Ticks and Tick-borne Diseases

Objectives: To characterise the national epidemiology of tick-induced mammalian meat allergy (MMA) in Australia, including temporal trends in Gal specific IgE testing and case detection, geographic distribution, demographic risk factors, and longitudinal antibody dynamics. Design: Retrospective analysis of Gal sIgE ImmunoCAP test results from 1 January 2014 to 31 December 2024. Setting, Participants: Deidentified laboratory records from 14,075 individuals tested across Australia, with residential postcodes mapped to Statistical Areas Level 3 (SA3). A subset of 1,515 individuals with repeat testing contributed to longitudinal analyses. Main outcome measures: Test volumes, suspected MMA case counts, positivity rates, spatial clustering metrics, demographic risk ratios, and longitudinal Gal sIgE trajectories. Results: Overall, 35.7% (5,025) of individuals tested positive. Testing volume increased 331% over the study period, with case detection accelerating sharply from 2020. Decomposition analysis attributed 59-81% of case growth to expanded testing, with the remainder unexplained by surveillance expansion alone. Cases were concentrated along the eastern seaboard within the range of Ixodes holocyclus, with extreme spatial clustering: three SA3 regions accounted for over one-quarter of national cases. Females comprised the majority of positive cases, and MMA risk increased with age, peaking at 45-74 years. Among 1,515 individuals with serial testing, Gal sIgE levels antibodies declined predictably in 93% of people. Conclusions: This first national assessment of MMA in Australia reveals a substantial, geographically concentrated, and growing burden. The extreme spatial concentration of cases suggests that targeted public health interventions could efficiently address a large proportion of national disease burden. While testing expansion is the dominant driver of rising case numbers, it does not fully account for observed trends, and prospective studies are needed to disentangle surveillance effects from genuine disease emergence. Declining antibody levels support the utility of serial testing for clinical monitoring, though persistent sensitisation underscores the need for sustained risk mitigation and continued surveillance.

Black-footed ferrets (Mustela nigripes) are highly susceptible to sylvatic plague caused by Yersinia pestis, but the genetic basis of this vulnerability remains poorly understood. Here, comparative immunogenomic analyses across Carnivora species identified a conserved class of immunoglobulin lambda variable (IGLV) genes with unusually long antigen-binding sites (CDRL1) that are common among Caniformia species but absent in Feliformia species. First discovered in the domestic ferret (Mustela putorius furo), these genes encode tyrosine-rich and anionic motifs resembling the chemokine receptor CCR5 and contain experimentally validated sulfotyrosines previously associated with pathogen-interacting interfaces. Evolutionary analyses revealed distinct selective pressures across Caniformia lineages and showed strong purifying selection acting on long-CDRL1 IGLV genes in mustelids and bears. Antibody repertoire sequencing demonstrated that these genes are actively utilized in expressed repertoires and that their usage correlates with evolutionary conservation. Functional analyses of monoclonal antibodies derived from the long-CDRL1 IGLV gene identified an antibody that significantly reduced intracellular Y. pestis survival in macrophages and revealed a positive correlation between anti-plague activity and sulfotyrosine signal. Notably, all analyzed black-footed ferrets carried a frameshifting deletion in the long-CDRL1 IGLV gene resulting in loss of its expression in antibody repertoires. Together, these findings uncover a germline-encoded immunoglobulin feature conserved across dog-like carnivores and suggest a potential link between antibody germline variation and immune responses to plague.

