Search Results (555)

Ticks are important arthropod vectors that transmit various pathogens to humans, livestock, and wildlife, thereby contributing significantly to the global burden of vector-borne diseases. The tick microbiome, consisting of bacteria, viruses, protozoa, and other microorganisms, plays a crucial role in pathogen transmission dynamics and the emergence of new zoonotic diseases. This review examines the characteristics of tick vectors, the composition and dynamics of tick-associated microbiomes, and their implications for zoonotic disease transmission. We analyze current knowledge of tick-borne pathogens, including Borrelia burgdorferi sensu lato, Rickettsia species, Anaplasma species, and Coxiella species, and highlight the potential for microbiome constituents to serve as reservoirs for emerging pathogens. The complex interactions between tick hosts, their microbiomes, and vertebrate hosts create opportunities for pathogen evolution and interspecies transmission. Recent advances in molecular techniques have revealed previously unknown microbial diversity within tick populations, suggesting that many potential zoonotic pathogens remain undiscovered. We discuss future research directions, including field screening methodologies for pathogen detection, microbiome-based risk assessment approaches, and the development of novel prevention strategies, including tick vaccines. Full article

Mosquito-borne diseases pose a significant public health concern globally; however, data on mosquito population dynamics in Taipei, Taiwan are limited and outdated. Updated information on species composition and seasonal abundance is crucial for enhancing vector surveillance and informing effective control strategies. In this study, to investigate the seasonal dynamics of mosquito populations in Taipei, Taiwan, adult females were collected biweekly from June 2023 to May 2025 using CDC light traps baited with ultraviolet light and dry ice. Species identification was performed based on morphological characteristics, and morphologically challenging Culex mosquito species were further confirmed using cytochrome c oxidase I barcoding. Mosquito surveillance from June 2023 to May 2025 yielded 1926 females representing 31 species. Of these, Culex quinquefasciatus, Culex pipiens molestus, Aedes albopictus, and Culex tritaeniorhynchus accounted for over 90% of all specimens. These dominant species exhibited distinct seasonal patterns: Cx. quinquefasciatus occurred year-round, Cx. pipiens molestus predominated during winter and spring, while Ae. albopictus and Cx. tritaeniorhynchus populations peaked in summer. Furthermore, spatial heterogeneity in both mosquito abundance and species composition was noted among the study sites. Monitoring the composition and seasonal dynamics of mosquito species is essential for understanding the epidemiology of mosquito-borne pathogens. These insights can inform more effective and targeted vector control strategies for reducing disease transmission. Such ecological insights can also support One Health approaches by linking human, animal, and environmental factors that influence the transmission of mosquito-borne diseases. Full article

Orthohepacivirus glareoli (RHVJ, Hepaciviridae) and its natural host, the bank vole (Myodes glareolus), have been proposed as a model system for human hepatitis C research, yet the mode of transmission remains largely unknown. Here, we investigated spatial patterns of RHVJ sequence diversity and evolutionary relationships using novel sequences from dense regional sampling alongside all published NS3 gene sequences. Phylogenetic analyses revealed mostly local clustering of RHVJ sequences, resulting in isolation-by-distance patterns at regional geographic scales. This suggests primarily local transmission of the virus. However, nucleotide sequence divergence of up to 19% within bank vole populations is difficult to reconcile with local transmission of RHVJ alone, implying that mechanisms beyond local evolution shape the extensive sequence diversity of RHVJ at local scales. Using spatially explicit computer simulations of sequence evolution, we contrasted the phylogenetic relationships resulting from exclusively short-distance transmission, e.g., from vole to vole, with those resulting when rare long-distance transmission events were included. The latter produced phylogenetic patterns comparable to those of RHVJ, including monophyletic clustering of samples from distant locations and unresolved basal nodes. We suggest that the transmission of RHVJ likely involves at least occasionally a vector, as the mobility of its natural rodent host is strongly limited. Full article

Leishmaniases are vector-borne diseases transmitted by phlebotomine sand flies. While bacterial associations in sand fly microbiota are well studied, fungal communities remain poorly characterized, despite their potential role in insect biology and parasite transmission. This study aimed to isolate and characterize yeast-like and filamentous fungi from different developmental stages of Lutzomyia longipalpis, the main vector of visceral leishmaniasis in the Americas, to expand knowledge on fungal microbiota and its possible relevance to vector–parasite interactions. Sand fly eggs, larvae, pupae, and adults were sampled from a laboratory colony. Fungi were isolated from insect tissues and diets using culture-based methods. Morphological identification was complemented by partial sequencing of the ITS1-5.8S-ITS2 rDNA region to identify the species. Four fungi were consistently recovered: Candida guilliermondii, Cutaneotrichosporon dermatis, Penicillium sp., and Aspergillus sp. Their presence varied across developmental stages. Presence in the gut was observed for Cu. dermatis, Penicillium sp. and Aspergillus sp. in larvae and C. guilliermondii in adult females. Evidence suggested their presence in different stages from larvae to pupae, and sex-specific differences in adults, with fungi detected only in females. This work documented the mycobiota that may be associated with L. longipalpis, including the first report of Cutaneotrichosporon in sand flies. These findings highlight fungi that may be potential modulators of sand fly biology and Leishmania development, warranting further investigation into their ecological and epidemiological roles. Full article

