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Acta Tropica

Elsevier BV

Preprints posted in the last 7 days, ranked by how well they match Acta Tropica's content profile, based on 13 papers previously published here. The average preprint has a 0.02% match score for this journal, so anything above that is already an above-average fit.

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Location-allocation modeling identifies strategic health facilities to expand access to snakebite antivenom in the Brazilian Amazon

Garcia Campos, M. A.; Rocha, T. A. H.; Perez de Souza, J. V.; Murase, L. S.; Murta, F.; Sartim, M. A.; Sachett, J.; Seabra de Farias, A.; Azevedo Machado, V.; Wen, F. H.; Staton, C. A.; Monteiro, W. M.; Gerardo, C. J.; Nickenig Vissoci, J. R.

2026-08-31 public and global health 10.64898/2026.08.28.26360696 medRxiv
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Background: Snakebite envenoming is a major cause of preventable death and disability in the Brazilian Amazon, where long distances, sparse roads, and dependence on river transport delay access to antivenom. We developed location-allocation models to identify community health centers that could strategically expand access to antivenom in Amazonas State, Brazil. Methodology/Principal Findings: We conducted an ecological geospatial study using a 2025 WorldPop population surface, locations of existing and candidate health facilities, and a multimodal road-and-river transportation network derived from OpenStreetMap and HydroSHEDS. Population demand was represented by 7,065 populated centroids, including 1,586 within Indigenous territories. We applied a maximize-coverage algorithm with a six-hour travel-time threshold. Two models were developed: one for Amazonas excluding Manaus and one for populations living in Indigenous territories. Both models began with 77 facilities already providing antivenom and progressively added candidate community health centers until coverage gains plateaued. The plateau occurred at 110 facilities, corresponding to 33 additional centers. In the model excluding Manaus, this configuration covered 1,118,831 people, or 75.11% of the target population; 87.61% of those covered could reach care within three hours. In Indigenous territories, coverage increased from 50.55% to 69.50%, reaching 50,434 people, of whom 81.39% were within three hours of care. Validation used 3,595 snakebite notifications from the 30 highest-burden municipalities in the Brazilian Notifiable Diseases Information System during 2023-2025. The median proportion reaching care within six hours was 40.81% in observed data and 72.17% in model estimates. Conclusions/Significance: Strategically equipping 33 additional existing community health centers could substantially expand timely access to antivenom, particularly in rural and Indigenous areas. Location-allocation modeling that incorporates river transportation can support evidence-based decentralization of time-sensitive health services in geographically complex settings.

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Rainfall and Leptospirosis in the Dominican Republic, 2012-2026: A Distributed-Lag Time-Series and Province-Panel Analysis

Sanchez, J. J.; Alcantara, L. V.; De Luna, D.; Aleuy, O. A.; Decicco, L. P.; Cruz Raposo, J. L.; Dye, T. D. V.

2026-09-04 public and global health 10.64898/2026.09.01.26361897 medRxiv
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Background: The biological mechanism linking rainfall with leptospirosis transmission is well established, but rigorous quantitative evidence for the insular Caribbean remains scarce, limited mostly to descriptive reports of post-hurricane outbreaks. We aimed to quantify the association between rainfall and leptospirosis incidence in the Dominican Republic, where leptospirosis is endemic, between 2012 and 2026 using a distributed-lag approach. Methods: We conducted an ecological time-series study complemented by a province panel with fixed effects. Case data (5,412 valid cases) were obtained from the national surveillance system (SIP-0276FA51); rainfall data were obtained from 15 INDOMET rain gauge stations across 13 provinces (2000 to 2026). We calculated the cross-correlation function between lagged monthly rainfall (0 to 6 months) and case counts, fitted a negative binomial distributed-lag regression model (lags 0 to 3 months) adjusted for seasonality and trend, triangulated findings with a 13-province fixed-effects panel, compared four rainfall exposure metrics, assessed extreme-rainfall threshold sensitivity, and estimated the population attributable fraction (PAF) with a parametric bootstrap. Results: The rainfall-case association peaked at a 1-month lag (r = 0.551; 95 % CI 0.437-0.647; p < 0.001) and remained significant through 3 months. In the distributed-lag model, all four lags were independently significant, with the 1-month lag showing the strongest effect (incidence rate ratio [IRR] = 1.156 per additional 50mm; 95 % CI 1.090-1.226; p < 0.001). The province panel yielded an almost identical 1-month lag effect (IRR = 1.147; 95 % CI 1.127-1.167). Rainfall above the historical 90th percentile increased case risk the following month (rate ratio = 1.95), with effect magnitude increasing monotonically with threshold stringency. An estimated 28.2 % (95 % CI 19.0-36.6 %) of cases were attributable to rainfall above the recorded historical minimum. Conclusions: Rainfall is a robust, consistent predictor of leptospirosis incidence in the Dominican Republic, with the strongest association observed at a 1-month lag and a lag pattern broadly consistent with findings from distributed-lag studies in Thailand and the Philippines. These findings, which to our knowledge constitute the first formal quantification of this association for the insular Caribbean, provide an evidence base for rainfall-linked early-warning systems, with the strongest signal at approximately one month and elevated risk extending through three months after rainfall.