Wildlife hosts play important roles in the ecology and transmission of vector-borne parasites, yet information on host associations remains scarce in many biodiverse tropical regions. Within a One Health framework, characterizing parasite diversity in wildlife can improve understanding of ecosystem health and disease emergence. Road-killed animals provide a non-invasive opportunity to investigate host-parasite interactions while minimizing disturbance to natural habitats. We screened 127 liver and intestinal tissue samples obtained from 76 road-killed vertebrates collected near protected areas in two Ecuadorian biodiversity hotspots, the Tropical Andes and Choco-Darien, for trypanosomatids and other vector-borne microorganisms. Molecular analyses targeted the 18S rRNA and cytochrome b genes of trypanosomatids and included additional screening for Trypanosoma cruzi, Trypanosoma rangeli, Rickettsia spp., and piroplasmids. Twenty-nine samples were positive for kinetoplastids. We detected diverse trypanosomatids representing the genera Leishmania, Porcisia, Trypanosoma, Phytomonas, Blastocrithidia, and Obscuromonas, as well as free-living kinetoplastids of the order Neobodonida. The most frequently detected species was Leishmania amazonensis, identified in 17 samples from at least 13 species of birds, reptiles, and caecilians, predominantly in liver tissue, suggesting previously unrecognized host associations. We also identified a putatively novel species of Porcisia and three potentially undescribed avian trypanosomes belonging to the subgenus Ornithotrypanum. No evidence of T. cruzi, T. rangeli, Rickettsia spp., or piroplasmids was found. Our findings identify birds, reptiles, and caecilians as potential reservoir hosts of L. amazonensis. In addition, we substantially expanded current knowledge of kinetoplastid diversity in Ecuadorian wildlife. This study demonstrates the value of road-killed animals as a practical, non-invasive resource for wildlife pathogen surveillance and highlights the importance of integrating biodiversity research into One Health approaches to better understand parasite transmission dynamics in rapidly changing tropical ecosystems. Author summaryMany parasites that affect humans circulate naturally in wildlife, but identifying their animal hosts is often difficult in remote, biodiverse regions. We used road-killed animals as a non-invasive source of biological material to investigate parasites in wildlife from two biodiversity hotspots in Ecuador. By analyzing tissues from birds, reptiles, amphibians, and mammals, we found a remarkable diversity of kinetoplastid flagellates, a group that includes the agents of Chagas disease and leishmaniasis. Although we did not detect human-infective trypanosomes, we repeatedly identified Leishmania amazonensis (a species causing human disease) in birds, reptiles, and caecilians. These vertebrate groups have not previously been recognized as potential hosts of this parasite. We also discovered several undescribed trypanosomatid species, emphasizing how little is known about parasite diversity in tropical wildlife. Our results show that road-killed animals can provide valuable information on host-parasite interactions without disturbing living populations. Such surveillance contributes to One Health efforts by improving our understanding of how environmental change, wildlife, and human health are interconnected.

Orientia tsutsugamushi is a mite-transmitted obligate intracellular bacterium that causes the potentially deadly zoonosis, scrub typhus. The absence of genetic tools for Orientia have limited studies of the microbe-host interactions that underlie scrub typhus. To address this gap, we developed a protocol for transforming and achieving allelic exchange in O. tsutsugamushi str. Ikeda. From evaluating multiple cell lines and antibiotics, we found that contact-inhibited EA.hy926 human endothelial-like cells best supported Orientia replication and that chloramphenicol was an effective selection marker. We engineered a homologous recombination cassette encoding a codon-modified version of the O. tsutsugamushi ank13 gene (OTT_RS04140) (CMank13) and its promoter alongside genes for mScarlet-I and chloramphenicol acetyltransferase under control of the O. tsutsugamushi tsa22-up and tsa56-down promoters, respectively. A PCR product encompassing the cassette and chromosomal flanking regions was transformed into O. tsutsugamushi via electroporation or CaCl2, the latter of which better preserved bacterial and host cell viability. EA.hy926 cells inoculated with transformed O. tsutsugamushi were grown in glass-bottom plates in the presence of chloramphenicol and imaged by live-cell microscopy to identify cultures containing mScarlet-I positive bacteria, which could be maintained in perpetuity. Chromosomal integration of the CMank13 cassette and loss of wild-type ank13 were verified by PCR and nanopore sequencing. This report establishes platforms for genetically manipulating O. tsutsugamushi and building additional genetic tools to investigate this globally significant pathogen. IMPORTANCEOrientia tsutsugamushi causes scrub typhus, a globally emerging rickettsiosis that can have a high mortality rate and has been a known human disease since the fourth century. Of the genera of obligate intracellular bacterial pathogens that cause human disease, Orientia is the only one for which genetic tools have not been developed. This has limited understanding of O. tsutsugamushi-host dynamics that drive the bacteriums pathobiology and hindered development of novel treatment or protection strategies against scrub typhus. Here, we successfully transformed and achieved allelic exchange in O. tsutsugamushi. Transgenic bacteria were selected via antibiotic resistance, validated by PCR and nanopore sequencing, and visualized by immunofluorescence and live-cell fluorescence imaging. Our report includes detailed descriptions of empirically determined host cell cultivation, multiplicity of infection, transformation, and selection conditions to provide a foundation on which other researchers can build. Overall, this work begins to establish a genetic toolbox for O. tsutsugamushi.

