ABSTRACT
Epizootic hemorrhagic disease virus (EHDV) is transmitted by Culicoides biting midges. Studies aiming to predict the likely spread of EHDV require an understanding of the viral infection and replication kinetics within these insects, including the proportion of the insect population that are able to support virus transmission. Here, we describe methods for the infection of Culicoides with EHDV in the laboratory via oral infection using an artificial membrane system or a cotton pledget and intrathoracic (IT) inoculation. Each method can be used to explore determinants of vector competence of Culicoides species and populations for EHDV.
Subject(s)
Ceratopogonidae , Hemorrhagic Disease Virus, Epizootic , Insect Vectors , Reoviridae Infections , Animals , Ceratopogonidae/virology , Hemorrhagic Disease Virus, Epizootic/physiology , Insect Vectors/virology , Reoviridae Infections/transmission , Reoviridae Infections/virology , Reoviridae Infections/veterinaryABSTRACT
The past three decades have seen an increasing number of emerging arthropod-borne viruses in temperate regions This process is ongoing, driven by human activities such as inter-continental travel, combined with the parallel emergence of invasive arthropods and an underlying change in climate that can increase the risk of virus transmission and persistence. In addition, natural events such as bird migration can introduce viruses to new regions. Despite the apparent regularity of virus emergence, arthropod-borne viruses circulating in temperate regions face the challenge of the late autumn and winter months where the arthropod vector is inactive. Viruses therefore need mechanisms to overwinter or they will fail to establish in temperate zones. Prolonged survival of arthropod-borne viruses within the environment, outside of both vertebrate host and arthropod vector, is not thought to occur and therefore is unlikely to contribute to overwintering in temperate zones. One potential mechanism is continued infection of a vertebrate host. However, infection is generally acute, with the host either dying or producing an effective immune response that rapidly clears the virus. There are few exceptions to this, although prolonged infection associated with orbiviruses such as bluetongue virus occurs in certain mammals, and viraemic vertebrate hosts therefore can, in certain circumstances, provide a route for long-term viral persistence in the absence of active vectors. Alternatively, a virus can persist in the arthropod vector as a mechanism for overwintering. However, this is entirely dependent on the ecology of the vector itself and can be influenced by changes in the climate during the winter months. This review considers the mechanisms for virus overwintering in several key arthropod vectors in temperate areas. We also consider how this will be influenced in a warming climate.
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BACKGROUND: Culex pipiens L. is a principal vector of zoonotic arboviruses in Europe, acting in both an amplification role in enzootic transmission between avian hosts and as a bridge vector between avian hosts and mammals. The species consists of two forms which are indistinguishable using morphological methods but possess varying ecological and physiological traits that influence their vector capacity. In this study we validate methods that can be used to extract trace DNA from single pupal exuviae of Cx. pipiens for use in molecular speciation of samples. These DNA extraction methods are compared using measurement of the total yield and successful identification using a real-time polymerase chain reaction (PCR) assay. RESULTS: Genomic DNA was initially extracted from colony-derived individuals using an ethanol precipitation method, two commercially available DNA extraction kits: DNeasy® Blood & Tissue Kit (Qiagen, UK) and Wizard® SV Genomic DNA Purification System (Promega, UK) and a direct real-time PCR method. Time elapsed between eclosion and processing of pupae significantly influenced Cx. pipiens form identification as nucleic acid concentration and PCR amplification success decreased with increased time elapsed. Real-time PCR amplification success, however, was not shown to vary significantly between the three extraction methods, with all methods successfully identifying all samples, but the direct real-time PCR method achieved a lesser amplification success rate of 70% (n = 20 for each treatment). More variable results were produced when field-derived exuviae were used, with no significant difference in real-time PCR amplification success found across the four methods and a lower overall rate of successful identification of 55-80%. CONCLUSIONS: This study shows that both colony and field derived Cx. pipiens pupal exuviae can be a useful non-invasive source of trace DNA permitting accurate biotype differentiation for at least twenty-four hours post-eclosion. The significance and utility of this technique in ecological and behavioural studies of Cx. pipiens is discussed and recommendations made for use according to experimental scenario.
