Biology subjects

Rund, S. S. C.

Publications and source records attributed to Rund, S. S. C..

9 recordsLinked to original sources

bioRxiv2026

Local trait responses and aquatic microclimates increase projected habitat suitability for field-collected Anopheles stephensi in southern Ethiopia

BackgroundTrait-based models of mosquito environmental suitability commonly use global thermal performance curves compiled from laboratory studies. These curves may misrepresent suitability when local populations or larval habitats differ from globally synthesised expectations. This issue is particularly relevant for Anopheles stephensi, an urban malaria vector expanding in the Horn of Africa, where artificial aquatic habitats may generate microclimates poorly represented by global trait datasets or gridded air-temperature products. Methodology/Principal FindingsWe compared juvenile survival, development, and projected maximal population growth rate, rm, using locally measured data from field-collected Ethiopian An. stephensi and a global comparator combining pub-lished juvenile trait data. We fitted thermal performance curves for juvenile survival and development, used these curves to estimate temperature-dependent rm as a metric of habitat suitability, and projected rm across two matched temperature inputs: logger-measured larval habitat water temperature and ERA5-Land 2 m air temperature. Local juvenile trait responses produced higher projected rm than the global comparator across monitored habitats. Measured aquatic temperatures were warmer than ERA5-Land air temperatures, with a mean daily water-air offset of 3.26{whitebullet}C, and were more spatially heterogeneous among habitats. ERA5-Land resolved only two unique temperature series across the six monitored habitats. Sensitivity analyses showed that the Local-Global difference was robust for logger-measured water temperatures, whereas the ERA5-based difference was partly amplified by cooler temperatures below the local experimental range. Conclusions/SignificanceThis study provides the first locally derived juvenile thermal performance curves and temperature-dependent population growth estimates for field-collected An. stephensi in Africa, demonstrating that locally measured juvenile traits consistently predict higher habitat suitability than globally synthesised trait data. These find-ings highlight the importance of incorporating local mosquito trait data and aquatic microclimate measure-ments into predictive models to improve assessments of An. stephensi establishment, spread, and malaria risk in newly invaded urban environments. Author SummaryAnopheles stephensi is an invasive malaria mosquito that is rapidly spreading in urban areas of Africa. Pre-dicting where this species can establish is difficult because many models use mosquito temperature-response data from long-maintained laboratory colonies rather than from recently collected African populations. We measured juvenile survival and development in An. stephensi collected from Ethiopia, and compared pro-jections based on these local data with projections based on published laboratory-colony data. We also compared field-measured larval habitat water temperature with ERA5-Land air temperature. We found that local juvenile trait responses produced higher projected population growth than the global comparator across monitored habitats. Field-measured water temperatures were warmer and more variable among habitats than gridded air temperatures, which reduced habitat-level differences. These findings show that local mosquito biology and larval habitat microclimate measurements can change fine-scale estimates of suitability. This matters for surveillance and control because urban water containers may create suitable conditions that are poorly represented by broad climate datasets.

ecology↗

bioRxiv2025

Early-evening biting by Anopheles stephensi in Southern Ethiopia: A Challenge for Bed Net Use as Vector Control in Africa

Anopheles stephensi is rapidly expanding across Africa, posing new challenges for malaria control. Its biting time patterns, however, remain poorly characterized, raising uncertainty about the effectiveness of bed nets against this invasive vector. To address this gap, we investigated diel biting activity, feeding propensity, and flight behavior using complementary behavioral assays on females reared from wild-caught larvae in Hawassa City, southern Ethiopia. Flight monitoring assays revealed that An. stephensi exhibited pronounced activity at dusk, beginning between 18:00 and 19:00 with the onset of scotophase, and little to no activity during the photophase. Blood-feeding propensity, defined as the proportion of mosquitoes taking a blood meal when offered, peaked during the early scotophase (18:00-22:00) at 33.3-51.7%, but was markedly reduced during daylight hours (0-16.7%). Human landing catches in large-cage enclosures confirmed this early evening activity: 83.5% of total landings occurred between 18:00 and 22:00 with a sharp peak at 18:00-19:00, corresponding to a mean biting rate of 17.8 bites per person per hour. These findings demonstrate that invasive An. stephensi primarily seek hosts and bite during the early evening, a time when people are often unprotected by bed nets. This behavior reduces the protective impact of conventional net-based interventions and underscores the need for African National Malaria Control Programs to deploy complementary measures such as spatial repellents and larval source management to mitigate early-evening transmission. Moreover, this study highlights the utility of integrated behavioral assays for estimating biting time, offering approaches that can be extended to other vector species across Africa.

