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  • Publication
    Accès libre
    Longitudinal study of Lyme borreliosis in a high risk population in Switzerland
    Zhioua, Elyes
    ;
    ; ;
    Sauvain, Marie-Josephe
    ;
    Van der Linden, Sjef M
    ;
    Fahrer, Heinz
    Des coureurs d'orientation venant de toutes les régions de Suisse (n = 416) ont participé à une étude prospective de la borréliose de Lyme. Au printemps 1986, la séroprévalence était de 28,1 %. Au début de l'étude, 84,3 % des coureurs d'orientation ont signalé avoir été piqués par des tiques. Durant la première période (printemps 1986-automne 1986), la deuxième (automne 1986-printemps 1987) et la troisième (printemps 1987-automne 1987), les taux de séroconversion ont été respectivement de 0,6 %, 2,7 %, et 2,1 %. Lors des première et deuxième périodes, l'incidence clinique a été respectivement égale à 1,0 % et 0,25 %. Aucun cas clinique n'a été observé durant la troisième période. Parmi les coureurs ayant présenté une séroconversion durant cette étude (n = 16), deux seulement ont développé des symptômes cliniques. Il semble donc que l'infection à Borrelia burgdorferi soit souvent asymptomatique., Orienteers from all parts of Switzerland (n = 416) were included in a longitudinal study for Lyme borreliosis. In spring 1986, the seroprevalence was 28.1 %. At the beginning of the study, 84.3 % of orienteers reported a history of tick bite, and 3.8 % reported a past history of Lyme borreliosis. During the first (spring 1986-autumn 1986), second (autumn 1986-spring 1987) and third (spring 1987-autumn 1987) period, rates of seroconversion were 0.6 %, 2.7 % and 2.1 % respectively. During the first and second period, clinical incidence were 1.0 % and 0.25 % respectively. No active Lyme borreliosis was detected during the third period. Among orienteers who seroconverted during the study (n = 16), only two developed clinical symptoms. Hence, Borrelia burgdorferi infection is often asymptomatic.
  • Publication
    Accès libre
    Infection of field-collected Ixodes ricinus (Acari: Ixodidae) larvae with Borrelia burgdorferi in Switzerland
    Free-living larvae from natural areas in five regions in Switzerland were collected to determine the infection rate of Ixodes ricinus L. larvae by Borrelia burgdorferi Johnson. Larvae were examined for the spirochetes using direct fluorescent antibody assay. Of 652 larvae examined, spirochetes were detected in 20 (3.1%). No differences in infection rate among sites were detected. The low prevalence of B. burgdorferi in larvae, compared with higher infection rate in nymphs (12.8%) and adults (14.5%), suggests that transovarial transmission is inefficient. These results suggest that I. ricinus can serve as a reservoir for B. burgdorferi in nature. Further study is needed on the relative importance of ticks, compared with mammals and birds, as reservoirs for B. burgdorferi.