Ticks and Tick-borne Diseases

Tickborne diseases are a significant burden in many parts of the world. In the upper Midwestern United States, Lyme disease is the most common tickborne disease. It is carried by Ixodes scapularis. This vector can also transmit the pathogens causing anaplasmosis, babesiosis, ehrlichiosis, and several more tickborne diseases in this region. There is also concern for other tick species, such as Amblyomma americanum, that are expanding their ranges northward. We launched a citizen science passive tick surveillance program in 2024 to investigate tick species ranges in the upper Midwest, as well as the pathogens carried by I. scapularis. We received over 12,000 ticks in the first two years of this program, primarily from Wisconsin. While we received submissions of adult A. americanum outside of their endemic range, we did not see evidence of establishment in our study area. We measured pathogen prevalence in adult female I. scapularis (n=707) and observed 51% positivity for Borrelia burgdorferi, 9% for Babesia microti, 9% for Anaplasma phagocytophilum, and 3% for Ehrlichia muris eauclairensis. Multiple pathogens were identified in 14% of tested specimens, and significant associations were observed between B. burgdorferi and B. microti, and B. burgdorferi and E. muris eauclairensis. Pathogen prevalences varied across time and geography. Our results can begin to inform risk assessment for tickborne diseases in our region. A non-technical version of this document with interactive maps is available here: https://storymaps.arcgis.com/stories/8008c9d710b5400599f3c6cf88b2c546 Our online data dashboard is available here: redcap.link/TICS

Knowledge, attitudes, and practices (KAP) studies help identify priority groups for control interventions. They include multiple factors, such as threat perception--encompassing perceived susceptibility and severity of a health risk--and sociodemographic data, which have been shown to be associated with individual prevention and control measures for mosquito-borne diseases. However, their application to tick-borne diseases (TBDs) remains largely unstudied in limited-resource settings. Ehrlichia canis, transmitted by Rhipicephalus sanguineus s.l. ticks, is highly prevalent in Iquitos, Peru, a city in the Peruvian Amazon. We analyzed data from a questionnaire completed by 285 dog owners in Iquitos to assess whether the perceived threat from ticks and TBDs is linked to preventive measures for homes and dogs. Secondary aims included examining the associations between TBD awareness and preventive/control measures, as well as identifying sociodemographic factors linked to these measures and threat perception. We used simple and multiple regression models to evaluate the associations of interest. We found that 31.6% of participants (n = 90) were unaware that TBDs could occur in humans. This group tended to be older, with lower education levels and lower income. Only a small portion of the included participants reported using preventive/control measures. After adjusting for sociodemographic factors, TBD awareness was associated with a higher likelihood of home spraying. Furthermore, those who perceived TBDs as moderate diseases were marginally more likely to apply spray acaricide to their dogs, while those who perceived these diseases as severe to very severe were more likely to administer oral acaricides to their dogs. These findings highlight variability in the link between threat perception and preventive measures. Results suggest TBD awareness campaigns may benefit from focusing on older individuals with lower education and income, while educational efforts promoting effective prevention measures like acaricidal pills should target all dog owners. Author summaryIn Iquitos, Peru, the high prevalence of Rhipicephalus sanguineus s.l. infestation in dogs and homes and the high prevalence of Ehrlichia canis infection in dogs, highlight the need for urgent tick prevention and control. Understanding the influence of awareness, attitudes (including perceived threat) and sociodemographic factors on practices is key to designing effective interventions and identifying target groups. We analyzed data from 285 dog owners to assess if perceived threat (susceptibility and severity) from ticks and tick-borne diseases (TBDs) was linked to self-reported preventive measures for homes and dogs. We also examined TBD awareness and sociodemographic factors potentially associated with preventive practices. Among participants, 31.6% were unaware that TBDs could affect humans, with this group tending to be older and have lower education and income levels. Perceived susceptibility to tick bites and TBDs was not linked to preventive measures, while perceiving TBDs as moderate to severe increased the likelihood of using spray and oral acaricides on dogs. However, usage remained low even among those with high perceived severity. These findings reveal varied associations between threat perception and preventive practices, as they may be influenced by factors such as perceived benefits, barriers, and self-efficacy. Educational efforts should target older adults, and those with lower education and income, while campaigns promoting effective measures like acaricidal pills should address all dog owners.

