Bartonella henselae in Ixodes ricinus ticks removed from dogs

Prospective serological and molecular cross-sectional study focusing on Bartonella and other blood-borne organisms in cats from Catalonia (Spain)

Background

There is limited clinical or epidemiological knowledge regarding Bartonella infection in cats, and no serological studies have compared the presence of antibodies against different Bartonella species. Moreover, there are limited feline Bartonella studies investigating co-infections with other vector-borne pathogens and the associated risk factors. Therefore, the objective of this study was to investigate Bartonella spp. infections and co-infections with other pathogens in cats from Barcelona (Spain) based on serological and/or molecular techniques and to determine associated risk factors.

Methods

We studied colony and owned cats (n = 135). Sera were tested for Bartonella henselae-, Bartonella quintana-, and Bartonella koehlerae-specific antibodies using endpoint in-house immunofluorescence antibody assays. Bartonella real-time PCR (qPCR) and conventional PCR (cPCR) were performed. In addition, cPCR followed by DNA sequencing was performed for other pathogenic organisms (Anaplasma, Babesia, Cytauxzoon, Ehrlichia, Hepatozoon, hemotropic Mycoplasma, and Theileria spp.).

Results

From 135 cats studied, 80.7% were seroreactive against at least one Bartonella species. Bartonella quintana, B. koehlerae, and B. henselae seroreactivity was 67.4, 77.0, and 80.7%, respectively. Substantial to almost perfect serological agreement was found between the three Bartonella species. Colony cats were more likely to be Bartonella spp.-seroreactive than owned cats. Moreover, cats aged ≤ 2 years were more likely to be Bartonella spp.-seroreactive. Bartonella spp. DNA was detected in the blood of 11.9% (n = 16) of cats. Cats were infected with B. henselae (n = 12), B. clarridgeiae (n = 3), and B. koehlerae (n = 1). Mycoplasma spp. DNA was amplified from 14% (n = 19) of cat blood specimens. Cats were infected with Mycoplasma haemofelis (n = 8), Candidatus M. haemominutum (n = 6), Candidatus Mycoplasma turicensis (n = 4), and Mycoplasma wenyonii (n = 1). Anaplasma, Babesia, Cytauxzoon, Ehrlichia spp., Hepatozoon, and Theileria spp. DNA was not amplified from any blood sample. Of the 16 Bartonella spp.-infected cats based on PCR results, six (37%) were co-infected with Mycoplasma spp.

Conclusions

Bartonella spp. and hemoplasma infections are prevalent in cats from the Barcelona area, whereas infection with Anaplasma spp., Babesia, Cytauxzoon, Ehrlichia spp., Hepatozoon, and Theileria infections were not detected. Co-infection with hemotropic Mycoplasma appears to be common in Bartonella-infected cats. To our knowledge, this study is the first to document M. wenyonii is infection in cats.

Graphical Abstract

Laboratory Methods for Detection of Infectious Agents and Serological Response in Humans With Tick-Borne Infections: A Systematic Review of Evaluations Based on Clinical Patient Samples

Background: For the most important and well-known infections spread by Ixodes ticks, Lyme borreliosis (LB) and tick-borne encephalitis (TBE), there are recommendations for diagnosis and management available from several health authorities and professional medical networks. However, other tick-borne microorganisms with potential to cause human disease are less known and clear recommendations on diagnosis and management are scarce. Therefore, we performed a systematic review of published studies and reviews focusing on evaluation of laboratory methods for clinical diagnosis of human tick-borne diseases (TBDs), other than acute LB and TBE. The specific aim was to evaluate the scientific support for laboratory diagnosis of human granulocytic anaplasmosis, rickettsiosis, neoehrlichiosis, babesiosis, hard tick relapsing fever, tularemia and bartonellosis, as well as tick-borne co-infections and persistent LB in spite of recommended standard antibiotic treatment.

Methods: We performed a systematic literature search in 11 databases for research published from 2007 through 2017, and categorized potentially relevant references according to the predefined infections and study design. An expert group assessed the relevance and eligibility and reviewed the articles according to the QUADAS (diagnostic studies) or AMSTAR (systematic reviews) protocols, respectively. Clinical evaluations of one or several diagnostic tests and systematic reviews were included. Case reports, non-human studies and articles published in other languages than English were excluded.

