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Factors Determining Immunological Response to Vaccination against Tick-Borne Encephalitis Virus in Older Individuals
by Pontus Lindblom, Peter Wilhelmsson, Linda Fryland, Andreas Matussek, Mats Haglund, Johanna Sjöwall, Sirkka Vene, Dag Nyman, Pia Forsberg, Per-Eric Lindgren
We performed a cross-sectional study including 533 individuals (median age 61) from the highly TBE endemic Åland Islands in the archipelago between Sweden and Finland. Blood samples, questionnaires and vaccination records were obtained from all study participants. The aim was to investigate if there was any association between TBEV antibody titer and 12 health-related factors. Measurement of TBEV IgG antibodies was performed using two commercial ELISA assays (Enzygnost and Immunozym), and a third in-house rapid fluorescent focus inhibition test was used to measure TBEV neutralizing antibodies. The age of the individual and the number of vaccine doses were the two most important factors determining the immunological response to vaccination. The response to each vaccine dose declined linearly with increased age. A 35 year age difference corresponds to a vaccine dose increment from 3 to 4 to achieve the same immunological response. Participants previously vaccinated against other flaviviruses had lower odds of being seropositive for neutralizing TBEV antibodies on average, while participants with self-reported asthma had higher odds of being seropositive. By comparing the 3 serological assays we show that the Enzygnost and Immunozym assay differ due to choice of cutoffs, but not in overall accuracy.Integrated surveillance for prevention and control of emerging vector-borne diseases in Europe
West Nile virus outbreak in humans, Greece, 2012: third consecutive year of local transmission
Identification of Parasitic Communities within European Ticks Using Next-Generation Sequencing
by Sarah Bonnet, Lorraine Michelet, Sara Moutailler, Justine Cheval, Charles Hébert, Muriel Vayssier-Taussat, Marc Eloit
BackgroundRisk assessment of tick-borne and zoonotic disease emergence necessitates sound knowledge of the particular microorganisms circulating within the communities of these major vectors. Assessment of pathogens carried by wild ticks must be performed without a priori, to allow for the detection of new or unexpected agents.
Methodology/Principal FindingsWe evaluated the potential of Next-Generation Sequencing techniques (NGS) to produce an inventory of parasites carried by questing ticks. Sequences corresponding to parasites from two distinct genera were recovered in Ixodes ricinus ticks collected in Eastern France: Babesia spp. and Theileria spp. Four Babesia species were identified, three of which were zoonotic: B. divergens, Babesia sp. EU1 and B. microti; and one which infects cattle, B. major. This is the first time that these last two species have been identified in France. This approach also identified new sequences corresponding to as-yet unknown organisms similar to tropical Theileria species.
Conclusions/SignificanceOur findings demonstrate the capability of NGS to produce an inventory of live tick-borne parasites, which could potentially be transmitted by the ticks, and uncovers unexpected parasites in Western Europe.
Do the Ticks of Birds at an Important Migratory Hotspot Reflect the Seasonal Dynamics of Ixodes ricinus at the Migration Initiation Site? A Case Study in the Danube Delta
by Attila D. Sándor, Daniel I. Mărcuţan, Gianluca D'Amico, Călin M. Gherman, Mirabela O. Dumitrache, Andrei D. Mihalca
Migratory birds play important roles as distributors of ticks within and between continents. In the Old World, the most important migratory route of birds links Asia, Europe and Africa. During their migration, birds use various stopover sites, where they feed and rest and where ticks may attach or detach, creating new natural foci for vector-borne diseases. Danube Delta is one of the most important migration hotspots and so far no studies were focused on ticks of migratory birds herein. The aim of the present study was to assess the species diversity and seasonal dynamics of ticks parasitizing migratory birds in Danube Delta Biosphere Reserve. Migratory birds were trapped on Grindul Lupilor (44°41′N; 28°56′E) using mist nets during 4 migratory seasons (2 spring and 2 autumn) in 2011 and 2012. From each bird, all the ticks were collected and identified based on morphological features. Epidemiological parameters (prevalence, mean abundance, mean intensity) were calculated and all data were analysed statistically based on the season (spring and autumn), regional status of birds (migrants and breeding) and foraging behaviour (ground feeders, reed-bed feeders, foliage