Rift Valley fever (RVF) is a zoonotic arboviral disease that causes adverse pregnancy outcomes and high mortality in domestic and wild ruminants. The disease is caused by the RVF virus (RVFV), which is transmitted by mosquitoes from several genera, mainly Aedes and Culex. However, whether ruminants can become infected by horizontal virus transmission remains unclear. In addition, how the route of RVFV inoculation may influence RVF pathogenesis and the host immune response in animals is still largely unknown. With this aim, we conducted a comparative experimental study in which young sheep were either inoculated subcutaneously (SC) or intranasally (IN) with the virulent RVFV 56/74 strain. We then evaluated disease dynamics, viremia, virus excretion, tissue damage, and the humoral immune response. We also aimed to determine whether RVFV can be transmitted from infected to in-contact animals, and to assess whether the inoculation route may influence virus excretion and the likelihood of subsequent horizontal transmission. The results showed that SC inoculated sheep had a shorter incubation period, an earlier onset of viremia, and an earlier seroconversion. In contrast, IN inoculated animals developed higher rectal temperatures, reached higher peak viremia, and developed a more robust neutralizing antibody response. They also exhibited increased concentrations of analytes indicative of moderate but more severe hepatic injury compared with the subcutaneous group, along with more pronounced histopathological damage in the central nervous system. These results demonstrate the influence of the route of inoculation on RVF pathogenesis and the host immune response. Our results also confirmed the horizontal transmission of RVFV between SC inoculated sheep and in-contact animals housed in the same room, a phenomenon not observed in the IN inoculated group. This finding underscores the influence of the inoculation route on virus transmission and the potentially significant role of horizontal transmission in RVF epidemiology and disease control. Author summaryAccording to the World Health Organization (WHO), RVFV is considered a priority pathogen due to its ability to strain animal and public health systems, especially in developing countries. RVF outbreaks have occurred across most of Africa and, since 2000, in the Arabian Peninsula. Evidence of RVFV circulation in North Africa further highlights the threat to Europe, where competent mosquito vectors are present. How the inoculation route shapes disease dynamics and hosts immunity is still largely unknown. Similarly, whether the virus can spread between infected and non-infected animals without competent vectors remains unclear. A comparative infection in which young sheep were inoculated SC or IN with the RVFV 56/74 strain showed that SC inoculated sheep had a shorter incubation period, an earlier onset of viremia, and earlier seroconversion. However, rectal temperature and peak viremia were higher in IN inoculated sheep, which also showed evidence of moderate but more severe hepatic damage, accompanied by greater central nervous system damage. Only the in-contact animals housed in the subcutaneous group became infected, demonstrating horizontal transmission. Our results show that the route of inoculation influences disease progression and that RVFV can be transmitted among sheep in the absence of mosquitoes.

Fasciolosis caused by Fasciola hepatica is an economically important disease in sheep and cattle. Knowledge of the population genetic structure of F. hepatica is important for understanding gene flow and informing disease control. In the present study, we designed, developed, and validated a multilocus sequence typing (MLST) scheme based on six markers. These markers were selected by aligning newly sequenced whole-genome sequence (WGS) data with available reference genomes and selecting variable regions with five or more single-nucleotide polymorphisms SNPs from different scaffolds of the F. hepatica reference genome Fasciola 10x pilon (GCA_900302435.1). Twenty markers were initially identified, of which 12 were multiplexed for deep amplicon sequencing after validation on worm and faecal eggs DNA; six markers were ultimately retained for downstream population genetics analysis. These markers were used to investigate population genetic structure in 15 cattle- and 27 sheep-derived F. hepatica populations in UK. A total of 53 unique alleles from six MLST markers were identified from 30 faecal (cattle = 13, sheep = 17) and 12 adult worm (cattle = 2, sheep = 10) populations. Shared alleles were observed in sheep- and cattle-derived populations. The highest allelic variation was observed in the Scottish Borders, Southern Scotland, and South-West England, and the lowest in North-West England. Minimal genetic differentiation was observed between cattle- and sheep-derived populations, with most genetic structuring within rather than between populations. Five markers showed high allelic polymorphism, whereas one marker showed low levels of allelic polymorphism, highlighting the importance of multilocus approaches. Overall, this six MLST-marker panel provides a tool for population genetic studies, revealing high gene flow and clonal expansion of F. hepatica across hosts and regions in the UK.

