Web of Parasite Interactions: We live under constant assault from a variety of pathogens. Pathogen exposure will be more or less harmful depending on host factors, including immune status, and, as Telfer et al. (p. 243 ; see the Perspective by Lafferty ) point out, the presence of co-infecting pathogens. In a time-series study of wild voles and four pathogens, co-infection had a larger effect on disease than any other factor. For example, infection with cowpox virus increased susceptibility and prolonged bacterial co-infections. Conversely, an ongoing infection with the bacterium Anaplasma reduced the rodents' susceptibility to the protozoan Babesia . In turn, chronic infection with Babesia limited susceptibility to the bacterium Bartonella .

Ticks are obligate haematophagous acarines that parasitise every class of vertebrate (including man) and have a worldwide distribution. An increasing awareness of tick-borne diseases among clinicians and scientific researchers has led to the recent description of a number of emerging tick-borne bacterial diseases. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 11 tick-borne human bacterial pathogens have been described in Europe. Aetiological diagnosis of tick-transmitted diseases is often difficult and relies on specialised laboratories using very specific tools. Interpretation of laboratory data is very important in order to establish the diagnosis. These guidelines aim to help clinicians and microbiologists in diagnosing infection transmitted by tick bites and to provide the scientific and medical community with a better understanding of these infectious diseases.

Veterinary Research, a journal on Animal Infection

Polypbasic methods were used to examine the taxonomic positions of three newly identified Grahamella species. A comparison of the 16S rRNA gene sequences of these organisms with the sequences available for other bacteria revealed that these three species form a tight monophyletic cluster with members of the genus Bartonella. This cluster is only remotely related to other members of the order Rickettsiales. Determinations of the levels of DNA relatedness between Grahamella species and Bartonella species (by using a modified hydroxatite method) revealed that all of the species belonging to these two genera are distinct but closely related. On the basis of these data and the results of guanine-plus-cytosine content and phenotypic characterization studies, we propose that the genera Grahamella and Bartonella should be unified and that the latter name should be retained. Bartonella talpae and Bartonella peromysci, new combinations for former Grahamella species, are created, and the following three new Bartonella species are described: Bartonella grahamii, Bartonella taylorii, and Bartonella doshiae. A taxonomic analysis of Grahamella species complete the study of all members of the family Bartonellaceae, and the results of this study support the proposal that the family should be transferred out of the order Rickettsiales.