Résultat de la recherche
Longitudinal study of Lyme borreliosis in a high risk population in Switzerland
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.
Longitudinal study of Lyme borreliosis in a high risk population in Switzerland
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.
The Prevalence and Incidence of Clinical and Asymptomatic Lyme Borreliosis in a Population at Risk
A past history of clinical Lyme borreliosis and the 6-month incidence of clinical and asymptomatic Lyme borreliosis was studied prospectively in a high-risk population. In the spring, blood samples were drawn from 950 Swiss orienteers, who also answered a questionnaire. IgG anti-Borrelia burgdorferi antibodies were detected by ELISA. Positive IgG antibodies were seen in 248 (26.1%), in contrast to 3.9%-6.0% in two groups of controls (n = 101). Of the orienteers, 1.9%-3.1% had a past history of definite or probable clinical Lyme borreliosis. Six months later a second blood sample was obtained from 755 participants, 558 (73.9%) of whom were seronegative initially; 45 (8.1%) had seroconverted from negative to positive. Only 1 (2.2%) developed clinical Lyme borreliosis. Among all participants, the 6-month incidence of clinical Lyme borreliosis was 0.8% (6/755) but was much higher (8.1%) for asymptomatic seroconversion (45/558). In conclusion, positive Lyme serology was common in Swiss orienteers, but clinical disease occurred infrequently.
Prävalenz der Lyme-Borreliose in einer schweizerichen Risikopopulation
L'épidémiologie de la borréliose de Lyme n'est pas encore suffisamment connue. La signification d'un litre d'anticorps positif n'est pas claire. Nous avons abordé ces deux questions en étudiant un grand groupe de coureurs d'orientation en Suisse car ils sont en contact étroit avec les biotopes habités par les tiques. - Nos chiffres prouvent que la prévalence de titres positifs d'anticorps est haute mais que la prévalence de symptômes est basse. Ces résultats établissent qu'une proportion importante des infections à Borrelia burgdorferi se déroule de manière asymptomatique. Un titre d'anticorps isolé, même très positif, n'a pas de valeur diagnostique., Die Epidemiologie der Lyme-Borreliose in Europa ist noch ungenügend bekannt, ebenso die Bedeutung positiver Antikörpertiter. Anhand eines grossen Kollektivs schweizerischer Orientierungsläufer, einer Bevölkerungsgruppe mit besonders engem Kontakt zu zeckenbewohnten Biotopen, suchten wir eine Annäherung an verschiedene der noch offenen Fragen. - Bei 964 regelmässig im Wald orientierungslaufenden gesunden Probanden fanden sich mittels Immunfluoreszenztechnik bei rund 20% auf eine Infektion hinweisende Antikörper vom IgG-Typ gegen Borrelia burgdorferi, bei rund 4% Antikörper vom IgM-Typ. Selbst bei hochtitrig positiven Individuen konnten jedoch in nur sehr wenigen Fällen aktuelle oder anamnestische Erkran- kungssymptome nachgewiesen werden. Die Läuferpopulation wird serologisch und klinisch weiterverfolgt. - Unsere Resultate zeigen in dieser Risikogruppe eine recht hohe Antikörper-, hingegen eine geringe Erkrankungsprävalcnz. Sie belegen den offensichtlich hohen Anteil klinisch stumm verlaufender Infektionen mit Borrelia burgdorferi. Ein einzelner, selbst hoher Antiborrelientiter ist diagnostisch nicht verwertbar., The epidemiology of "Lyme borreliosis" in Europe and the significance of positive antibody tilers against Borrelia burgdorferi is not well known. Since "orienteering", a competitive cross country sport with a map and a compass, usually in forests, elevates the risk of being bitten by ticks and infected by B. burgdorferi, nearly 1000 orienteerers were included in a prospective study. - In this population the prevalence of positive IgG-antibodies (immunofluorcscence technique) was almost 20% and of IgM-antibodies 4%. However, the frequency of associated symptoms in the clinical history of the pro- bands was very low, even in individuals with highly positive liters. - We conclude that the rate of asymptomatic Borrelia infections is high in this special group, and probably also in the general population, and that one has therefore to be cautious in interpreting an isolated positive "Lyme titer". Further investigations are needed, and, in particular, follow-up of the many "positive" subjects without clinical symptoms may be helpful in under- standing this fascinating disease better.