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Medical and Veterinary Entomology

Wiley

Preprints posted in the last 30 days, ranked by how well they match Medical and Veterinary Entomology's content profile, based on 10 papers previously published here. The average preprint has a 0.01% match score for this journal, so anything above that is already an above-average fit.

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Estimating mosquito bionomics parameters with a hierarchical Bayesian model

Lemant, J.; Tarroux, A.; Smith, T. A.; Zogo, B.; Golumbeanu, M.; Odufuwa, O. G.; Irish, S.; Moore, S. J.; Pothin, E.; Champagne, C.

2026-03-26 zoology 10.64898/2026.03.24.713291 medRxiv
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BackgroundThe malaria transmission potential and the vulnerability of Anopheles mosquitoes to different vector control methods depend, among other factors, on the endophily, endophagy, anthropophagy and survival of each species. Local information on these bionomic parameters is generally unavailable. MethodsTo address this, we estimated species-specific values of these parameters using an augmented version of the global database of bionomics data by Massey et al. (2016). We applied inclusion and exclusion criteria to select eligible studies with relevant experimental designs that minimise bias from collection methods for parous, sac, endophagy, and endophily rates as well as for the resting duration. For the human blood index (HBI), we separated data from indoor and outdoor collections. We fitted hierarchical Bayesian models with levels based on Anopheles taxonomy to estimate these quantities. Based on the estimated bionomics, we quantified the expected vectorial capacity reduction after the introduction of a pyrethroid-pyrrole insecticide-treated net (ITN) for 57 Anopheles species. ResultsWe identified 26 eligible studies for endophagy and 61 for the parous rate, leading to a Bayesian posterior average for the Anopheles genus of 42% (95% credible interval: 18-70) and 55% (32-77) respectively. HBI values widely varied depending on the location of collection, except for some species showing strong anthropophilic behaviours. Resting duration was estimated to be 2.1 days (1.2 - 4.8) at the genus level. Few studies were available to estimate the sac and endophily rates, which prevented us from deriving precise estimates for the whole Anopheles genus. Our estimates of the vectorial capacity reduction following the introduction of a pyrrole-pyrethroid ITN ranged between 48% and 76% across species, highlighting the important differences among mosquito species in vulnerability to vector control interventions. ConclusionThis work demonstrates how data from both Anopheles species complexes and individual species can be leveraged to generate species-specific estimates of bionomic parameters, capturing the local characteristics and behaviour of malaria vectors. The dataset is readily updatable as new data become available. However, more frequent and standardised field surveys are still needed to accurately characterise local vector behaviour.

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Study of the molecular nature of resistance to bifenazate in a Tetranychus urticae Koch Laboratory Strain

Okulova, E. S.; Skrypka, D. D.; Bogomaz, O. D.; Zhidkin, R. R.; Ivanova, G. P.; Tulaeva, I. A.; Jiang, X.; Matveeva, T. V.

2026-03-20 molecular biology 10.64898/2026.03.18.712698 medRxiv
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BACKGROUNDThe two-spotted spider mite, Tetranychus urticae Koch, is a major agricultural pest with a rapid propensity for developing acaricide resistance. Bifenazate targets mitochondrial cytochrome b (CYTB). While the G126S mutation is frequently associated with resistance, its independent role remains unclear as it often occurs with other substitutions. This study explores the molecular basis of bifenazate resistance in a Russian laboratory strain derived from a St. Petersburg greenhouse population. RESULTSDisruptive selection with increasing bifenazate concentrations generated resistant and susceptible isofemale lines. AlphaFold2 structural modeling of CYTB indicated that G126S causes a steric clash, leading to conformational destabilization, whereas other reported mutations primarily affect the ligand-binding pocket. Oxford Nanopore sequencing revealed a very low initial frequency of the G126S allele (<1%; 226/35,895 reads) in the unselected population. After one year of stepwise selection (0.00005-0.031% a.i.), the mutant allele frequency surged to 90% (7,272/8,056 reads). No other known resistance-associated mutations were found in the analyzed cytb fragment. CONCLUSIONWe report the first identification of the G126S mutation in a Russian T. urticae population and demonstrate its rapid fixation under bifenazate selection. Within this genetic background, G126S alone appears sufficient to confer high-level resistance, emphasizing the population-specific nature of resistance evolution and the critical need for local monitoring.

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Determination of suitable reference genes for RT-qPCR analysis in Gryllodes sigillatus (Orthoptera: Gryllidae)

Houda, H. B. M.; Bonhomme, R.; Renois, F.; Deschamps, M.-H.; Benoit-Biancamano, M.-O.; Meurens, F.