Ticks transmit pathogens across wildlife, domestic animals, and humans, and are therefore considered important vectors under the One Health framework. In India, the burden of tick-borne diseases, such as Kyasanur Forest Disease and Crimean-Congo Hemorrhagic Fever, remains poorly quantified due to fragmented surveillance and limited spatial data. Here, we present TickMapKB, a curated spatial knowledgebase documenting 72 tick species across more than 600 georeferenced locations in India. The majority of the species belonged to the genera Haemaphysalis, Rhipicephalus, and Hyalomma. Additionally, the resource integrates host associations, pathogen and disease information, morphological identification keys, acaricide resistance profiles, and protein annotations into a single, interactive platform accessible at https://cb.imsc.res.in/tickmapkb/. Specifically, the resource captures 53 pathogens, over 3000 protein annotations, and morphological keys from 26 published resources. TickMapKB thus provides researchers, clinicians, and other stakeholders with integrated spatial, biological, and resistance information to support surveillance planning, resistance management, and tick-borne disease risk assessment.

Naturally occurring variation in the bovine mannose receptor C-type 1 gene (MRC1) may shape macrophage responses to Mycobacterium (M.) bovis, a key driver of bovine tuberculosis (bTB). We identified four coding region SNPs in MRC1 across Bos taurus (Holstein Friesian, Brown Swiss) and Bos indicus (Boran, Sahiwal) cattle breeds, including a non-synonymous variant, rs380943118 (c.2963G>A; Ser988Asn) in C-type lectin-like domain (CTLD) 6, most prevalent in Sahiwal cattle. Structural modelling suggested that the S988N substitution, which is spatially separated from the monosaccharide binding site of CTLD4, might indirectly affect glycan binding, perhaps through a conformational change in the receptor. Monocyte-derived macrophages upregulated MR expression during differentiation, with heterozygous (G/A) animals showing higher MR expression and increased uptake of GFP-M. bovis BCG, although differences were not statistically significant. Anti-CD206 blockade did not inhibit BCG internalization, either indicating that this specific antibody did not bind to a CTLD involved in ligand binding or that MR is not the sole entry receptor. These results highlight naturally occurring MRC1 polymorphisms that may influence MR structure and macrophage function, providing a foundation for future studies to assess their role in bTB susceptibility.

While emerging diseases pose a global threat to amphibians, the dynamics of understudied vector-borne blood pathogens remain poorly understood. Pathogen occurrence is driven by a combination of environmental, ecological, and phylogenetic factors, yet how these drivers shape blood pathogen communities in tropical amphibians is largely unknown. In this study, we used molecular screening and phylogenetic linear models (PGLMMs) to evaluate how climate and ecomorphology influence the incidence of three blood pathogen groups (Trypanosomatidae, Hepatozoon, and Rickettsia) in wild anurans from a protected area in the Brazilian Atlantic Forest. Among 93 individuals sampled, over 93% were infected with at least one pathogen. Trypanosomatidae was the most common (76.3%), followed by Rickettsia (69.9%) and Hepatozoon (16.1%). Pathogen responses to temperature were contrasting: Hepatozoon occurrence increased in warmer periods, while Trypanosomatidae declined. Furthermore, rheophilic species showed a lower probability of Rickettsia infection, providing the first evidence that microhabitat use influences blood pathogen dynamics in amphibians. Our findings demonstrate that hemoparasites prevalence is driven by a multifaceted interplay of variables, highlighting that conservation strategies must account for these pathogen-specific responses to habitat use and environmental change, even within protected areas.

