Infection Kinetics and Tropism of Borrelia burgdorferi sensu lato in Mouse After Natural (via Ticks) or Artificial (Needle) Infection Depends on the Bacterial Strain.

Borrelia burgdorferi sl is a complex of pathogen bacteria transmitted to the host by Ixodes ticks. European Ixodes ricinus ticks transmit different B. burgdorferi species, pathogenic to human. Bacteria are principally present in unfed tick midgut, then migrate to salivary glands during blood meal and infect a new host via saliva. In this study, efficiency of transmission in a mouse model of three pathogen species belonging to the B. burgdorferi sl complex, B. burgdorferi sensu stricto (B31, N40, and BRE-13), B. afzelii (IBS-5), and B. bavariensis (PBi) is examined in order to evaluate infection risk after tick bite. We compared the dissemination of the Borrelia species in mice after tick bite and needle injection. Location in the ticks and transmission to mice were also determined for the three species by following infection kinetics. After inoculation, we found a significant prevalence in the brain for PBi and BRE-13, in the heart, for PBi, in the skin where B31 was more prevalent than PBi and in the ankle where both B31 and N40 were more present than PBi. After tick bite, statistical analyses showed that BRE-13 was more prevalent than N40 in the brain, in the bladder and in the inguinal lymph node. When Borrelia dissemination was compared after inoculation and tick bite, we observed heart infection only after tick inoculation of BRE-13, and PBi was only detected after tick bite in the skin. For N40, a higher number of positive organs was found after inoculation compared to tick bite. All European B. burgdorferi sl strains studied were detected in female salivary glands before blood meal and infected mice within 24 h of tick bite. Moreover, Borrelia-infected nymphs were able to infect mice as early as 12 h of tick attachment. Our study shows the need to remove ticks as early as possible after attachment. Moreover, Borrelia tropism varied according to the strain as well as between ticks bite and needle inoculation, confirming the association between some strains and clinical manifestation of Lyme borreliosis, as well as the role played by tick saliva in the efficiency of Borrelia infection and dissemination in vertebrates.

Dominance in a ground-dwelling ant community of banana agroecosystem.

In tropical ecosystems, ants represent a substantial portion of the animal biomass and contribute to various ecosystem services, including pest regulation and pollination. Dominant ant species are known to determine the structure of ant communities by interfering in the foraging of other ant species. Using bait and pitfall trapping experiments, we performed a pattern analysis at a fine spatial scale of an ant community in a very simplified and homogeneous agroecosystem, that is, a single-crop banana field in Martinique (French West Indies). We found that the community structure was driven by three dominant species (Solenopsis geminata, Nylanderia guatemalensis, and Monomorium ebeninum) and two subdominant species (Pheidole fallax and Brachymyrmex patagonicus). Our results showed that dominant and subdominant species generally maintained numerical dominance at baits across time, although S. geminata, M. ebeninum, and B. patagonicus displayed better abilities to maintain dominance than P. fallax and N. guatemalensis. Almost all interspecific correlations between species abundances, except those between B. patagonicus and N. guatemalensis, were symmetrically negative, suggesting that interference competition prevails in this ground-dwelling ant community. However, we observed variations in the diurnal and nocturnal foraging activity and in the daily occurrence at baits, which may mitigate the effect of interference competition through the induction of spatial and temporal niche partitioning. This may explain the coexistence of dominant, subdominant, and subordinate species in this very simplified agroecosystem, limited in habitat structure and diversity.

Differential expression of Ixodes ricinus salivary gland proteins in the presence of the Borrelia burgdorferi sensu lato complex.

