Journal of Medical Entomology

Insecticide spraying is a common strategy for controlling dengue outbreaks, but its effectiveness is compromised by the development of resistance in mosquito populations. In this study, we subjected a strain of Aedes aegypti known for its exceptional ability to develop resistance to controlled permethrin and lambda-cyhalothrin insecticides pressure using two different concentrations. We analyzed resistance mechanisms that are enhanced at each concentration and used RNA sequencing to identify transcripts specifically associated with these exposure levels. Our objective was to uncover the molecular mechanisms triggered by different insecticide concentrations and to distinguish responses between type I and type II pyrethroids, which differ in chemical structure. Our results showed that kdr mutations confer only moderate levels of resistance, as do detoxifying enzymes. For lambda-cyhalothrin, we identified genes involved in the electron transport chain, mitochondrial function, and overall responses to oxidative stress. tRNA transcripts were also upregulated, along with mitochondrial and stress-response transcripts, suggesting a metabolic shift, particularly toward maintaining homeostasis under oxidative stress. These changes point to mechanisms that sustain resistance to this type II insecticide beyond direct detoxification in this population. On the contrary, permethrin induced marked overexpression of cuticle genes, CYP450 genes (especially CYP4), and Odorant Binding Proteins. These expression patterns, together with metabolic enzymes, point to detoxification, reduced penetration, or even sequestration of insecticide, all of which intensify with increasing concentrations. This overregulation of genes suggests an integrated response complemented by classical metabolic detoxification and accompanied by overregulation of mitochondrial complexes. We showed that despite the shared mode of action of the insecticides permethrin and lambda-cyhalothrin, they elicit distinct responses in this Ae. aegypti population. We also showed that the transcriptomic response depends on insecticide concentration and may modulate insecticide tolerance. This article advances understanding of the complexity of pyrethroid resistance in Aedes aegypti and underscores the importance of considering both the insecticide type and the concentration used in vector control programs. Author summaryAedes aegypti mosquitoes transmit dengue and other arboviruses, being a major public health problem in tropical regions like Colombia, where control relies on pyrethroid insecticide spraying. Based on reports of inconsistent results in the field due to different effects of insecticide concentrations, we recreated variable doses by exposing a resistant Colombian Aedes aegypti strain to low (LC25) and high (LC75) concentrations of permethrin (type I) and lambda-cyhalothrin (type II) to identify concentration-dependent resistance mechanisms. Using genetic mutation analysis, enzyme activity assays, and RNA sequencing, we identified the molecular mechanisms these mosquitoes use to survive. Knockdown resistance (kdr) and detoxification enzymes contributed to some extent to resistance but varied by insecticide type and concentration. RNAseq identified that lambda-cyhalothrin upregulated genes for mitochondrial energy production, oxidative stress defense, immune signaling, and transfer RNAs, facilitating homeostasis under chemical stressors. Permethrin instead upregulated genes for cuticle thickening, cytochrome P450 enzymes, and odorant-binding proteins, which are associated with improved penetration barriers, and metabolic breakdown that intensified with higher concentrations. This reveals pyrethroid resistance as complex beyond classic mechanisms, as even low field doses favor stress tolerance or physical defenses to evade sprays. We detected transcripts that improve survival at high concentrations and could be selected in these mosquitoes. Carefully selecting the type of pyrethroid to be used and the dose should be an important factor in vector control. This optimizes current interventions, prolongs their efficacy, and aids researchers in modeling resistance to protect communities.