BackgroundLyme borreliosis is a common tick-borne disease in Europe caused by spirochetes of the Borrelia burgdorferi sensu lato complex, including Borrelia afzelii, which is maintained in nature through interactions with rodent reservoir hosts. These spirochetes have evolved several surface proteins to manipulate rodent host immunity, some of which remain polymorphic in Borrelia populations. Among these proteins, OspE, which binds the host complement-regulating factor CFH to evade destruction by complement, is one of the most variable. Yet, what evolutionary forces maintain this polymorphism is not well understood. Motivated by a recent discovery of CFH polymorphism in the bank vole (Clethrionomys glareolus), the main reservoir host of B. afzelii, we hypothesized that the polymorphism is maintained by host-parasite coevolution involving specific associations between host and parasite genetic variants. MethodsWe analyzed associations between bank vole CFH alleles and B. afzelii OspE variants across three datasets sampled in Poland. Selection acting on OspE was evaluated using omegaMap. Host-pathogen genotype associations were tested using partial redundancy analysis (RDA), and co-structure was assessed using co-correspondence analysis (CoCA). ResultsWe found that OspE evolves under positive selection, however, we found no evidence for an association between OspE and host CFH variants at the individual level based on RDA or at the population level based on CoCA. ConclusionsDespite evidence of positive selection acting on OspE, we found no support for specific genetic matching between B. afzelii and its bank vole host at the CFH-OspE interface. These results suggest that the evolution of CFH and OspE may be shaped by broader selective pressures, potentially including interactions with multiple host species.

Lipoarabinomannan (LAM) is a useful biomarker for detection of M. tuberculosis infection and disease. Related antigens can be detected in urine samples of TB patients by combinations of monoclonal antibodies (mAbs) directed against specific epitopes expressed in LAM. While sensitive for samples from patients with active TB disease who have HIV-1 co-infections, these assays are less effective for other populations, and there is therefore a need for more sensitive antibodies that can improve the sensitivity of these assays. Here we characterize the antigen and epitope specificities, sequence diversity and isotype dependencies of eight LAM-specific human mAbs that target five distinct arabinose- and mannose-dependent epitopes present in LAM and lipoarabinomannan (LM). Whereas all of the mAbs recognized ManLAM, only a few, including A194-01, consistently detected antigens in TB+ urine samples. Converting A194-01 from the IgG1 to the IgM isotype resulted in broader recognition of poly-Ara glycan epitopes, and increased sensitivity for clinical antigens when combined with several capture reagents, including RU95-C1, a novel antibody targeting the mannan domain of LAM. These results define novel epitopes that are differentially expressed in bacterial and urinary forms of LAM, and identify novel antibody combinations which possess enhanced diagnostic utility for clinical forms of LAM.

Dengue is a mosquito-borne, viral disease of increasing public health significance. Currently, most public health interventions target the vector, with efficacy dependent on timing within the season. Whilst seasonal profiles have been characterised in some endemic settings a global assessment is lacking. Here, we develop and apply a proportion-based measure of dengue seasonality to reported case time series from 1990 to 2024 across 106 countries and territories, the largest assessment of this phenomenon to date. We identify regional differences in seasonality such that every month of the year saw cases peak in at least one country or territory. Latitude was identified as influencing seasonality, with cases peaking between March and April in the southern hemisphere and July and October in the northern hemisphere. Equatorial locations displayed flat seasonality, and amplitude increased with distance from the equator. K-means clustering identified three seasonal profile types: two with pronounced seasonal outbreaks (with distinct peak timing and shape) and one with flatter, more endemic transmission. Peak month timing covaried among locations within the same seasonality cluster, with phase differences meaning that information on shifts in peak timing may be available several months in advance in some settings, of potential significance for prediction and intervention planning. Beyond aiding public health planning, identification of seasonal clusters suggests that information on dynamics in one location could be leveraged to improve forecasting power in others with similar seasonal dynamics.