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Patterns of Post-Traumatic Stress Disorder and Associated Cognitive Factors Among Flood Victims in Hanang District, Tanzania

Mwana, E. M.; Katalambula, L.; Emidi, B.; Nyundo, A.

2026-09-03 public and global health 10.64898/2026.09.01.26361894 medRxiv
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Background Floods are among the most devastating natural disasters worldwide and are increasingly associated with adverse mental health outcomes, particularly Post-Traumatic Stress Disorder (PTSD). In December 2023, Hanang District in northern Tanzania experienced catastrophic mud floods that resulted in extensive loss of life, destruction of property, displacement of households, and disruption of livelihoods. While emergency humanitarian responses focused primarily on physical needs, limited evidence exists regarding the long-term psychological consequences among survivors. Therefore, this study aimed to determine the patterns of PTSD manifestations and assess cognitive factors associated with PTSD symptoms among flood victims in Hanang District, Tanzania. Methods A community-based cross-sectional study was conducted among 360 flood victims one year after the disaster. PTSD symptoms were assessed using the PTSD Checklist for DSM-5 (PCL-5). Descriptive statistics summarized PTSD severity, while chi-square tests and regression analyses examined associations between socio-demographic characteristics and PTSD manifestations. Cognitive factors were assessed based on participants' exposure to traumatic experiences and perceptions of traumatic events. Results The mean PCL-5 score was 39.2 (SD = 20.6), indicating a high burden of psychological distress. Approximately 45% of respondents had severe PTSD symptoms (PCL-5 [&ge;]45), while another substantial proportion demonstrated moderate symptom severity. PTSD manifestations varied significantly by geographical location (p < 0.001), household income (p = 0.011), and marital status (p = 0.002). Age positively predicted PTSD severity ({beta} = 0.019, p = 0.001), whereas household income negatively predicted symptom severity ({beta} = -0.297, p = 0.001). Exposure to natural disasters constituted the predominant cognitive factor, with 45% directly experiencing the flood and 38.3% witnessing the event. Exposure to secondary traumatic experiences through witnessing or learning about violent events was also common. Cognitive trauma exposure demonstrated a significant association with PTSD symptoms ({chi}2, p < 0.001). Conclusion PTSD remains highly prevalent among flood survivors in Hanang district. Both direct and indirect trauma exposure significantly contributed to PTSD manifestations. Comprehensive disaster recovery programmes should integrate trauma-focused psychological services, cognitive behavioural interventions, routine PTSD screening, and community-based psychosocial support alongside socioeconomic recovery initiatives.

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A mechanistic statistical model of dengue dynamics in an endemic region

Luna-Martinez, N.; Cruz-Rodriguez, E. X.; Bernal-Castro, E. A.

2026-09-03 epidemiology 10.64898/2026.09.01.26361961 medRxiv
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Background Dengue is a major public health challenge, and predictive models are crucial for early warning systems. However, many current modeling practices rely exclusively on climatic factors or employ complex algorithms that lack the interpretability needed for informed public health decision-making. To address these shortcomings, we developed and validated a multidimensional, interpretable statistical model to predict monthly dengue incidence. Methodology/Principal Findings We used a Generalized Linear Mixed Model (GLMM) with a Negative Binomial distribution to analyze 14 years (2010-2023) of spatiotemporal data from 37 municipalities in Huila, Colombia, an endemic region. The model integrates non-linear and lagged effects of climatic, demographic, and socioeconomic factors. The final model underwent rigorous external validation on an independent test set (2021-2023). Our model demonstrated high predictive discrimination (R2 = 0.743, Spearman's {rho} = 0.657), accurately capturing the timing of epidemic outbreaks. Key findings include the identification of an optimal thermal window for transmission at 27-28{degrees}C, a threshold effect for precipitation above 800 mm, and a saturation dynamic in outbreak autocorrelation. Conclusions/Significance This mechanistically-informed statistical approach provides a robust and transparent tool for epidemiological surveillance, successfully balancing high predictive performance with the explanatory power needed for effective, data-driven public health interventions.

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Chemoproteomic profiling of Plasmodium falciparum Hsp90 inhibition reveals functional link to DNA replication pathways

Ibrasheva, G.; Chen, Y.; Chirgwin, M. E.; Hughes, C. J.; Fitzgerald, M. C.; Derbyshire, E. R.