Results: A total of 48 studies fulfilled the inclusion criteria for evaluation. The majority of these studies were based on small sample sizes. There were no eligible studies for evaluation of tick-borne co-infections or for persistent LB after antibiotic treatment.

Conclusions: Our findings highlight the need for larger evaluations of laboratory tests using clinical samples from well-defined cases taken at different time-points during the course of the diseases. Since the diseases occur at a relatively low frequency, single-center cross-sectional studies are practically not feasible, but multi-center case control studies could be a way forward.

Evaluating Transmission Paths for Three Different Bartonella spp. in Ixodes ricinus Ticks Using Artificial Feeding

Bartonellae are facultative intracellular alpha-proteobacteria often transmitted by arthropods. Ixodes ricinus is the most important vector for arthropod-borne pathogens in Europe. However, its vector competence for Bartonella spp. is still unclear. This study aimed to experimentally compare its vector competence for three Bartonella species: B. henselae, B. grahamii, and B. schoenbuchensis. A total of 1333 ticks (1021 nymphs and 312 adults) were separated into four groups, one for each pathogen and a negative control group. Ticks were fed artificially with bovine blood spiked with the respective Bartonella species. DNA was extracted from selected ticks to verify Bartonella-infection by PCR. DNA of Bartonella spp. was detected in 34% of nymphs and females after feeding. The best engorgement results were obtained by ticks fed with B. henselae-spiked blood (65.3%) and B. schoenbuchensis (61.6%). Significantly more nymphs fed on infected blood (37.3%) molted into adults compared to the control group (11.4%). Bartonella DNA was found in 22% of eggs laid by previously infected females and in 8.6% of adults molted from infected nymphs. The transovarial and transstadial transmission of bartonellae suggest that I. ricinus could be a potential vector for three bacteria.

A review on the occurrence of companion vector-borne diseases in pet animals in Latin America

Companion vector-borne diseases (CVBDs) are an important threat for pet life, but may also have an impact on human health, due to their often zoonotic character. The importance and awareness of CVBDs continuously increased during the last years. However, information on their occurrence is often limited in several parts of the world, which are often especially affected. Latin America (LATAM), a region with large biodiversity, is one of these regions, where information on CVBDs for pet owners, veterinarians, medical doctors and health workers is often obsolete, limited or non-existent. In the present review, a comprehensive literature search for CVBDs in companion animals (dogs and cats) was performed for several countries in Central America (Belize, Caribbean Islands, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Puerto Rico) as well as in South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana (British Guyana), Paraguay, Peru, Suriname, Uruguay, Venezuela) regarding the occurrence of the following parasitic and bacterial diseases: babesiosis, heartworm disease, subcutaneous dirofilariosis, hepatozoonosis, leishmaniosis, trypanosomosis, anaplasmosis, bartonellosis, borreliosis, ehrlichiosis, mycoplasmosis and rickettsiosis. An overview on the specific diseases, followed by a short summary on their occurrence per country is given. Additionally, a tabular listing on positive or non-reported occurrence is presented. None of the countries is completely free from CVBDs. The data presented in the review confirm a wide distribution of the CVBDs in focus in LATAM. This wide occurrence and the fact that most of the CVBDs can have a quite severe clinical outcome and their diagnostic as well as therapeutic options in the region are often difficult to access and to afford, demands a strong call for the prevention of pathogen transmission by the use of ectoparasiticidal and anti-feeding products as well as by performing behavioural changes.

Combination of microbiome analysis and serodiagnostics to assess the risk of pathogen transmission by ticks to humans and animals in central Germany

BACKGROUND

Arthropod-borne diseases remain a major health-threat for humans and animals worldwide. To estimate the distribution of pathogenic agents and especially Bartonella spp., we conducted tick microbiome analysis and determination of the infection status of wild animals, pets and pet owners in the state of Hesse, Germany.