AimTo resolve the topological branching patterns, the timing of demographic events, and the effective population size changes associated with major demographic events. LocationMidwestern (eastern North Central) and Northeastern USA TaxonBlacklegged tick, Ixodes scapularis (Say, 1821) MethodsUsing three independent genomic datasets, single-nucleotide variants were analyzed for demographic inference. Maximum likelihood topologies and prior ecological knowledge were used to generate nested demographic hypotheses. The best-fit scenario and the associated demographic parameter estimates were determined using approximate Bayesian computation under a random forest statistical model. The topologies and parameters supported in the three independent datasets were compared to generate insights about the demographic history of blacklegged ticks in the region. ResultsThe emergence of extant northern populations of blacklegged ticks began between 10-15 k.y.a. (thousand years ago), with independent population splits from the common ancestor during the Early-Mid-Holocene, and never more recent than 4 k.y.a. All populations sustained moderately large population sizes without bottlenecks, with Michigan as the exception. Michigan appears to have an uncertain placement that depends on sampling, reflecting its admixed origin. Main conclusionsThere are multiple populations of northern blacklegged ticks that have persisted independently as deglaciated regions in the northern U.S. were recolonized following the Last Glacial Maximum (26.5 to 19 k.y.a.). The current ecological expansions across the northern U.S. are likely seeded by separate relictual populations with distinctive genomic ancestry rather than a range expansion from a single source, with important implications for vector-borne disease management.

Cystic echinococcosis (CE), caused by the larval stage of Echinococcus granulosus, remains a significant public health and veterinary problem in endemic regions. Although chemotherapy and control programs exist, the development of complementary immunotherapeutic tools is increasingly needed. This study evaluated the generation and functional activity of hyperimmune serum (HIS) produced in three adult male castrated llamas (Lama glama) immunized with antigenic material derived from protoscoleces (PSCs) of the parasite. Sera collected after each of the first six immunizations were assessed by ELISA to quantify antigen-specific IgG responses, and their biological effects were tested in vitro using viable PSCs. Motility was measured using video-assisted paired-image scoring across serial serum dilutions (1:2-1:2048), and the methylene blue exclusion assay was used to assess viability. Hyperimmune serum produced a clear, reproducible, dose-dependent inhibition of PSC motility and viability. Higher titers of early inoculations reduced motility by 70-85%, while sera from the fifth and sixth inoculations achieved complete suppression. Naive serum and PBS controls showed no inhibitory effect. ELISA titers strongly correlated with biological activity, indicating that higher humoral responses predicted functional inhibition. These findings demonstrate the feasibility of generating potent anti-Echinococcus granulosus polyclonal antibodies in camelids and support their potential application in passive immunization strategies. The study establishes a foundation for future development of llama-derived immunobiological reagents, including nanobody-based tools, for the control of cystic echinococcosis.

Filoviruses, particularly Ebola virus (EBOV), remain a major public health concern in Central Africa. However, their circulation in wildlife during inter-epidemic periods remains poorly documented. Non-human primates (NHPs) may serve as ecological sentinels of viral dynamics at human-forest interfaces, yet surveillance is constrained by the limitations of invasive sampling. We conducted a non-invasive investigation of EBOV exposure in free-ranging NHPs from the Mabali Forest Reserve (Equateur Province, Democratic Republic of Congo) for Ebola virus disease. A total of 630 fecal samples were collected and screened for active infection by PCR targeting the EBOV nucleoprotein gene; all samples tested negative. Molecular identification of host species was achieved in 569 samples (90.3%). Fecal serology using an automated capillary western blot platform (JESS), targeting EBOV nucleoprotein, glycoprotein and viral protein 40 antigens, identified four seropositive individuals (0.70%), including two Cercopithecus ascanius and two C. wolfi. The detection of discrete immunoreactive bands consistent with EBOV-specific antibodies suggests prior exposure despite the absence of active outbreaks. These findings provide the first serological evidence compatible with EBOV exposure in these two Cercopithecus species and support the hypothesis of low-level or cryptic viral circulation in forest ecosystems. The study highlights the feasibility and value of fecal serology as a non-invasive One Health surveillance tool for monitoring zoonotic pathogens at wildlife-human interfaces.

Zoos may serve as sentinel sites for zoonotic vector-borne diseases. West Nile virus (WNV) and Usutu virus (USUV) are closely related orthoflaviviruses transmitted between Culex mosquitoes and a bird reservoir. Both viruses can also infect mammals, including humans, where they may cause symptoms and, more rarely, hospitalization and death. However, serological cross-reactivity between WNV and USUV complicates their differential diagnosis. Here, we aimed to reconstruct the dynamics of emergence of WNV in a zoo located in a newly affected area in Europe, using ELISA and Virus Neutralization Test (VNT) serological analysis of 1707 animal sera collected between 2015 and 2024. Combining this data in a model accounting for cross-reactivity with USUV, we estimated yearly forces of infection (FOI) by both viruses, and thus found that WNV likely circulated in the area one year prior to the first cases reported to the passive surveillance system. Our results also showed that, in the zoo, mammals and reptiles had a lower risk of infection than birds (relative risk of 0.14 [0.05; 0.28]), and that the exposure of birds to water (aquatic lifestyle or proximity to stagnant water) affected the risk. Finally, we estimated diagnosis parameters, including the sensitivity of the VNT (80.4% [76.5%; 84.3%]), the expected VNT titer value, and the level of serological cross-reactivity between viruses during the VNT. To conclude, our modelling framework allowed to disentangle the co-circulation of two closely related viruses, a crucial point in ensuring the reliable sentinel surveillance of these vector-borne zoonotic pathogens.

