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.
Confirmation that Rickettsia helvetica sp. nov. Is a Distinct Species of the Spotted Fever Group of Rickettsiae
We propose the name Rickettsia helvetica sp. nov. for a rickettsial serotype of unknown pathogenicity isolated in 1979 in Switzerland from Ixodes ricinus ticks and designated the Swiss agent. The growth characteristics and the results of microimmunofluorescence serologic typing, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting (immunoblotting) with specific mice sera, and a polymerase chain reaction followed by restriction fragment length polymorphism analysis confirmed previously reported preliminary findings which suggested that this rickettsia, to which a name was given provisionally, does represent a new member of the spotted fever group of rickettsiae. The type strain is C3 (Reference Center for Rickettsioses, Marseille, France).
Etude morphologique des Ixodidae S. Str. (Schultze, 1937) de Suisse au microscope électronique à balayage
Le rôle épidémiologique de certaines espèces de tiques du genre Ixodes est actuellement bien démontré. La nécessité de mieux connaître leur morphologie nous a donc conduit à mener une étude au microscope électronique à balayage (M.E.B.) des Ixodes de Suisse, dans le but d'identifier les espèces avec sûreté quelque soit le stade évolutif considéré. I. ricinus, 1. apronophorus, I. trianguliceps, I. hexagonus, I. canisuga, I. rugicollis, I. arboricola, I. lividus et I. vespertilionis ont pu être étudiés. La plupart des spécimens proviennent de la « collection AESCHLIMANN » déposée au Musée Zoologique de Lausanne. Les principales caractéristiques morphologiques ont été passées en revue et sont illustrées par des photographies, tandis que les résultats sont résumés sous forme de clés de détermination., The epidemiological importance of some ticks of the genus Ixodes has already been proved. Necessity of a better knowledge of their morphology has led us to undertake a scanning electron microscope (S.E.M.) study of Ixodes ticks in Switzerland, in order to be able to accurately identify the species independent of the development stage examined. I. ricinus, I. apronophorus, I. trianguliceps, I. hexagonus, I. canisuga, I. rugicollis, I. arboricola, I. lividus and I. vespertilionis have been studied. Most of these tick specimens were from the « collection AESCHLIMANN » deposited at the Lausanne Zoological Museum. The main morphological features are illustrated by micrographs, and results presented in determination keys.
Comparative considerations on the epidemiology of Lyme borreliosis and tick-borne encephalitis in Switzerland
In Switzerland, the spirochete Borrelia burgdorferi and tick-borne encephalitis virus infect the human population. These infections may cause serious pathogenic effects to men and domestic animals. The tick Ixodes ricinus is the vector of both microorganisms. The distribution of the virus is concentrated in small foci scattered in some regions. In these areas, the infection occurs in less than 1 % of the ticks. The distribution of the spirochete is larger and more regular in the Swiss territory and B. burgdorferi is present in 5 to 50 % of/, ricinus. It is the aim of this paper to try to explain how both types of foci occur, considering especially the problem of small mammals as reservoirs for the bacterium and the virus.
Etude faunistique et biologique d'Ixodes (Pholeoixodes) hexagonus Leach, 1815 en Suisse et de son rôle dans la transmission de Borrelia Burgdorferi agent pathogène de la Borreliose de Lyme
Biology of Ixodes (Pholeoixodes) hexagonus under laboratory conditions. Part I. Immature stages
A rearing method for Ixodes (Pholeoixodes) hexagonus, the hedgehog tick, was established which enabled the life cycle of immature stages to be studied under laboratory conditions. Larvae were fed on Swiss mice and nymphs on the cars of New Zealand rabbits. The feeding time of the larvae and nymphs on both hosts was 4–17 days. Larvae moulted to nymphs 15–21 days after detachment from mice. The premoulting period was 13–26 days for newly emerged males and 15–27 days for females. Engorged nymphs which developed into males weighed less (5.64±0.91 mg) than those that developed into females (6.019±88mg). The sex ratio (male: female) under laboratory conditions was 1:1.13.
Etude séroépidémiologique de l'encéphalite à tiques et de la Borreliose de Lyme en Suisse
Ixodes ricinus immatures on birds in a focus of Lyme borreliosis
The infestation of birds by immature Ixodes ricinus was studied during 6 months in a Swiss woodland, where Lyme borreliosis is endemic. Thirteen passerine species were found to be parasitized by /. ricinus subadults and specially Turdus merula, T, philomelos and Erithacus rubecula. Overall, 300 larvae and 162 nymphs were collected on 95 avian hosts. Prevalence of infestation of nymphs on birds was higher in spring; larvae peaked in summer. The infection of birds by Borrelia burgdorferi was also studied using blood cultivation and examinations of ticks. Motionless spirochetes were isolated from two E. rubecula. Infected ticks were removed from five species of passerines, and mainly three species of Turdidae (T. merula, T. phllomelos and E. rubecula}. Infection rate of larvae and nymphs by spirochetes averaged 16.3% and 21.7%, respectively. These percentages, compared to the infection rate of questing ticks collected through dragging, suggest that some Turdidae may play a role as amplifying hosts for spirochetes in the focus.