2026-04-05 molecular biology 10.64898/2026.04.04.716481 medRxiv
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The tropical house cricket Gryllodes sigillatus is a major species used in the edible insect farming industry. Despite the rapid expansion of this sector, diagnostic tools for detecting infections in these species remain limited. The lack of validated reference genes compromises the reliability of RT-qPCR-based gene expression analyses, which are essential for the development of molecular tools for disease diagnosis and health monitoring in insect production systems. To address this gap, we evaluated the expression stability of six candidate reference genes (ACTB, EF1, GAPDH, HisH3, RPL5, and 18SrRNA) across four body parts (abdomen, head, legs, and whole body) using a combination of complementary statistical approaches, including geNorm, NormFinder, BestKeeper, the {Delta}Ct method, the R statistical environment, and the integrated RefFinder tool. Candidate genes were identified and annotated using the recently published G. sigillatus genome, through sequence comparisons with closely related insect species using BLAST and reciprocal BLAST analyses, multiple sequence alignments. All procedures complied with MIQE 2.0 guidelines to ensure methodological rigor and transparency. The results showed that ACTB, EF1, RPL5, and 18SrRNA exhibited stable and consistent expression across all analyzed tissues, whereas GAPDH and HisH3 displayed high variability and were generally unsuitable for normalization, except in head tissue where GAPDH remained stable. This study provides the first validated set of reference genes for G. sigillatus, establishing a robust foundation for accurate, reproducible, and comparable gene expression analyses. Furthermore, these findings support the development of RT-qPCR-based diagnostic tools, contributing to improved health monitoring and biosafety in insect production systems.

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Accurate identification of invasive Aedes mosquito species using low-cost imaging and geometric wing morphometrics

Sauer, F. G.; Joest, H.; Sulesco, T.; Duve, P.; Loc, D. H.; Nolte, K.; Luehken, R.

2026-04-10 zoology 10.64898/2026.04.08.717229 medRxiv
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Accurate species identification is crucial to assess the medical and veterinary relevance of a mosquito specimen, but it requires high experience of the observers and well-equipped laboratories. This study aimed to evaluate whether low-cost imaging in combination with geometric wing morphometrics can provide accurate identification of invasive, morphologically similar Aedes species. The right wings of 670 female specimens covering 184 Ae. aegypti, 156 Ae. albopictus, 166 Ae. j. japonicus and 164 Ae. koreicus, were removed, mounted and photographed with a professional stereomicroscope (Olympus SZ61, Olympus, Tokyo, Japan) and a macro lens (Apexel-24XMH, Apexel, Shenzhen, China) attached to a smartphone. The coordinates of 18 landmarks on the vein crosses were digitalized by a single observer for each image. In addition, the landmarks of 20 specimens per species and imaging device were digitalized by six different observers to assess the degree of the observer error. The superimposed shape variables were used to compare the species classification accuracy of linear discriminant analysis (LDA), support vector machine (SVM), Random Forest (RF), and XGBoost. In the single-observer landmark data, the LDA achieved the best classification results with a mean accuracy of 95 % for landmarks from microscope images and 92 % for those obtained from smartphone images. In the multi-observer landmark data, LDA consistently performed worse than the other three classifiers, and the reduction in the accuracy was more pronounced for smartphone images than for microscope images. This pattern was associated with a higher degree of observer error for smartphone images, as confirmed by a landmark-wise comparison across all landmarks. Geometric wing morphometrics provides a reliable method to distinguish the most common invasive Aedes species in Europe. Thereby, the image quality obtained by smartphones equipped with a macro lens is sufficient and represents a cost-effective alternative to professional microscopes. However, due to the greater degree of observer variation for smartphone images, landmark coordinates for such images should ideally be collected by a single observer.

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Comparative studies of transmission mode and localisation patterns of common RNA viruses in Queensland fruit fly (Bactrocera tryoni) reveal most are vertically transmitted

Bidari, F.; Morrow, J. L.; Pradhan, S. K.; Riegler, M.

2026-03-23 microbiology 10.64898/2026.03.20.713308 medRxiv
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RNA viruses are common in tephritid fruit flies including the Queensland fruit fly, Australias most significant horticultural pest. For many their transmission, tissue tropism and load across host development remain unexplored. Yet these factors are important for host biology, ecology and pest management. We investigated Bactrocera tryoni orbivirus (OV), Bactrocera tryoni xinmovirus (XV), Bactrocera tryoni toti-like virus (TLV) and Bactrocera tryoni iflavirus species 2 (IVsp.2) that commonly coinfect B. tryoni laboratory populations. OV and XV transmission was vertical within and on eggs, while TLV transmission was vertical within eggs. IVsp.2 was not detected in eggs but was present in adults; however, IVsp.2 was horizontally transmitted, with viral load increasing with cohabitation time with infected flies. Horizontal transmission was not observed for the other viruses. OV had a similar load across all tissues, while XV was consistently more abundant in ovaries. TLV had a high viral load in the brain whereas IVsp.2 was abundant in the thorax, foregut and midgut. Besides differences in eggs, the viruses were detected in all other developmental stages, but viral load patterns differed: viral load remained constant for TLV, fluctuated for OV and XV, and was low in pre-adult stages and high in adults for IVsp.2. Our findings demonstrate distinct transmission strategies and tissue tropism among the viruses, providing new insights into their epidemiology and role in host biology. Furthermore, contrary to prevailing views that viruses are generally horizontally transmitted, most known RNA viruses of B. tryoni are vertically transmitted affecting the evolution of host-virus interactions.