RESULTS

In total, 189 engorged ticks collected from 163 animals were tested. Selected ticks were analyzed by next generation sequencing (NGS) and confirmatory PCRs, blood specimens of 48 wild animals were analyzed by PCR to confirm pathogen presence and sera of 54 dogs, one cat and 11 dog owners were analyzed by serology. Bartonella spp. were detected in 9.5% of all ticks and in the blood of 17 roe deer. Further data reveal the presence of the human and animal pathogenic species of genera in the family Spirochaetaceae (including Borrelia miyamotoi and Borrelia garinii), Bartonella spp. (mainly Bartonella schoenbuchensis), Rickettsia helvetica, Francisella tularensis and Anaplasma phagocytophilum in ticks. Co-infections with species of several genera were detected in nine ticks. One dog and five dog owners were seropositive for anti-Bartonella henselae-antibodies and one dog had antibodies against Rickettsia conorii.

CONCLUSIONS

This study provides a snapshot of pathogens circulating in ticks in central Germany. A broad range of tick-borne pathogens are present in ticks, and especially in wild animals, with possible implications for animal and human health. However, a low incidence of Bartonella spp., especially Bartonella henselae, was detected. The high number of various detected pathogens suggests that ticks might serve as an excellent sentinel to detect and monitor zoonotic human pathogens.

Bartonella infections in cats and dogs including zoonotic aspects

Bartonellosis is a vector-borne zoonotic disease with worldwide distribution that can infect humans and a large number of mammals including small companion animals (cats and dogs). In recent years, an increasing number of studies from around the world have reported Bartonella infections, although publications have predominantly focused on the North American perspective. Currently, clinico-pathological data from Europe are more limited, suggesting that bartonellosis may be an infrequent or underdiagnosed infectious disease in cats and dogs. Research is needed to confirm or exclude Bartonella infection as a cause of a spectrum of feline and canine diseases. Bartonella spp. can cause acute or chronic infections in cats, dogs and humans. On a comparative medical basis, different clinical manifestations, such as periods of intermittent fever, granulomatous inflammation involving the heart, liver, lymph nodes and other tissues, endocarditis, bacillary angiomatosis, peliosis hepatis, uveitis and vasoproliferative tumors have been reported in cats, dogs and humans. The purpose of this review is to provide an update and European perspective on Bartonella infections in cats and dogs, including clinical, diagnostic, epidemiological, pathological, treatment and zoonotic aspects.

Bartonella, Rodents, Fleas and Ticks: a Molecular Field Study on Host-Vector-Pathogen Associations in Saxony, Eastern Germany

Bartonellae cause zoonotic diseases and are transmitted by arthropods. Rodents are reservoirs for most Bartonella spp. As the knowledge about Bartonella in rodents and their parasitizing ectoparasites is scarce in Germany, this study's objectives were to investigate Bartonella spp. in small mammals and in their ectoparasites. A total of 79 small mammals (seven species) were captured and their ectoparasites collected at seven sites around Leipzig, Saxony, Germany, in 2010 and 2011. Altogether, 79 spleen samples, 135 fleas (five species) and 365 ticks (three species) were investigated for Bartonella spp. by PCR targeting the ITS 16S-23S rRNA region. In total, 52 (65.8 %) small mammals, 73 (54.1 %) fleas and 51 (16.3 %) ticks were positive for Bartonella spp. Most small mammals were positive for uncultured Bartonella sp. (n = 29) followed by Bartonella grahamii (n = 12), Bartonella taylorii (n = 8) and Bartonella sp. N40 (n = 3). Likewise, most fleas were positive for uncultured Bartonella sp. (n = 45) followed by B. grahamii (n = 14), B. taylorii (n = 8), B. sp. N40 (n = 5) and Bartonella elizabethae (n = 2). Most ticks were positive for B. sp. (n = 19) followed by B. grahamii (n = 10), Bartonella chomelii (n = 3), B. taylorii (n = 2) and B. sp. N40 (n = 1). This study's results suggest that rodents and fleas may be reservoirs and vectors, respectively. Zoonotic B. grahamii and B. elizabethae were found in rodents and their fleas. Therefore, humans may contract Bartonella infection by contact to wild rodents. Ticks seem of minor importance in transmitting Bartonella spp. found in fleas and rodents. However, ticks might be vectors of B. chomelii.