BackgroundThe malaria transmission potential and the vulnerability of Anopheles mosquitoes to different vector control methods depend, among other factors, on the endophily, endophagy, anthropophagy and survival of each species. Local information on these bionomic parameters is generally unavailable. MethodsTo address this, we estimated species-specific values of these parameters using an augmented version of the global database of bionomics data by Massey et al. (2016). We applied inclusion and exclusion criteria to select eligible studies with relevant experimental designs that minimise bias from collection methods for parous, sac, endophagy, and endophily rates as well as for the resting duration. For the human blood index (HBI), we separated data from indoor and outdoor collections. We fitted hierarchical Bayesian models with levels based on Anopheles taxonomy to estimate these quantities. Based on the estimated bionomics, we quantified the expected vectorial capacity reduction after the introduction of a pyrethroid-pyrrole insecticide-treated net (ITN) for 57 Anopheles species. ResultsWe identified 26 eligible studies for endophagy and 61 for the parous rate, leading to a Bayesian posterior average for the Anopheles genus of 42% (95% credible interval: 18-70) and 55% (32-77) respectively. HBI values widely varied depending on the location of collection, except for some species showing strong anthropophilic behaviours. Resting duration was estimated to be 2.1 days (1.2 - 4.8) at the genus level. Few studies were available to estimate the sac and endophily rates, which prevented us from deriving precise estimates for the whole Anopheles genus. Our estimates of the vectorial capacity reduction following the introduction of a pyrrole-pyrethroid ITN ranged between 48% and 76% across species, highlighting the important differences among mosquito species in vulnerability to vector control interventions. ConclusionThis work demonstrates how data from both Anopheles species complexes and individual species can be leveraged to generate species-specific estimates of bionomic parameters, capturing the local characteristics and behaviour of malaria vectors. The dataset is readily updatable as new data become available. However, more frequent and standardised field surveys are still needed to accurately characterise local vector behaviour.

Carausius morosus, the Indian stick insect, is a slender twig-like insect endemic to India. Though widely introduced through captivity around the world and commonly used in laboratories or kept as a household pet, standardized animal husbandry laboratory protocols are lacking. Here we report detailed laboratory culture conditions for C. morosus. We maintain stocks at 23 {degrees}C, 70% relative humidity, and a 12:12 hour light-dark photoperiod. This culture has been successfully sustained under these conditions for over two years, with standardized protocols in place for dietary and cage setup conditions. We also report methods for egg and hatchling care to support ongoing experiments with C. morosus. These standardized methods improve reproducibility and accessibility, enabling the broader use of C. morosus as a laboratory model system for developmental, behavioral, and physiological studies. SummaryThis paper outlines detailed protocols for maintaining a Carausius morosus laboratory colony, including key procedures for animal husbandry, egg and hatchling care, and an overview of the species lifespan and biological characteristics.

BackgroundAnopheles mosquitoes vector pathogens responsible for more than 600,000 human deaths annually. Ecological studies of these insects are important to guide effective vector-control campaigns and to understand their broader ecological consequences. Molecular ecology methods, particularly qPCR, provide a valuable tool in such studies. By detecting trace DNA of a taxon of interest within mixed or environmental samples, qPCR can facilitate identification of prey taxa of interest in the diets of consumers. However, no protocol for the detection of An. gambiae complex mosquitoes in dietary samples has been available. MethodsWe introduce a new set of qPCR primers (Agam_CO1_F1 and Agam_CO1_R1) and a probe-based assay for detection of Anopheles gambiae-complex mosquitoes, even with short reads common in dietary and environmental samples. The primers were tested in vitro for their specificity and sensitivity, and in silico using Primer-BLAST to assess potential off-target amplification. ResultsThe qPCR primers amplified An. gambiae DNA even at low starting concentrations (5 copies {micro}l-1). The primers did not amplify any non-target DNA in either the in vitro or in silico tests, but consistently amplified An. gambiae complex DNA. The primers can therefore provide reliable tests for the presence or absence of An. gambiae complex in dietary or eDNA samples. ConclusionsThe new qPCR primers should allow advances in research into mosquito ecology by allowing detection of even trace amounts of An. gambiae DNA in dietary and environmental samples. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=72 SRC="FIGDIR/small/707393v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@1fcce3corg.highwire.dtl.DTLVardef@47e5f5org.highwire.dtl.DTLVardef@4a7063org.highwire.dtl.DTLVardef@1188d60_HPS_FORMAT_FIGEXP M_FIG C_FIG