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Genetic Variability and Population Structure within the Anopheles tessellatus complex (Theobald, 1901) in Indonesia using ITS2 nuclear and COI, COII mitochondrial sequences

Nurwidayati, A.; Purwanto, H.; Astuti, R. R. U. N. W.; Nugraheni, Y. R.; Susanti, L.; Srikandi, Y.; Daryono, B. S. W.; Garjito, T. A.; Manguin, S.

2026-04-10 molecular biology 10.64898/2026.04.08.717322 medRxiv
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Some Anopheles species that act as malaria vectors are members of species complexes, a concept whereby sibling species cannot be differentiated solely on the basis of morphological characters. Therefore, species complexes represent a major problem in malaria vector control, because within an Anopheles complex, vectors cannot be differentiated from non-vector species, unless molecular techniques are used to identify them. The Anopheles tessellatus species complex is an important potential vector in South, East, and Southeast Asia, including certain regions of Indonesia. However, no in-depth studies have been conducted on this species complex in that country. Therefore, this study investigated the taxonomic status of An. tessellatus from diverse populations across five Indonesian islands (Sumatra, Java, West Nusa Tenggara, East Nusa Tenggara, and Sulawesi) and identified interpopulation genetic variation based on molecular data of the ITS2, COI, and COII genes. Phylogenetic relationships were constructed using the Maximum Likelihood method. Haplotype and network analysis were also conducted. The results indicate that An. tessellatus constitutes a monophyletic group comprising three well-defined lineages that exhibit clear intraspecific genetic differentiation. Cluster 1 corresponds to the population of Sumatra, Cluster 2 represents population from Sulawesi, and Cluster 3 encompasses populations from Java, West Nusa Tenggara, and East Nusa Tenggara. These findings demonstrate high haplotype diversity and low nucleotide diversity within the species. Populations from West Sumatra, Manado, Tojo Una - Una, and North Morowali (Sulawesi) have the potential for speciation with a genetic distance of 0.61 - 0.94% for COI, between 0.81 - 0.95% for ITS2, and between 0.62 - 0.71% for COII. These findings underscore the need for further integrative studies to obtain a more comprehensive understanding of the An. tessellatus complex in Indonesia and its role in malaria transmission.

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Insecticide temephos alters thermal dependence of dengue vector

Heffernan, P. M.; Murdock, C. C.; Rohr, J. R.

2026-04-03 ecology 10.64898/2026.04.01.715840 medRxiv
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O_LIAlthough ecological research has long focused on the effects of temperature on population growth, arthropod pests are exposed to a wide variety of environmental factors that affect their performance, such as chemical pesticides targeted against them. Moreover, these environmental factors likely do not act in isolation. Identifying the extent to which abiotic factors interact to affect pest population dynamics can strengthen current and future pest management programs. C_LIO_LIHere, we investigated the extent to which temephos, a common pesticide applied to aquatic environments for mosquito control, influences the thermal performance of juvenile survival and development rate, as well as the intrinsic population growth rate, of the invasive mosquito pest, Aedes aegypti. We implemented a response surface experimental design to measure these traits across seven temperatures and five temephos concentrations and fit temperature- and insecticide-dependent performance curves to assess impacts on the overall performance and the thermal optimum, minimum, and maximum. C_LIO_LITemephos exposure profoundly altered the thermal performance of juvenile survival by reducing survival across all temperatures, shrinking the thermal breadth, and shifting the thermal optimum to warmer temperatures. Through this, temephos also altered the thermal performance of population growth primarily by reducing its thermal breadth. C_LIO_LISynthesis and applications: Our findings demonstrate that interactions between temperature and insecticide exposure can fundamentally reshape pest population dynamics, rather than acting as independent stressors. By quantifying this interaction, we showed that temphos is most effective below the pests thermal optimum, suggesting that larvicides may yield the greatest population suppression in cooler regions or during cooler periods of the year. Incorporating such temperature-dependent efficacy into pest management strategies could improve the timing and spatial targeting of control efforts. More broadly, these results highlight the need to integrate anthropogenic stressors with climatic drivers when predicting pest risk and optimizing management under ongoing environmental change. C_LI

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Drivers of mosquito presence and abundance in urban and garden ponds in a European city

Tornero, I.; Barta, B.; Hamer, A. J.; Soltesz, Z.; Huynh, T.-H.; Meszaros, A.; Horvath, Z.