2026-08-31 cell biology 10.64898/2026.08.28.747854 medRxiv
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Plasmodium falciparum heat shock protein 90 (PfHsp90) is a promising antimalarial target, but the molecular pathways influenced by its inhibition remain poorly understood. Herein, we leveraged chemoproteomic profiling employing geldanamycin and XL888 Hsp90 inhibitors to investigate proteins and pathways dependent on the chaperone during the Plasmodium blood stage. This study revealed 131 proteins reduced in abundance after inhibition, of which 40% co-immunoprecipitated with PfHsp90. Bioinformatic analyses identified DNA replication as the most enriched pathway. This link was investigated in phenotypic studies demonstrating reduced parasite DNA content after PfHsp90 inhibition. To assess nascent DNA synthesis, we utilized a 7-deaza-7-ethynyl-2'-deoxyadenosine (EdA) assay, yielding dual-stage attenuation of nucleoside incorporation following Hsp90 inhibition. We further show that parasite co-treatment with Hsp90 and DNA replication inhibitors produces synergistic interactions, highlighting the therapeutic potential of the discovered link. Overall, these findings expand our understanding of PfHsp90 function and uncover novel PfHsp90-dependent pathways.

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Female contraceptive cover duration for miltefosine-containing regimens for the treatment of women with leishmaniasis

Chu, W.-Y.; Alves, F.; Dorlo, T. P. C.

2026-09-02 infectious diseases 10.64898/2026.08.31.26360682 medRxiv
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Introduction Miltefosine is the only approved oral antileishmanial agent, but its use in women of childbearing potential (WOCBP) is restricted due to preclinical teratogenicity. Current labeling recommends contraception during treatment and for at least five months thereafter, based solely on its long terminal elimination half-life. This study re-evaluated the required contraceptive duration using an exposure margin-based approach. Methods Virtual populations were generated from anthropometric data of 382 Indian, 4,462 Eastern African, and 4,019 Brazilian WOCBP with leishmaniasis. Published population pharmacokinetic models were used to simulate miltefosine exposure following 14-42-day regimens for visceral leishmaniasis (VL), post-kala-azar dermal leishmaniasis (PKDL), and cutaneous leishmaniasis (CL). A developmental safety exposure threshold was derived from the rat no-observed-adverse-effect level (0.6 mg/kg/day for 10 days) and adjusted using a 10-fold safety margin. Contraceptive durations resulting in median residual post-contraception exposure (AUCEOC-{infty}) below this threshold were considered supportive of contraceptive discontinuation. Results The developmental safety exposure threshold was estimated at 2.5 mg{middle dot}day/L. Despite pharmacokinetic differences across geographical regions and disease manifestations, required minimum contraceptive durations were consistent: three months from treatment initiation for the 14-day regimen, four months for 21- and 28-day regimens, and five months for the 42-day regimen. For the 14-day regimen, a single dose of a long-acting injectable contraceptive administered at treatment initiation would provide sufficient coverage. Conclusion An exposure margin-based approach supports shorter contraceptive durations than current recommendations. For the 14-day VL regimen, three months of contraception may provide a practical alternative to current labeling.

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Seroprevalence of viral hemorrhagic fevers and arboviral infections among febrile patients in Forest Guinea

Koundouno, F. R.; Sidibe, Y.; Soubrier, H.; Kourouma, K.; Koulemou, S.; Millimouno, T. E.; Tolno, F. M.; Millimono, S. L.; Ifono, K.; Kamano, F. M.; Barry, M. D.; Sonomy, B.; Traore, M.; Keita, K.; Hinrichs, M.; Becker Ziaja, B.; Nelson, E. V.; Jacobsen, C.; Thielebein, A.; Oestereich, L.; Pahlmann, M.; Escudero-Perez, B.; Krumkamp, R.; Guenther, S.; Kolie, M.; Keita, K.; Guilavogui, S. H.; Magassouba, N.; Boumbaly, S.; Annibaldis, G.; Duraffour, S.

2026-09-04 infectious diseases 10.64898/2026.09.02.26362016 medRxiv
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Between 2017 and 2024, routine diagnostics surveillance in Guinea detected several confirmed viral hemorrhagic fever (VHF) cases among febrile patients. To assess exposure to Lassa virus and other viral pathogens, we conducted a retrospective cross-sectional seroprevalence study in Forest Guinea (Gueckedou and N'Zerekore). Lassa virus seroprevalence was 56.0% in the Gueckedou study group and 29.8% in the N'Zerekore study group. Seropositivity increased with age in both study groups, suggesting cumulative exposure. Samples from Gueckedou laboratory were also tested for other pathogens, and antibodies against Marburg virus (5.8%), Zika virus (5.4%) and Crimean-Congo haemorrhagic fever virus (1.2%) were detected.

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Comprehensive study of Trypanosoma cruzi genetic diversity from Triatominae vectors in the Southern United States: Geographic structuring, mitochondrial introgression, and multiclonality

Hernandez, J. C.; Beatty, N. L.; Vogel, K. J.; Zima, J.; Novakova, E.

