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Université de Neuchâtel

Evolution of a local population of a multiple-strain pathogen in its vector

Durand, Jonas ; Voordouw, Maarten (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2016.

Mixed-strain infections are the rule rather than the exception in most infectious diseases, and have important implication for the ecology and evolution of pathogens. The presence of multiple strains results in competitive interactions that can have a strong impact on the population structure of the pathogen. In vector-borne diseases, most of the research on competition between pathogen strains...

Université de Neuchâtel

Effects of acquired immunity on co-feeding and systemic transmission of the Lyme disease bacterium, "Borrelia afzelii"

Jacquet, Maxime ; Voordouw, Maarten (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2015.

Lyme borreliosis is a tick-borne zoonotic disease and the causative spirochete bacteria are predominantly found in wildlife reservoirs such as rodents and ground-dwelling birds. Borrelia afzelii is one of the most common Lyme borreliosis pathogens in Europe, and is transmitted by the sheep tick Ixodes ricinus. During the tick blood meal, the pathogen can infect the host. The...

Université de Neuchâtel

Rickettsia-like microorganisms in the ovarian primordial of molting Ixodes ricinus (acari : ixodidae) larvae and nymphs

Zhu, Z ; Aeschlimann, André ; Gern, Lise

In: Annales de parasitologie humaine et comparée, 1992, vol. 67, no. 4, p. 99-110

A large number of coccoid, or oval to spindle-shaped rickettsialike microorganisms are detected intracellularly within the primordial ovaries of all examined molting larvae and nymphs, descendants of a female Ixodes ricinus collected in a forest near Neuchâtel, Switzerland, and within all molting nymphal I. ricinus captured as starved ticks in the same area. The morphology of the...

Université de Neuchâtel

Infection of field-collected Ixodes ricinus (Acari: Ixodidae) larvae with Borrelia burgdorferi in Switzerland

Zhioua, Elyes ; Aeschlimann, André ; Gern, Lise

In: Journal of Medical Entomology, 1994, vol. 31, no. 5, p. 763-766

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....

Université de Neuchâtel

Do the level of energy reserves, hydration status and Borrelia infection influence walking by Ixodes ricinus (Acari: Ixodidae) ticks?

Herrmann, Coralie ; Gern, Lise

In: Parasitology, 2011, vol. 139, no. 3, p. 330-337

Ixodes ricinus horizontal movement within a humidity gradient and the influence of infection by Borrelia burgdorferi sensu lato (s.l.) on tick walking were investigated. Nymphs were placed within an arena containing a humidity gradient ranging from 45 to 95% relative humidity (RH). After 1 h of acclimation at 70% RHticks were released so that they could either stay, or walk...

Université de Neuchâtel

A standardised in vivo and in vitro test method for evaluating tick repellents

Kröber, Thomas ; Bourquin, Florence ; Guerin, Patrick M.

In: Pesticide Biochemistry and Physiology, 2013, vol. 107, no. 2, p. 160-168

The threat of transmission of Lyme borelliosis and tick-borne encephalitis by ixodid ticks has resulted in an increasing number of tick repellents coming onto the market. To allow proper evaluation of the efficacy of different types of compounds and their formulations, there is a need for standardised methods for testing ticks repellents. Ticks show a marked negative geotactic response following...

Université de Neuchâtel

Ixodid ticks avoid contact with liquid water

Kröber, Thomas ; Guerin, Patrick M.

In: The Journal of Experimental Biology, 1999, vol. 202, no. 14, p. 1887-1883

Larvae of the cattle tick Boophilus microplus and all life stages of the European sheep tick Ixodes ricinus avoid walking on a wet membrane surface surrounding a dry patch. Of 170 reactions made at a border with liquid water by 22 B. microplus larvae, 40% consisted of immediate turns to the opposite side to bring all the legs back onto a dry patch, 41% were walks along the border, during which...

Université de Neuchâtel

Biology of 'Borrelia burgdorferi'-infected and non-infected 'Ixodes ricinus' ticks in the context of climate change

Herrmann, Coralie ; Gern, Lise (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2013.

Ixodes ricinus is known to display little resistance to desiccation. This tick is particularly exposed to desiccating conditions while questing for a host on the vegetation. Therefore, survival under hot and dry conditions in field-collected I. ricinus nymphs and adults was studied by exposing ticks to desiccating conditions created in the laboratory using saturated salt solutions...

Université de Neuchâtel

Dynamique de transmission de 'Borrelia afzelii' par 'Ixodes ricinus' : comparaisons entre groupes ospC

Tonetti, Nicolas ; Gern, Lise (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2012.

Borrelia burgdorferi sensu lato (sl) outer surface protein C (OspC) is involved in numerous crucial mechanisms during the life cycle of the pathogen, influencing its dissemination in the vector and in the host. The genetic diversity at the ospC locus has led to a classification into groups of alleles. While there is a linkage between invasiveness in human and the different...

Université de Neuchâtel

Agents pathogènes d'importance médicale et vétérinaire chez 'Ixodes ricinus' en Suisse : infections et co-infections chez les tiques en quête et les tiques d'oiseaux

Lommano, Elena ; Gern, Lise (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2012.

In temperate regions of the northern hemisphere, ticks are considered as the primary vector of infectious agents of human and medical relevance. Among them, Ixodes ricinus is the most abundant in Europe. This tick species transmits to humans and animals many microorganisms that may cause zoonoses, including bacteria, viruses and protozoa like, for example, Borrelia spp.,...