2026-04-09 ecology 10.64898/2026.04.07.716928 medRxiv
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Mosquitoes in urban environments are considered unpleasant by citizens, and they can represent serious health risks as disease vectors. Invasive Aedes species are continuously spreading in Europe and have been increasingly reported from urban settlements. Some of these mosquito species have been associated with small artificial habitats. Therefore, their presence may also be expected in small plastic garden ponds, which are numerous in urban settings across many parts of Europe. Here, we aimed to determine whether urban waters host a high occurrence of mosquitoes and to identify the potential abiotic, biotic and landscape drivers of mosquito presence and abundance in urban ponds. We sampled 53 urban ponds in the city of Budapest (Hungary) of both natural and anthropogenic origin, and 40 garden ponds, which cover both highly urbanised areas and those with high green index in the suburbs. We collected data on macroinvertebrate communities, pond management, physico-chemical parameters, and pond characteristics (mainly morphology and vegetation cover) measured in situ. Two different mosquito detection techniques were used: dip-net sampling and eDNA. While only one invasive species (Aedes koreicus) was detected, occurring in a single pond, several other species were present, including potential malaria vectors increasingly reported from urban environments: the Anopheles maculipennis complex, An. claviger and An. plumbeus. Fish presence was negatively associated with both the presence and abundance of mosquitoes, regardless of pond type. Contrary to expectations, urbanisation did not play a major role in explaining mosquito presence or abundance. These results highlight the importance of local pond characteristics, and particularly the role of fish presence, in regulating mosquito populations in ponds in the urban landscape, although the broader ecological effects of fish on pond communities should also be considered.

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Semen collection, short term storage, and cryopreservation in the Texas horned lizard (Phrynosoma cornutum)

Julien, A. R.; Griffioen, J. A.; Perry, S. M.; Doege, R.; Burger, I. J.; Barber, D. R.

2026-04-06 zoology 10.64898/2026.04.03.716302 medRxiv
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As global reptile populations continue to decline, improving reproductive success in managed populations of listed species, such as Phrynosoma cornutum (the Texas horned lizard) has become increasingly critical for species survival. One understudied area of reproductive research in reptile species is gamete collection and storage, a crucial component for maintaining genetic diversity. In Texas, semen was collected from wild P. cornutum (n = 20) in June 2025. Semen collection was performed via electroejaculation (EEJ) under alfaxalone anesthesia. Prior to semen collection, snout-vent-lengths (SVL) and weights were recorded and testes measurements were taken using a portable ultrasound. Average sperm motility and concentration across all lizards was 83.7% and 85.7 x 106 sperm/mL, respectively. While lizards with longer SVLs had higher sperm motility, weight and testis size did not affect sperm parameters. Samples were extended in INRA96 and divided for use in cold-storage longevity or cryopreservation trials. Samples under cold-storage conditions were assessed for motility daily for 10 days. Motility was not significantly reduced until 48 hours post-collection and maintained 19% motility at day 10. For cryopreservation, samples were diluted 1:1 in INRAFreeze cryopreservation media and frozen in liquid nitrogen, then immediately thawed. Average post-thaw sperm motility was 13.9%, with the highest post-thaw motility recorded at 38.2%. This is the first report of semen storage and cryopreservation in Phrynosoma and provides valuable insight into semen storage potential in reptile species.

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Forensic Identification of Confiscated Helmeted Hornbill (Rhinoplax vigil) Casques and Implications for Individual Quantification in Wildlife Crimes

Shen, Y.; He, K.; Wang, W.; Huang, L.; Chen, J.

2026-04-06 zoology 10.64898/2026.04.02.715475 medRxiv
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In wildlife forensic practice, species identification and estimation of the Minimum Number of Individuals (MNI) for highly processed specimens have long relied on weight-based conversion methods, which may result in underestimation of the number of individuals involved in a case. Focusing on confiscated casque products of the helmeted hornbill (Rhinoplax vigil), this study combines macroscopic morphological examination with mitochondrial DNA barcoding (16S rRNA, COI, and Cytb) to explore a more robust approach for individual quantification. The results demonstrate that the conventional "weight-based" approach overlooks critical biological information contained in anatomical structures and cannot accurately reflect the actual number of individuals involved. Based on this, we propose an anatomy-based criterion centered on the principle of structural uniqueness: specimens retaining biologically unique beak or casque structures should be directly assigned to a single individual, whereas weight-based estimation should only be applied when original anatomical features are entirely absent. In addition, considering material loss during processing, we propose approximately 85 g as a reference threshold for estimating the number of individuals in heavily processed solid casque products. This approach improves the scientific rigor and accuracy of forensic identification and provides reliable technical support for the conviction, sentencing, and law enforcement of wildlife trafficking cases involving helmeted hornbill and other endangered species.