Lyme disease, caused by Borrelia burgdorferi and transmitted by Ixodes scapularis ticks, remains a significant vector-borne illness in the United States. Small mammal reservoirs, particularly Peromyscus leucopus, play a critical role in B. burgdorferi maintenance. Here we conducted a five-year, randomized, double-blinded, placebo-controlled field trial deploying an oral OspA-based reservoir targeted vaccine (RTV) across seven Maryland sites. Bayesian modeling provided estimates of vaccine impact on mouse anti-OspA antibody levels, nymphal tick infection prevalence (NIP), mouse infection rates, and seroconversion to B. burgdorferi in hunting dogs. RTV sites exhibited an estimated 10.5% proportional increase in protective murine anti-OspA antibody levels and a 15.4% reduction in NIP by year five. We also found a lower infection prevalence in mouse blood fed nymphal ticks (9.8%). RTV sites exhibited modest decreases in mouse infection prevalence and dog seroconversion rates were similar between groups. Our results indicate that anti-OspA antibody in vaccinated-infected P. leucopus reduced B. burgdorferi summertime larval infection prevalence, measured as NIP reductions the following spring. This suggests that OspA-based oral RTV reduces B. burgdorferi transstadial transmission within tick populations. Our findings advance development of reservoir targeted solutions for Lyme disease prevention. Further evaluation of impacts on incidental hosts is needed.

Tick-borne diseases are now reported from nearly every county in Illinois, and three vector tick species (Amblyomma americanum, Dermacentor variabilis, and Ixodes scapularis) are of particular concern because these are responsible for most of the tick-borne disease transmission in the state. However, active surveillance is patchy, many counties have little or no sampling, and there is no statewide, quantitative map of relative abundance that can be used to anticipate risk in unsampled areas. To address these gaps, we developed Bayesian hierarchical spatial models to estimate the county-level abundance of these three vector tick species in Illinois. Using active surveillance data from 2019-2022, we modeled county-level abundance as a function of climate, land cover, forest fragmentation, and deer habitat suitability. Spatial dependence was captured using a Besag-York-Mollie 2 (BYM2) prior implemented in INLA, along with spatial 5-fold cross-validation to assess predictive performance. A. americanum showed the highest predicted abundance in southern and central Illinois, D. variabilis was widespread but diffuse, and I. scapularis was concentrated in northern and selected central counties. Together, these models provide the first spatial, statewide, uncertainty-aware assessment of tick abundance in Illinois, highlighting priority counties where surveillance lags disease risk.

Background Rabies is a zoonotic neglected public health problem associated with animal bites, especially domestic carnivores claiming 59,000 deaths annually predominantly in developing countries of Africa and Asia. There is a high risk of exposure among rural communities endemic with animal rabies where adoption of prevention strategies is minimal. This study determined the prevalence of suspected rabies exposure, associated factors, and delayed post-exposure care-seeking among animal-bite human cases in Busia district, Uganda. Methods: This was a cross-sectional study that involved 332 consecutively sampled animal bite human cases that occurred within the period 2023 to 2024. Data for the bite cases from records were collected using a data abstraction tool. In addition, interviewer-administered semi-structured questionnaires were used to collect data on sociodemographic, animal-related and environmental characteristics. Approximate bite locations were collected using Global Positioning System (GPS) coordinates via Kobo collect. Analysis was carried out in STATA 17 using mixed effects modified Poisson regression for factors associated with suspected rabies exposure. Results: The median age of the bite cases was 18 (IQR: 9-36) with the male gender predominantly affected. The prevalence of suspected rabies exposure was 53.6% (95% Confidence interval - CI: 46.8-60.3). Factors associated were urban versus (vs) rural residence (adjusted prevalence ratio-aPR: 1.04, 95%CI: 1.00-1.08), being bitten by a stray animal (aPR: 1.28, 95% CI: 1.22-1.35) and wild animal (aPR: 1.22, 95% CI: 1.14-1.30) vs domestic animal, vaccination status of the biting animal i.e. vaccinated vs unvaccinated (aPR: 0.76, 95% CI: 0.69-0.85), provoked vs unprovoked bites (aPR: 0.82, 95% CI: 0.79-0.86), and distance to nearest river ([&ge;]5km) vs <5km (aPR: 0.93, 95% CI: 0.87-0.99). The prevalence of delayed post-exposure seeking was 23.0% (95% CI: 16.5-31.1) among the suspected rabies exposures. Conclusion: The study reveals a high prevalence of suspected rabies exposure. Factors associated are multidimensional i.e. are of human, animal and environmental origin. The one health paradigm should be emphasized during routine surveillance of rabies-related cases. The study observed that 1 in 5 bite cases delayed to seek care post bite exposure. We recommend collaborations between sectors, routine vaccination and awareness campaigns, and monitoring of wild carnivore populations and environmental dynamics in rabies-related surveillance.