Study on coinfecting vector-borne pathogens in dogs and ticks in Rio Grande do Norte, Brazil

Since dogs presenting several vector borne diseases can show none or nonspecific clinical signs depending on the phase of infection, the assessment of the particular agents involved is mandatory. The present study aimed to investigate the presence of Babesia spp., Ehrlichia spp., Anaplasma spp., Hepatozoon spp. and Leishmania spp. in blood samples and ticks, collected from two dogs from Rio Grande do Norte showing suggestive tick-borne disease by using molecular techniques. DNA of E. canis, H. canis and L. infantum were detected in blood samples and R. sanguineus ticks collected from dogs. Among all samples analyzed, two showed the presence of multiple infections with E. canis, H. canis and L. infantum chagasi. Here we highlighted the need for molecular differential diagnosis in dogs showing nonspecific clinical signs.

Bartonella spp. - a chance to establish One Health concepts in veterinary and human medicine

Infectious diseases remain a remarkable health threat for humans and animals. In the past, the epidemiology, etiology and pathology of infectious agents affecting humans and animals have mostly been investigated in separate studies. However, it is evident, that combined approaches are needed to understand geographical distribution, transmission and infection biology of “zoonotic agents”. The genus Bartonella represents a congenial example of the synergistic benefits that can arise from such combined approaches: Bartonella spp. infect a broad variety of animals, are linked with a constantly increasing number of human diseases and are transmitted via arthropod vectors. As a result, the genus Bartonella is predestined to play a pivotal role in establishing a One Health concept combining veterinary and human medicine.

Tick-borne bacterial pathogens in southwestern Finland

Background

Ixodes ricinus and Ixodes persulcatus are the main vectors of Lyme borreliosis spirochetes and several other zoonotic bacteria in northern Europe and Russia. However, few studies screening bacterial pathogens in Finnish ticks have been conducted. Therefore, reports on the occurrence and prevalence of several bacterial pathogens detected from ticks elsewhere in Europe and Russia are altogether missing from Finland. The main aim of the current study was to produce novel data on the occurrence and prevalence of several tick-borne bacterial pathogens in ticks collected from southwestern Finland.

Methods

Ticks were collected in 2013–2014 by blanket dragging from 25 localities around southwestern Finland, and additionally from a dog in Lempäälä. Collected ticks were molecularly identified and screened for Borrelia burgdorferi s.l., Borrelia miyamotoi, Rickettsia, Bartonella and Candidatus Neoehrlichia mikurensis using quantitative PCR. Furthermore, detected Rickettsia spp. were sequenced using conventional PCR to determine species.

Results

A total of 3169 ticks in 1174 DNA samples were screened for the listed pathogens. The most common bacteria detected was B. burgdorferi (s.l.) (18.5 % nymphal and 23.5 % adult ticks), followed by Rickettsia spp. (1.1 %; 5.1 %) and B. miyamotoi (0.51 %; 1.02 %). B. miyamotoi and Rickettsia spp. were also detected in larval samples (minimum infection rates 0.31 % and 0.21 %, respectively). Detected Rickettsia spp. were identified by sequencing as R. helvetica and R. monacensis. All screened samples were negative for Bartonella spp. and Ca. N. mikurensis.

Conclusions

In the current study we report for the first time the presence of Rickettsia in Finnish ticks. Furthermore, Rickettsia spp. and B. miyamotoi were found from larval tick samples, emphasizing the importance they may have as vectors of these pathogens. Comparisons of tick density estimates and B. burgdorferi (s.l.) prevalence made between the current study and a previous study conducted in 2000 in ten out of the 25 study localities suggest that an increase in tick abundance and B. burgdorferi (s.l.) prevalence has occurred in at least some of the study localities.