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Environmental factors that impact the development of infective juveniles of entomopathogenic nematode Steinernema hermaphroditum

Cao, M.

2026-04-08 developmental biology 10.64898/2026.04.07.717109 medRxiv
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Animals sense and integrate complex external cues to make developmental decisions that help them better survive and adapt to their natural habitats. Under environmental adversity, nematodes can enter an alternative developmental pathway to form a diapautic and stress-resistant stage, termed the dauer larvae. While dauer formation has been well characterized in Caenorhabditis elegans, how environmental factors influence analogous stages in other nematode species remains largely unexplored. This study examines how symbiotic bacteria, temperature, and pheromones affect the formation of the infective juvenile (IJ), a dauer-like stage, of the insect-parasitic nematode Steinernema hermaphroditum. In contrast to C. elegans, where dauer entry is promoted by heat, IJ development in S. hermaphroditum development is enhanced by reduced temperature. Moreover, the presence and absence of live symbiotic bacterium Xenorhabdus griffiniae functions as an ON-and-OFF switch that regulates the host IJ formation. Crude pheromone extracts from S. hermaphroditum liquid culture do not robustly induce IJ formation in a dose-responsive manner, unlike the potent pheromone-driven dauer entry observed in C. elegans. Nutrient-rich liver-kidney media that mimics host insect environment showed IJ entry induction in a pheromone-dependent manner. These data suggest that external cues, such as temperature, microbial diet, and pheromone, are perceived differently by S. hermaphroditum in comparison to that of C. elegans, reflecting species-specific adaptations to distinct ecological niches and life history strategies.

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Divergent venoms among two closely related co-distributed centipede species, Scolopendra morsitans and S. hardwickei in tropical Asia

Sinha, A.; Roy, P.; Parikh, R.; Marathe, A.; Majhi, K.; Jenner, R.; Joshi, J.

2026-04-03 ecology 10.64898/2026.04.01.715817 medRxiv
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Venom is an important functional trait that helps predatory animals capture prey. Centipede predatory venoms are complex cocktails of multiple proteins, such as neurotoxins (scoloptoxins), cytotoxins, {beta}-pore-forming toxins, and enzymes. We examined venom phenotypes in two closely related and co-occurring centipede species, Scolopendra morsitans (n=28) and S. hardwickei (n=11), in peninsular India to determine whether their venoms are similar or dissimilar. An integrated proteo-transcriptomic approach was used to characterise the venom phenotypes of the two species across multiple individuals in peninsular India. We used species occurrence records and species distribution models to assess the distributional overlap among these species within the peninsular Indian region. The species showed significant overlap in their current and projected geographical ranges, corresponding with their co-occurrence. We characterised the venom profiles of both species and found that the venoms were cocktails of enzymes, {beta}-pore-forming toxins, and neurotoxins comprising 110 and 84 proteins in S. morsitans and S. hardwickei, respectively. However, the venom composition of both species differed significantly in toxin abundance and species-specific protein repertoires. This indicates trait divergence in venom phenotypes, suggesting that distinct venom compositions may facilitate coexistence among ecologically similar predatory centipedes. The observed variation in venom phenotypes among co-distributed species opens up important avenues for future research into their ecological roles and functional significance. In this study, we provided a detailed account of venom composition across multiple individuals from the species geographic range and highlighted the importance of investigating the role of venom as a trait that could influence species interactions and shape communities in these diverse tropical forests.

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Pathogenic Leptospira in dogs and rodents in Tha Wang Pha, Thailand - Prevalence, diversity and linked environments

Jaiwung, W.; Dokhelar, T.; Morand, S.; Chaisiri, K.; De Garine-Wichatitsky, M.; Kritiyakan, A.; Guernier-Cambert, V.

2026-03-20 molecular biology 10.64898/2026.03.16.712015 medRxiv
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Human leptospirosis is a disease of public health importance in Thailand, but the animal species involved in the transmission cycle have not been fully uncovered. This study investigated Leptospira infection in dogs and terrestrial micromammals in rural Nan Province, Thailand, and the pathogen diversity. Sera from 95 seemingly healthy dogs and kidney samples from 399 micromammals were analyzed using real-time PCR for Leptospira detection, followed by conventional PCR and sequencing of infecting Leptospira. We investigated environmental factors associated with Leptospira infection in micromammals, using data collected during trapping. Real-time PCR revealed ongoing infection in 8.4% (8/95) of dogs and 10.0% (40/399) of terrestrial micromammals, with 12 infected species including Bandicota indica, Berylmys berdmorei, Berylmys bowersi, Mus cervicolor, Mus cookii, and Hylomys suillus. In this qPCR-positive micromammals, three pathogenic Leptospira species were identified: L. interrogans, L. weilii, and L. borgpetersenii. This represents the first confirmed detection of L. weilii in rodents in Thailand. Infected micromammals were found in agricultural and forest habitats but not in human settlements. Our study demonstrates potential complex leptospirosis epidemiology in rural Thailand, with multiple species serving as pathogenic Leptospira reservoirs across diverse habitats, and some shared pathogen diversity with human leptospirosis cases in Thailand. Free-roaming dogs may serve as bridge hosts, transmitting zoonotic Leptospira from micromammals to humans by visiting both animal habitats and human settlements. These findings emphasize the need for integrated One Health surveillance approaches to control leptospirosis in rural communities.