zoology↗

bioRxiv2025

Biting time of day in malaria mosquitoes is modulated by nutritional status

BackgroundTransmission of vector-borne pathogens follows daily rhythms, occurring at the time of day that vectors forage for blood. Control measures such as insecticide-treated bed nets (ITNs) have been particularly successful for reducing malaria transmission, because they exploit the nocturnal biting behaviour of the Anopheles spp. that vector malaria. However, shifts in biting behaviour to earlier or later hours when people are unprotected can undermine the efficacy of ITNs. Despite the implications for malaria transmission, the mechanisms underlying these shifts remain poorly understood. Because food availability mediates activity and foraging rhythms, and ITNs block access to human blood as a food source, we hypothesized that nutritional deprivation could cause mosquitoes to shift their biting behaviour to earlier or later in the diel cycle. MethodsWe provided female Anopheles gambiae s.l. mosquitoes with a blood meal on day 3 post-emergence, and access to one of three feeding treatments that varied in nutritional resources: (i) 0.5% sucrose, (ii) 10% sucrose, or (iii) 10% sucrose plus an additional blood meal on day 6. We released mosquitoes into a semi-field system on day 10 with human-mimic traps to investigate how food availability impacted the time of day that mosquitoes host seek. ResultsNutritional resources determine both the likelihood and time of day that host seeking occurs. Specifically, low-resourced mosquitoes were 2-3 fold more likely to host seek overall, and 5-10 fold more likely to host seek at an earlier time of day than well-resourced mosquitoes (fed 10% sucrose with and without an additional blood meal), which predominantly sought a host in the second half of the night time. ConclusionsWe reveal that mosquito nutritional condition drives plasticity in biting time of day, suggesting it is an underappreciated contributor to residual malaria transmission. Furthermore, our results suggest that targeting mosquito nutrition (e.g. sugar-baited traps) could influence mosquito behaviour in ways that affect the success of ITNs. More broadly, understanding the drivers of biting time of day variation is crucial for the future success of vector control tools and controlling malaria transmission.

ecology↗

bioRxiv2025

Prediction of mosquito vector abundance for threespecies in the Anopheles gambiae complex

BackgroundThe dynamics of vector borne disease transmission depend on the abundances of vectors. The dominant malaria vector species complex of Anopheles gambiae sensu lato is a target of vector control strategies designed to reduce and eliminate malaria transmission. The three most widely distributed dominant malaria vectors within the species complex are An. arabiensis, An. coluzzii and An. gambiae sensu stricto. MethodsPrevious studies across the extent of the species complex range have been restricted to annual predictions of species occurrence or relative abundance. This study incorporated relative abundance data at the species level and abundance data at the species complex level to estimate and predict daily equilibrium vector abundances of each species. Statistical models with interpretable parameters were used to gain insight into how factors such as meteorological conditions, insecticide treated net use, and human density affect the spatial and temporal predictions. The statistical models were used to predict daily equilibrium vector abundance that is an important factor in indices of malaria transmission such as the basic reproduction number and vectorial capacity. ResultsMeteorological factors, such as precipitation and relative humidity, and human factors, such as population density and insecticide treated nets, were important predictors of these three malaria vector species in Africa. Insecticide treated net use was negatively associated with per capita vector abundance of the An. gambiae species complex and interacted with year to suggest an a negative effect on the ratio of An. gambiae s.s. to An. arabiensis at the end of the prediction period that extended from 2002 to 2020. A predicted increasing interannual trend for An. coluzzii was potentially caused by changing species identification methods. ConclusionThe predicted equilibrium abundances of the three species showed potentially high levels of geographical overlap, niche overlap, and evidence for stable coexistence despite substantial interspecific competition. Improving collection of longitudinal species abundance data across the spatial range of the An. gambiae species complex will facilitate future explorations of causal hypotheses that relate vector abundance to control measures, malaria interventions and meteorological conditions.

ecology↗

bioRxiv2025

MIReVTD, a Minimum Information Standard for Reporting Vector Trait Data

Vector-borne diseases pose a persistent and increasing challenge to human, animal, and agricultural systems globally. Mathematical modeling frameworks incorporating vector trait responses are powerful tools to assess risk and predict vector-borne disease impacts. Developing these frameworks and the reliability of their predictions hinge on the availability of experimentally derived vector trait data for model parameterization and inference of the biological mechanisms underpinning transmission. Trait experiments have generated data for many known and potential vector species, but the terminology used across studies is inconsistent, and accompanying publications may share data with insufficient detail for reuse or synthesis. The lack of data standardization can lead to information loss and prohibits analytical comprehensiveness. Here, we present MIReVTD, a Minimum Information standard for Reporting Vector Trait Data. Our reporting checklist balances completeness and labor- intensiveness with the goal of making these important experimental data easier to find and reuse, without onerous effort for scientists generating the data. To illustrate the standard, we provide an example reproducing results from an Aedes aegypti mosquito study.