2026-08-31 microbiology 10.64898/2026.08.21.746190 medRxiv
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Background Trypanosoma cruzi, the causative agent of Chagas disease, is subdivided into distinct genetic groups known as Discrete Typing Units (DTUs), each with distinct genetic traits that influence epidemiology and transmission dynamics. Several triatomine species serve as potential vectors of T. cruzi in the United States. However, despite the growing number of Chagas disease cases in the country, little is known about the genetic diversity and population structure of T. cruzi in natural vector populations. Methodology/Principal Findings We applied a multilocus metabarcoding approach to improve DTU resolution and characterize the genetic diversity and structure of T. cruzi in triatomines collected across five states of the southern United States. Five single-copy nuclear markers and one mitochondrial marker were amplified and processed by high-throughput sequencing to assess genetic diversity. We recovered 35 nuclear and 15 mitochondrial haplotypes from 70 infected specimens. Overall, genetic diversity was low ({pi} < 0.01 at all nuclear loci), with DTUs TcI and the North American lineage of TcIV detected, TcI being the most prevalent. Geographic structuring was particularly evident in TcI strains, which exhibited a distinctive haplotype profile in Florida populations, potentially linked to the recently revalidated vector species Triatoma ambigua. Mitochondrial introgression from TcIV into TcI suggests inter-DTU genetic exchange in these populations. Multiple haplotypes within individual insects detected across single-copy nuclear markers, support multiclonal infection as common feature of T. cruzi in natural vectors. Conclusions/Significance These findings provide new insights into the genetic landscape and evolution of T. cruzi in the United States. Evolutionary connectivity through mitochondrial introgression and frequent multiclonality highlights the importance of deep sequencing approaches for resolving T. cruzi genetic diversity, with direct implications for understanding for transmission dynamics, disease monitoring and control.

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Post-Discharge Experiences of Survivors Following the 2022 Ebola Virus Disease Outbreak in Uganda: An Exploratory Qualitative Study

Natukunda, J.; Muwanguzi, P.; Ngabirano, T. D.; Atuhaire, B.; Nalubega, S. J.; Auma, C.; Nabunya, R.

2026-09-03 public and global health 10.64898/2026.08.29.26361698 medRxiv
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Background: Ebola virus disease is a life-threatening illness caused by the Ebolavirus, with symptoms manifesting two to twenty-one days after infection. Although Uganda has faced multiple Ebola outbreaks, many patients survive only to encounter persistent challenges. Therefore, this study explored the post-discharge experiences of survivors following the 2022 Ebola Virus Disease outbreak in Uganda. Methods: An exploratory qualitative study comprising of in-depth participant interviews was conducted at Mubende Regional Referral Hospital in central Uganda. Interviews were face-to-face and data were analyzed manually by inductive content analysis. Ten male and female participants were Ebola Virus Disease survivors in Mubende district who had lived in the community for at least six months post-discharge from the Ebola Treatment Unit. Results: Four themes emerged: (i) Psychosocial Burdens and Social Exclusion, (ii) Economic Hardship and Loss of Financial Stability, (iii) Chronic Physical and Health Burdens Post-Recovery and (iv) Rebuilding Lives: Psychological, Social, and Medical Pathways to Recovery. Survivors faced significant emotional burdens such as survivor guilt, grief, trauma from loss, and anxiety about transmission risks. They experienced social isolation, stigma, and discrimination, which often led to their exclusion from community activities. Financially, they struggled with debt and the loss of livelihoods, compounded by ongoing health issues. Additionally, survivors endured chronic physical complications, including pain and fatigue, which hindered their recovery. Despite these challenges, survivors sought psychological, social, and medical pathways to recovery, including confirmation of their recovery, support from family and organizations, and health maintenance practices. Supportive medical care and community assistance were crucial in their physical and emotional rehabilitation. Conclusion: Ebola Virus Disease survivors in Uganda face significant psychosocial, health, social, and economic challenges post-discharge. The findings highlight the critical need for comprehensive medical and community-based support systems to aid survivors' recovery and well-being. Further research on long-term neurological effects and community reintegration programmes is needed to inform targeted interventions that support Ebola survivors and reduce stigma and discrimination.

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Understanding urgent blood-donor mobilisability: a cross-sectional online survey of digitally reachable adults in Ghana

Shen, H.; Agorinya, I. A.; Ayanore, M. A.; Brede, M.; Chapman, A.; Head, M.