Subject(s)
Cryosurgery , Hiccup , Phrenic Nerve , Humans , Hiccup/etiology , Hiccup/surgery , Cryosurgery/methods , Phrenic Nerve/injuries , Male , Middle Aged , Tomography, X-Ray Computed , AgedABSTRACT
OBJECTIVE: To conduct an overview of systematic reviews that explore the effectiveness of interventions to enhance medical student well-being. DESIGN: Overview of systematic reviews. DATA SOURCES: The Cochrane Library of Systematic Reviews, MEDLINE, APA PsychInfo, CINAHL and Scopus were searched from database inception until 31 May 2023 to identify systematic reviews of interventions to enhance medical student well-being. Ancestry searching and citation chasing were also conducted. DATA EXTRACTION AND SYNTHESIS: The Assessing the Methodological Quality of Systematic Reviews V.2 tool was used to appraise the quality of the included reviews. A narrative synthesis was conducted, and the evidence of effectiveness for each intervention was rated. RESULTS: 13 reviews (with 94 independent studies and 17 616 students) were included. The reviews covered individual-level and curriculum-level interventions. Individual interventions included mindfulness (n=12), hypnosis (n=6), mental health programmes (n=7), yoga (n=4), cognitive and behavioural interventions (n=1), mind-sound technology (n=1), music-based interventions (n=1), omega-3 supplementation (n=1), electroacupuncture (n=1) and osteopathic manipulative treatment (n=1). The curriculum-level interventions included pass/fail grading (n=4), problem-based curriculum (n=2) and multicomponent curriculum reform (n=2). Most interventions were not supported by sufficient evidence to establish effectiveness. Eleven reviews were rated as having 'critically low' quality, and two reviews were rated as having 'low' quality. CONCLUSIONS: Individual-level interventions (mindfulness and mental health programmes) and curriculum-level interventions (pass/fail grading) can improve medical student well-being. These conclusions should be tempered by the low quality of the evidence. Further high-quality research is required to explore additional effective interventions to enhance medical student well-being and the most efficient ways to implement and combine these for maximum benefit.
Subject(s)
Students, Medical , Systematic Reviews as Topic , Humans , Students, Medical/psychology , Mental Health , Curriculum , MindfulnessABSTRACT
Five experiments (combined N = 4,915) tested the prediction that the moral boost of happiness would persist for social targets with moral failings. In Studies 1 and 2, White and Black participants, respectively, judged happy (versus unhappy) racist targets more morally good. In Study 3, happy (versus unhappy) racist targets were judged more morally good and less (more) likely to engage in racist (good) behavior. Behavioral expectations explained the link between happiness and moral evaluations. Study 4 replicated Studies 1 to 3 in the context of sexism. In Study 5, happy (versus unhappy) targets who engaged in racially biased behavior were evaluated as more morally good, and this effect was explained by behavioral forecasts. Happiness boosts attributions of moral goodness for prejudiced people and does so via expectations for future behavior. Future directions are discussed.