ecology↗

bioRxiv2018

Minimum Information for Reusable Arthropod Abundance Data (MIReAAD)

Introduction Introduction Discussion Conclusion References Arthropods play a dominant role in the dynamics of practically all natural and human-modified terrestrial ecosystems1-3, and have significant economic and health effects. For example, certain insects provide significant economic benefits (e.g. pollination) exceeding $57 billion a year to the United States alone4. Meanwhile, invasive insects cost an estimated $70 billion dollars per year globally5 and insect pests may reduce agricultural harvests by up to 16%, with an equal amount of further losses of harvested goods6. Particularly noteworthy is a subset of arthropods that are disease vectors, transmitting pathogens to and between animals as well as plan ...

ecology↗

bioRxiv2018

Adaptive periodicity in the infectivity of malaria gametocytes to mosquitoes

That periodicity in the biting activity of mosquito vectors explains why malaria parasites have evolved rhythms in cycles of asexual replication in the hosts blood was proposed almost 50 years ago. Yet, tests of this hypothesis have proved inconclusive. Using the rodent malaria Plasmodium chabaudi, we examine rhythms in the density and infectivity of transmission forms (gametocytes) in the hosts blood, parasite development inside mosquitoes, and onwards transmission.Moreover, we control for the confounding effects of rhythms in mosquito susceptibility. We reveal that at night, gametocytes are twice as infective to mosquitoes, despite being less numerous in the blood. This enhanced infectiousness at night interacts with mosquito rhythms to increase sporozoite burdens by almost four-fold when mosquitoes feed during their day. Thus, daytime blood-feeding (e.g. driven by the use of bed nets) may render gametocytes less infective, but this is compensated for by the greater susceptibility of mosquitoes.

microbiology↗

bioRxiv2017

Costs and benefits of sub-lethal Drosophila C virus infection

Viruses are major evolutionary drivers of insect immune systems. Much of our knowledge of insect immune responses derives from experimental infections using the fruit fly Drosophila melanogaster. Most experiments, however, employ lethal pathogen doses through septic injury, frequently overwhelming host physiology. While this approach has revealed a number of immune mechanisms, it is less informative about the fitness costs hosts may experience during infection in the wild. Using both systemic and oral infection routes we find that even apparently benign, sub-lethal infections with the horizontally transmitted Drosophila C Virus (DCV) can cause significant physiological and behavioral morbidity that is relevant for host fitness. We describe DCV-induced effects on fly reproductive output, digestive health, and locomotor activity, and we find that viral morbidity varies according to the concentration of pathogen inoculum, host genetic background and sex. Notably, sub-lethal DCV infection resulted in a significant increase in fly reproduction, but this effect depended on host genotype. We discuss the relevance of sub-lethal morbidity for Drosophila ecology and evolution, and more broadly, we remark on the implications of deleterious and beneficial infections for the evolution of insect immunity.

evolutionary biology↗

bioRxiv2016

Creating a National Vector Surveillance System: Integrated mosquito trap data and digital epidemiology

According to the World Health Organization, every year more than a billion people are infected with vector-borne diseases worldwide. There are no vaccines for most vector-borne diseases. Vector control, therefore, is often the only way to prevent outbreaks. Despite the major impact of vectors on human health, knowledge gaps exist regarding their natural population dynamics. Even the most basic information--such as spatiotemporal abundance-- is not available. Mosquitoes transmit malaria and the viruses causing Yellow Fever, West Nile, Dengue, Chikungunya, and Zika in the Americas. The Americas have a long history of mosquito control efforts, including the unsustained but successful Aedes aegypti eradication initiative. In the US, municipalities have independently created agencies for mosquito control and monitoring. We propose that the ensemble of US mosquito control agencies can, and should, be used to develop a national--and potentially international--system for Cross-Scale Vector Monitoring and Control (CSVMaC), in which local level monitoring and control efforts are cross-linked by unified real-time data streaming to build the data capital needed to gain a mechanistic understanding of vector population dynamics. Vectors, and the pathogens they transmit, know no jurisdictions. The vision of CSVMaC is, therefore, to provide data for (i) the general study of mosquito ecology and (ii) to inform vector control during epidemics/outbreaks that impact multiple jurisdictions (i.e., counties, states, etc.). We reveal >1000 mosquito control agencies in the US with enormous troves of data that are hidden among many data silos. For CSVMaC, we propose the creation of a nationally-coordinated open-access database to collate mosquito data. The database would provide scientific and public health communities with highly resolved spatiotemporal data on arboviral disease vectors, empowering new interventions and insights while leveraging pre-existing human efforts, operational infrastructure, and investments already funded by taxpayers.

ecology↗