Molecular detection of emerging tick-borne pathogens in Vojvodina, Serbia

Ticks play an important role in disease transmission globally due to their capability to serve as vectors for human and animal pathogens. The Republic of Serbia is an endemic area for a large number of tick-borne diseases. However, current knowledge on these diseases in Serbia is limited. The aim of this study was to investigate the presence of new emerging tick-borne pathogens in ticks collected from dogs and the vegetation from different parts of Vojvodina, Serbia. A total of 187 ticks, including 124 Rhipicephalus sanguineus, 45 Ixodes ricinus and 18 Dermacentor reticulatus were collected from dogs. In addition, 26 questing I. ricinus ticks were collected from the vegetation, using the flagging method, from 4 different localities in Vojvodina, Serbia. DNA was extracted from each tick individually and samples were tested by either conventional or real-time PCR assays for the presence of Rickettsia spp.-DNA (gltA and ompA gene fragments), Ehrlichia/Anaplasma spp.-DNA (16S rRNA gene fragment) and Hepatozoon spp./Babesia spp.-DNA (18S rRNA gene fragment). In addition, all I. ricinus DNA samples were tested for Bartonella spp.-DNA (ITS locus) by real-time PCR. In this study, the presence of novel emerging tick-borne pathogens including Rickettsia raoultii, Rickettsia massiliae, Babesia venatorum, Babesia microti, Hepatozoon canis and Candidatus Neoehrlichia mikurensis was identified for the first time in Serbia. Our findings also confirmed the presence of Rickettsia monacensis, Babesia canis and Anaplasma phagocytophilum in ticks from Serbia. The findings of the current study highlight the great diversity of tick-borne pathogens of human and animal importance in Serbia. Physicians, public health workers and veterinarians should increase alertness to the presence of these tick-borne pathogens in this country.

Bartonella henselae in eastern Poland: the relationship between tick infection rates and the serological response of individuals occupationally exposed to tick bites

To explore the potential role of Ixodes ricinus as the presumed vector of Bartonella henselae in eastern Poland, ticks collected in various geographic locations were examined for the presence of B. henselae, and the results were matched against the prevalence of anti-B. henselae antibodies in individuals occupationally exposed to tick bites. The presence of Bartonella DNA was investigated by PCR in a total of 1,603 unfed Ixodes ricinus ticks. The presence of IgG antibodies against B. henselae was investigated in serum samples from 332 people occupationally exposed to tick bites (94 farmers and 238 forestry workers). The total prevalence of B. henselae in ticks was 1.7%; the infection rates in males (3.1%) and females (2.7%) were nearly ten times greater than in nymphs (0.3%). The prevalence of seropositive results in the risk group (30.4%), farmers (27.7%) and forestry workers (31.5%), was significantly greater compared to the control group (8.9%). The results showed a weak positive correlation between the degree of infection of ticks and humans living in the same geographic region. The lack of a direct relationship indicates that exposure to tick bites is only one of the factors contributing to the significant preponderance of a seropositive response to B. henselae in the forestry workers and farmers over the control group. Other factors must be considered, such as contact with cats, which are popular domestic animals in Polish villages, and exposure to cat fleas.

Assessment of persistence of Bartonella henselae in Ctenocephalides felis

Bartonella henselae (Rhizobiales: Bartonellaceae) is a Gram-negative fastidious bacterium of veterinary and zoonotic importance. The cat flea Ctenocephalides felis (Siphonaptera: Pulicidae) is the main recognized vector of B. henselae, and transmission among cats and humans occurs mainly through infected flea feces. The present study documents the use of a quantitative molecular approach to follow the daily kinetics of B. henselae within the cat flea and its excreted feces after exposure to infected blood for 48 h in an artificial membrane system. B. henselae DNA was detected in both fleas and feces for the entire life span of the fleas (i.e., 12 days) starting from 24 h after initiation of the blood meal.