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Introduction: Bluetongue virus (BTV) is an arthropod-borne Orbivirus that is almost solely transmitted by Culicoides biting midges and causes a globally important haemorrhagic disease, bluetongue (BT), in susceptible ruminants. Infection with BTV is characterised by immunosuppression and substantial lymphopenia at peak viraemia in the host. Methods: In this study, the role of cell-mediated immunity and specific T-cell subsets in BTV pathogenesis, clinical outcome, viral dynamics, immune protection, and onwards transmission to a susceptible Culicoides vector is defined in unprecedented detail for the first time, using an in vivo arboviral infection model system that closely mirrors natural infection and transmission of BTV. Individual circulating CD4+, CD8+, or WC1+ γδ T-cell subsets in sheep were depleted through the administration of specific monoclonal antibodies. Results: The absence of cytotoxic CD8+ T cells was consistently associated with less severe clinical signs of BT, whilst the absence of CD4+ and WC1+ γδ T cells both resulted in an increased clinical severity. The absence of CD4+ T cells also impaired both a timely protective neutralising antibody response and the production of IgG antibodies targeting BTV non-structural protein, NS2, highlighting that the CD4+ T-cell subset is important for a timely protective immune response. T cells did not influence viral replication characteristics, including onset/dynamics of viraemia, shedding, or onwards transmission of BTV to Culicoides. We also highlight differences in T-cell dependency for the generation of immunoglobulin subclasses targeting BTV NS2 and the structural protein, VP7. Discussion: This study identifies a diverse repertoire of T-cell functions during BTV infection in sheep, particularly in inducing specific anti-viral immune responses and disease manifestation, and will support more effective vaccination strategies.
Subject(s)
Arboviruses , Bluetongue virus , Bluetongue , Ceratopogonidae , Sheep , Animals , Livestock , Viremia , CD8-Positive T-Lymphocytes , Ruminants , T-Lymphocyte Subsets , Bluetongue/prevention & control , Ceratopogonidae/physiologyABSTRACT
BACKGROUND: Textured implants and expanders are associated with an increased risk of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). As a result, plastic surgeons are utilizing smooth expanders, but many perceive these produce undesirable outcomes including infection, seroma, and lateral displacement. OBJECTIVES: The aim of this study was to compare clinical outcomes of smooth and textured expanders. METHODS: Breast reconstruction patients from January 2018 to May 2021 were retrospectively reviewed. Included patients underwent placement of tissue expanders at the time of mastectomy. Primary outcomes included postoperative seroma, infection, malposition, days to final reconstruction, explantation, and the need for capsulorrhaphy. RESULTS: In total, 233 patients were reviewed, of whom 167 met both inclusion and exclusion criteria. There was no statistically significant difference in poor outcomes comparing smooth and textured expanders. Days to final reconstruction was lower with smooth expanders per breast (P = .0424). The subpectoral group was associated with an increased likelihood of undergoing capsulorrhaphy (P = .004). Prepectoral placement was associated with more seromas (P = .0176) and infections (P = .0245). Demographic factors included older age as a protective factor for undergoing capsulorrhaphy (odds ratio [OR] = 0.962, P = .038), obesity increased the risk of infection (OR = 5.683, P = .0279) and malposition (OR = 6.208, P = .0222), and radiation was associated with malposition (OR = 3.408, P = .0246). CONCLUSIONS: There was no significant difference in poor outcomes between smooth and textured expanders. Patient demographics and anatomical plane placement had greater effects on infection, seroma, and the need for capsulorrhaphy compared with tissue expander texturing.
Subject(s)
Breast Implantation , Breast Implants , Breast Neoplasms , Mammaplasty , Humans , Female , Tissue Expansion Devices/adverse effects , Mastectomy , Retrospective Studies , Breast Neoplasms/etiology , Breast Neoplasms/surgery , Seroma/epidemiology , Seroma/etiology , Mammaplasty/adverse effects , Breast Implants/adverse effects , Breast Implantation/adverse effectsABSTRACT
BACKGROUND: Arthropods transmit a wide range of pathogens of importance for the global health of humans, animals, and plants. One group of these arthropod vectors, Culicoides biting midges (Diptera: Ceratopogonidae), is the biological vector of several human and animal pathogens, including economically important livestock viruses like bluetongue virus (BTV). Like other arthropod-borne viruses (arboviruses), Culicoides-borne viruses must reach and replicate in the salivary apparatus, from where they can be transmitted to susceptible hosts through the saliva during subsequent blood feeding. Despite the importance of the salivary gland apparatus for pathogen transmission to susceptible animals from the bite of infected Culicoides, these structures have received relatively little attention, perhaps due to the small size and fragility of these vectors. RESULTS: In this study, we developed techniques to visualize the infection of the salivary glands and other soft tissues with BTV, in some of the smallest known arbovirus vectors, Culicoides biting midges, using three-dimensional immunofluorescence confocal microscopy. We showed BTV infection of specific structures of the salivary gland apparatus of female Culicoides vectors following oral virus uptake, related visualisation of viral infection in the salivary apparatus to high viral RNA copies in the body, and demonstrated for the first time, that the accessory glands are a primary site for BTV replication within the salivary apparatus. CONCLUSIONS: Our work has revealed a novel site of virus-vector interactions, and a novel role of the accessory glands of Culicoides in arbovirus amplification and transmission. Our approach would also be applicable to a wide range of arbovirus vector groups including sand flies (Diptera: Psychodidae), as well as provide a powerful tool to investigate arbovirus infection and dissemination, particularly where there are practical challenges in the visualization of small size and delicate tissues of arthropods.
