiotic (climate and vegetation) conditions have revealed the fine-tuning of the ticks and the pathogens they transmit, together with the biological effects of host and the driving features by the climate. The studies on tick-transmitted pathogens have been on the rise in the last years. There is a growing interest in understand the somewhat complex relationships between the landscape, the climate, the vectors and the pathogens, because the concerns of spread, probably driven by subtle changes in climate and man made alterations of the landscape. Studies on Lyme borreliosis are addressing the interesting issue of the relationships between the climate, the tick activity patterns, and the selection of strains according to the reservoir availability. Furthermore, the expanding field of habitat suitability modeling has been applied with different degrees of success to evaluate and quantify the risk of disease transmission. In such exponentially growing field, revisionary books are clearly welcome additions to the bibliographical tools of researchers. It is however necessary the compilation of works devoted to explore the tip of the iceberg in the field of research. In this Research Topic, we wish to summarize and review the studies on ecology, molecular biology, and tick-host-pathogens interactions, provided to resolve the important issues of ticks and pathogens. We want not only the results obtained by newly developed molecular tools, but rigorous reviews of the most recent advances in these issues. This Topic will cover aspects of both human and animal health, with special interest on zoonoses. Aspects of the biology of the ticks, as affecting the transmission of pathogens, are of special interest in this Topic. Studies on ticks of the poorly known family Argasidae, as related to their involvement on pathogen transmission, are especially welcome. We also wish to describe the perspective of the field in the future. Finally, the presentation of ongoing original works is greatly encouraged.

Arboviruses, or arthropod-borne viruses, such as West Nile virus, Dengue virus, and Zika virus, pose a serious threat to public health worldwide. West Nile virus was introduced to the United States in 1999, and is now endemic, causing over 2,000 domestically acquired cases in the U.S. annually in mammals. Similarly, dengue and Zika viruses are endemic in the Americas and pose novel threats to the human population. Tick-borne viruses such as Powassan virus and Heartland virus are increasing in frequency in the U.S. At this time, there is no commercially available vaccine or therapeutic to treat these viral infections. Because nearly every mammalian case of these virus infections originates from the insect vector, it is imperative that we also understand viral pathogenesis, transmission, and the immune response in insect models as well as pathogenesis and the host responses in infected mammals. The development of methods to block arbovirus transmission from the vector may be effective at ceasing arthropod-to-human infection since the current recommendation to prevent these viral infections is to decrease contact with mosquitoes. Additionally, improving our understanding of epidemiology and ecology will also help develop measures to reduce virus spread. In order to better study mammalian and insect host responses to infection, a number of genetic tools are available, such as fly, mosquito, and tick models, recombinant viruses, mouse models, and bioinformatics tools. The studies described in this eBook will illustrate host responses to infection using mammalian and insect models, identify critical signaling nodes of the innate immune response, and discuss virus transmission from insect to mammal or among infected hosts. Taken together, these studies will elucidate means of decreasing infections in human populations and provide potential targets for future study and therapeutic design.

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