feeders). A total of 1434 birds (46 species) were captured. Ticks were found on 94 birds (10 species). Significantly more migratory birds hosted ticks, compared to resident birds. The 400 collected ticks belonged to four species: Ixodes ricinus (92.25%), I. arboricola (6.25%), I. redikorzevi (1.00%) and Haemaphysalis punctata (0.50%). A higher prevalence was found for I. ricinus in spring, with higher prevalence of nymphs in this season, while larvae occurred with the same prevalence in both seasons. Larval intensity was higher during spring and nymphs were more abundant during autumn. The seasonal differences in our study may be related not to the local seasonal dynamics of ticks, but on the seasonal dynamics at the site of migration initiation.Full-Genome Characterisation of Orungo, Lebombo and Changuinola Viruses Provides Evidence for Co-Evolution of Orbiviruses with Their Arthropod Vectors
by Fauziah Mohd Jaafar, Mourad Belhouchet, Manjunatha Belaganahalli, Robert B. Tesh, Peter P. C. Mertens, Houssam Attoui
The complete genomes of Orungo virus (ORUV), Lebombo virus (LEBV) and Changuinola virus (CGLV) were sequenced, confirming that they each encode 11 distinct proteins (VP1-VP7 and NS1-NS4). Phylogenetic analyses of cell-attachment protein ‘outer-capsid protein 1′ (OC1), show that orbiviruses fall into three large groups, identified as: VP2(OC1), in which OC1 is the 2nd largest protein, including the Culicoides transmitted orbiviruses; VP3(OC1), which includes the mosquito transmitted orbiviruses; and VP4(OC1) which includes the tick transmitted viruses. Differences in the size of OC1 between these groups, places the T2 ‘subcore-shell protein’ as the third largest protein ‘VP3(T2)’ in the first of these groups, but the second largest protein ‘VP3(T2)’ in the other two groups. ORUV, LEBV and CGLV all group with the Culicoides-borne VP2(OC1)/VP3(T2) viruses. The G+C content of the ORUV, LEBV and CGLV genomes is also similar to that of the Culicoides-borne, rather than the mosquito-borne, or tick borne orbiviruses. These data suggest that ORUV and LEBV are Culicoides- rather than mosquito-borne. Multiple isolations of CGLV from sand flies suggest that they are its primary vector. OC1 of the insect-borne orbiviruses is approximately twice the size of the equivalent protein of the tick borne viruses. Together with internal sequence similarities, this suggests its origin by duplication (concatermerisation) of a smaller OC1 from an ancestral tick-borne orbivirus. Phylogenetic comparisons showing linear relationships between the dates of evolutionary-separation of their vector species, and genetic-distances between tick-, mosquito- or Culicoides-borne virus-groups, provide evidence for co-evolution of the orbiviruses with their arthropod vectors.Next Generation Sequencing Uncovers Unexpected Bacterial Pathogens in Ticks in Western Europe
by Muriel Vayssier-Taussat, Sara Moutailler, Lorraine Michelet, Elodie Devillers, Sarah Bonnet, Justine Cheval, Charles Hébert, Marc Eloit
Background and AimsTicks are highly susceptible to global environmental and socio-economical changes. Several tick-borne pathogens have been reported in new geographical regions while new species, strains or genetic variants of tick-borne microorganisms are continually being detected. However, tick-borne pathogens are still poorly understood, and it is estimated that half of all human tick-borne disease has an unknown origin. Therefore in order to prevent these diseases, more effort is required to identify unknown or unexpected tick-borne pathogens. Ixodes ricinus is the vector for a broad range of bacterial pathogens and the most prevalent tick in Europe. The aim of the present study was to evaluate the capability of Next Generation Sequencing (NGS) to extend the inventory of pathogenic bacteria carried by this species of tick in France.
MethodsRNA and DNA were extracted from 1450 I. ricinus questing nymphs collected by flagging in Alsace, France. RNA was pooled and used for NGS. Following de novo assembly, bacterial contigs were assigned to the closest known taxonomy. DNA was used for real time PCR to confirm taxonomic species assignment of NGS-derived contigs for the doubtful cases, and for determination of prevalence.
ResultsWe have generated a global in-depth picture of tick-borne bacteria. We identified RNA from the main pathogenic bacterial species known to be transmitted by I. ricinus. In addition we also identified unanticipated bacterial species for which we have estimated the prevalence within those ticks inhabiting the studied areas.
ConclusionsThe data obtained from this study has proven that NGS has an enormous potential to detect the unexpected and provides the means to monitor pathogen occurrence.