West Nile virus (WNV) transmission risk is typically estimated from pooled whole-mosquito infection data, which may overestimate the proportion of mosquitoes capable of transmission. To assess natural viral dissemination in field-collected Culex tarsalis, we tested infection rates in tissues of 1,793 individual mosquitoes collected from Northern Colorado in August 2023. Abdomens were screened for WNV RNA, and corresponding thorax and head tissues from positive mosquitoes were tested. Fifteen mosquitoes had detectable abdominal infections, but WNV RNA was detected in only 53% (8/15) of both the thorax and head tissues, while another 27% (4/15) had WNV RNA detected in either the thorax or the head alone. Logistic regression suggests an inconsistent relationship between abdominal viral ribonucleic acid (RNA) load and virus dissemination, whereas receiver operating characteristic analysis identifies a threshold of [~]59,000 RNA copies in the abdomen predictive of dissemination (AUC 0.80, 95% CI: 0.545, 1). These results suggest whole-body RNA detection may overestimate transmission potential from field-captured mosquitoes, and that incorporating infection data could refine surveillance-based risk indices for WNV.

O_LIAlthough ecological research has long focused on the effects of temperature on population growth, arthropod pests are exposed to a wide variety of environmental factors that affect their performance, such as chemical pesticides targeted against them. Moreover, these environmental factors likely do not act in isolation. Identifying the extent to which abiotic factors interact to affect pest population dynamics can strengthen current and future pest management programs. C_LIO_LIHere, we investigated the extent to which temephos, a common pesticide applied to aquatic environments for mosquito control, influences the thermal performance of juvenile survival and development rate, as well as the intrinsic population growth rate, of the invasive mosquito pest, Aedes aegypti. We implemented a response surface experimental design to measure these traits across seven temperatures and five temephos concentrations and fit temperature- and insecticide-dependent performance curves to assess impacts on the overall performance and the thermal optimum, minimum, and maximum. C_LIO_LITemephos exposure profoundly altered the thermal performance of juvenile survival by reducing survival across all temperatures, shrinking the thermal breadth, and shifting the thermal optimum to warmer temperatures. Through this, temephos also altered the thermal performance of population growth primarily by reducing its thermal breadth. C_LIO_LISynthesis and applications: Our findings demonstrate that interactions between temperature and insecticide exposure can fundamentally reshape pest population dynamics, rather than acting as independent stressors. By quantifying this interaction, we showed that temphos is most effective below the pests thermal optimum, suggesting that larvicides may yield the greatest population suppression in cooler regions or during cooler periods of the year. Incorporating such temperature-dependent efficacy into pest management strategies could improve the timing and spatial targeting of control efforts. More broadly, these results highlight the need to integrate anthropogenic stressors with climatic drivers when predicting pest risk and optimizing management under ongoing environmental change. C_LI

Kissing bugs are the primary vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Kissing bugs are exposed to thermal variability, including short periods of heat stress, which can induce mortality or exert sublethal effects. This study investigated Rhodnius prolixus following brief periods of high thermal stress with respect to survival, blood feeding, developmental processes, and T. cruzi infection, with a focus on sublethal effects. Our results demonstrated a significant decrease in survival for R. prolixus at 42 {degrees}C for 8 hours. When exposed to sub-lethal thermal stress (40{degrees}C for 8 hours), blood ingestion (amount and proportion) was reduced after 24 hours of recovery from thermal stress. Among the bugs that fed after 24 hours, molting was not impacted by temperature exposure. The infection rate decreased after heat exposure, likely due to reduced blood volume ingested when feeding 24 hours after heat stress. A week of recovery after exposure to higher temperatures improved feeding and increased infection rates to levels comparable to those of kissing bugs not exposed to thermal stress. Our findings offer insights into how extreme temperature events may influence Chagas disease. Specifically, these studies highlight the need to clarify how temperature, particularly at sublethal levels, interacts with vector biology to alter parasite transmission.