ABSTRACT
Acute pulmonary embolism (PE) is a common, and sometimes fatal, diagnosis that results in over 11,000 deaths in hospitalized patients in the USA annually. In patients with high-risk or high-intermediate-risk PE and especially in whom thrombolytic therapy is contraindicated, mechanical thrombectomy can be an effective treatment option. This case series outlines three patients with PE who were successfully treated with large bore aspiration thrombectomy by Interventional Radiology at a community-based military treatment facility (MTF). Two patients had presented to the emergency department with acute PE and a third of patients with acute PE were transferred from an outside hospital specifically for mechanical thrombectomy due to a complication from systemic anticoagulation. The patients were categorized as good candidates for immediate large-bore aspiration thrombectomy, a recently added capability at the MTF. The patients showed immediate improvement post-procedure and required only one night admission for observation to the intensive care unit. Implementation of this new capability for patients with acute high-risk or high-intermediate-risk PE or with contraindications to thrombolysis provides an alternative treatment with immediate, life-saving capability.
Subject(s)
Pulmonary Embolism , Thrombolytic Therapy , Humans , Thrombolytic Therapy/methods , Thrombectomy/adverse effects , Thrombectomy/methods , Pulmonary Embolism/surgery , Pulmonary Embolism/etiology , Treatment Outcome , Acute Disease , HospitalsABSTRACT
Rectus sheath hematomas (RSH) are increasing in prevalence, presumably correlating with increased use of anticoagulation medications and an aging population. Comorbidities such as blood dyscrasias, atherosclerosis, and hypertension are associated with an increased risk of developing an RSH. Iatrogenic origin of RSH, secondary to treatment of various abdominal pathologies, is not uncommon. Due to its exceptionally non-specific array of clinical signs and symptoms, RSH can be challenging to diagnose in the clinical setting without the aid of radiological images. Abdominal computed tomography (CT) is generally the modality of choice through which the RSH can be successfully identified and characterized. CT imaging can play an important role in the planning of RSH management, as effective management varies depending on the size and position of the RSH. Recurrent bleeding, hypovolemic shock, abdominal compartment syndrome, myonecrosis, and infection have been traditionally considered as the more prominent complications of RSH. However, with more cases occurring, more complications are being described in the literature. The following case presents a previously unreported complication of RSH, that of bowel herniation into a potential space created by a previously treated RSH.