Dengue transmission is strongly influenced by climatic conditions that affect mosquito population dynamics and virus circulation. In Southern Brazil, where dengue historically occurred at low levels, recent climatic anomalies may be contributing to the expansion of Aedes vectors and an increase in local dengue incidence. This study investigated the spatiotemporal association between climatic variables, Aedes mosquito infestation and dengue cases in Porto Alegre (Southern Brazil, 2018 to 2025). Entomological, surveillance and climatic data were analyzed using Morans I and LISA for spatial association, Kendall correlation, polynomial regression and LASSO to identify relevant drivers and develop predictive models of mosquito infestation and dengue incidence. A strong spatial association between Aedes aegypti and Aedes albopictus was observed, with persistent local clusters detected across all years. Annual climatic variables were associated with mosquito abundance in several districts. Overall, rainfall frequency had a stronger effect on Aedes aegypti abundance than accumulated rainfall. Temperature and lagged infestation indices showed strong association with both species and dengue incidence, with effects observed up to four weeks prior. Predictive models demonstrated good agreement between observed and predicted values, particularly within low to moderate infestation levels. Lagged variables were consistently retained in both mosquito infestation abundance and dengue incidence models, highlighting the importance of temporal predictors for anticipating vector dynamics and dengue risk. This approach is generally applicable for predicting Aedes infestation and disease incidence and emphasizes the importance of integrating entomological and climatic surveillance data to improve anticipation and detection of dengue risk periods and support more effective public health interventions.

Chronic Wasting Disease (CWD) is a transmissible spongiform encephalopathy (TSE) of cervids (elk, deer, moose, and reindeer) that is increasing in prevalence and expanding to new geographical areas. TSEs, commonly referred to as prion diseases, are fatal neurodegenerative diseases that occur in a variety of mammals, including humans, and typically exhibit species-specific characteristics. This study reports the sequencing of the prion protein gene (PRNP) in retropharyngeal lymph node samples from 358 Montana mule deer (Odocoileus hemionus) and the identification of 36 PRNP genetic variants, many of which have not been reported previously. Further investigations tracked spatiotemporal characteristics of variants to hunting districts, year of harvest, and CWD status. PRNP polymorphisms V12F, D20G, R40Q, and S225F were examined with EmCAST computational predictions to determine the relationship between sequence and structural variations providing further insights into mechanisms affecting CWD outcomes. EmCAST predictions suggest the novel variant V12F phenotype is attributable to functional changes such as altered protein-protein interactions that might be linked to the CWD positive status of the samples. Notably, the analysis of S225F by EmCAST predicted that S225F is a neutral mutation for folded PrP and incompatible with fibril PrP, suggesting a potential structural mechanism for why this previously known variant may provide protection against CWD based on reduced fibril PrP formation. The CWD-positive samples harboring PRNP variants were examined with the prion RT-QuIC assay, including the novel variant V12F, which resulted in prion seeding activity. Author SummaryChronic Wasting Disease (CWD) is a fatal disease of cervids, which include deer, elk, and moose. Since its discovery in 1967, CWD has spread to 36 U.S. states and four Canadian provinces, with prevalences exceeding 20% in select free-ranging populations. With the popularity of hunting big game animals and the role of these species in the ecosystem, concerns have arisen regarding the transmission of disease to humans, as well as how to mitigate long term consequences of disease on animal populations. Given the significant risk of species spillover and the limitations of current management, innovative genetic research is essential. Our study identified novel PRNP genetic variants in Montana mule deer, cataloging their regional distribution and CWD status across several hunting seasons. By investigating the impact of these polymorphisms on protein stability and seeding activity, we provide critical insights into the genetic factors that influence disease phenotypes and transmissibility in wild cervid populations.