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A joint Bayesian framework for modeling Plasmodium vivax transmission

Ejigu, L. A.; Chali, W.; Bousema, T.; Drakeley, C.; Tadesse, F. G.; Bradley, J.; Ramjith, J.

2026-04-08 microbiology 10.64898/2026.04.07.717120 medRxiv
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Plasmodium vivax transmission from humans to mosquitoes depends on the density of gametocytes that in turn depends on asexual parasite replication and gametocyte commitment. These processes are often analyzed separately, despite being biologically linked and measured with substantial uncertainty. We used a joint Bayesian latent-variable model to simultaneously analyze parasite density, gametocyte density, and mosquito infectivity while accounting for measurement error and propagating uncertainty across linked processes. The model was applied to individual-level data from three P. vivax transmission studies conducted in Ethiopia (n = 455). A tenfold increase in gametocyte density was associated with more than a twofold increase in the odds of mosquito infection (odds ratio [OR] = 2.32, 95% credible interval [CrI]: 2.12-2.54). Asexual parasite density was also positively associated with infectivity after accounting for gametocyte density (OR = 1.74, 95% CrI: 1.60-1.90), and inclusion of parasite density improved predictive performance. Pathway decomposition within the joint model indicated that approximately 41% of the parasite-infectivity association operated through gametocyte density. Increasing age was associated with lower asexual parasite density but higher gametocyte density, resulting in minimal overall association with infectivity. Predicted infection probability increased sigmoidally with gametocyte density, remaining low at lower densities before increasing sharply and approaching a plateau at higher densities. Gametocyte density produced the largest predicted changes in the proportion of infected mosquitoes, while asexual parasite density added predictive information not fully captured by measured gametocyte density alone. This approach links molecular parasite measurements with mosquito infection risk while accounting for measurement uncertainty and provides an interpretable framework for studying the P. vivax infectious reservoir. Author SummaryMalaria transmission occurs when mosquitoes ingest sexual-stage parasites, called gametocytes, during a blood meal. In Plasmodium vivax infections, human-to-mosquito transmission depends on linked biological stages, including asexual parasite replication, gametocyte production, and mosquito infection. These processes are closely connected and often measured with uncertainty, making them difficult to study using standard approaches that analyze them separately. In this study, we applied a joint Bayesian model that analyzes parasite density, gametocyte density, and mosquito infectivity together while accounting for uncertainty in laboratory measurements. Using data from three studies in Ethiopia, we quantified how parasite density, gametocyte density, and host characteristics relate to mosquito infection. The analysis showed that measured gametocyte density alone did not fully explain variation in infectivity, and that asexual parasite density provided additional predictive information. We also found that age was associated differently with asexual parasite and gametocyte densities, resulting in little overall association with infectivity. This approach helps link molecular parasite measurements with transmission outcomes and improves understanding of the P. vivax infectious reservoir in endemic settings.

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Exposure of non-target white-footed mice (Peromyscus leucopus) to Second-generation Anticoagulant Rodenticides in an urban context

Richardson, L. F.; Schulte-Hostedde, A.

2026-04-09 ecology 10.64898/2026.04.06.715702 medRxiv
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The pathways of non-target exposure to anticoagulant rodenticides (ARs) are poorly understood, and have yet to be examined in Ontario, Canada. The spillover of ARs into non-target rodents and high-risk landscapes has been investigated numerous times, but usually in agricultural regions as opposed to urban ones. We used snap traps to capture white-footed mice (Peromyscus leucopus) in urban wildland areas of Toronto and Vaughan, Ontario near ongoing rodenticide baiting programs. Our goal was to determine if second-generation anticoagulant (SGAR) baiting practices used by pest management professionals targeting commensal rodents may be causing rodenticide spillover into non-target rodents in urban wildland areas, which could act as a vector of ARs to predators. Only 11 out of 111 mature white-footed mice trapped near ongoing urban rodenticide operations tested positive for an anticoagulant, at five out of seven study sites. Concentrations were between 0.008-0.03 ppm, which may be sublethal for raptors. We did not detect brodifacoum, despite its detection in a recent study on Ontario raptors. Exposed individuals were caught at 0m, 5m, 20m, 40m, 70m and 100m from active rodenticide stations. They did not differ from unexposed individuals in terms of sex, age, body condition, distance to the AR source, capture date or capture site. This indicates that the pest management industrys use of rodenticides in urban and suburban settings is causing some degree of non-target spillover in Toronto and the Greater Toronto Area, and that SGAR usage should be avoided near naturalized landscapes.