ABSTRACT
BACKGROUND: Culicoides biting midges (Diptera: Ceratopogonidae) are biological vectors of livestock arboviruses that cause diseases with significant economic, social and welfare impacts. Within temperate regions, livestock movement during arbovirus outbreaks can be facilitated by declaring a 'seasonal vector-free period' (SVFP) during winter when adult Culicoides are not active. In this study we carry out long-term monitoring of Culicoides adult emergence from larval development habitats at two farms in the UK to validate current definitions of the SVFP and to provide novel bionomic data for known vector species. METHODS: Standard emergence traps were used to collect emerging adult Culicoides from dung heaps at two cattle farms in the south-east of England from June to November 2016 and March 2017 to May 2018. Culicoides were morphologically identified to species or complex level and count data were analysed using a simple population dynamic model for pre-adult Culicoides that included meteorological components. RESULTS: More than 96,000 Culicoides were identified from 267 emergence trapping events across 2 years, revealing clear evidence of bivoltinism from peaks of male populations of Culicoides obsoletus emerging from dung heaps. This pattern was also reflected in the emergence of adult female Obsoletus complex populations, which dominated the collections (64.4% of total catch) and emerged throughout the adult active period. Adult male C. obsoletus were observed emerging earlier than females (protandry) and emergence of both sexes occurred throughout the year. Culicoides chiopterus and Culicoides scoticus were also identified in spring emergence collections, providing the first evidence for the overwintering of larvae in dung heaps for these species. CONCLUSIONS: This study demonstrates continual and highly variable rates of emergence of Culicoides throughout the year. A lack of evidence for mass emergence in spring along with the ability to observe male generations highlights the need for complementary surveillance techniques in addition to light-trap data when investigating seasonality and phenology. Evidence was found of other vector species, C. chiopterus and C. scoticus, utilising cattle dung heaps as an overwintering habitat, further highlighting the importance of these habitats on farms.
Subject(s)
Ceratopogonidae , Animals , Cattle , Ecosystem , England/epidemiology , Farms , Female , Male , SeasonsABSTRACT
Bayesian methods are becoming increasingly used in applied psychological research. Previous researchers have thoroughly written about much of the details already, including the philosophy underlying Bayesian methods, computational issues associated with Bayesian model estimation, Bayesian model development and summary, and the role of Bayesian methods in the so-called replication crisis. In this paper, we seek to provide case studies comparing the use of frequentist methods to the use of Bayesian methods in applied psychological research. These case studies are intended to 'illustrate by example' the ways that Bayesian modelling differs from frequentist modelling and the differing conclusions that one may arrive at using the two methods. The intended audience is applied psychological researchers who have been trained in the traditional frequentist framework, who are familiar with mixed-effects models and who are curious about how statistical results might look in a Bayesian context. Along with our case studies, we provide general opinions and guidance on the use of Bayesian methods in applied psychological research.
Subject(s)
Bayes Theorem , HumansABSTRACT
Lumpy skin disease virus (LSDV) is a poxvirus that causes severe systemic disease in cattle and is spread by mechanical arthropod-borne transmission. This study quantified the acquisition and retention of LSDV by four species of Diptera (Stomoxys calcitrans, Aedes aegypti, Culex quinquefasciatus, and Culicoides nubeculosus) from cutaneous lesions, normal skin, and blood from a clinically affected animal. The acquisition and retention of LSDV by Ae. aegypti from an artificial membrane feeding system was also examined. Mathematical models of the data were generated to identify the parameters which influence insect acquisition and retention of LSDV. For all four insect species, the probability of acquiring LSDV was substantially greater when feeding on a lesion compared with feeding on normal skin or blood from a clinically affected animal. After feeding on a skin lesion LSDV was retained on the proboscis for a similar length of time (around 9 days) for all four species and for a shorter time in the rest of the body, ranging from 2.2 to 6.4 days. Acquisition and retention of LSDV by Ae. aegypti after feeding on an artificial membrane feeding system that contained a high titer of LSDV was comparable to feeding on a skin lesion on a clinically affected animal, supporting the use of this laboratory model as a replacement for some animal studies. This work reveals that the cutaneous lesions of LSD provide the high-titer source required for acquisition of the virus by insects, thereby enabling the mechanical vector-borne transmission. IMPORTANCE Lumpy skin disease virus (LSDV) is a high consequence pathogen of cattle that is rapidly expanding its geographical boundaries into new regions such as Europe and Asia. This expansion is promoted by the mechanical transmission of the virus via hematogenous arthropods. This study quantifies the acquisition and retention of LSDV by four species of blood-feeding insects and reveals that the cutaneous lesions of LSD provide the high titer virus source necessary for virus acquisition by the insects. An artificial membrane feeding system containing a high titer of LSDV was shown to be comparable to a skin lesion on a clinically affected animal when used as a virus source. This promotes the use of these laboratory-based systems as replacements for some animal studies. Overall, this work advances our understanding of the mechanical vector-borne transmission of LSDV and provides evidence to support the design of more effective disease control programmes.
