Reliability of molecular host-identification methods for ticks: an experimental in vitro study with Ixodes ricinus

Background: Reliable information on host use by arthropod vectors is required to study pathogen transmission ecology and to predict disease risk. Direct observation of host use is often difficult or impossible and indirect methods are therefore necessary. However, the reliability of currently available methods to identify the last host of blood-feeding arthropods has not been evaluated, and may be particularly problematic for ticks because host blood has been digested at capture. Biases in host detection may lead to erroneous conclusions on both vector ecology and pathogen circulation. Methods: Here, we experimentally tested for biases in host detection using the generalist three-host tick Ixodes ricinus as a model system. We fed ticks using an artificial feeding system and amplified blood meal traces post-moult (i.e., in the succeeding unfed life stage) via both a quantitative real-time polymerase chain reaction assay and a reverse line blotting method. We then experimentally tested for three types of biases in host detection: 1) time post-moult, 2) tick life stage and 3) host type (non-nucleated mammal blood versus nucleated avian blood), and compared these biases between the two molecular methods. Results: Our results show that all three factors can influence host detection in ticks but not necessarily in the expected way. Although host detection rates decreased with time post-moult, mammal blood tended to be more readily detected than bird blood. Tick life stage was also an important factor; detection was higher in nymphs than in adults and, in some cases, remnants from both larval and nymphal blood meals could be detected in the adult stage. These biases were similar for the two detection techniques. Conclusions: We show that different factors associated with questing ticks may influence our ability to correctly infer previous host use and that these factors may bias inferences from field-based studies. As these biases may be common to other vector-borne disease systems, their implications for our understanding of vector ecology and disease transmission require more explicit consideration

Impact of recycler information sharing on supply chain performance of construction and demolition waste resource utilization

In recent years, the generation of a large amount of construction and demolition waste (CDW) has threatened the public environment and human health. The inefficient supply chain of CDW resource utilization hinders the green development of countries around the world, including China. This study aims to reveal the impact of information sharing regarding recyclers’ market demand forecast on the performance of CDW resource utilization supply chains. Therefore, this paper uses the incomplete information dynamic game method to establish and solve the decision-making model of the construction and demolition waste resource utilization supply chain under the conditions of recyclers sharing and not sharing their information. The paper then obtains the Bayesian equilibrium solution and the optimal expected profit for each party. Finally, a numerical simulation was used in order to verify the validity of the model and conclusions. The main conclusions are as follows. In the CDW resource utilization supply chain, if the recycler is more pessimistic about the market’s demand forecast, their information sharing makes the remanufacturer more motivated to improve their level of environmental responsibility. In addition, information sharing by recyclers is always beneficial in increasing the profit of the remanufacturer, but it also may make the recycler lose profit. When the efficiency of the environmental responsibility investment of remanufacturers is in a high range, information sharing increases the profits of recyclers. Conversely, information sharing has no significant effect on the profits of recyclers. The impact on the profits of the entire CDW resource utilization supply chain depends on the intensity of competition among channels, the market share of offline recycling channels and the efficiency of environmental responsibility investments

Identification de facteurs des glandes salivaires d’Ixodes ricinus impliqués dans la transmission de Bartonella henselae