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FIKK1, a member of the FIKK kinase family, phosphorylates VAR2CSA and regulates adhesion of Plasmodium falciparum-infected erythrocytes to the placental receptor CSA

Dorin-Semblat, D.; Semblat, J.-P.; Eavis, H.; Belda, H.; Hamelin, R.; Paquereau, C.-E.; Doerig, C.; Treeck, M.; Gamain, B.

2026-03-23 biochemistry 10.64898/2026.03.23.713582 medRxiv
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Plasmodium falciparum promotes the adhesion of infected erythrocytes (IEs) to host cells by extensively remodeling their surface. For this process, the parasite exports a large number of proteins to its host erythrocyte, including members of the P. falciparum Erythrocyte Membrane Protein-1 (PfEMP1) adhesin family and members of the FIKK family. Several FIKK have been shown to play a role in P. falciparum virulence, notably affecting IES cell surface remodeling, rigidity and cytoadhesion. VAR2CSA, a member of the PfEMP1 adhesin family, is associated with IES sequestration in the placenta and has been shown to be phosphorylated. In view of the previously described importance of VAR2CSA phosphorylation, we investigated the role of FIKK1. We show that FIKK1 is capable of phosphorylating VAR2CSA in vitro, and that this phosphorylation increases the binding of recombinant VAR2CSA to the placental receptor chondroitin sulphate A (CSA). In an inducible transgenic cell line expressing HA-tagged FIKK1, immunofluorescence assays indicate that the kinase localizes to punctuated foci within Maurers Cleft, similarly to VAR2CSA. Rapamycin-induced knock out of FIKK1 reduces IEs cytoadhesion to CSA, even though levels of VAR2CSA are not affected. In vitro phosphorylation assays show that FIKK1 can phosphorylate recombinant DBL1-3 domains on several residues, including S429 and T934, previously implicated in in vitro binding and IES cytoadhesion to CSA. Taken together, these data support a model whereby FIKK1 contributes to placental malaria virulence through IEs sequestration mediated by VAR2CSA phosphorylation. Having no orthologs in mammals, this orphan kinase therefore represents an attractive target for the development of drugs against placental malaria. Author summarySequestration of Plasmodium falciparum infected erythrocytes (IEs) in the placenta is a hallmark of placental malaria and a major driver of adverse maternofetal outcomes. This process is mediated by VAR2CSA, a member of the P. falciparum Erythrocyte Membrane Protein (PfEMP1) family. VAR2CSA binds to chondroitin sulfate A (CSA) on the placental syncytium, facilitating IEs sequestration. In a previous study, we demonstrated that endogenous VAR2CSA is phosphorylated and identified specific phosphosites important for its cytoadhesive function. To elucidate the molecular mechanisms underlying these post-translational modifications, we examined the role of the P. falciparum FIKK1 kinase in VAR2CSA phosphorylation and its impact on IEs adhesion. Using a FIKK1::HA conditional knockout transgenic line, we found that FIKK1 deletion impairs IEs cytoadhesion, likely due to altered VAR2CSA phosphorylation. Importantly, both endogenous and recombinant FIKK1 interact with and phosphorylate the extracellular region of VAR2CSA. Furthermore, recombinant FIKK1 also enhances VAR2CSA binding to CSA in vitro and phosphorylates a residue previously identified as important for CSA binding and IEs adhesion. Collectively, these findings highlight a pivotal role for FIKK1 in placental adhesion and underscore the potential of targeting this kinase family for interventions against placental malaria.

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Behavioral characteristics of an extremely old rhesus macaque in a zoo: Dementia-like symptoms and implications for quality of life of geriatric animals

Yamanashi, Y.; Bando, H.; Niimi, K.; Nakagawa, D.; Iwaide, S.; Murakami, T.

2026-03-19 zoology 10.64898/2026.03.17.712497 medRxiv
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Documenting and understanding the welfare of aging animals are crucial for maintaining their well-being and making appropriate management decisions. This study details the behaviors of an extremely old rhesus macaque (ISK) in which senile plaques and phosphorylated tau deposition were observed in post-mortem pathological analyses of the brain. We report on the activity bsudgets, behavioral rhythms, gait, quality of life (QoL) scores, and anecdotal episodes of this individual. The average 24-hour activity budgets, analyzed from surveillance camera recordings, revealed that ISK spent most of her time inactive. ISK was sometimes active at night, though her behavior remained predominantly diurnal. Gait analysis suggested that her movement patterns changed between the first (December 2020) and the last (June 2021) assessment. QoL assessments, using a scoring sheet, indicated relatively good well-being until the later stage of her life. An anecdotal episode, along with the husbandry diary, suggested signs of cognitive decline. These results suggest possible signs of physical decline, and some behavioral changes that could be associated with cognitive decline in an extremely old rhesus macaque. However, we could not confirm cognitive dysfunction without further controlled cognitive testing. We hope that future studies will consider the behavioral symptoms observed in this study as monitoring items to better understand physical and cognitive decline, and possible relationships with QoL in primates.