Bartonella henselae bacteremia in a mother and son potentially associated with tick exposure

BACKGROUND

Bartonella henselae is a zoonotic, alpha Proteobacterium, historically associated with cat scratch disease (CSD), but more recently associated with persistent bacteremia, fever of unknown origin, arthritic and neurological disorders, and bacillary angiomatosis, and peliosis hepatis in immunocompromised patients. A family from the Netherlands contacted our laboratory requesting to be included in a research study (NCSU-IRB#1960), designed to characterize Bartonella spp. bacteremia in people with extensive arthropod or animal exposure. All four family members had been exposed to tick bites in Zeeland, southwestern Netherlands. The mother and son were exhibiting symptoms including fatigue, headaches, memory loss, disorientation, peripheral neuropathic pain, striae (son only), and loss of coordination, whereas the father and daughter were healthy.

METHODS

Each family member was tested for serological evidence of Bartonella exposure using B. vinsonii subsp. berkhoffii genotypes I-III, B. henselae and B. koehlerae indirect fluorescent antibody assays and for bacteremia using the BAPGM enrichment blood culture platform.

RESULTS

The mother was seroreactive to multiple Bartonella spp. antigens and bacteremia was confirmed by PCR amplification of B. henselae DNA from blood, and from a BAPGM blood agar plate subculture isolate. The son was not seroreactive to any Bartonella sp. antigen, but B. henselae DNA was amplified from several blood and serum samples, from BAPGM enrichment blood culture, and from a cutaneous striae biopsy. The father and daughter were seronegative to all Bartonella spp. antigens, and negative for Bartonella DNA amplification.

CONCLUSIONS

Historically, persistent B. henselae bacteremia was not thought to occur in immunocompetent humans. To our knowledge, this study provides preliminary evidence supporting the possibility of persistent B. henselae bacteremia in immunocompetent persons from Europe. Cat or flea contact was considered an unlikely source of transmission and the mother, a physician, reported that clinical symptoms developed following tick exposure. To our knowledge, this is the first time that a B. henselae organism has been visualized in and amplified from a striae lesion. As the tick bites occurred three years prior to documentation of B. henselae bacteremia, the mode of transmission could not be determined.

A mathematical epidemiological model of gram-negative Bartonella bacteria: does differential ectoparasite load fully explain the differences in infection prevalence of Rattus rattus and Rattus norvegicus?

We postulate that the large difference in infection prevalence, 24% versus 5%, in R. norvegicus and R. rattus, respectively, between these two co-occurring host species may be due to differences in ectoparasite and potential vector infestation rates. A compartmental model, representative of an infectious system containing these two Rattus species and two ectoparasite vectors, was constructed and the coefficients of the forces of infection determined mathematically. The maximum difference obtained by the model in the prevalence of Bartonella in the two Rattus species amounts to 4.6%, compared to the observed mean difference of 19%. Results suggest the observed higher Bartonella infection prevalence in Rattus norvegicus compared to Rattus rattus, cannot be explained solely by higher ectoparasite load. The model also highlights the need for more detailed biological research on Bartonella infections in Rattus and the importance of the flea vector in the spread of this disease.

Occurrence of Babesia spp., Rickettsia spp. and Bartonella spp. in Ixodes ricinus in Bavarian public parks, Germany

Background

Only limited information is available about the occurrence of ticks and tick-borne pathogens in public parks, which are areas strongly influenced by human beings. For this reason, Ixodes ricinus were collected in public parks of different Bavarian cities in a 2-year survey (2009 and 2010) and screened for DNA of Babesia spp., Rickettsia spp. and Bartonella spp. by PCR. Species identification was performed by sequence analysis and alignment with existing sequences in GenBank. Additionally, coinfections with Anaplasma phagocytophilum were investigated.

Results

The following prevalences were detected: Babesia spp.: 0.4% (n = 17, including one pool of two larvae) in 2009 and 0.5 to 0.7% (n = 11, including one pool of five larvae) in 2010; Rickettsia spp.: 6.4 to 7.7% (n = 285, including 16 pools of 76 larvae) in 2009. DNA of Bartonella spp. in I. ricinus in Bavarian public parks could not be identified. Sequence analysis revealed the following species: Babesia sp. EU1 (n = 25), B. divergens (n = 1), B. divergens/capreoli (n = 1), B. gibsoni-like (n = 1), R. helvetica (n = 272), R. monacensis IrR/Munich (n = 12) and unspecified R. monacensis (n = 1). The majority of coinfections were R. helvetica with A. phagocytophilum (n = 27), but coinfections between Babesia spp. and A. phagocytophilum, or Babesia spp. and R. helvetica were also detected.