Tick serine protease inhibitors (serpins) are critical for tick feeding success and pathogen transmission. We previously demonstrated that two unique serpins, S12c5 and S13c5, are tandemly duplicated on Ixodes scapularis chromosome 5 and are injected into the host at heightened levels during feeding by Borrelia burgdorferi (Bb)-infected nymphs. Here, we characterize the biochemical properties and immunomodulatory functions of these serpins and investigate their roles in promoting Bb transmission. Despite their response to Bb infection, S12c5 and S13c5 share less than 20% overall amino acid identity and differ critically at their reactive center loop (RCL) P1 site, which determines substrate specificity: S13c5 contains a basic arginine residue, while S12c5 contains a polar serine residue. Consistent with these differences, recombinant S13c5 efficiently inhibited innate immune proteases including fXa, plasmin, and trypsin IV (SI: 2.5, 1.9, and 1.0; ka: 8.56 x 103, 3.97 x 10, and 1.08 x 10 M-{superscript 1}s-{superscript 1}, respectively), and consequently delayed plasma clotting via the common pathway, whereas rS12c5 did not inhibit these proteases. However, despite molecular modeling predicting stronger interactions between S13c5 and complement proteases, both serpins inhibited MBL-pathway complement activation by targeting MASP1/3. Deletion of the RCL domain abolished this inhibitory activity, confirming both proteins function as typical inhibitory serpins. Functionally, rS13c5 enhanced Bb colonization in C3H mouse organs. Interestingly, immune response assays revealed a trade-off: S13c5, despite its broader inhibitory activity, was less immunogenic than S12c5. Collectively, these findings establish S12c5 and S13c5 as Bb transmission factors that promote spirochete survival through disruption of host innate immunity.

The tick Ixodes ricinus is the main vector of human and animal pathogens in Europe. Despite its importance in epidemiology and medicine, our understanding of physiological mechanisms controlling blood feeding, osmoregulation, or development are still limited. Here, we identify novel neuropeptide invertebrate parathyroid hormone-like peptide (iPTH) and its two receptors - PTHR1 and PTHR2 in I. ricinus. Functional aequorin-based assay confirmed specific activation of both receptors by iPTH. Using RT-qPCR we detected the PTHR1 transcript in the synganglion, while increased expression levels of PTHR2 were found in the salivary glands, hindgut and female gonads. RNA-mediated knockdown of iPTH receptors in nymphs resulted in delayed blood feeding, and a high incidence of defects in adult ecdysis. Consistent with observed phenotypes, iPTH is expressed in multiple neurons of the synganglion which project arborizing axons to the salivary glands, rectal sack and skeletal muscles. iPTH was colocalized with orcokinin-immunoreactivity (OK-IR) in all neurons that innervate these peripheral tissues. iPTH is further colocalized with tachykinin (TK) in Pd1DL1 neurons, suggesting coordinated action with other neuropeptides. Our findings indicate that iPTH signaling is required for normal feeding, development and successful ecdysis.

Background: Dirofilaria repens is a zoonotic parasite expanding unnoticed across Europe due to climate change. We hypothesised that in this process, the Carpathian Basin has a facilitating effect. Methods: Using 426 georeferenced European cases, the probability of infection occurrence was determined in relation to climatic factors, surface water availability, regional social deprivation, and stray dog population density. To analyse the potential impacts of ecological and social factors (deprivation and stray dog population density), the MaxEnt algorithm, and spatial Empirical Bayes smoothing and Bivariate Local Indicators of Spatial Association (BiLISA) index calculation were employed, respectively. Results: MaxEnt analysis revealed that the mean warmest month temperature (22.8 - 25.1 oC), winter mean minimum temperature (> -2.1 oC), and summer precipitation (28.6 - 231 mm) have the strongest impact on the probability of the parasite's occurrence in Europe. Social factors have significance in the eastern Balkans and the Carpathian Basin, but not in Western Europe. The Carpathian Basin appears to be a hotspot, similar to Mediterranean coastal areas. Furthermore, the Danube Valley acts as an ecological corridor for subtropical vector-borne parasites. Conclusions: Our findings confirm that summer warmth is the primary ecological driver of the parasite's range expansion, which is facilitated by the Carpathian Basin due to climatic and socioeconomic conditions.