2026-08-31 public and global health 10.64898/2026.08.27.26361538 medRxiv
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Introduction Safe and timely blood availability remains a major global health challenge, especially in low- and middle-income countries. Digital tools may accelerate donor contact, but digital reachability alone does not ensure that people will notice, trust and act on urgent requests to support blood donation efforts. We examined factors associated with anticipated engagement in digitally coordinated urgent blood-donor mobilisation among digitally reachable adults in Ghana. Methods We conducted a cross-sectional online survey from September 2025 to January 2026 across Ghana's 16 regions. Participants were recruited via Facebook advertising and snowball sampling. Factors associated with urgent blood-donor mobilisability were assessed under four criteria: high future-donation willingness; high willingness to install a trusted donation app; high willingness to respond to a trusted urgent-request; and high practical flexibility to leave current activities. Descriptive analyses and multivariable logistic regression examined prevalence and associated factors. Results Among 1,067 participants, 577 (54.1%) met all four criteria. Future-donation willingness (91.8%), trusted-app installation willingness (83.2%) and trusted-request response willingness (82.7%) were common, whereas practical flexibility was lower (66.6%). In the adjusted model, high formal health-system trust (adjusted OR (AOR) 3.95, 95% CI 2.08-7.50), high digital-response readiness (AOR 2.26, 1.66-3.08), previous donation (AOR 1.47, 1.08-2.01), high donation knowledge (AOR 1.42, 1.03-1.97) and willingness to donate to strangers were positively associated with high mobilisability. Women (AOR 0.60, 0.43-0.83), participants reporting a work-schedule barrier (AOR 0.43, 0.29-0.66) and those travelling over 30 min to the nearest healthcare facility at night (AOR 0.66, 0.45-0.96) had lower adjusted odds. Conclusions Digital reachability and stated donation willingness may overestimate the population pool available for emergency donation. Digital blood-donor solutions should consider verifiable health-system requests, account for response readiness and current availability, and connect willing individuals with accessible collection options and transport support where needed.

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Inhibition of JEV infection using β-Catenin specific inhibitor, iCRT-14

Datey, A.; Ghosh, S.; Chatterjee, S.; Bhowmick, B.; Ghatak, A.; Subudhi, B. B.; Chattopadhyay, S.

2026-08-31 molecular biology 10.64898/2026.08.29.747967 medRxiv
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The lack of effective anti-JEV therapy possesses significant challenge to control JEV. {beta}-catenin, a key mediator of Wnt signaling pathway regulates different viral replication and host immune responses. However, its role in JEV infection remains to be elucidated. Thus, the current study focused on evaluating iCRT-14, a specific {beta}-catenin inhibitor, against JEV. Treatment with iCRT-14 following JEV infection resulted efficient reduction in viral progeny release, viral RNA and protein levels in Huh7 and HEK293T cells. Further, active and total {beta}-catenin, Cyclin D-1 and GSK3-{beta}, the other key pathway players were also modulated in infected and inhibitor treated cells. Moreover, iCRT-14 showed an IC of 4.56 in Huh7 cell and maximal inhibition at the early stages of the JEV life cycle. Interestingly, the overexpression of {beta}-catenin in both the cells and siRNA-mediated {beta}-catenin knockdown (in Huh7 cells) significantly abrogated JEV replication, as evidenced by decreased viral titers, viral protein expression, and viral as well as total RNA levels. Moreover, the reduction in extracellular (84%) and intracellular (60%) viral titers following iCRT-14 treatment highlights its role in impairing JEV infection. Further, in silico molecular docking and co-immunoprecipitation studies demonstrated interactions between {beta}-catenin and the JEV NS5 and E proteins. Collectively, these findings suggest that optimum level of {beta}-catenin is required for efficient JEV infection, highlighting its potential as a target for designing host-directed control strategies to regulate viral infection.

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Comparative analysis of the neural and muscle systems in the subumbrella of hydrozoan jellyfish.

Norekian, T. P.; Moroz, L. L.

2026-08-31 zoology 10.64898/2026.08.30.748097 medRxiv
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Hydrozoa is a group of relatively simple animals with a well-developed nervous system. The nervous system in all hydrozoan medusae is highly conserved and includes outer and inner nerve rings at the bell margin, a neural network in the manubrium, and radial neural pathways that connect them. However, one element of the nervous system shows substantial variability among species: the subumbrella neural network. We examined the structure of the nervous and muscular systems in the subumbrella of 14 species of hydrozoan medusae. The main conclusion of this study is that the distribution of neural networks in the subumbrella strongly correlates with the distribution of smooth radial muscles. This correlation suggests that smooth radial muscles are the primary target of the subumbrella nervous system. Most species in the order Anthoathecata show a trend toward secondary loss of the neural networks and radial smooth muscle fibers in the subumbrella region, concentrating neural elements and smooth muscles only in the radial pathways along the radial canals. By contrast, all studied species in the order Leptothecata have neural networks in the subumbrella area, as well as radial smooth muscle fibers spread throughout the entire subumbrella region. The correlation between radial smooth muscles and the nervous system is also observed in the radial pathways along the radial canals. All species with thick bundles of smooth radial muscles along the radial canals have clearly defined, dense neural pathways running along or even embedded within the smooth muscle bundles.

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Spatiotemporal Mapping of Point-of-Care Diagnostic Accessibility: A Data-Driven Pipeline for Point-of-Care Distribution Analysis in Western Uganda

Bergman, D.; Nyehangane, D.; Besancon, L.; Podkorytova, M.; Tsoumari, V.; Staikoglou, D.; Kimuli, A. N.; Richard, M. R.; Ogwok, P.; Nankoma, C.; Alfven, T.; Mwanga-Amumpaire, J.; Gaudenzi, G.