Ultra-low volume (ULV) insecticide spraying with deltamethrin as the active ingredient is widely used in mosquito control programs, yet its effectiveness against target mosquitoes and its ecological side effects remain poorly quantified under field conditions in Central Europe. Here, we experimentally evaluated the short-term impact of ground ULV spraying on both mosquito populations and non-target flying insects in Hungary using a paired before-after-control-impact (BACI) design. Mosquitoes were sampled with BG Sentinel traps, while non-target insects were collected using malaise traps. ULV treatment resulted in a significant reduction in mosquito abundance at treated sites, with an average decline of approximately 45%. Native and invasive mosquito species, including Aedes albopictus and Aedes koreicus, showed similar proportional decreases. However, treatment effectiveness varied substantially among sites and was influenced by initial mosquito abundance and wind conditions. In parallel, malaise trap samples revealed a marked decline in non-target flying insects, with reductions exceeding 40% across multiple taxonomic groups, particularly among small- and medium-sized insects, and also when considering pollinator taxa together. Our results indicate that while ULV spraying can temporarily reduce mosquito abundance, it also imposes considerable short-term impacts on non-target insect communities, highlighting trade-offs between vector control and insect conservation within mosquito management programs.

There is empirical evidence that biophysical factors determine the spatio-temporal distribution of mosquito vectors, and identifying the variables that shape their ecology allows decision-makers to design effective surveillance and control strategies. This study evaluated the spatiotemporal distribution of Aedes albopictus in relation to environmental and biotic variables in the Iguazu Department, Misiones Province, Argentina, within the tri-border region shared with Brazil and Paraguay. Environmental characterization integrated field data and remotely sensed biophysical variables, and vector occurrence was analyzed at micro- and meso-spatial scales using generalized linear mixed models. Eleven sampling sessions were conducted between April 2019 and February 2020 at 81 sites representing urban, periurban, and wild environments. A total of 1,614 Ae. albopictus and 4,358 Ae. aegypti specimens were identified. Rainfall, minimum temperature, exposure days, and land cover were the main predictors of Ae. albopictus presence, showing nonlinear responses to precipitation and vegetation. The selected model explained 67% of the variance. The species exhibited clear spatiotemporal stratification, with periurban and disturbed wild areas functioning as ecotones favorable to its establishment. These findings provide key insights to guide preventive actions and strengthen integrated vector management strategies in the region.

Climate change driven saltwater intrusion is expanding coastal brackish water habitats, promoting the proliferation of salinity-tolerant mosquitoes such as Culex sitiens, a vector of lymphatic filariasis and Japanese encephalitis. This study investigated whether environmental salinity affects mosquito morphology, specifically proboscis length, a trait of ecological significance related to feeding efficiency and vector competence. Late fourth-instar larvae and pupae of Cx. sitiens were collected from habitats with varying salinity levels in the Muttukadu Backwater, Tamil Nadu, India, and reared under controlled conditions using habitat specific water. Adult female body and proboscis lengths were measured, and water quality parameters were analysed to characterize environmental variation. Statistical analyses (Welchs ANOVA, regression, and ANCOVA) revealed a significant positive relationship between salinity and body length (R2 = 0.94, p=0.0003) as well as with proboscis length (R2 = 0.90, p=0.001). Additionally, ANCOVA indicated that the proboscis elongation remained significant after adjusting for body length (F{square}, {square}{square}{square} = 32.36, p < 0.001, partial 2 = 0.257). This confirmed that the salinity exerts an independent effect on this morphological trait. These findings provide the first field-based evidence that the environmental salinity drives proboscis elongation in Cx. sitiens, indicating an adaptive response under saline stress. This may have implications for disease transmission in climate-affected coastal regions.

BackgroundTemperature choice is a vector trait that influences microhabitat selection and can have important implications for vector species, as it may affect how often vectors encounter hosts. Aedes aegypti and Ae. albopictus are disease vectors whose geographic ranges continue to expand each year. One aspect that remains largely understudied is the altitudinal range of these species and the extent of differences in thermal behavior between lowland and highland populations. MethodsI collected Ae. aegypti and Ae. albopictus on the islands of Bioko and Sao Tome. I compared the distribution of the two species along an altitudinal cline spanning 2,000 m of elevation. I then used live specimens to test temperature preference for both species in a laboratory thermocline. ResultsI report the distribution of these two species on the island of Bioko and show that the abundance of immature stages of both species follows a negative exponential decay with altitude. I compare this distribution with that observed on the neighboring island of Sao Tome, also in the Gulf of Guinea. Overall, the distribution patterns of the two species are similar, but models indicate a higher abundance at sea level in Sao Tome than in Bioko. I used specimens from this survey to study temperature preference under controlled conditions. I found no significant differences between species or between sexes; however, I detected an altitudinal cline in temperature preference, with high-elevation populations preferring cooler temperatures on both islands. ConclusionsThese results indicate the presence of phenotypic variation in a key trait--temperature choice--that may alter the likelihood of contact between these vectors and humans.