Background Venezuelan haemorrhagic fever (VHF), caused by Guanarito virus (GTOV), is a zoonotic disease endemic to the western plains of Venezuela. Despite decades of recognition, its epidemiology and clinical profile remain poorly characterised. Methodology We analysed individual level data from standardised case report forms submitted to the Venezuelan National Epidemiological Surveillance System between 2017 and 2024 for suspected VHF cases in Barinas, Apure, and Portuguesa. Demographic, clinical, and laboratory variables were examined to characterise temporal and geographical patterns and to define the clinical profile of VHF compared with endemic arboviral infections. Principal Findings Among 480 suspected cases, 72 (15.0%) were laboratory confirmed GTOV infections. Confirmed cases occurred predominantly in men engaged in agricultural or service related occupations, with the highest prevalence among individuals aged 46 to 90 years. A marked seasonal pattern was observed, with most cases occurring between September and January. The most frequently reported symptoms included headache, haemorrhage, sore throat, and diarrhoea. Compared with other endemic arboviral infections, GTOV was more strongly associated with headache, myalgia, sore throat, haemorrhage, and abdominal pain, delineating a distinct clinical phenotype relative to diseases caused by encephalitic alphaviruses, chikungunya virus, dengue virus, and Zika virus. The case fatality ratio among laboratory confirmed cases was 36.1% (95% CI: 25.1 to 48.3). GTOV infection was independently associated with mortality (adjusted relative risk [aRR] 3.66; 95% CI 2.28 to 5.87; p < 0.001), underscoring its substantial clinical severity. Conclusion GTOV remains endemically transmitted in western Venezuela, disproportionately affecting older men engaged in agricultural and service related occupations. Its seasonality and clinical phenotype, characterised by haemorrhage, sore throat, and gastrointestinal symptoms, highlight the need for clinical awareness and improved differential diagnosis, particularly in remote endemic settings with limited access to laboratory testing.

The black legged tick, Ixodes scapularis, is a vector of the bacterium that causes Lyme disease and several other illnesses, including anaplasmosis, babesiosis, and tick-borne encephalitis. Although high-quality genome annotations are available for I. scapularis, functional understanding of I. scapularis genes is limited. To address this, we developed a platform for genome-wide CRISPR-Cas9 knockout screening in I. scapularis cells. To evaluate the platform, we performed a screen to identify genes associated with cellular fitness, and screens for resistance to treatment with copper chloride, Antimycin A, or Destruxin A (DA), a cyclic hexadepsipeptide produced by the pathogenic fungus Metarhizium anisopliae. In each case, the screens implicate specific sets of conserved and non-conserved I. scapularis genes in relevant cellular functions, providing the first experimental evidence of function for a large set of I. scapularis genes. Altogether, in this first-of-its-kind effort for the arthropod subclass Acari, we present an unbiased genome-wide CRISPR-Cas9 knockout cell screening platform, related resources, and datasets that will be broadly useful to efficiently uncover cellular functions of I. scapularis genes.

In 2025 Guinea was validated as achieving elimination as a public health problem for the highly pathogenic, vector-borne infection, gambiense human African trypanosomiasis (gHAT) after reaching several years of low-level case reporting. gHAT cases in Guinea have overall seen a large decrease between 2000 and 2024, however there have been notable fluctuations. Transmission modelling was used to assess these trends in observed cases for the foci Boffa East, Boffa West, Dubreka, and Forecariah and evaluate transmission changes. This study quantifies the impact of interruptions due to Ebola and the introduction of new interventions (particularly the rapid diagnostic tests in the passive health system and vector control) in each focus. The model suggests that transmission of gHAT has fallen 97% (83-100%) between 2000 and 2024, with disease burden measured in disability-adjusted life years (DALYs) reduced by 94% (63-100%). We estimated that Ebola interruptions caused an additional 1,147 gHAT DALYs due to the suspension of gHAT activities, however passive screening improvements and the introduction of vector control likely averted 1,719 and 9,038 DALYs respectively. This study quantifies the impact of Ebola related interruptions on gHAT transmission and disease burden and highlights the success of medical and vector control interventions in Guinea.