2026-09-01 public and global health 10.64898/2026.08.28.26361594 medRxiv
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All primary healthcare centers owned by the Ugandan government in the Western Region of Uganda were submitted to a questionnaire concerning current availability of POCT from the Essential diagnostic List 2 part 1a and 1b, and the African laboratory inventory done by African Society of Laboratory Medicine and AfricaCDC. The data from the questionnaire was then linked to open source geodata provided by TomTom, and population data to calculate and visualize the accessibility of captured POCT. Findings: Availability of POCT Malaria is almost 100%, HIV 68-90%, and >30% for a majority of the POCT in the EDL-2 panel. 90% of the population in Western Region live within 1 hour by car from most of the essential POCT. Figures in the complementary web-based application visualize the accessibility of POCT for Western Uganda. Diagnostic deserts are visualized. Interpretation: Access to POCT at primary health care facilities in western Uganda has expanded substantially over the past decades. The geo-mapping tool presented here could inform policy decisions on strengthening diagnostic capacity at the national, regional, and provincial level. Funding: Swedish Research Council and Infravis All supplementary materials and a preprint of this submission are available on our OSF repository https://osf.io/j7puk/.

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Access to malaria diagnosis and treatment in Zambia in the context of scaling-up community case management: results from repeated national cross-sectional surveys

Mao, Z.; Bennett, A.; Silumbe, K.; Miller, J. M.; Millar, J.; Slater, H.; Yukich, J. O.; Ashton, R. A.; Kyomuhangi, I.; Andrada, A.; Karabo, R.; Eisele, T.

2026-08-31 public and global health 10.64898/2026.08.25.26361362 medRxiv
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Background: Community case management has been scaled up nationally in Zambia over the last decade. However, there is limited evidence on how this nationwide implementation has affected febrile patients' access to malaria diagnosis and treatment in Zambia. Methodology: This study analyzed four rounds of Malaria Indicator Survey (MIS) data (2012-2021) to evaluate: 1) proportion of all-ages individuals with fever who sought treatment from a formal provider, 2) proportion of individuals going to CHWs over time, among those who sought treatment at a formal provider, 3) time duration between fever onset and treatment seeking at a formal provider, and 4) proportion of children <5 with malaria that received Artemether-Lumefantrine (AL) treatment. Mixed-effect logit models were employed to examine determinants of treatment-seeking behavior and factors affecting AL receipt among children <5 with malaria cases. Results: The proportion of febrile patients seeking treatment remained below 60% throughout 2012-2021, and AL receipt among children with malaria cases consistently stayed below 50%. The mean interval between fever onset and initial treatment-seeking encounter decreased from 2.42 days in 2012 to 1.71 days in 2021. Among formal care seekers, CHW utilization increased from 1.5% in 2012 to 10.0% in 2018 before declining to 3.2% in 2021. Longer walking time to the nearest health facility was associated with lower odds of treatment seeking, whereas CHW density was not associated with treatment seeking or AL receipt. Children who did not went to formal providers had lower odds of AL receipt than those who sought treatment from CHWs. Conclusion: Despite nationwide CCM scale-up over the last decade, significant barriers persist in malaria patients' access to diagnosis and treatment in Zambia. Our results indicate that while CCM coverage should be maintained and further expanded, additional complementary interventions are also needed to overcome remaining access barriers.

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Drought and Syphilis Exposure in Zambia, Uganda, and Tanzania: Are There Urban/Rural Disparities?

Simo Fotso, A.; Charline Maltat, C. M.; Gbaguidi-Sekpon, B.; Marzouk, H.; Trickey, A.; Low, A.; Becquet, V.

2026-09-04 infectious diseases 10.64898/2026.08.31.26361827 medRxiv
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Eastern and southern Africa are highly affected by drought, and projections indicate that droughts will become more common in the coming decades. Whilst there has been research on the impact of drought on HIV, attributable to its effect on food insecurity and increased risky sexual behaviour, the link between drought and other sexually transmitted infections (STIs), particularly syphilis, remains largely unexplored. This study therefore assesses the association between drought and active syphilis, history of syphilis, and recovery from syphilis in Zambia, Uganda, and Tanzania, while examining disparities between urban and rural settings. It uses data on 75,225 people from Population-based HIV Impact Assessment surveys (2016-17), which include biomarker information, combined with rainfall data from the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) dataset to define drought in the two years prior to the survey. Multivariate logistic regression models with country-level fixed effects show that in urban areas, drought was associated with a significant increase in the probability of having active syphilis (average marginal effects (AME) = 0.5%, 95% confidence interval (CI): 0.2%-1.0%) and of having ever had syphilis (AME = 2%, 95% CI: 0.8%-4%). No significant association was found in rural areas. Exposure to drought was not associated with recovery from syphilis in either setting, though confidence intervals were wide. Our results underscore the importance of strengthening healthcare systems to make them more resilient to drought shocks in urban areas, and the need to reinforce syphilis prevention and treatment programmes in those areas when such shocks occur.