West Nile virus (WNV) is a globally distributed mosquito-borne flavivirus with significant implications for both veterinary and public health. While horses are incidental dead-end hosts, their epidemiological role extends beyond clinical disease, as they can serve as effective sentinel hosts for detecting local viral circulation. Their frequent exposure to mosquito vectors, ability to mount measurable antibody responses, geographic stability, accessibility for monitoring, and the possibility of observation within managed owner–veterinarian systems make them particularly suitable for surveillance within a One Health framework. Evidence from Europe and the Americas demonstrates that equine seroprevalence and field surveillance can identify transmission hotspots, reveal silent circulation, and contribute to the understanding of spatial and temporal risk patterns. The review also addresses key limitations, including vaccination effects, flavivirus cross-reactivity, methodological heterogeneity, and challenges in interpreting serological data across different ecological contexts. Strengthening equine sentinel surveillance through standardized methodologies and integration with predictive and geospatial approaches may improve early warning capacity and support more effective control of WNV and other emerging arboviral diseases. Full article

Tick-borne encephalitis virus (TBEV) is a major arthropod-borne flavivirus responsible for severe neurological disease in humans across Europe and Asia. It is maintained in nature through complex interactions within ticks and between tick vectors, vertebrate hosts and environmental factors. This review summarizes current knowledge on TBEV–tick interactions, focusing on virus acquisition, dissemination, vector competence, and long-term persistence within tick vectors. TBEV is acquired by ticks during blood feeding on viremic hosts or through co-feeding transmission under experimental conditions. Transovarial transmission has also been reported, as indicated by the detection of infected larvae in nature, although its efficiency appears to be low and variable. Following ingestion, TBEV infects and replicates in the tick midgut before dissemination via the hemolymph to secondary tissues, including the salivary glands and reproductive organs, which are essential for viral persistence and transmission. Vector competence and capacity vary between tick species and are shaped by intrinsic and extrinsic factors. Although transstadial transmission and transovarial transmission contribute to long-term virus maintenance, their efficiency is generally low and variable. In vitro models, including tick cell lines, have provided valuable insights into virus–tick interactions. Nevertheless, important knowledge gaps remain, particularly in understanding early events at the tick–host interface and mechanisms underlying viral dissemination and persistence within ticks. Full article

Nipah virus (NiV) is an animal-borne RNA virus of the genus Henipavirus that poses a significant global health threat. This threat is driven by the virus’s high mortality rate, its capacity to cause epidemics, and the lack of licensed therapeutic interventions or vaccines. Since its initial identification during the 1998–1999 outbreak in Malaysia and Singapore, recurrent episodes have occurred primarily in Bangladesh and India, with mortality rates frequently exceeding 70%. Fruit bats of the genus Pteropus serve as the biological host for the virus. Transmission to humans occurs via contact with infected wildlife, consumption of contaminated products, such as freshly harvested date palm sap, or direct person-to-person exposure. Other modes of transmission, such as transplacentally or via breast milk, are still under investigation. The clinical presentation of NiV infection varies widely, from mild flu-like symptoms to life-threatening respiratory disease and acute encephalitis. It frequently attacks the nervous system, which can lead to coma, permanent neurological damage, or relapsing encephalitis. The virus enters host cells via ephrin-B2/B3 receptors, enabling systemic dissemination and infiltration of the central nervous system. Diagnosis relies primarily on RT-PCR and serological assays, and virus isolation requires high-containment laboratories. Management remains largely supportive, as no approved antiviral therapy exists. Experimental agents, such as remdesivir, favipiravir, and monoclonal antibodies such as m102.4, have shown promise in preclinical studies. Multiple vaccine platforms—including subunit, viral vector, mRNA, and nanoparticle-based approaches—are under development, though none is yet licensed for human use. Strengthened surveillance, infection control measures, and continued research are essential to mitigate the threat posed by this emerging pathogen. This review summarizes current knowledge on NiV, including its virology, epidemiology, pathogenesis, transmission, and recent progress in therapeutic and vaccine development. Full article