IntroductionBy 2025, Aedes albopictus had spread across France, leading to a rise in indigenous arboviral cases since 2021. While urban greening is promoted for its health and climate benefits, its potential adverse effects on arboviral risk remain understudied. Urban green spaces may enhance mosquito habitats and human-vector contact. MethodsThis study investigates the variation in Aedes albopictus longevity across months and urban environments in Montpellier, a green Mediterranean city, and its impact on the theoretical basic reproductive number (R0) for Chikungunya, Dengue, and Zika viruses. From May to October 2023, female mosquitoes were sampled monthly using CO2 traps in three urban environments: urban parks, impervious areas, and residential areas composed of houses with gardens. Daily mosquito survival was estimated from parity rate measurements, and the associated environmental determinants were analysed. Modelled predictions, crude field estimates of vector density and parity rates, and microclimatic data were used to parameterize and feed R0 models. For each environment (or sampling area), 1000 monthly R0 simulations were run, followed by sensitivity analyses. Results/DiscussionThe highest mean daily survival (0.917) was observed in residential areas, compared to parks (0.887) and impervious areas (0.873). A daily average exposure of 10% of possible bites induces potential transmission risks for CHIKV and DENV. R0 varied by environment and month, with higher values in residential areas and with greater variability in impervious areas. Parity rate emerged as the main driver of R0 variability. These results highlight the value of fine-scale field data for arboviral risk assessment.

A field trial was conducted using 10% lambda-cyhalothrin microcapsule suspension to provide a method for killing ticks and preventing diseases in outdoor gatherings of people or temporary resettlement places after disasters. In this study, three field experimental sites were selected, and each experimental site was set up with a test area and a control area. Before pesticide application, the tick density in three test areas and three control areas was surveyed using the flagging method. Subsequently, two methods were used for pesticide spraying: motorized fogging and electric constant-volume spraying (with the pesticide diluted 300 times). The relative density decline rate of ticks was calculated in three test sites on days 1, 7, 14, 21, and 28 after spraying, and all experimental areas achieved good tick-killing effects. Even without prohibiting wild animals, grazing sheep, and dogs (which are often infested with ticks and not treated) from entering the trial sites, spraying 10% lambda-cyhalothrin microcapsule suspension could maintain a tick-free (low-density) state for approximately 3-4 weeks. Our study provides an idea for controlling epidemics through tick elimination during the high incidence period of tick-borne diseases.

BACKGROUNDThe two-spotted spider mite, Tetranychus urticae Koch, is a major agricultural pest with a rapid propensity for developing acaricide resistance. Bifenazate targets mitochondrial cytochrome b (CYTB). While the G126S mutation is frequently associated with resistance, its independent role remains unclear as it often occurs with other substitutions. This study explores the molecular basis of bifenazate resistance in a Russian laboratory strain derived from a St. Petersburg greenhouse population. RESULTSDisruptive selection with increasing bifenazate concentrations generated resistant and susceptible isofemale lines. AlphaFold2 structural modeling of CYTB indicated that G126S causes a steric clash, leading to conformational destabilization, whereas other reported mutations primarily affect the ligand-binding pocket. Oxford Nanopore sequencing revealed a very low initial frequency of the G126S allele (<1%; 226/35,895 reads) in the unselected population. After one year of stepwise selection (0.00005-0.031% a.i.), the mutant allele frequency surged to 90% (7,272/8,056 reads). No other known resistance-associated mutations were found in the analyzed cytb fragment. CONCLUSIONWe report the first identification of the G126S mutation in a Russian T. urticae population and demonstrate its rapid fixation under bifenazate selection. Within this genetic background, G126S alone appears sufficient to confer high-level resistance, emphasizing the population-specific nature of resistance evolution and the critical need for local monitoring.

