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

Web Mining for Web Personalization

Web personalization is the process of customizing a Web site to the needs of specific users, taking advantage of the knowledge acquired from the analysis of the user\u27s navigational behavior (usage data) in correlation with other information collected in the Web context, namely, structure, content, and user profile data. Due to the explosive growth of the Web, the domain of Web personalization has gained great momentum both in the research and commercial areas. In this article we present a survey of the use of Web mining for Web personalization. More specifically, we introduce the modules that comprise a Web personalization system, emphasizing the Web usage mining module. A review of the most common methods that are used as well as technical issues that occur is given, along with a brief overview of the most popular tools and applications available from software vendors. Moreover, the most important research initiatives in the Web usage mining and personalization areas are presented

Web Usage Mining: Sequential Pattern Extraction with a Very Low Support

Abstract. The goal of this work is to increase the relevance and the interestingness of patterns discovered by a Web Usage Mining process. Indeed, the sequential patterns extracted on web log files, unless they are found under constraints, often lack interest because of their obvious content. Our goal is to discover minority users ’ behaviors having a coherence which we want to be aware of (like hacking activities on the Web site or a users ’ activity limited to a specific part of the Web site). By means of a clustering method on the extracted sequential patterns, we propose a recursive division of the problem. The developed clustering method is based on patterns summaries and neural networks. Our experiments show that we obtain the targeted patterns whereas their extraction by means of a classical process is impossible because of a very weak support (down to 0.006%). The diversity of users ’ behaviors is so large that the minority ones are both numerous and difficult to locate

Identifying the last bloodmeal of questing wood tick nymphs (Ixodes ricinus L.) by DNA amplification: three approaches tested

Tick-borne disease risk can be modelled more accurately when the main hosts of the most common European tick vector, I. ricinus, are known for a given area. However, I. ricinus is known to feed on more than 300 species in Europe, and estimating their relative importance from field observations (which includes live-trapping of hosts to count ticks) is time-consuming and likely to be highly biased, since individual ticks spend only a few days a year feeding. On the other hand, I. ricinus ticks are easily collected from vegetation while questing; therefore, more recent studies have focussed on using molecular markers in these individuals to identify their last bloodmeal. Here we present three different protocols that we optimized to detect bloodmeal sources and discuss the quality of the results: Reverse Line Blot Hybridization (RLBH), Next Generation Sequencing (NGS) and, for the first time, High Resolution Melting Analysis (HRMA). Regarding RLBH and NGS, we managed to limit contamination and increase the quality of results, but some uncertainty remained. Instead, using HRMA, we showed that with six newly designed host-group primers (Muroidea, Soricidae, Passeriformes, Canidae, Caprinae, Artiodactyls), we could successfully amplify 20 target host species and genera. When first tested on a limited number of questing nymphs, the new protocol showed high sensitivity (bloodmeal sources were identified in 65.4 % of nymphs), reliable mixed bloodmeal identification and high identification success (35 out of 42 amplified bloodmeals were identified to genus or species), and low contamination levels. In order to improve the cost-effectiveness and productivity of the HRMA protocol, we then automated both the extraction method and PCR reaction setup for an additional 741 nymphs. Although mean sensitivity decreased to 21.5 % (159/741 nymphs), identification success and contamination control were maintained. HRMA results confirm the importance of Apodemus spp. as larval hosts (58/173 bloodmeals), but also indicate that the domestic dog, C. l. familiaris (37/173) may support larval populations. In conclusion, we present the pros and cons of these and other published techniques and the prospects for improvements. We also discuss the epidemiological implications of the results

Les risques associés aux tiques dans les parcs urbains et périurbains lyonnais

National audienc

Identifying the last bloodmeal of questing wood tick nymphs (<em>Ixodes ricinus L.</em>) by DNA amplification: three approaches tested

International audienc