BackgroundLeishmaniasis is endemic in southern Europe with high risks of outbreaks and geographical spread. However, the risk factors for human leishmaniasis are understudied in this region. MethodologyTo evaluate these risk factors, we tested associations between leishmaniasis incidence and an array of variables related to socioeconomics, immunocompetence, climate, land use, biodiversity, and ecology (i.e., the pathogen and its vectors and reservoirs). FindingsSocioeconomic factors, such as demography, occupation, and housing conditions, were strongly associated with leishmaniasis incidence in endemic regions. The specific factors and the magnitude of their impacts varied among the five countries studied. Human immunosuppressive condition was highly correlated with leishmaniasis risk in Spain and Italy. Climate likely delineated leishmaniasis-free regions from endemic regions in France. Our results suggest that climate change alone may not drive the spread of leishmaniasis within this century. Pathogen hazard and reservoir abundance affected leishmaniasis risk more than vector hazard in countries where data were available. Biodiversity was weakly, negatively related to leishmaniasis. SignificanceOur results highlight the importance of socioeconomic risk factors and immunosuppression for human leishmaniasis, suggesting potential implications for disease control and prevention policies. Surveillance of Leishmania spp. in humans, vectors, and reservoirs; assessment of reservoir abundance; and data accessibility are crucial for disease prevention and preparedness. Because of possible biodiversity regulation, efforts to understand and control leishmaniasis could benefit from a One Health approach that involves epidemiologists, social scientists, and ecologists, among others. Author summaryLeishmaniasis is a common disease in tropical and subtropical regions, but it also occurs in southern Europe. While some infectious disease experts are concerned that climate change might lead to the emergence of new diseases in new areas, the main factors shaping leishmaniasis in Europe are not well understood. This study considered a wide array of potential risk factors in a variety of categories, ranging from climate and nature to how people live and work. We found that the risk for leishmaniasis is mostly related to occupation, housing type, age, and sex, though the exact risk factors change from country to country. People with weakened immune systems face high risk, and infected animals pose a major threats, but climate change alone may not drive the spread of leishmaniasis as much as once feared. Interestingly, a healthy variety of wildlife may help keeping the disease in check. To limit the impacts of leishmaniasis, we need to protect the most vulnerable populations, such as people living with weakened immune systems, working in high-risk sectors, residing in single-dwelling buildings, or experiencing or facing homelessness. We need to monitor the parasite in people and animals and share those surveillance data openly. Ultimately, we need a "One Health" approach where doctors, social workers, and scientists work together to keep our ecosystems healthy and our communities safe.

BackgroundOnchocerciasis remains a public-health challenge in the Democratic Republic of the Congo (DRC). The Kakoi-Koda focus, Ituri Province, exhibited high endemicity in the early 2000s and received community-directed treatment with ivermectin (CDTI) in some health zones (e.g., Nyarambe), but not in others (e.g., Logo). Moxidectin clinical trials were conducted in these health zones, alongside onchocerciasis-associated epilepsy studies. MethodologyWe synthesised epidemiological (including nodule prevalence), entomological and CDTI programmatic data. We collated anti-Ov16 serological data from epilepsy-related studies (community, cohort, case-control designs, 2015-2021) and skin-snip microscopy results from two moxidectin trial screenings (2009-2011; 2021-2023) and epilepsy-related studies (2015-2017). Geospatial analyses were used to describe land-cover change relevant to vector ecology and to identify areas with recent transmission. Principal findingsOnchocerca volvulus transmission declined markedly over time. In CDTI-naive Logo villages, microfilarial prevalence fell from 69-79% (first trial, 2009-2011) to 9% (second trial, 2021-2023), and mean infection intensity from 17-26 to 1 microfilariae per skin snip, similar to declines observed in Nyarambe villages under CDTI (72% to 3% and 11 to 0.4, respectively). Anti-Ov16 seroprevalence among children aged 3-10 years was low (0-5%) from 2016 onwards, and seropositivity was geographically circumscribed, mirroring contemporary skin-snip results. Human landing catches and breeding-site prospections (2015-2017) identified Simulium dentulosum and S. vorax as the current anthropophagic species, with no evidence of S. neavei after 2009. Progressive deforestation and canopy opening provide a plausible mechanism for a shift from crab-associated S. neavei habitats towards more open-habitat vectors. SignificanceConsistent parasitological, serological, entomological and geospatial evidence indicates substantially reduced transmission across Kakoi-Koda, with spatially-circumscribed residual transmission. Whether the current simuliid species can sustain transmission above elimination thresholds remains uncertain. Targeted, integrated surveillance is warranted to guide CDTI and stop-CDTI decisions. The dataset assembled here can be used to inform transmission modelling of these dynamics. Author SummaryOnchocerciasis, also known as river blindness, is a parasitic disease of public health concern in sub-Saharan Africa, transmitted by blackfly vectors. The disease is responsible for skin and eye clinical manifestations and is associated with neurological complications. We investigated an area in north-eastern Democratic Republic of the Congo called the Kakoi-Koda onchocerciasis focus, where the infection was once common. We reviewed and assembled data from past studies on infection in humans and blackflies, and analysed satellite imagery to assess the loss of tree cover that can affect where blackflies live and breed. We found that the prevalence of onchocerciasis in Kakoi-Koda has declined markedly in recent years. This decline appears linked to the disappearance (by deforestation) of the habitat suitable for some blackfly species, and to ivermectin distribution to treat onchocerciasis in parts of the focus. Our findings help to understand why onchocerciasis has decreased across the Kakoi-Koda focus and highlight a small number of fast-flowing river segments where other blackfly species may allow small pockets of local transmission. These results support continued, targeted monitoring to determine whether the disease is still transmitted in specific locations where elimination interventions may be needed.

