Gern, Lise

2007, Humair, Pierre-François, Douet, Véronique, Cadenas, Francisca Moran, Schouls, Leo M, Van de Pol, Ingrid, Gern, Lise

We developed an efficient molecular method for the identification of the bloodmeal sources in the tick Ixodes ricinus (L.), the European vector of the agents of Lyme borreliosis and tick-borne encephalitis. A approximate to 145-bp orthologous fragment of the vertebrate mitochondrial 12S rDNA was used as a molecular marker to discriminate host vertebrate species. The method consists of a single run polymerase chain reaction amplification of the 12S rDNA molecular marker by using nondegenerate primers followed by a reverse line blot hybridization assay by using specific oligonucleotide probes. The palette of probes allowed us to distinguish major groups of host vertebrates (e.g., mammals, small rodents, artiodactyls, birds, lizards) and to identify the bloodmeal sources at the genus or species level. External primers were designed and used to sequence the 12S rDNA molecular marker of a broad range of known or potential host vertebrate species (n = 60), including mammal (n = 28), bird (n = 31), and reptile (n = 1) species. The use of this technique coupled with known methods for identification of tick-borne pathogens (e.g., Borrelia burgdorferi sensu lato) allowed us to determine the source of infective bloodmeal and to identify reservoir species. The present method was successfully used to identify the source of bloodmeals in all feeding I. ricinus ticks and in half of questing field-collected L ricinus ticks. Moreover, the bloodmeal source was identified in 65% of ticks infected with B. burgdorferi sensu lato. Further development of this technique may be envisaged for the detection of other vector-borne patbogens and their reservoir hosts.

1998, Humair, Pierre-François, Gern, Lise

The infection and reservoir status of red squirrels (Sciurus vulgaris) for Borrelia burgdorferi sensu late were studied in Switzerland. B. burgdorferi sensu late was isolated from 15 skin samples from 4/6 dead red squirrels, victims of road traffic. Isolates were identified using restriction fragment length polymorphism (RFLP): B. burgdorferi sensu stricto was present in 14 culture tubes containing skin samples and B. afzelii in two other tubes. A mixed infection was revealed in one case. A total of 227 ticks attached to squirrels were cultivated in BSKII medium and 90 isolates were obtained. Genotypic identification by RFLP showed that B. afzelii (59%) and B. burgdorferi sensu stricto (46%) dominated in ticks feeding on red squirrels. Data collected from one particular animal, highly infested with Ixodes ricinus and harbouring numerous Borrelia-infected Ixodes ricinus ticks, showed that transmission of B. burgdorferi sensu late occurred from S. vulgaris to feeding ticks. More precisely, B. burgdorferi sensu stricto and B. afzelii were mainly transmitted from S. vulgaris to ticks. The present data emphasized the results obtained previously from small rodents and birds in Japan and in Switzerland, showing the occurrence of specific associations between host species and Borrelia genospecies. (C) 1998 Elsevier Science B.V. All rights reserved.