Mosquito-borne diseases are a major global health concern, infecting up to 700 million people annually and causing over one million deaths. Of the several genera of biting mosquitoes, species of Anopheles are mostly studied for their ability (vector competence) to transmit Plasmodium protozoan parasites, some species of which cause malaria. More than 480 species of Anopheles have been described worldwide, and about 70 of these are responsible for Plasmodium spp. transmission. However, the focus on Anopheles as vectors of Plasmodium has led to a relative lack of study about the ability of Anopheles to transmit viruses. Some Anopheles species have been experimentally confirmed as competent for various arboviruses. In most cases, they are secondary vectors, with relatively low competence, contributing to overall transmission while other species of mosquito or other vectors are responsible for sustained transmission. Although secondary vectors may contribute less to transmission, they may play important epidemiological roles by extending transmission seasons and/or providing a means of overwintering viruses. Here, we conducted a review of scientific repositories to build a database of known Anopheles competence for arboviruses. After exclusions, we retained 427 laboratory-confirmed studies from 7343 papers reviewed. Our analysis suggests some Anopheles spp. could contribute to arbovirus overwintering in temperate regions. Full article

Tick-borne viruses (TBVs) are a diverse group of arthropod-borne pathogens maintained in complex transmission cycles involving both tick vectors and vertebrate hosts. Among the known TBV transmission routes, co-feeding transmission, in which virus is transferred from an infected tick to an uninfected tick feeding on the same vertebrate host even in the absence of a detectable viremia, represents an important route that contributes to viral maintenance in nature. Although co-feeding transmission has been demonstrated across multiple vector, host, and virus combinations, the mechanisms governing this transmission route remain poorly defined. This review synthesizes current understanding of co-feeding transmission and highlights the importance of ecological and immunological factors that shape this process in nature. Specifically, we emphasize the role of the cutaneous microenvironment at the tick co-feeding site, where localized viral replication and tick salivary factors create conditions favorable for virus transfer between co-feeding ticks. We also highlight the requirements for co-feeding transmission to occur in nature and across seasons. Together, these insights support a model in which localized skin infection is a central feature of co-feeding transmission while underscoring key gaps in our understanding of the cellular and molecular mechanisms that govern this process. Full article

Ticks harbor complex microbial communities composed of symbionts, commensals, and tick-borne pathogens (TBPs). Together, these microorganisms form the tick holobiont. Within this system, the tick’s physiological architecture structures microbial communities by distributing microorganisms across distinct tissues. This compartmentalization creates spatially distinct ecological niches, which in turn shape how microbial communities assemble and interact. In this review, we integrate ecological theory with current knowledge of tick microbiome research to examine how pathogen–pathogen and pathogen–microbiome interactions emerge within these tissue-structured microbial communities. We first outline how baseline ecological filters, including tick species, developmental stage, tissue identity, vertical transmission, and environmental context, shape the microbiome configuration through community assembly processes. We then examined how TBPs, as high-impact colonizers, can further modify microbial networks by altering host-mediated selective pressures, influencing interaction topology, and reshaping community stability. Based on these observations, we propose a dual selective pressure framework in which (i) baseline ecological structuring processes and (ii) pathogen-associated selective pressures interact to determine the microbial network configuration and functional outcomes within the tick holobiont. These interacting forces may drive shifts in diversity, modularity, keystone taxa emergence, and network resilience, ultimately influencing vector competence. This review frames the microbial communities within the tick holobiont as spatially structured ecological systems shaped by multilevel selective pressures. This conceptual foundation provides a coherent framework for understanding microbial interactions in arthropod vectors and highlights avenues for mechanistic research and microbiome-based strategies to mitigate tick-borne diseases. Full article

Yellow fever (YF) remains a re-emerging vector-borne zoonotic disease in tropical regions of the Americas despite the availability of an effective vaccine. In South America, the virus is maintained through a jungle transmission cycle involving Haemagogus and Sabethes mosquitoes and non-human primates (NHPs), which act as amplifying hosts and key epidemiological sentinels. This narrative review examines the current status of YF epizootics in South America, with a focus on the role of NHPs in viral circulation, early detection, and spillover risk to human populations. We synthesize recent evidence on epizootic patterns across endemic countries, the differential susceptibility of neotropical primates, and the ecological and environmental drivers influencing transmission, including deforestation, habitat fragmentation, and human encroachment into forested areas. In addition, we analyze current surveillance strategies, including wildlife monitoring, entomological and genomic surveillance, and their integration within a One Health framework. This review highlights that YF epizootics are expanding geographically and are closely linked to environmental change and human–ecosystem interactions. Strengthening integrated, multidisciplinary surveillance systems is essential to improve early detection, guide vaccination strategies, and prevent human outbreaks. These findings underscore the critical importance of operationalizing the One Health approach to enhance preparedness and response to YF in South America. Full article