Anthelmintic resistance in cyathostomins is escalating worldwide, threatening equine health and highlighting the need for sustainable, ecology based parasite control strategies. Chicory (Cichorium intybus, Puna II) has emerged as a promising antiparasitic forage, yet its broader effects on the equine holobiont, parasites, microbiota, and host physiology remain poorly understood. We conducted a 32 day longitudinal grazing trial in young horses to assess how chicory affects parasitological outcomes, gut microbial ecology, nemabiome composition, behaviour, and host physiological and immune responses. Twenty-six naturally infected Anglo-Arabian horses were monitored weekly, with 13 grazing a chicory-based sward and 13 grazing a permanent pasture. Clinical parameters, body weight, and serum biochemistry remained stable across treatments, indicating that chicory was well tolerated. Immune profiles showed limited variation, although IL 10 increased in chicory fed horses, suggesting subtle immune modulation. Behavioural observations revealed no signs of discomfort and indicated slightly enhanced social interactions in the chicory group. Chicory grazing produced a marked reduction in cyathostomin egg excretion, accompanied by species specific shifts in nemabiome composition. Several cyathostomin taxa, including Cylicocyclus ashworthi, C. leptostomus, and C. nassatus, declined in chicory fed horses, whereas certain Cylicostephanus spp increased, indicating differential sensitivity rather than uniform suppression. Concomitantly, chicory induced profound ecological changes in the gut microbiota, including reduced alpha diversity, increased beta dispersion, and destabilised individual microbial trajectories. Several bacterial lineages, particularly Oscillospiraceae, Clostridiaceae, Lachnospiraceae, and Bacteroidales, were differentially enriched, reflecting a functional reorganisation of the intestinal ecosystem. Together, these findings demonstrate that chicory reduces parasite fitness, reshapes nemabiome composition, and alters gut microbial ecology while maintaining host physiological stability. Chicory thus emerges as a promising ecological tool for parasite control, capable of modulating the equine holobiont in ways that complement and potentially reduce reliance on conventional anthelmintic strategies. However, because its effects on gut microbial ecology remain uncertain, and may include shifts resembling dysbiosis, future studies are needed to monitor microbial dynamics more closely and clarify the long term ecological consequences of chicory grazing.

Background Brucellosis is a severe zoonotic disease with pronounced seasonality and regional heterogeneity in high-incidence areas of China. Reliable forecasting tools are needed to inform prevention strategies, but the optimal modeling approach across different regions remains unclear. Principal Findings We collected monthly brucellosis incidence and 17 environmental variables from 2014 to 2024 across five high-incidence provinces: Inner Mongolia, Xinjiang, Shanxi, Heilongjiang, and Hebei. A three-step procedure--cross-correlation analysis, multicollinearity diagnostics, and stepwise regression--was used to select exogenous predictors. We then compared four time-series models: seasonal autoregressive integrated moving average (SARIMA), SARIMA with exogenous variables (SARIMAX), long short-term memory (LSTM), and LSTM with exogenous variables (LSTMX). All five provinces showed a unimodal seasonal pattern with peaks between April and July, though environmental drivers and optimal lag periods varied substantially by region, ranging from 1 to 6 months. In forecasting performance, LSTM achieved the highest accuracy in Shanxi (R2=0.925), Hebei (R2=0.876), and Xinjiang (R2=0.829), outperforming SARIMA and SARIMAX. LSTMX performed best in Inner Mongolia (R2=0.759) and Heilongjiang (R2=0.772) but showed weaker performance than LSTM in Shanxi and Hebei. Overall, adding exogenous variables did not consistently improve predictions across provinces. Conclusions Our findings demonstrate that LSTM-based models offer clear advantages for brucellosis forecasting in most high-incidence provinces, but the value of incorporating environmental predictors is region-dependent. These results support the development of tailored early warning systems and precision prevention strategies for brucellosis in high-risk areas of China.

In September 2023, the first infections with a novel lineage of mpox were detected in South Kivu. Since then, the virus has spread regionally, nationally and internationally. As part of continued efforts to understand the mpox ecology and epidemiology, the South Kivu district of public health and partners have set up systematic case finding and follow-up, including strain characterisation through PCR and sequencing. Samples were collected from 595 hospitalized patients with a confirmed mpox virus infection. A clade differentiating RT-PCR showed that 545 (92%) of samples were positive for clade Ib but also remarkably that Clade Ia infections were diagnosed for the first time in South Kivu. First detected in cases in week 7 in Kamituga, 50 cases were identified over the whole study period (8,40% of all cases). Phylogenetic analysis of initial cases revealed introductions of clade Ia into the South Kivu province alongside the continuation of the clade Ib mpox virus outbreak. These findings underscore the increasing complexity of clade I mpox virus outbreaks in the DRC.

