Aeschlimann, André

1993, Humair, Pierre-François, Turrian N., Aeschlimann, André, Gern, Lise

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.

1993, Beati, Lorenza, Péter, Olivier, Burgdorfer, Willy, Aeschlimann, André, Raoult, Didier

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).

1991, Aeschlimann, André

Tick species vary in the number of hosts fed upon during the life cycle, the specificity they have for certain host taxa, and the mode of transmission, among other life history details. What, then, is the definition of a 'natural focus' of a tick disease in an endemic region? It is the smallest possible intersection of a habitat (or microhabitat) in which the whole cycle of a parasitosis may be achieved in the wild, including the reservoir hosts, nutritional hosts, ticks and transmissible pathogens. Humans or domestic animals may reveal such a focus, when entering one. They become sick, and one observes the acquired disease clinically or serologically. Such a natural, focus may 'export' infected ticks with hosts. If such ticks are infected and leave the hosts out of a natural focus, they can begin new foci. I call such emigrations a 'pulsation' from an original focus. Young rodents, birds, or migrating large mammals may play an important role in originating new foci of diseases and then creating new endemic regions. The possibility that ticks transmit their pathogens through the eggs, over many generations (transovarial transmission), means that ticks act not only as vectors but also as reservoirs of the pathogens they transmit.

1991, Toutoungi, L. N., Gern, Lise, Aeschlimann, André, Debrot, S.

Une étude faunistique a été entreprise en Suisse sur trois espèces de tiques pholéophiles, parasites des carnivores sauvages. Il s'agit de Ph. hexagonus, Ph. canisuga, Ph. rugicollis.
Nous avons concentré nos recherches sur la repartition géographique, les hôtes et la nature de l'infestation.
Le matériel provient de la collection AESCHLIMANN et DEBROT du Musée Zoologique de Lausanne, ainsi que des tiques prélevées récemment sur des carnivores par le Centre de la rage à Berne.
La répartition de Ph. hexagonus recouvre la Suisse entière, au Nord comme au Sud des Alpes. On l'observe en altitude jusqu'à 1 380 m. Cette tique a été récoltée sur 15 espèces animales. Elle parasite surtout les renards et tous les Mustélidés, mais elle a également été souvent observée sur des animaux domestiques tels que le chat et le chien.
Ph. canisuga apparaît fréquemment sur le Plateau Suisse et dans le Jura. Cette espèce parasite essentiellement le renard et le blaireau.
L'existence en Suisse de Ph. rugicollis, espèce apparemment rare, est démontrée sur 2 fouines et un chat.
58 % des renards examinés et 87 % des Mustélidés sont infestés par une seule espèce de tique. Par contre 42 % de ces renards présentent des infestations mixtes avec plusieurs espèces de tiques, dans 18% des cas il s'agit de Ph. hexagonus et I. Ricinus., A study concerning 3 tick species ectoparasitic on camivora : Pholeoixodes hexagonus. Ph. canisuga and Ph. rugicollis was conducted in Switzerland.
Our research focused on the geographical distribution of these ticks and their hosts. The material was supplied from AESCHLIMANN'S collection deposited in the Zoological Museum in Lausanne and from the Rabies Center in Bern.
Ph. hexagonus is spread all over the country up to 1 380 m. It was collected from 15 animal species, especially from foxes and Mustelidae. Domestic animals like dogs and cats were also found infested.
Ph. canisuga is widespread on the Swiss Plateau and in the Jura up to 900 m. It was mainly collected from foxes and badgers.
Ph. Rugicollis seems to be rare in Switzerland where it was recorded only three times, twice on a stone marten and once on a cat.
A monospecific infestation was observed in respectively 58 % and 87 % of the infested foxes and Mustelidae. Ph. hexagonus and I. ricinus were found simulta- neously on the same host on 18 % of the foxes.

1993, Cordas, T., Aeschlimann, André, Morel, P. C.

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.

1992, Gern, Lise, Burgdorfer, Willy, Aeschlimann, André, Krampitz, H. E.

1991, Gern, Lise, Toutoungi, L. N., Hu, Chang Min, Aeschlimann, André

Borrelia burgdorferi Johnson et al. was first isolated from the midgut of Ixodes dammini Spielman et al. in the U.S.A. and from the midgut of Lricinus (L.) in Europe. I.ricinus was considered to be the only tick vector of this borrelia, in Europe, until I.hexagonus Leach, the hedgehog tick, was found to harbour spirochaetes. This paper reports an evaluation of the vector competence of I. hexagonus for the spirochaete B. burgdorferi. Transovarial and trans-stadial survival were demonstrated and the spirochaete was transmitted to laboratory mice via the bites of trans-stadially infected I.hexagonus females.

1993, Toutoungi, L. N., Gern, Lise, Aeschlimann, André

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.

1991, Liz, Jorge S., Aeschlimann, André, Pfister, Kurt

1991, Zhu, Z., Gern, Lise, Aeschlimann, André

A peritrophic membrane was found in all three stages of Ixodes ricinus at no later than 18 h after their placement on rabbits. It was found to remain intact until at least 11, 30 and 10 days after repletion in larvae, nymphs and females, respectively. In blood-feeding I. ricinus, the peritrophic membrane is an uneven single layer with a thickness of about 0.03–0.48 μm in larvae, 0.03–0.79 μm in nymphs and 0.04–0.93 μm in females. It covers the whole surface of the midgut epithelium at a distance of about 0.2–0.8 μm. After repletion, the peritrophic membrane becomes thicker and thicker and more and more winding and simultaneously becomes multi-layered mainly in its arched parts. The distance between the peritrophic membrane and the midgut epithelium increases considerably and in the arched parts can reach as much as about 13 and 16 μm in metamorphosing larvae and nymphs, respectively and 25 μm in ovipositing females.