In Europe, Ixodes ricinus is the main vector of Lyme borreliosis. Their salivary glands play a critical role in the biological success of ticks. To better understand the cross-talk between Borrelia burgdorferi and tick salivary glands, we analyzed protein expression in the salivary glands of I. ricinus adult ticks that were infected by various strains of the B. burgdorferi sl complex. iTRAQ allowed the identification of more than 120 proteins, providing the first proteomic data pertaining to I. ricinus salivary glands. Among these proteins, only 12 were modulated in the presence of various Borrelia strains. Most of them are up-regulated and are involved in cell defense and protein synthesis and processing. Down-regulated proteins are mostly implicated in the cytoskeleton. The DIGE analysis allowed us to identify 35 proteins and showed the down-regulation of 4 proteins. All 15 proteins were not modulated by all strains. Overall, these observations showed that the presence of Borrelia in tick salivary glands is a factor of stress for the protein machinery, and also that some Borrelia strains produce a dysregulation of cytoskeletal proteins. Interestingly, a protein from Borrelia, OspA, was found in infected salivary glands. The consequence of its presence in salivary glands is discussed. BIOLOGICAL SIGNIFICANCE: Lyme borreliosis is still the most prevalent arthropod-borne disease in the temperate regions of the northern hemisphere. The geographical distribution of Lyme borreliosis is expanding, especially towards higher altitudes and latitudes. Human pathogenic spirochetes causing Lyme borreliosis belong to the B. burgdorferi sensu lato complex. They are extracellular pathogens transmitted to humans through the bite of Ixodes spp. ticks. The bioactive molecules present in tick saliva not only promote tick feeding, but also create an advantageous microenvironment at the tick bite site for survival and replication of Borrelia bacteria. Investigation of the tick-host-pathogen interface would provide new strategies to control tick-borne infections. We chose to analyze the interaction of several strains of the B. burgdorferi sensu lato complex with I. ricinus salivary glands. We also investigated the presence of bacterial proteins in salivary glands. For these purposes, we undertook a proteomic study implying the complementary approaches of iTRAQ and DIGE. Our study allowed identifying several salivary markers of infection that were shown to vary according to the strain. Moreover, OspA, a bacterial protein was shown to be expressed in salivary glands and may be implied in the pathogenicity of some Borrelia strains.

Strategies of exploitation of mammalian reservoirs by Bartonella species.

Numerous mammal species, including domestic and wild animals such as ruminants, dogs, cats and rodents, as well as humans, serve as reservoir hosts for various Bartonella species. Some of those species that exploit non-human mammals as reservoir hosts have zoonotic potential. Our understanding of interactions between bartonellae and reservoir hosts has been greatly improved by the development of animal models for infection and the use of molecular tools allowing large scale mutagenesis of Bartonella species. By reviewing and combining the results of these and other approaches we can obtain a comprehensive insight into the molecular interactions that underlie the exploitation of reservoir hosts by Bartonella species, particularly the well-studied interactions with vascular endothelial cells and erythrocytes.

Ecological factors characterizing the prevalence of bacterial tick-borne pathogens in Ixodes ricinus ticks in pastures and woodlands.

Ecological changes are recognized as an important driver behind the emergence of infectious diseases. The prevalence of infection in ticks depends upon ecological factors that are rarely taken into account simultaneously. Our objective was to investigate the influences of forest fragmentation, vegetation, adult tick hosts, and habitat on the infection prevalence of three tick-borne bacteria, Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Rickettsia sp. of the spotted fever group, in questing Ixodes ricinus ticks, taking into account tick characteristics. Samples of questing nymphs and adults were taken from 61 pastures and neighboring woodlands in central France. The ticks were tested by PCR of pools of nymphs and individual adults. The individual infection prevalence was modeled using multivariate regression. The highest infection prevalences were found in adult females collected in woodland sites for B. burgdorferi sensu lato and A. phagocytophilum (16.1% and 10.7%, respectively) and in pasture sites for Rickettsia sp. (8.7%). The infection prevalence in nymphs was lower than 6%. B. burgdorferi sensu lato was more prevalent in woodlands than in pastures. Forest fragmentation favored B. burgdorferi sensu lato and A. phagocytophilum prevalence in woodlands, and in pastures, the B. burgdorferi sensu lato prevalence was favored by shrubby vegetation. Both results are probably because large amounts of edges or shrubs increase the abundance of small vertebrates as reservoir hosts. The Rickettsia sp. prevalence was maximal on pasture with medium forest fragmentation. Female ticks were more infected by B. burgdorferi sensu lato than males and nymphs in woodland sites, which suggests an interaction between the ticks and the bacteria. This study confirms the complexity of the tick-borne pathogen ecology. The findings support the importance of small vertebrates as reservoir hosts and make a case for further studies in Europe on the link between the composition of the reservoir host community and the infection prevalence in ticks.