Background Leptospirosis is substantially underdiagnosed across sub-Saharan Africa, with its contribution to acute undifferentiated fever (AUF) poorly characterized. We determined the prevalence, risk factors, and clinical profile of leptospirosis among adolescents and adults presenting with AUF at a referral hospital and health centre in Hoima, western Uganda. Methods: In a prospective health facility-based study with convalescent follow-up, blood and urine from AUF patients were tested by LipL32 real-time PCR (qPCR) and microscopic agglutination (MAT). Leptospirosis was confirmed by qPCR positivity, a single test MAT titre of 1:800, or at least a fourfold titre rise or seroconversion in paired sera. Seroconversion was defined as a change from negative or 1:50 to 1:100 (conservative) or 1:200 (lenient). Seroprevalence was defined as a MAT titre of 1:100 or above in any sample. Risk factors were identified by multivariable logistic regression. Results: Among 330 AUF patients, acute leptospirosis prevalence was 27.0% (95% CI 22.3 to 32.1; conservative) and 32.7% (95% CI 27.7 to 38.1; lenient), comparable to malaria at 30.3% (95% CI 25.3 to 35.3), with co-infection in 8.8% (95% CI 5.7 to 11.8). qPCR detected Leptospira DNA in 9.1%, with 63.3% of qPCR-positive cases serologically confirmed and 24.4% of serological cases, qPCR-positive. Seroprevalence was 35.8% (95% CI 30.6 to 41.2); L. interrogans serovar Bataviae was predominant (18.2% of serological cases), reported here for the first time in Uganda. Skinning animals (aOR 5.19, 95% CI 1.40 to 21.16) and mosquito exposure (aOR 2.31, 95% CI 1.17 to 4.70) were the only independent risk factors in multivariable analysis. Discussion: Leptospirosis occurs as frequently as malaria among AUF patients in Hoima and warrants inclusion in Uganda's national febrile illness guidelines. The association of leptospirosis with skinning of animals suggests a potential role of animal exposure in leptospirosis transmission. Poor qPCR-MAT concordance confirms that accurate case ascertainment requires combined molecular and serological diagnostics.

Lyme arthritis, a manifestation of Lyme disease, is triggered by the spirochetal bacterium Borrelia burgdorferi (Bb), which is transmitted through the bite of the Ixodes tick. Although multiple studies have been conducted on the complex host immune response in Lyme arthritis, the spatial gene expression environment in the joint tissue remains unexplored. Here, we applied spatial transcriptomics to ankle joints of C3H mice infected with Bb, profiling tissues at peak inflammation (two weeks post infection) and after antibiotics (four weeks post-infection) during inflammation resolution. Analysis revealed spatially restricted signatures: pro-inflammatory responses dominated synovial and fibroblast populations two weeks post-infection, with elevated levels of Vimentin and I-Ek gene - and Vimentin protein - expression localized to these regions. By four weeks post-infection during the inflammation resolution phase, levels of Vimentin and I-Ek related gene and protein expression were reduced. Further, we noted an increase in the CD54+ and CD106+ double-positive population in infected mice joints compared to the vehicle treated controls. Notably, fibroblasts and synoviocytes in the medial joint regions adopted immune-like phenotypes during peak inflammation, while the same cell types in the exterior humeroradial joint displayed a more infection-resilient phenotype. These spatially resolved maps demonstrate that joint microenvironments play a crucial role in pathogenesis, offering unique insights into Lyme arthritis pathology.