Subject(s)
Blood , Diptera , Feeding Behavior , Insect Vectors , Lumpy Skin Disease , Lumpy skin disease virus , Aedes/anatomy & histology , Aedes/virology , Animals , Cattle/virology , Ceratopogonidae/anatomy & histology , Ceratopogonidae/virology , Culex/anatomy & histology , Culex/virology , Diptera/anatomy & histology , Diptera/physiology , Diptera/virology , Insect Vectors/anatomy & histology , Insect Vectors/physiology , Insect Vectors/virology , Lumpy Skin Disease/virology , Lumpy skin disease virus/isolation & purification , Lumpy skin disease virus/physiology , Membranes, Artificial , Muscidae/anatomy & histology , Muscidae/virology , Time FactorsABSTRACT
Segmented RNA viruses are a taxonomically diverse group that can infect plant, wildlife, livestock and human hosts. A shared feature of these viruses is the ability to exchange genome segments during coinfection of a host by a process termed "reassortment." Reassortment enables rapid evolutionary change, but where transmission involves a biological arthropod vector, this change is constrained by the selection pressures imposed by the requirement for replication in two evolutionarily distant hosts. In this study, we use an in vivo, host-arbovirus-vector model to investigate the impact of reassortment on two phenotypic traits, virus infection rate in the vector and virulence in the host. Bluetongue virus (BTV) (Reoviridae) is the causative agent of bluetongue (BT), an economically important disease of domestic and wild ruminants and deer. The genome of BTV comprises 10 linear segments of dsRNA, and the virus is transmitted between ruminants by Culicoides biting midges (Diptera: Ceratopogonidae). Five strains of BTV representing three serotypes (BTV-1, BTV-4, and BTV-8) were isolated from naturally infected ruminants in Europe and ancestral/reassortant lineage status assigned through full genome sequencing. Each strain was then assessed in parallel for the ability to replicate in vector Culicoides and to cause BT in sheep. Our results demonstrate that two reassortment strains, which themselves became established in the field, had obtained high replication ability in C. sonorensis from one of the ancestral virus strains, which allowed inferences of the genome segments conferring this phenotypic trait. IMPORTANCE Reassortment between virus strains can lead to major shifts in the transmission parameters and virulence of segmented RNA viruses, with consequences for spread, persistence, and impact. The ability of these pathogens to adapt rapidly to their environment through this mechanism presents a major challenge in defining the conditions under which emergence can occur. Utilizing a representative mammalian host-insect vector infection and transmission model, we provide direct evidence of this phenomenon in closely related ancestral and reassortant strains of BTV. Our results demonstrate that efficient infection of Culicoides observed for one of three ancestral BTV strains was also evident in two reassortant strains that had subsequently emerged in the same ecosystem.