Conclusions

I. ricinus ticks in urban areas of Germany harbor several tick-borne pathogens and coinfections were also observed. Public parks are of particularly great interest regarding the epidemiology of tick-borne pathogens, because of differences in both the prevalence of pathogens in ticks as well as a varying species arrangement when compared to woodland areas. The record of DNA of a Babesia gibsoni-like pathogen detected in I. ricinus suggests that I. ricinus may harbor and transmit more Babesia spp. than previously known. Because of their high recreational value for human beings, urban green areas are likely to remain in the research focus on public health issues.

Vector competence of the tick Ixodes ricinus for transmission of Bartonella birtlesii

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.

Bartonella species and their ectoparasites: selective host adaptation or strain selection between the vector and the mammalian host?

A wide range of blood-sucking arthropods have either been confirmed or are suspected as important vectors in Bartonella transmission to mammals, including humans. Overall, it appears that the diversity of Bartonella species DNA identified in ectoparasites is much broader than the species detected in their mammalian hosts, suggesting a mechanism of adaptation of Bartonella species to their host-vector ecosystem. However, these mechanisms leading to the fitness between the vectors and their hosts still need to be investigated.

Absence of zoonotic Bartonella species in questing ticks: first detection of Bartonella clarridgeiae and Rickettsia felis in cat fleas in the Netherlands

Background

Awareness for flea- and tick-borne infections has grown in recent years and the range of microorganisms associated with these ectoparasites is rising. Bartonella henselae, the causative agent of Cat Scratch Disease, and other Bartonella species have been reported in fleas and ticks. The role of Ixodes ricinus ticks in the natural cycle of Bartonella spp. and the transmission of these bacteria to humans is unclear. Rickettsia spp. have also been reported from as well ticks as also from fleas. However, to date no flea-borne Rickettsia spp. were reported from the Netherlands. Here, the presence of Bartonellaceae and Rickettsiae in ectoparasites was investigated using molecular detection and identification on part of the gltA- and 16S rRNA-genes.

Results

The zoonotic Bartonella clarridgeiae and Rickettsia felis were detected for the first time in Dutch cat fleas. B. henselae was found in cat fleas and B. schoenbuchensis in ticks and keds feeding on deer. Two Bartonella species, previously identified in rodents, were found in wild mice and their fleas. However, none of these microorganisms were found in 1719 questing Ixodes ricinus ticks. Notably, the gltA gene amplified from DNA lysates of approximately 10% of the questing nymph and adult ticks was similar to that of an uncultured Bartonella-related species found in other hard tick species. The gltA gene of this Bartonella-related species was also detected in questing larvae for which a 16S rRNA gene PCR also tested positive for "Candidatus Midichloria mitochondrii". The gltA-gene of the Bartonella-related species found in I. ricinus may therefore be from this endosymbiont.

Conclusions

We conclude that the risk of acquiring Cat Scratch Disease or a related bartonellosis from questing ticks in the Netherlands is negligible. On the other hand fleas and deer keds are probable vectors for associated Bartonella species between animals and might also transmit Bartonella spp. to humans.

Adhesins of Bartonella spp

Adhesion to host cells represents the first step in the infection process and one of the decisive features in the pathogenicity of Bartonella spp. B. henselae and B. quintana are considered to be the most important human pathogenic species, responsible for cat scratch disease, bacillary angiomatosis, trench fever and other diseases. The ability to cause vasculoproliferative disorders and intraerythrocytic bacteraemia are unique features of the genus Bartonella. Consequently, the interaction with endothelial cells and erythrocytes is a focus in Bartonella research. The genus harbours a variety of trimeric autotransporter adhesins (TAAs) such as the Bartonella adhesin A (BadA) of B. henselae and the variably expressed outer-membrane proteins (Vomps) of B. quintana, which display remarkable variations in length and modular construction. These adhesins mediate many of the biologically-important properties of Bartonella spp. such as adherence to endothelial cells and extracellular matrix proteins and induction of angiogenic gene programming. There is also significant evidence that the laterally acquired Trw-conjugation systems of Bartonella spp. mediate host-specific adherence to erythrocytes. Other potential adhesins are the filamentous haemagglutinins and several outer membrane proteins. The exact molecular functions of these adhesins and their interplay with other pathogenicity factors (e.g., the VirB/D4 type 4 secretion system) need to be analysed in detail to understand how these pathogens adapt to their mammalian hosts.