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides (Mmm), remains a major burden to cattle health and the agricultural industry. Mmm is an atypical bacterial pathogen that appears to lack classical virulence factors that cause direct tissue injury (i.e. toxins), and little is known about the mechanisms driving its pathogenicity. The host immune response is believed to be implicated in CBPP pathology, though the molecular mechanisms underlying lesion initiation, progression and chronicity are poorly defined. Classical pathology describes a continuum of lung lesions starting from early inflammation to more mature necrotic lesions and formation of fibrotic sequestra. However, the host transcriptional response driving this potentially immunopathological progression during Mmm infection has never been resolved in vivo. Here, we performed lesion-stage-resolved transcriptomic profiling of pathological lung tissue collected from experimentally infected animals and compared to healthy lung tissue collected from unchallenged controls. Differential gene expression and functional enrichment analyses were used to identify biological pathways relevant to Mmm infection and pathological lesion formation. Early infection was dominated by interferon-stimulated genes and cytokine-responsive pathways, creating a primarily antiviral-like response environment despite the bacterial etiology. Red hepatization showed strong induction of neutrophil chemoattractants, epithelial remodeling markers, and early matrix-remodeling enzymes. Consolidation, spanning red and grey stages, was enriched for innate immune activation, leukocyte adhesion, extracellular matrix organization, and persistent interferon signaling. Grey hepatization reflected late-stage consolidation with heightened neutrophil effector activity, oxidative and proteolytic injury, and macrophage and fibroblast-linked collagen processing. Necrosis/Sequestra lesions showed reduced inflammatory signaling, robust extracellular matrix organization, adhesion, and morphogenetic pathways consistent with encapsulation and sequestrum formation. Our data indicate that the dynamic continuum of CBPP lung pathology is initiated by interferon-primed myeloid recruitment and amplified by neutrophil-driven injury and macrophage- and fibroblast-mediated matrix remodeling. These data further substantiate the role of dysregulated immunity in the development of disease during Mmm infection.

Rift Valley fever (RVF) is a mosquito-borne disease that can cause severe illness and death in both humans and livestock. Since 2016, Uganda has experienced recurrent but localized RVF outbreaks concentrated in the countrys southwestern region. The ecological drivers of this emergence remain unclear, as outbreaks have occurred throughout the year and show little association with meteorological patterns. We evaluated whether crop cultivation, particularly banana cultivation, is associated with RVF outbreak occurrence after controlling for likely confounders. We conducted a longitudinal study of human-inhabited 5 x 5 km grid cells across southwestern Uganda from 2016-2024. Annual Sentinel-2 satellite imagery composites were used to classify land cover into banana, coffee, ground crops, and non-crop categories, and the proportion of each land type was calculated for every grid-cell year. Because land cover proportions are compositional, isometric log-ratio transformations were used to estimate the independent effects of each land type. Confounding was addressed through propensity weighting, and crop substitution effects were estimated using g-computation. Banana land cover was the only land type consistently associated with increased RVF outbreak likelihood. In grid-cell years with low baseline banana cover, a 10-percentage point substitution from other land classes into banana was associated with a 1.64-fold increase in the odds of an RVF outbreak (95% CI: 1.17-2.29). In a simplified banana-only model, each 10-percentage point increase in banana cover was associated with a 1.21-fold increase in outbreak odds (95% CI: 1.02-1.43). Holding banana cover constant, substitutions among coffee, ground crop, and non-crop land showed weak or null associations. These findings suggest that banana cultivation may be an important ecological feature influencing RVF transmission dynamics and outbreak risk in southwestern Uganda. Author SummaryRift Valley fever (RVF) is a mosquito-borne disease that affects both humans and livestock and has caused repeated outbreaks in southwestern Uganda since 2016. While rainfall and flooding are often linked to RVF outbreaks elsewhere, Ugandas recent outbreaks have occurred across seasons and are not well explained by weather patterns alone. We investigated whether agricultural land use could help explain where outbreaks occur. Using satellite imagery from 2016-2024, we measured the amount of banana cultivation, coffee cultivation, ground crops, and non-crop land across southwestern Uganda and evaluated their association with RVF outbreak occurrence. We found that areas with greater banana cultivation were consistently more likely to experience RVF outbreaks, even after accounting for environmental and demographic factors. In contrast, coffee, ground crops, and non-crop land showed little evidence of an independent association with outbreak risk. These findings suggest that banana cultivation may create ecological conditions that favor RVF transmission. Rather than indicating that bananas themselves cause disease, the results point to banana-growing landscapes as potential environments where interactions among mosquitoes, livestock, and humans may increase transmission opportunities. Understanding these local ecological drivers could help improve surveillance, risk assessment, and prevention strategies for RVF in Uganda and other endemic regions.