Ticks are obligate blood-feeding ectoparasites of many hosts including mammals, birds and reptiles. After mosquitoes, they are the most important vectors worldwide, and are able to transmit the highest variety of pathogens including virus, bacteria and parasites. Ixodes ricinus (Acari: Ixodidae), the most common tick species in Europe, is a three-life stage hard tick. It is frequently associated with bites in humans, and transmits several pathogens, including Tick-Borne Encephalitis, Babesia spp., Borrellia spp., Anaplasma spp., and to a lesser extent Bartonella spp. Bartonella spp. are facultative intracellular bacteria associated with a number of emerging diseases in humans and animals. It has been demonstrated that I. ricinus is a competent vector for B. henselae that causes cat scratch disease as well as being increasingly associated with a number of other syndromes, particularly ocular infections and endocarditis. Recently, emergence or re-emergence of tick-borne diseases (TBDs) is increasingly becoming a problem. Indeed, and because of the limited success and disadvantages of controlling TBDs via acaricides, new approaches are urgently needed. Therefore, vaccine strategies that target conserved components of ticks that play roles in vector infestation and vector capacity have become particularly attractive. Accordingly, the identification of suitable antigenic targets is a major challenge for the implementation of tick and TBDs control strategies. In the present work, the main objective is to elucidate molecular interactions between I. ricinus and B. henselae in order to identify some targets that may be used as vaccines against ticks and tick-borne pathogens. Two principal points are focused on: primarily, to identify I. ricinus salivary gland differentially expressed transcripts in response to B. henselae infection with next generation sequencing techniques (454 pyrosequencing and HiSeq 2000); secondly, to validate the implication of one of these transcripts in the transmission of B. henselae. For that purpose, and at first, we validated artificial membrane feeding technique for ticks infection by B. henselae and evaluated the impact of several parameters on tick feeding. Results showed that membrane feeding technique is a suitable method to infect I. ricinus with B. henselae and that the proportion and weight of engorged ticks are decreased by B. henselae infection of the blood meal. Transcriptional analysis of the tick salivary glands generated a reference databank containing 24,539 transcripts, and the comparison of B. henselae-infected and non-infected I. ricinus female salivary glands showed that 839 and 517 transcripts were significantly up- and down-regulated in response to bacteria infection, respectively. Among them, 161 transcripts corresponded to 9 groups of ticks salivary gland gene families already described, when the other ones corresponded to genes of unknown function. Silencing the most up-regulated gene IrSPI, which belongs to BPTI/Kunitz family of serine protease inhibitor, resulted in reduction of tick feeding and bacteria load in tick salivary gland. In conclusion, this work demonstrated that artificial-membrane feeding technique is a powerful tool for investigating the interactions between tick and tick-borne pathogens as B. henselae. It also increases the available genomic information for I. ricinus and the knowledge to improve our understanding of the molecular interaction between tick and tick-borne pathogens. At last, it provides a potential vaccine candidate to control tick-borne diseases. In the future, and depending of differentially expressed genes' role confirmation, more and more vaccine candidate will be provided by this work, and the strategy of controlling tick and tick-borne disease will come to a new stageAujourd'hui, l'émergence ou la réémergence de maladies transmises par les tiques (TBDs) devient un problème majeur. En raison des problèmes générés par l'utilisation des acaricides (pollution, résistance), il est donc urgent d'identifier de nouvelles approches pour contrôler les populations de tiques. Parmi ces stratégies, la vaccination visant des molécules conservées chez les tiques et impliquées dans leur capacité vectorielle, sont devenues particulièrement attractives. En conséquence, l'identification de cibles antigéniques appropriées est un défi majeur pour la mise en œuvre de ces stratégies de contrôle des tiques et des TBDs. Dans le présent travail, l'objectif principal est d'élucider les interactions moléculaires entre I. ricinus et B. henselae, afin d'identifier des molécules qui pourraient représenter des cibles vaccinales contre les tiques et les agents pathogènes qu'elles transmettent. Dans ce but, nous avons identifié, par séquençage à haut débit, des transcrits d'Ixodes ricinus différentiellement exprimés au niveau des glandes salivaires de la tique en réponse à une infection par B. henselae. Dans un second temps, l'implication d'un de ces transcrits surexprimés lors de l'infection dans la transmission de B. henselae, a été évaluée. Enfin, et en premier lieu, nous avons validé l'utilisation de la technique de gorgement artificiel sur membrane pour infecter I. ricinus par B. henselae et évalué l'impact de différents paramètres sur le gorgement des tiques. Les résultats ont montré que la technique de gorgement sur membrane est bien adaptée à l'infection d'I. ricinus par B. henselae en laboratoire, et que la proportion et le poids des tiques gorgées sont diminués lors de l'infection du sang par la bactérie Le séquençage en 454 des glandes salivaires de tiques a généré une banque de référence contenant 24, 539 transcrits, et la comparaison des glandes salivaires d'I. ricinus infectés et non-infectés par B. henselae a montré que 839 et 517 transcrits étaient respectivement significativement surexprimés et sous-exprimés en réponse à l'infection par des bactéries. Parmi les gènes de fonction connue, 161 transcrits correspondent à 9 familles déjà identifiées, quand les autres correspondent à des gènes de fonction inconnue. L'extinction par RNA interférence du gène le plus surexprimé, IrSPI qui appartient à la famille des inhibiteurs de sérine protéase BPTI/Kunitz, a entraîné une réduction de la taille du repas sanguin prit par les tiques (et donc sa descendance) ainsi que du niveau d'infection au niveau des glandes salivaires. En conclusion, cette étude a démontré que la technique de gorgement artificiel des tiques sur membrane est un outil puissant pour étudier les interactions entre les tiques et les agents pathogènes qu'elles transmettent comme B. henselae. Ce travail apporte aussi une nette avancée en termes de données génétiques sur I. ricinus (dont le génome n'est pas séquencé) et sur les interactions moléculaires entre une bactérie et son vecteur. Enfin, ce travail a permis la mise en évidence d'une molécule représentant un candidat vaccinal très prometteur à la fois pour diminuer la population de tiques et lutter contre les agents pathogènes qu'elles transmettent. Dans le futur, et en fonction de la confirmation du rôle des gènes identifiés ici dans la transmission bactérienne, de nombreux candidats vaccins pourront ainsi être évalués, ouvrant alors de nouvelles perspectives dans la lutte contre les tiques et les maladies dues aux agents qu'elles transmetten