Male mosquitoes are mass-reared around the globe for use in mosquito control programs like Sterile Insect Technique and Incompatible Insect Technique. During larval development, mosquitoes co-exist with complex microbial communities that serve as food and also form the internal microbiota of the organism. The microbiota can impact multiple larval and adult life history traits including development rate and male body size. In the present study, we investigated how male wing length and adult male longevity is impacted by the addition of a single bacterial isolate to otherwise conventional larval rearing water. Of three isolates tested, we found that larval exposure to one, Cedecea sp., resulted in adult males with significantly reduced wing length and longevity. Our findings suggest that minor modifications of the microbial community during larval development can have life-long effects on mosquitoes which, like many organisms, acquire their microbiota from the environment. Moreover, they suggest that mosquito life history traits can be influenced by small shifts in the microbial rearing community, which could impact the efficacy and efficiency of mosquito mass rearing for vector control.

Istocheta aldrichi (Diptera: Tachinidae), a specialist parasitoid of the invasive Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae), was released to eastern North America in the 1920s as part of a classical biological control program. Further releases are being considered in different regions of North America and Europe where P. japonica is establishing. Successful releases of the biocontrol agent depend on identifying efficient techniques for collecting parasitized hosts from the field and rearing the parasitoid through diapause to obtain I. aldrichi adults. In this study, we evaluated how the collection date, the collection method (hand-picking vs. regular traps vs. modified traps) and rearing conditions (food provision and substrate type) of parasitized hosts influence I. aldrichi pupariation and emergence. The proportion of parasitized beetles yielding I. aldrichi puparia decreased considerably as the season progressed. Rearing conditions immediately after collection influenced both puparium yield and quality: withholding food from parasitized P. japonica slightly increased puparium yield but reduced puparium weight, while the effect of food provision on subsequent overwintering survival depended on rearing substrate. Finally, simple modifications to commercial traps (larger, ventilated, containers with added food source and substrate) collected more beetles than regular traps and promoted successful development of the parasitoid to the puparium stage. Our results are used to suggest basic guidelines for collecting and rearing I. aldrichi in experimental research and applied biological control of P. japonica.

The globally distributed arbovirus West Nile virus (WNV) continues to expand across Europe, with rising numbers of human cases and an increasingly broad geographic distribution. WNV is primarily transmitted by mosquitoes of the genus Culex. Out of nine WNV lineages, human pathogenicity has been clearly established for lineages 1 and 2, but differences in their transmission dynamics, such as minimal infectious dose and transmission efficiency, remain poorly understood. In this study, we investigated how viral lineage, mosquito species, and blood meal titer influence the vector competence of two primary WNV vectors from Europe, Cx. pipiens biotype pipiens and Cx. torrentium, as well as the invasive mosquito species Aedes albopictus. Female mosquitoes were fed with increasing blood meal titers containing either of the WNV lineages. After an incubation period of 14 days at a mean temperature of 24{degrees}C, mosquito body titers were quantified, and the presence of infectious viral particles in the saliva was assessed. Our results revealed clear differences between the two lineages. Lineage 2 resulted in higher transmission efficiencies across all three species and required lower infectious doses to cause transmission. Among the tested species, Cx. torrentium proved to be a highly competent vector (max. transmission efficiency = 30%, minimum infectious dose = 105 TCID50/mL), despite its underrepresentation in research. These findings provide detailed insights into how viral lineage, mosquito species, and blood meal titer might shape WNV transmission, informing future risk assessments and efforts to mitigate WNV transmission in Europe.