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Epidemiology, Temporal and Seasonal Trends, and Geographic Distribution of Leptospirosis in the Dominican Republic, 2012 to 2026

Alcantara, L. V.; Sanchez, J. J.; De Luna, D.; Aleuy, O. A.; Miller, B.; Mace, C.; Scott, H.; Smejkal, L.; Cruz Raposo, J. L.; Hennekens, C.; Dye, T. D. V.

2026-09-04 infectious diseases 10.64898/2026.09.02.26362038 medRxiv
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Leptospirosis is a widespread zoonotic infection and a growing public health concern in tropical, resource-limited settings, yet remains underrecognized and underreported where diagnostic and surveillance infrastructure is limited. We conducted an analytical cross-sectional study of national surveillance data from the Dominican Republic (2012-June 2026), integrating geospatial meteorological data to characterize disease burden, trends, seasonality, and clinical risk factors. Of 8,425 records, 5,412 met case-definition criteria (3,441 suspected, 1,448 probable, 523 confirmed), yielding a cumulative incidence of 3.55 per 100,000 person-years (2012-2025). Laboratory confirmation rose markedly, from 9.7% overall to half of 2025 cases and over half in 2026. Overall incidence remained stable across all years (p = 0.15), though with three distinct periods: declining infection pre-COVID, low infection during COVID, and increasing infection post-COVID. Cases clustered in the rainy/hurricane season (61.1%, May-November; p< 0.001), with a marginal rainfall correlation (r= 0.553, p= 0.062). Rural provinces bore disproportionate risk, led by Hermanas Mirabal (16.43/100,000 person-years), while large urban and coastal provinces had rates 80% lower. Men had 2.73-fold higher incidence than women (95% CI 2.56-2.90), peaking at younger ages 10-29. Comorbidity was the strongest predictor of complications (OR 2.84, 95% CI 2.01-4.02, p< 0.001). Limited diagnostic confirmation remains the central obstacle to characterizing leptospirosis burden in the Dominican Republic, with confirmation rates exceeding 40% only from 2023 onward. This first multi-decade national analysis identifies high-risk provinces, demographic groups, and seasonal windows for targeted surveillance, highlighting expanded diagnostic capacity as a priority for burden estimation and case management.

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Pharmacovigilance organization and training needs of health personnels in health facilities of Cameroon: a cross-sectional study

MURHABAZI BASHOMBWA, A.; TCHIO-NIGHIE, K. H.; NANA DJAPOU, M. C.; BUH NKUM, C.; BLAMA ABBA, I.; BEKOLO, C. E.; ATEUDJIEU, J.

2026-08-31 public and global health 10.64898/2026.08.26.26361382 medRxiv
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Health facilities (HFs) routinely administer medicines and are expected to ensure patient safety by detecting, reporting, investigating, and analysing adverse events following exposure to drugs (AEFED). This study aimed to assess the implementation of pharmacovigilance activities in referral and regional health facilities in Cameroon and to identify pharmacovigilance training needs among healthcare personnel (HP). This was a cross-sectional descriptive study targeting referral and regional health facilities and healthcare personnel involved in patient care and pharmacovigilance activities in Cameroon. Health facilities were selected using stratified purposive sampling, while healthcare personnel were selected through exhaustive sampling. Data were collected using semi-structured electronic questionnaires administered face-to-face by trained enumerators. The questionnaires assessed the organization, resources, and implementation of pharmacovigilance activities at health facilities, as well as healthcare personnel knowledge of pharmacovigilance concepts, previous training, and perceived training needs. Of the 14 eligible health facilities, 10 (71.4%) consented to participate in the study. Of the 10 health facilities, 4 (40.0%) had an established pharmacovigilance unit, while 3 (30.0%) reported conducting neither detection nor notification activities. Among the 261 healthcare personnel approached, 214 (81.9%) participated. Only 41.6% had needed knowledge to detect an adverse event, while 72.9% were aware of adverse event notification procedures. Previous exposure to pharmacovigilance training was reported by 37.9% of healthcare personnel, and all participants expressed a need for additional training, particularly on national pharmacovigilance regulations (69.2%), organization of the pharmacovigilance system (67.3%), and adverse event detection (67.3%). The main reported challenges by healthcare personnel in the implementation of pharmacovigilance activities included insufficient budget allocation, limited access to pharmacovigilance training, lack of pharmacovigilance guidelines and insufficient qualified human resources. Pharmacovigilance implementation in referral and regional health facilities in Cameroon remains limited, with gaps in organizational structures, resources, healthcare personnel knowledge, and training. Strengthening pharmacovigilance systems through improved facility capacity, availability of essential tools, and targeted healthcare personnel training is needed to enhance drug safety surveillance.

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Male Age and Sexual Maturity: Lipopolysaccharide-induced tumor necrosis factor influences sperm quality and reproduction in Anopheles culicifacies

Rohilla, P.; Saini, V.; Srivastava, V.; Yadav, P.; Sankhala, N.; Singh, T.; Sharma, G.; Tandon, G.; Tyagi, S.; Rani, J.; Dixit, R.