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Reassessing display behavior from Bels et al. (2025) given the complexity of anthropogenic hybridization and intraspecific diversity in Iguana iguana

van den Burg, M. P.; Thibaudier, J.

2026-03-23 zoology 10.64898/2026.03.19.713079 medRxiv
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Understanding behavioral differences between non-native and closely related endangered species could be important to aid conservation management. In volume 169 of Zoology, Bels et al. (2025) reported on their comparison of display-action-patterns (DAP) between native Iguana delicatissima and non-native iguanas present on islands of the Guadeloupe Archipelago in the Caribbean Lesser Antilles. Here, we address conceptual and methodological concerns about their work and reanalyze their data given our proposed corrections, primarily a literature-informed adjustment of their "species" category. We additionally utilize online videos from South American mainland I. iguana populations, from where the non-native iguanas in the Guadeloupe Archipelago originate, to better understand the different DAPs between native and non-native iguanas in the Guadeloupe Archipelago. Significant differences in DAP characteristics among "species" categories (native I. delicatissima, non-native iguanas, and hybrids) show that Bels et al. (2025) oversimplified their data analyses by merging all non-native populations into one group. This result indicates the presence of behavioral variation among subpopulations within widely hybridizing iguanid populations, which has been poorly studied. Additionally, videos from mainland populations across two major mitochondrial clades of Iguana iguana show that non-native iguanas on Guadeloupe retained DAP characteristics of those populations from which they originate. We discuss these findings in light of the proposed hypotheses put forward by Bels et al. (2025), of which two can be excluded. Overall, our reanalysis shows that studies focusing on characteristics within settings of complex hybridization in diverse species should acknowledge this complexity.

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Age-dependent effects of infection on survival of a wild rodent reservoir host

Wearing, K. E.; Veitch, J. S. M.; Mistrick, J.; Harp, D. F.; Haile, B. B.; Fragel, C. G.; Sironen, T.; Craft, M. E.; Cressler, C. E.; Hall, R. J.; Budischak, S. A.; Forbes, K. M.

2026-03-20 ecology 10.64898/2026.03.17.712390 medRxiv
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Due to long co-evolutionary histories, many zoonotic pathogens are thought to exert little or no negative effects on their wildlife reservoir hosts. However, there remains a lack of rigorous investigations in natural settings. We conducted a 3-year factorial field experiment to investigate how survival of the Puumala hantavirus (PUUV) reservoir, the bank vole, is impacted by PUUV infection, nematode infections, and food availability. We hypothesized that PUUV would not impact survival, but that coinfection with nematodes would negatively impact survival, and that increased food availability would mitigate the negative effects of coinfection. Surprisingly, we demonstrated that PUUV infected voles had substantially reduced survival when compared to uninfected voles, and this strong negative effect manifested in young voles. Nematode removal increased survival of young voles and food supplementation interacted with movement rather than survival. Our results provide empirical evidence in a natural system for infection reducing survival of its reservoir host.

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A faster incubation explains Usutu leading West Nile in temperate Europe

Paton, R. S.; Vollans, M.; Glenn, L.; Fyles, M.; Vaux, A. G. C.; Medlock, J.; Day, J.; Ward, T.

2026-04-04 ecology 10.64898/2026.04.02.716093 medRxiv
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Usutu virus (USUV) is a mosquito-borne flavivirus that has recently expanded northwards in Europe and become endemic in the UK [1-3]. USUV emergence often precedes the closely related West Nile virus (WNV), potentially reflecting differences in epidemiological parameters [4, 5]. One key parameter is the extrinsic incubation period (EIP), the time required for a mosquito to become infectious following an infected blood meal. Here we present the first ever estimate of the temperature-dependent EIP for USUV in the vector Culex pipiens molestus. We were able to quantify the shortening of the EIP with temperature by re-analysing published laboratory data with bespoke Bayesian model that accounted for key features of the experimental design. Under typical UK summer temperatures, the median EIP (EIP50) of USUV is shorter than that of WNV, and the potential transmission season of USUV is both longer and geographically more extensive. Under RCP8.5 climate projections, WNV transmission suitability is expected to match or exceed current USUV levels between 2055 and 2065, highlighting the future threat to the UK from emerging mosquito-borne pathogens. Our findings support USUV as a precursor for WNV in northern Europe and provide a robust characterisation of a key epidemiological parameter of USUV, enabling accurate modelling of its transmission dynamics.