Istocheta aldrichi (Diptera: Tachinidae) is a specialist parasitoid of the invasive Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae). Research and releases for biological control depend on field collecting parasitized hosts and rearing the parasitoid through diapause to obtain I. aldrichi adults. This study investigated how rearing practices before, during and after the seasonal overwintering period affected the proportion of I. aldrichi pupae that emerged as adults, the timing of parasitoid emergence, and their longevity. Increasing cold exposure duration during overwintering increased adult I. aldrichi emergence from puparia and reduced development time after transfer to warm conditions. Adult I. aldrichi emergence from overwintered puparia depended on interactions between overwintering environment (indoors vs. outdoors), spring thermal regime, and the timing of host collection in the previous season. Burying puparia in the soil in late summer/early fall resulted in higher subsequent adult I. aldrichi emergence. Manipulating spring temperatures in controlled environments allowed parasitoid emergence to be staggered over several weeks without reducing emergence success. Emergence under outdoor spring conditions was unreliable. Adult longevity was affected by temperature and diet: cooler conditions extended lifespan, honey-water increased longevity relative to pollen alone or honey-water and pollen together. These results provide a foundation to further improve I. aldrichi rearing techniques for use in experimental research and applied biological control of P. japonica.

Tick-borne pathogens are transmitted by tick bites to cause infectious diseases in humans and domestic animals. To anticipate the occurrence of tick-borne diseases, it is required to understand high resolution distribution of infection risk and associated ecological factors. The aim of the present study is to reveal the spatial distribution of ticks and ticks infected with pathogens in central Hokkaido, Japan. Adult and nymphal ticks were collected with a constant effort at 171 sites from 13 May to 26 June 2024, followed by screening tick-borne pathogens. The potential suitable habitats of seven tick species and the endemic tick-borne pathogens in the study area (i.e. tick-borne encephalitis virus, Yezo virus, Beiji nairovirus, Lyme disease group borreliae, and relapsing fever group borreliae) were predicted using ecological niche modeling. Ixodes persulcatus and Ixodes ovatus were identified as the primary ticks to determine the distributions of all the pathogens. Besides, the predicted suitable habitats were specific to each pathogen/tick species. Among the environmental variables considered for modeling, snow depth appeared to significantly contribute to the distribution differences between ticks and pathogens. The findings of this study expand our understanding of the spatial risk distribution of tick-borne pathogen infections and its ecological context.

BackgroundThe recent spread of mosquito-borne pathogens and their vectors within Europe highlights the impact of climate change on vector-borne disease (VBD) distributions. Mosquito surveillance has been implemented in many European countries to monitor expansion of vector populations and VBDs, but ability to predict disease risk is constrained by geographic data gaps, particularly in northern areas. In the United Kingdom, wetland mosquito surveillance has been conducted extensively in England, with a knowledge deficit for Scotland. Here, we addressed this gap through a nationwide survey of mosquitoes at Scottish wetlands, with aims of 1) confirming the geographic distribution and environmental drivers of mosquito occurrence and abundance, and 2) identifying the presence of vector species of epidemiological concern, including the Culex pipiens molestus biotype, an important vector of emerging VBDs in mainland Europe. MethodsMonthly mosquito sampling was conducted between June and October 2023 at 22 sites across Scotland comprising six wetland types: coastal saltmarsh, wet grassland, wet woodland, reedbeds, ponds and blanket bog. Adult and larval populations were sampled using Biogents BG-Pro traps and larval dipping respectively. Microclimatic and hydrological variables were recorded at collection sites and used in generalised linear mixed models to identify predictors of mosquito presence and abundance. Results1951 adults (17 species/ groups) and 860 larvae (six species/ groups) were collected from wetlands over 183 and 164 sampling events respectively. Mosquitoes were widely distributed across the Scottish mainland including up to the northern coast, being found at all but one site. Several potential vector species including Culex pipiens s.l. and Anopheles claviger were common. Amongst the adult Culex pipiens s.l. specimens, approximately 8% were Culex pipiens biotype molestus or hybrid forms. Total mosquito abundance and that of key vector species were positively associated with temperature and rainfall. ConclusionsWe report the widespread distribution of mosquitoes in wetlands throughout Scotland, including potential vector species previously unconfirmed in Scotland. Predicted associations between mosquito abundance, rainfall and temperature indicate that climate change could favour mosquito populations in Scotland. Our results provide the first comprehensive description of mosquito ecology in Scotland, as required to update assessment of VBD risk under climate change.