Potential for tick-borne bartonelloses

Although possible, tick transmission to a vertebrate host has not been proven.

As worldwide vectors of human infectious diseases, ticks are considered to be second only to mosquitoes. Each tick species has preferred environmental conditions and biotopes that determine its geographic distribution, the pathogens it vectors, and the areas that pose risk for tick-borne diseases. Researchers have identified an increasing number of bacterial pathogens that are transmitted by ticks, including Anaplasma, Borrelia, Ehrlichia, and Rickettsia spp. Recent reports involving humans and canines suggest that ticks should be considered as potential vectors of Bartonella spp. To strengthen this suggestion, numerous molecular surveys to detect Bartonella DNA in ticks have been conducted. However, there is little evidence that Bartonella spp. can replicate within ticks and no definitive evidence of transmission by a tick to a vertebrate host.

Prevalence of Bartonella henselae and Borrelia burgdorferi sensu lato DNA in ixodes ricinus ticks in Europe

Bartonella spp. can cause persistent bloodstream infections in humans and animals. To determine whether Bartonella henselae is present in questing Ixodes ricinus ticks, we analyzed the prevalence of B. henselae DNA among tick stages compared to the prevalence of DNA from Borrelia burgdorferi sensu lato, the pathogen most frequently transmitted by ticks. B. henselae DNA was present with a prevalence of up to approximately 40% in tick populations sampled in four European sites (Eberdingen, Germany; Klasdorf, Germany; Lembach, France; and Madeira, Portugal). The odds of detecting B. henselae DNA in nymphal ticks was approximately 14-fold higher than in adult ticks. No tick was found to be coinfected with B. henselae and B. burgdorferi sensu lato. Taken together, our data indicate that ticks might serve as a vector for the transmission of B. henselae to humans.

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

The causative agent of cat-scratch disease in humans can be transmitted by this tick through saliva.

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.

Rickettsial Seroepidemiology among farm workers, Tianjin, People's Republic of China

High seroprevalence rates for Anaplasma phagocytophilum (8.8%), Coxiella burnetii (6.4%), Bartonella henselae (9.6%), and Rickettsia typhi (4.1%) in 365 farm workers near Tianjin, People's Republic of China, suggest that human infections with these zoonotic bacteria are frequent and largely unrecognized. Demographic features of seropositive persons suggest distinct epidemiology, ecology, and risks.

Vector transmission of Bartonella species with emphasis on the potential for tick transmission

Bartonella species are gram-negative bacteria that infect erythrocytes, endothelial cells and macrophages, often leading to persistent blood-borne infections. Because of the ability of various Bartonella species to reside within erythrocytes of a diverse number of animal hosts, there is substantial opportunity for the potential uptake of these blood-borne bacteria by a variety of arthropod vectors that feed on animals and people. Five Bartonella species are transmitted by lice, fleas or sandflies. However, Bartonella DNA has been detected or Bartonella spp. have been cultured from numerous other arthropods. This review discusses Bartonella transmission by sandflies, lice and fleas, the potential for transmission by other vectors, and data supporting transmission by ticks. Polymerase chain reaction (PCR) or culture methods have been used to detect Bartonella in ticks, either questing or host-attached, throughout the world. Case studies and serological or molecular surveys involving humans, cats and canines provide indirect evidence supporting transmission of Bartonella species by ticks. Of potential clinical relevance, many studies have proposed co-transmission of Bartonella with other known tick-borne pathogens. Currently, critically important experimental transmission studies have not been performed for Bartonella transmission by many potential arthropod vectors, including ticks.