Bartonella spp. are facultative intracellular vector-borne bacteria associated with several emerging diseases in humans and animals all over the world. The potential for involvement of ticks in transmission of Bartonella spp. has been heartily debated for many years. However, most of the data supporting bartonellae transmission by ticks come from molecular and serological epidemiological surveys in humans and animals providing only indirect evidences without a direct proof of tick vector competence for transmission of bartonellae. We used a murine model to assess the vector competence of Ixodes ricinus for Bartonella birtlesii. Larval and nymphal I. ricinus were fed on a B. birtlesii-infected mouse. The nymphs successfully transmitted B. birtlesii to naïve mice as bacteria were recovered from both the mouse blood and liver at seven and 16 days after tick bites. The female adults successfully emitted the bacteria into uninfected blood after three or more days of tick attachment, when fed via membrane feeding system. Histochemical staining showed the presence of bacteria in salivary glands and muscle tissues of partially engorged adult ticks, which had molted from the infected nymphs. These results confirm the vector competence of I. ricinus for B. birtlesii and represent the first in vivo demonstration of a Bartonella sp. transmission by ticks. Consequently, bartonelloses should be now included in the differential diagnosis for patients exposed to tick bites.

The role of Ixodes ricinus ticks in the transmission of pathogens of public health importance such as Borrelia burgdorferi s.l. is widely recognized and is suspected in several emerging vector-borne pathogens in Europe. Here, we assess prevalence rates of several endemic and emerging zoonotic pathogens in tick populations in an area of high human population density in France, to contribute to a risk assessment for potential transmission to humans. Pathogen prevalence rates were evaluated by polymerase chain reaction detection and sequencing in questing ticks, individually for adults and in pools of 10 for nymphs. In addition to finding micro-organisms corresponding to symbionts, we found high prevalence rates of B. burgdorferi s.l. (32% of adult females and 10% of nymphs) and low to moderate ones of Anaplasma phagocytophilum (~1%), spotted fever group Rickettsia spp. (~6%), Babesia sp. EU1 (~1%), Bartonella birtlesii (0.1%), and Francisella tularensis (!1%). Our findings extend the knowledge of the geographical distribution of these endemic and emergent pathogens and support the conclusion that ticks are important vectors of pathogenic micro-organisms in suburban forests. Moreover, tick coinfection with multiple pathogens was found to occur frequently, which poses a serious challenge for diagnosis and appropriate treatment. The incrimination of these pathogens in potentially severe pathologies requires widespread surveillance to assess the risk of infection, thereby facilitating diagnosis and treatment, as well as raising local awareness of tick-borne diseases.

Pollen traps are used by beekeepers to collect pollen harvested by honeybees. Here, we set up an experiment to evaluate whether pollen traps are a risk factor involved in the development of the chronic bee paralysis, a viral honeybee disease affecting adult bees and transmitted by contact. After a recent episode of chronic bee paralysis in an apiary, pollen traps were installed on three hives while two hives without pollen traps were used as control. During the experiment, the chronic bee paralysis virus (CBPV) loads in foragers from the control hives remained lower than 10 8 equivalent copies of CBPV genome per bee but were higher than 10 10 equivalent copies of CBPV genome per bee in the many symptomatic bees and in the hundreds of dead bees found in front of trap hives. Clinical signs of the disease persisted for 3 weeks at the entrance of the trap hives. These signs disappeared after the pollen traps were removed, accompanied by a decrease in the viral loads in foragers. Despite the small number of colonies examined, the results of this study suggest the impact of pollen traps on the relapse of chronic paralysis outbreaks in colonies infected by CBPV.