Prevalence of five pathogenic agents in questing Ixodes ricinus ticks from western France.

In Europe, Ixodes ricinus ticks are vectors of many emerging pathogens, including Borrelia burgdorferi sensu lato (sl), Anaplasma phagocytophilum, spotted fever group Rickettsia sp., Babesia sp., and very likely Bartonella sp. In this study, we looked for the presence of DNA of these microorganisms in 572 ticks from two forests in the west of France. DNA extraction and polymerase chain reaction (PCR) amplification were performed on individual nymphal, male, and female I. ricinus ticks. Amplification from 1 tick among the 572 samples (0.2%) resulted in PCR products with Bartonella-specific primers. Sequence analysis of the amplified fragment did not lead to species identification. Two ticks (0.3%) carried A. phagocytophilum-specific DNA. Eight ticks (1.4%) were positive with spotted fever group Rickettsia-specific primers, and all PCR fragments were related to Rickettsia helvetica. Thirty-five ticks (6.1%) were positive with B. burgdorferi sl-specific primers; the sequences were all related to Borrelia garinii or Borrelia afzelii, except one that was related to Borrelia carolinensis, a newly described species never reported in Europe so far. Thirty-five ticks (6.1%) carried Babesia sp. DNA. Female adults were more infected by B. burgdorferi sl than male adults. The prevalence of B. burgdorferi sl and Babesia sp. was significantly different between the two forests, with a higher prevalence of B. burgdorferi sl in ticks from the forest of Princé and a higher prevalence of Babesia sp. in ticks from the forest of Gâvre. To our knowledge, this is the first study that has detected all five pathogens in questing I. ricinus in the west of France and the first report of B. carolinensis DNA in ticks in Europe.

Insights in Bartonella host specificity.

The genus Bartonella comprises a unique group of emerging gram-negative, intracellular bacteria that can cause a long-lasting intraerythrocytic bacteremia in their reservoir hosts. In recent years, the widespread occurrence and diversity of these bacteria has been increasingly recognized. This has resulted in a dramatic expansion of the genus Bartonella to 24 currently described species or subspecies, among which at least half have been associated with human disease. Bartonella infections have been observed in virtually all species examined, extending from humans to carnivores, ungulates, rodents, lagomorphs, insectivores, and bats. Adaptation by Bartonellae to such a diverse range of mammals has resulted in host specificity, and all validated Bartonella species described to date are capable of parasitizing only a limited number of animal species. In this review, the possible mechanisms explaining the specificity of each Bartonella species for its reservoir host are discussed.

Transmission of Bartonella henselae by Ixodes ricinus.

Bartonella spp. are facultative intracellular bacteria associated with several emerging diseases in humans and animals. B. henselae causes cat-scratch disease and is increasingly associated with several other syndromes, particularly ocular infections and endocarditis. Cats are the main reservoir for B. henselae and the bacteria are transmitted to cats by cat fleas. However, new potential vectors are suspected of transmitting B. henselae, in particular, Ixodes ricinus, the most abundant ixodid tick that bites humans in western Europe. We used a membrane-feeding technique to infect I. ricinus with B. henselae and demonstrate transmission of B. henselae within I. ricinus across developmental stages, migration or multiplication of B. henselae in salivary glands after a second meal, and transmission of viable and infective B. henselae from ticks to blood. These results provide evidence that I. ricinus is a competent vector for B. henselae.

Prevalence of Anaplasma phagocytophilum, Rickettsia sp. and Borrelia burgdorferi sensu lato DNA in questing Ixodes ricinus ticks from France.

A total of 4701 Ixodes ricinus, collected during the summer of 2003, were analyzed for three pathogens. DNA was detected from the three pathogens. Co-detection of more than one pathogen was observed.