In 2024 Kenya had a population of 4.78 million camels that contributed to the livelihoods of pastoralist communities in northern Kenya. Previous studies in Kenya, Saudi Arabia and eastern Africa demonstrated high seroprevalence of Middle East respiratory syndrome coronavirus (MERS-CoV)-specific antibodies in dromedary camels, as well as sporadic transmission of MERS-CoV from camels to humans. Based on the MERS-CoV data and the very close contact between owners and their camels in northern Kenya, we speculated that camels may also transmit other zoonotic viruses, such as Rift Valley fever virus (RVFV). In this study, 493 camel and 197 human sera were collected in Marsabit, Kenya, through a cross-sectional survey in 2018 and analyzed for the presence of RVFV IgG antibodies using a laboratory-developed indirect enzyme-linked immunosorbent assay (ELISA). Overall, 15.6% of camels and 7.6% of humans were RVFV IgG-positive; IgG-positive camels were predominantly females in large population herds and IgG-positive humans were engaged in farming-related activities and were greater than 18 years old. Of the eight location groups sampled, two had high camel (site 2 and site 6) and two had high human (site 5 and site 6) RVFV seropositivity rates. These data suggest that camelids, such as dromedary camels, may serve as amplifying hosts for vector-borne zoonotic diseases, such as RVFV, and that humans with frequent farming and camel meat, milk, or camel product contact may have increased risk for RVFV exposure or infection. Full article

Ticks serve as primary vectors for a wide array of RNA viruses, yet the diversity and distribution of tick-associated RNA viruses remain incompletely characterized in Hebei province. To address this gap, we conducted a systematic metatranscriptomic investigation of 986 ticks representing six species, collected from the diverse ecological landscapes of Hebei Province in northern China. Our analysis recovered 25 complete or near-complete viral genomes spanning 12 families, including Phenuiviridae, Flaviviridae, and Nairoviridae. Of critical public health significance, we identified Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) in both Haemaphysalis longicornis and Dermacentor nuttalli. Phylogenetic reconstruction revealed marked geographic stratification where strains from the coastal plains clustered with the dominant Genotype F, while those from the mountainous north formed a characteristic and divergent lineage phylogenetically linked to isolates from Inner Mongolia. Furthermore, a novel viral agent provisionally named Zhangjiakou Hepacivirus was discovered in Haemaphysalis japonica. This virus shared less than 80% nucleotide identity with the rodent-associated Hepacivirus P, consistent with a rodent origin and possible cross-species transmission. Collectively, these findings reveal descriptive variation associated with vector identity, physiological status, and ecological context in shaping viral evolution and underscore the need for continuous metagenomic surveillance to mitigate emerging tick-borne disease risks within a One Health framework. Full article

Onchocerca flexuosa is a vector-borne filarial nematode infecting red deer (Cervus elaphus) throughout Europe. Despite numerous reports from Central, Northern, and Southern Europe, its occurrence in South-Eastern Europe has remained largely undocumented. This study provides the first molecularly confirmed report and the first systematic epidemiological assessment of O. flexuosa in red deer in Croatia. During the 2024–2025 hunting season, 110 legally harvested red deer from central Croatia were examined for subcutaneous nodules. Nodules were evaluated morphologically, and adult nematodes were identified and confirmed by sequencing of a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Subcutaneous nodules were detected in 53.6% (59/110) of examined animals. O. flexuosa was confirmed in 52 deer, corresponding to an overall prevalence of 47.3%. Co-infection with Hypoderma diana occurred in 21.2% of infected animals. Sequence similarity ranged from 96.37% to 99.85% compared to published European O. flexuosa isolates. Phylogenetic analysis placed Croatian sequences within the established European lineage, without evidence of regional genetic divergence. The observed prevalence falls within the intermediate range reported across Europe and indicates stable local transmission. These findings close an important geographical knowledge gap and demonstrate that nodular onchocercosis is established in red deer populations in South-Eastern Europe. Full article

The most common species of tick in Europe is the castor bean tick (Ixodes ricinus), which is found in forests, parks, and gardens and is active almost all year round. Ticks are among the most important arthropods and vectors of disease, transmitting a wide range of parasites that sometimes lead to the death of infected organisms. The peak incidence of tick-borne diseases occurs between May and September; however, due to global warming, people are increasingly exposed to tick-borne diseases throughout the year. In order to increase the possibility of preventing the transmission of diseases by ticks, it is necessary to become thoroughly familiar with the life cycle of ticks and the environment in which they live. Vaccines are available for some diseases, such as tick-borne encephalitis, while others require a highly specific diagnosis. Another major problem is the long period between the tick bite, which often goes unnoticed or is even ignored by the patient or the doctor, and the development of tick-borne diseases. Increasing attention is being paid to the prevention of tick-borne diseases through prevention of tick bites, quick tick removal, use of repellents, appropriate land management, vaccinations, and the use of plants as natural acaricides. Full article