Subject(s)
Arthropod Vectors , Bluetongue virus , Bluetongue , Ceratopogonidae , Sheep Diseases , Animals , Arthropod Vectors/virology , Bluetongue/transmission , Bluetongue/virology , Bluetongue virus/classification , Bluetongue virus/genetics , Bluetongue virus/pathogenicity , Ceratopogonidae/virology , Deer , Phenotype , Reassortant Viruses/metabolism , Sheep , Sheep Diseases/transmission , Sheep Diseases/virology , Virus ReplicationABSTRACT
Polymethylmethacrylate (PMMA) is a commonly used substrate in vertebroplasty procedures. Well-known for its dependable strength and relative lack of toxic side effects, PMMA administration is useful for the stabilization of vertebral bodies in the setting of common spinal pathologies such as osteoporosis. Unfortunately, as the popularity of vertebroplasty has increased, so has the incidence of a potentially lethal complication of the procedure, PMMA pulmonary embolism. Extravasation of PMMA from the vertebral body into the adjacent vasculature can provide a route through which PMMA may travel until it becomes lodged in the pulmonary vasculature, thereby forming a PMMA pulmonary embolism. While the vast majority of PMMA embolism cases are relatively mild, others are severe and demand swift recognition and potentially life-saving intervention. Despite the increasing incidence of PMMA embolism, a clear algorithm for management does not yet exist. Controversy abounds regarding the most effective strategies to diagnose and manage patients with PMMA embolism. Described is a case of delayed diagnosis of a PMMA embolism in a patient who underwent percutaneous vertebroplasty for an osteoporotic vertebral body fracture. Multiple visits to the emergency department (ED) for chest discomfort or cough after the vertebroplasty eventually led to cross-sectional imaging that revealed the diagnosis. Her acute symptoms resolved with conservative management. Given that her final outcome was positive with no long-term morbidity, the aim of this report is to explore the current treatment algorithms for PMMA embolism and to consider whether or not this patient would have been managed differently had the correct diagnosis been uncovered earlier.
ABSTRACT
Lumpy skin disease virus (LSDV) is a vector-transmitted poxvirus that causes disease in cattle. Vector species involved in LSDV transmission and their ability to acquire and transmit the virus are poorly characterized. Using a highly representative bovine experimental model of lumpy skin disease, we fed four model vector species (Aedes aegypti, Culex quinquefasciatus, Stomoxys calcitrans, and Culicoides nubeculosus) on LSDV-inoculated cattle in order to examine their acquisition and retention of LSDV. Subclinical disease was a more common outcome than clinical disease in the inoculated cattle. Importantly, the probability of vectors acquiring LSDV from a subclinical animal (0.006) was very low compared with that from a clinical animal (0.23), meaning an insect feeding on a subclinical animal was 97% less likely to acquire LSDV than one feeding on a clinical animal. All four potential vector species studied acquired LSDV from the host at a similar rate, but Aedes aegypti and Stomoxys calcitrans retained the virus for a longer time, up to 8 days. There was no evidence of virus replication in the vector, consistent with mechanical rather than biological transmission. The parameters obtained in this study were combined with data from studies of LSDV transmission and vector life history parameters to determine the basic reproduction number of LSDV in cattle mediated by each of the model species. This reproduction number was highest for Stomoxys calcitrans (19.1), followed by C. nubeculosus (7.1) and Ae. aegypti (2.4), indicating that these three species are potentially efficient transmitters of LSDV; this information can be used to inform LSD control programs.IMPORTANCE Lumpy skin disease virus (LSDV) causes a severe systemic disease characterized by cutaneous nodules in cattle. LSDV is a rapidly emerging pathogen, having spread since 2012 into Europe and Russia and across Asia. The vector-borne nature of LSDV transmission is believed to have promoted this rapid geographic spread of the virus; however, a lack of quantitative evidence about LSDV transmission has hampered effective control of the disease during the current epidemic. Our research shows subclinical cattle play little part in virus transmission relative to clinical cattle and reveals a low probability of virus acquisition by insects at the preclinical stage. We have also calculated the reproductive number of different insect species, therefore identifying efficient transmitters of LSDV. This information is of utmost importance, as it will help to define epidemiological control measures during LSDV epidemics and of particular consequence in resource-poor regions where LSD vaccination may be less than adequate.