BackgroundMosquito-borne arboviruses present persistent public health threats in Mexico. Multiple vector species are often considered to influence the local transmission of arboviral diseases; however, the structure and spatial dynamics of mosquito-arbovirus associations are unknown. MethodsWe conducted a systematic review to synthesize research investigating natural arboviral infections across mosquito taxa. PRISMA-guided search was done in PubMed, Scopus, Web of Science and Google Scholar, resulting in 46 included articles from 2007 to 2025. To delineate mosquito-arbovirus associations, spatial autocorrelation, bipartite network analysis, generalized linear mixed models (GLMMs) and comparative analysis of infection across sex and life stages were used to resolve spatial dynamics, species-specific viral detection and maintenance profiles. ResultsMinimum Infection Rate (MIR) revealed significant positive spatial autocorrelation (Global Morans I = 0.139; p = 0.016), indicating structured but diffuse spatial patterns (Local Morans I = 0.092; p = 0.045). Sampling intensity negatively correlated with the MIR (Spearman {rho} = -0.680, p < 0.001), indicating that sampling effort did not obscure the spatial structure. Elevated values were observed in a few municipalities across south-central and southeastern Mexico, where vegetation and land use interface. Network analysis (connectance = 0.40) and GLMM characterized an Aedes-centered network with broader taxonomic patterns driven by ZIKV; detection was significantly higher in Culex quinquefasciatus (OR = 1.88, p < 0.001) relative to Aedes aegypti. DENV detection patterns contrasted with other key viruses; no significant differences in transmission modes ({chi}{superscript 2} = 1.01, p = 0.315), suggesting a distinct maintenance profile. ConclusionsThis review unveils spatially diffuse and virus-specific detection patterns across heterogeneous communities in Mexico, findings that transcend Aedes-centric frameworks. These resolutions provide an evidence-based baseline that encourages an integrated, community-scale approach in regional surveillance programs. AUTHOR SUMMARYMosquito-borne arboviruses continue to threaten human and animal health across Mexico. Previous research has investigated arboviral infections and mosquito fauna as separate entities, but not their associations. This systematic review aims to resolve the spatial structure and multi-species dynamics of mosquito-arbovirus associations. We synthesized a long-term dataset of mosquito-borne virus surveillance from academic articles. Spatial models determined if localized detections were random and/or clustered with hotspots. Network and mixed models estimated the likelihood of positive arbovirus detection in mosquito species and a comparison test quantified the influence of vertical transmission on viral maintenance. Arboviral infection rates showed a diffuse spatial pattern with elevated values across urban and interface settings. Aedes aegypti shaped the mosquito-arbovirus network as expected; however, Culex quinquefasciatus showed significantly higher odds of ZIKV detection, supporting broader surveillance. These findings clarify species-specific detection and maintenance profiles across mosquito taxa, informing improved and targeted control strategies for arboviral diseases in Mexico.

Red Mark Syndrome (RMS) is a widespread skin disease affecting rainbow trout (Onchorhynchus mykiss). It provokes substantial economic losses in aquaculture, and is putatively caused by a Rickettsiales bacterium named Midichloria-like organism (RMS-MLO), which is strongly associated with RMS lesions. However, RMS-MLO ecology and epidemiology in aquaculture systems remain poorly understood. In this study, we analysed environmental DNA to monitor the presence of RMS-MLO and its putative vector Ichthyophthirius multifiliis in a trout farm in Northern Italy over one year. Water and sediment samples were monthly collected from multiple water tanks. RMS-MLO was consistently detected by PCR throughout the study in all trout-containing tanks, both in water and sediment samples, but never in the trout-free inflow tank. We did not observe an increase in RMS-MLO abundance during the single RMS outbreak recorded nor in relation with the co-occurrence of I. multifiliis. Our findings indicate a long-term persistence of RMS-MLO in the aquaculture, possibly as a consequence of infections with low prevalence or abundance, rather than its entry from the external environment at the time of RMS outbreaks. Additionally, hints were recorded for a potential role of free-living aquatic microeukaryotes as additional occasional reservoirs. In contrast, I. multifiliis was negatively related with RMS-MLO, while it significantly increased in abundance during the RMS outbreak, particularly in the inflow tank. This supports that, rather than a stable reservoir, I. multifiliis may act as a facilitator of RMS outbreaks, which might indeed be triggered by the entry of this parasite in trout farms.