Hard Tick Factors Implicated in Pathogen Transmission

International audienceTicks are the most common arthropod vector, after mosquitoes, and are capable of transmitting the greatest variety of pathogens. For both humans and animals, the worldwide emergence or re-emergence of tick-borne disease is becoming increasingly problematic. Despite being such an important issue, our knowledge of pathogen transmission by ticks is incomplete. Several recent studies, reviewed here, have reported that the expression of some tick factors can be modulated in response to pathogen infection, and that some of these factors can impact on the pathogenic life cycle. Delineating the specific tick factors required for tick-borne pathogen transmission should lead to new strategies in the disruption of pathogen life cycles to combat emerging tick-borne disease

Laboratory artificial infection of hard ticks: a tool for the analysis of tick-borne pathogen transmission

Despite its importance, our knowledge of pathogen transmission by ticks is incomplete. Detailed studieson the transmission, maintenance, infectivity, virulence, and pathogenicity of tick-borne microparasites all require the use of large numbers of live ticks raised under controlled conditions and difficulties in rearing ticks in the laboratory could partly explain the current lack of data. The most complex part in maintaining tick colonies doubtlessly lies in their engorgement, as ticks are strict haematophagous arthropods. Indeed, relatively few research teams have worked on artificial feeding systems for ticks due to the long, complex, and poorly understood feeding patterns of these arthropods. It is nonetheless essential to investigate the mechanisms underlying tick infection and infectiousness in order to better understand parasite-host-vector relationships and elaborate new control strategies for transmitted pathogens. The various methods used to date to feed ticks and infect them with their associated pathogens are reviewed here and their advantages and inconveniences are discussed

Theoretical and Experimental Analysis of DOP Used as Control Signal in PMD Compensation

Abstract: Since polarization mode dispersion (PMD) is a major impairment for high bit rate fiber optics systems, it is an important thing for system performance that an proper designed PMD compensate component. In orderto use degree of polarization (DOP) as the feedbacd control signal in PMD dynamic compensation, the relationship beween DOP and differential group delay (DGD) must be ascertain first. Firstly, with a mono-chromatic assumption, the mathematics expression ofDOP is derived in this paper. Then, the relationship beween DOP and DGDm pulse width, and power splitting ratio is analyzde when optic pulse is Gaussian. At last, an experiment is presented, in which 10Gbit/s RZ pseudo random sequence is adopted, and the experimental results prove the validity of theoretical analysis

Changes of vegetation and its forces driving in the Aral Sea Basin of Central Asia

Global change brings great uncertainty to the fragile ecological environment of arid area. In order to understand the driving role of climatic factors and socio-economic activity on changes, the distribution and change of vegetation in the Aral Sea basin were examined using data from remote sensing, population data sets from 2000 to 2015, transfer matrix, and the centre of gravity model. The salient results of the analysis were as follows. (1) Although the index increased slightly in the past 20 years overall, it fluctuated greatly over that time. From 2000 to 2015, the NDVI decreased in approximately 62% of the area; increased in 24%; and remained unchanged in 14%. (2) From 2000 to 2015, the geographic centre of the area under forest land to the northeast, marking the advancement of urbanization upstream. The geographic centre of grassland moved to the west. (3) The overall impact of precipitation on vegetation was greater than that of temperature. Areas showing a strong correlation were mostly concentrated in forest land; the impact of precipitation on grasslands was weak. (4) The distribution of vegetation was adversely affected by the increase in population and in GDP. The present study is of particular significance to the restoration and reconstruction of the Aral Sea basin ecosystem

Dynamic Changes in Surface Damage Induced by High-Intensity Mining of Shallow, Thick Coal Seams in Gully Areas

This study proposes a novel approach to study the mechanism of mining and dynamic changes in surface subsidence and geological hazard-prone regions caused by shallow, thick coal seam mining in gully areas. This approach combines field observation, three-dimensional modeling, numerical simulation, and theoretical analysis based on the conditions of the Chuancao Gedan coal mine. The in situ stress field of coalbeds is influenced by the gully terrain. Shear stress becomes concentrated on the surface, causing geological disasters such as landslides and collapse of gully slopes. High-intensity mining activities increase the concentration and are more likely to cause such geological disasters. The influence area and severity vary dynamically with the expansion of the excavation area. With the continuous expansion of coal seam mining, the amplification ratio η (the ratio of the maximum impact range of surface subsidence and the mined-out area) first increased to 3.35, then decreased, and finally reached a constant value of 2.1. The principle of road line selection is proposed based on an analysis of surface subsidence and gully slope stability on the goaf edge. The principle of subsection reinforcement of the gully slope under the dynamic influence of coal seam mining is also determined