Subject(s)
Insect Vectors , Lumpy Skin Disease/transmission , Lumpy skin disease virus/physiology , Animals , Cattle , Insect Vectors/physiology , Insect Vectors/virology , Male , Virus ReplicationABSTRACT
BACKGROUND: Culicoides biting midges (Diptera: Ceratopogonidae) are biological vectors of internationally important arboviruses and inflict biting nuisance on humans, companion animals and livestock. In temperate regions, transmission of arboviruses is limited by temperature thresholds, in both replication and dissemination of arboviruses within the vector and in the flight activity of adult Culicoides. This study aims to determine the cold-temperature thresholds for flight activity of Culicoides from the UK under laboratory conditions. METHODS: Over 18,000 Culicoides adults were collected from the field using 4 W down-draught miniature ultraviolet Centers for Disease Control traps. Populations of Culicoides were sampled at three different geographical locations within the UK during the summer months and again in the autumn at one geographical location. Activity at constant temperatures was assessed using a bioassay that detected movement of adult Culicoides towards an ultraviolet light source over a 24-h period. RESULTS: The proportion of active adult Culicoides increased with temperature but cold temperature thresholds for activity varied significantly according to collection season and location. Populations dominated by the subgenus Avaritia collected in South East England had a lower activity threshold temperature in the autumn (4 °C) compared with populations collected in the summer (10 °C). Within the subgenus Avaritia, Culicoides scoticus was significantly more active across all temperatures tested than Culicoides obsoletus within the experimental setup. Populations of Culicoides impunctatus collected in the North East of England were only active once temperatures reached 14 °C. Preliminary data suggested flight activity of the subgenus Avaritia does not differ between populations in South East England and those in the Scottish Borders. CONCLUSIONS: These findings demonstrate seasonal changes in temperature thresholds for flight and across different populations of Culicoides. These data, alongside that defining thresholds for virus replication within Culicoides, provide a primary tool for risk assessment of arbovirus transmission in temperate regions. In addition, the study also provides a comparison with thermal limits derived directly from light-suction trapping data, which is currently used as the main method to define adult Culicoides activity during surveillance.
Subject(s)
Ceratopogonidae/physiology , Cold Temperature , Insect Vectors/physiology , Movement , Animals , Arbovirus Infections/transmission , Arboviruses/physiology , Ceratopogonidae/virology , Cohort Studies , Female , Insect Vectors/virology , Laboratories , Male , Seasons , United KingdomABSTRACT
BACKGROUND: Bovine ephemeral fever virus (Rhabdoviridae: Ephemerovirus) (BEFV) causes bovine ephemeral fever (BEF), an economically important disease of cattle and water buffalo. Outbreaks of BEF in Africa, Australia, Asia and the Middle East are characterized by high rates of morbidity and highly efficient transmission between cattle hosts. Despite this, the vectors of BEFV remain poorly defined. METHODS: Colony lines of biting midges (Culicoides sonorensis) and mosquitoes (Aedes aegypti, Culex pipiens and Culex quinquefasciatus) were infected with a strain of BEFV originating from Israel by feeding on blood-virus suspensions and by intrathoracic inoculation. In addition, in vivo transmission of BEFV was also assessed by allowing C. sonorensis inoculated by the intrathoracic route to feed on male 6 month-old Holstein-Friesian calves. RESULTS: There was no evidence of BEFV replication within mosquitoes fed on blood/virus suspensions for mosquitoes of any species tested for each of the three colony lines. In 170 C. sonorensis fed on the blood/virus suspension, BEFV RNA was detected in the bodies of 13 individuals and in the heads of two individuals, indicative of fully disseminated infections and an oral susceptibility rate of 1.2%. BEFV RNA replication was further demonstrated in all C. sonorensis that were inoculated by the intrathoracic route with virus after 5, 6 or 7 days post-infection. Despite this, transmission of BEFV could not be demonstrated when infected C. sonorensis were allowed to feed on calves. CONCLUSIONS: No evidence for infection or dissemination of BEFV (bovine/Israel/2005-6) in mosquitoes of three different species was found. Evidence was found for infection of C. sonorensis by the oral route. However, attempts to transmit BEFV to calves from infected C. sonorensis failed. These results highlight the challenge of defining the natural vector of BEFV and of establishing an in vivo transmission model. The results are discussed with reference to the translation of laboratory-based studies to inference of vector competence in the field.