2026-09-01 developmental biology 10.64898/2026.08.31.748190 medRxiv
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Elucidating the biological and molecular mechanisms that govern male fertility and mating behavior in mosquitoes is critical for optimizing genetic and sterile insect technique-based vector control strategies. Here, we examined age-related changes in male reproductive capacity in Anopheles culicifacies, using female egg output as an indirect indicator of male fertility. Our results demonstrated that male reproductive age follows a non-linear pattern of fertility. Morphometric analysis from emergence to day 13 post-eclosion revealed a strong correlation between seminal vesicle capacity and female fecundity, suggesting that age-dependent gonadal development directly influences reproductive potential. At the molecular level, we identified AcLITAF6 as a key regulator of male reproductive homeostasis. RNAi-mediated knockdown of AcLITAF6 impaired apoptosis-associated and phagocytic clearance, reduced sperm viability, and decreased female productive outcomes. Conclusively, we reveal a previously unrecognized role of LITAF in sperm quality control and male reproductive fitness, highlighting AcLITAF6 as a potential target for mosquito population suppression strategies.

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Case Fatality of Leptospirosis in the Dominican Republic, 2012-2026: A 14-Year National Surveillance Analysis

Sanchez, J. J.; Alcantara, L. V.; De Luna, D.; Aleuy, O. A.; Bellon, M. B.; Cruz Raposo, J. L.; Dye, T. D. V.

2026-09-03 epidemiology 10.64898/2026.09.01.26361950 medRxiv
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Background: Case fatality reflects the quality and timeliness of clinical care for leptospirosis, yet no study has examined it at a national level in the Dominican Republic (DR), where leptospirosis is endemic. We describe the case fatality rate (CFR) of leptospirosis in the DR between 2012 and 2026 and identify associations with mortality. Methods: We conducted an analytical cross-sectional study, using national surveillance records merged with a discharge-condition extract via a composite key. We calculated CFR with Wilson 95% confidence intervals among 5,412 valid cases (suspected, probable, or confirmed) reported from January 2012 through June 2026. We compared proportions with Pearson's chi-square test, assessed annual trend with ordinary least squares linear regression, and fitted multivariable logistic regression models to account for confounding. Results: Overall CFR was 8.5% (460/5,412), with no significant annual trend (p=0.372). CFR was higher in men than women (p < 0.001) and increased significantly with age (p < 0.001). Male gender (OR: 1.79; 95%CI: 1.18-2.73) and pre-existing comorbidity (OR: 1.76; 95% CI: 1.21- 2.57) were independent predictors of death. Clinical complications were the strongest predictor in the adjusted model (OR: 3.16; 95%CI: 2.17-4.61), attenuating the gender effect. CFR varied widely by province (2.43-22.22%) and correlated negatively with incidence at the province level (p = 0.066). Conclusions: Leptospirosis case fatality is concentrated among men, people with comorbidity, and those who develop clinical complications. These national, long-term findings can help prioritize clinical and surveillance resources as extreme weather events are expected to intensify across the Caribbean.

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Identification of genetic variants in Pfs25 and functional evaluation in mosquito infection

Orfano, A.; Cisse, A.; Guo, Y.; Han, L.; Fikadu, N.; Thiam, L. G.; Ba, A.; Li, R.; Pouye, M. N.; Mangou, K.; Moore, A. J.; Sene, S. D.; Diallo, F.; Ngom, E. M.; Sadio, B.; Mbengue, A.; Membi, C.; Ngasala, B.; Bazie, T.; Some, F. A.; Olson, N.; Patel, S. D.; Shapiro, L.; Parikh, S.; Foy, B. D.; Cappello, M.; Vigan-Womas, I.; Premji, Z.; Dabire, R. K.; Ouedraogo, J.-B.; Sheng, Z.; Bei, A. K.

2026-08-31 infectious diseases 10.64898/2026.08.25.26361130 medRxiv
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Transmission-blocking vaccines (TBVs) are a promising strategy to reduce malaria transmission by targeting parasite stages within the mosquito. However, parasite genetic diversity may limit vaccine efficacy. We used next-generation amplicon deep sequencing to identify non-synonymous single nucleotide polymorphisms (SNPs) in Pfs25 from 184 Plasmodium falciparum isolates from Senegal, Tanzania, Ghana, and Burkina Faso. Prioritized SNPs were introduced into P. falciparum via CRISPR-Cas9. For the G116C variant, gametocyte development was evaluated by microscopy and qPCR, and mosquito infectivity was assessed by SMFAs. We identified 26 SNPs, including 24 novel variants. Functional assays showed that the Pfs25 G116C mutation did not affect gametocyte development or exflagellation. SMFA showed no significant differences in oocyst prevalence or intensity between mutant and WT parasites. These findings highlight the importance of integrating genetic surveillance with functional validation to guide the development of effective transmission blocking interventions