Detection and identification of Ehrlichia, Borrelia burgdorferi sensu lato, and Bartonella species in Dutch Ixodes ricinus ticks

PCR-reverse line blot typing method underscores the genomic heterogeneity of Borrelia valaisiana species and suggests its potential involvement in Lyme disease

Detection of the Borrelia burgdorferi sensu lato complex in biological samples is currently done by conventional immunological and molecular biological methods. To improve on the accuracy of these methods and to simplify the procedure for testing large numbers of samples, a solid-phase sandwich hybridization system readily applicable to the detection of PCR products has been designed. This colorimetric detection system relies on the use of polybiotinylated detection probes and of specific capture oligonucleotides covalently linked at allocated positions on nylon membrane strips. From a phylogenetic analysis on a great number of ospA gene sequences, we have designed and synthesized a set of PCR primers specific to the five Borrelia burgdorferi sensu lato genospecies present in Europe and a subset of probes (capture and detection probes) specific to these five genospecies (B. burgdorferi sensu stricto, B. garinii, B. afzelii, B. valaisiana, and B. lusitaniae). This combined PCR hybridization system was evaluated with a large number of various B. burgdorferi isolates and clinical specimens. These analyses clearly showed that the system could be used as a typing method to distinguish five genospecies belonging to the B. burgdorferi sensu lato complex. In addition, the study showed that B. valaisiana strains might be more heterologous than suspected up to now and clustered into three genomic groups.

Canine borreliosis

A guild of organisms carried by the same vector (Ixodes ticks) in Lyme-endemic areas may be confounding the understanding of Lyme disease in dogs. A new diagnostic method, the C6 peptide test for Lyme, and serology and PCR testing for Ehrlichia, Babesia, and Bartonella species will help to sort out seroprevalence and symptomatology caused by exposure to these agents or by coinfections. In addition, Rickettsia, Leptospira, Mycoplasma species, and more could be involved in dogs diagnosed with a "doxycycline-responsive" disease. The author does not recommend treating asymptomatic Borrelia carrier dogs, but does recommend screening them for proteinuria and for exposure to other agents. A positive Lyme titer is a marker of exposure to Ixodes ticks and the agents they carry. The risk/benefit of vaccination will be understood better as the symptomatology and immunopathogenesis of Lyme disease are defined. Meanwhile, tick control is highly recommended for all dogs in Lyme-endemic areas.

Ehrlichia-like organism gene found in small mammals in the suburban district of Guangzhou of China

The 16S rRNA gene of Ehrlichia genus was examined from the blood and spleen of 26 wild small mammals that were captured at a canine feed lot where the first case of canine ehrlichiosis was found in south of China in 1998. Samples (3 blood and 1 spleen) from Rattus norvegicus were positive by polymerase chain reaction. The amplimers were then cloned and sequenced. All of the 16S rRNA gene sequence of these samples were found to be same and unique when compared with the other members of genus EHRLICHIA: The most closely related species was Ehrlichia-like sp. Schotti variant (99.03% related), which was detected and identified in Dutch Ixodes ricinus ticks by Schouls in 1999. The organism found on these animals was obviously not the species of E. muris, which was isolated and identified from a wild mouse in Japan in 1995, since the relatedness of this gene between the former and the latter was 93.28%. It is unclear whether this organism can cause disease in other mammals, including human beings.

Candidatus Ehrlichia walkerii: a new Ehrlichia detected in Ixodes ricinus tick collected from asymptomatic humans in Northern Italy

Ixodes ricinus harbors many infectious agents pathogenic for humans. A cause of fever is found in less than 50% of patients exposed to ticks. Investigations on 359 Ixodes ticks removed from asymptomatic patients in Northern Italy revealed the presence of a new ehrlichial agent in 10 ticks. Comparison of the 16S rRNA and the gltA gene sequences showed the organism is most closely related to Ehrlichia ruminantium. We propose this new Ehrlichia be named "candidatus Ehrlichia walkerii."

Prevalence of Borrelia Burgdorferi sensu lato genomospecies and of the human granulocytic ehrlichiosis (HGE) agent in Ixodes ricinus ticks collected in the area of Monti Lepini, Italy

Ticks are obligate hematophagous arthropods that are parasites in every class of vertebrates in most regions of the world. They are also considered to be important vectors for the transmission of human infectious diseases. In the present study we used polymer chain reaction (PCR) amplification analysis to determine the prevalence of Borrelia burgdorferi and Ehrlichia phagocytophila, the agents of, respectively, Lyme borreliosis and human granulocytic ehrlichiosis, among ticks inhabiting the area of Monti Lepini, a wild area located in the Latium Region of Italy. A total of 141 I. ricinus ticks (125 nymphs and 16 adults) were collected in the studied area. Total DNAs were extracted from I. ricinus nymphs (pooled in groups of five) and from individual adults. The DNA samples were examined for the presence of B. burgdorferi sensu lato and E. phagocytophila by PCR using two specific pairs of oligonucleotides that specifically amplify distinct DNA regions of the 16S rRNA genes of the two species. The prevalence of vectors infected with B. burgdorferi s. l. was 16% in pooled nymphs samples, and 12.5% in adult ticks, while E. phagocytophila was found only in pooled nymphs samples (8%). Three genomospecies were identified, namely Borrelia afzelii, Borrelia garinii, and Borrelia valaisiana, in samples found positive for B. burgdorferi s. l. No sample was found positive for Borrelia burgdorferi sensu stricto.

Prevalence of Anaplasma phagocytophila and Borrelia burgdorferi in Ixodes persulcatus ticks from northeastern China

A total of 1,345 Ixodes persulcatus ticks collected from northeastern China were investigated for the presence of Anaplasma phagocytophila and Borrelia burgdorferi by a nested polymerase chain reaction (PCR). Sixty-two (4.6%) ticks were positive for A. phagocytophila and 454 (33.8%) were positive for B. burgdorferi. Seven (0.5%) were coinfected with both agents. Sequence analysis of 919-basepair PCR amplicons revealed three types of A. phagocytophila. Type 1 was identical to the published sequences of A. phagocytophilas responsible for human granulocytic ehrlichiosis (HGE). The other two variants differed from the HGE agent sequence at one and four positions, respectively. These findings imply that infection with A. phagocytophila poses a potential health threat to both humans and animals in northeastern China, and that ehrlichiosis should be considered in the differential diagnosis of febrile patients with a history of tick bite, particularly when clinical manifestations are atypical for Lyme disease.

Epidemiology and ecology of TBE relevant to the production of effective vaccines

This review focuses on the epidemiology and ecology of the tick-borne encephalitis (TBE) virus including all the factors influencing the ecology of the TBE virus, environmental and climatic conditions, the vectors and reservoir hosts and their interactions. Consequently, the structure and the conditions of natural foci of TBE are described, as well. Special emphasis is given on data regarding the virus prevalence in ticks in the field. In the second part of this review all the epidemiological and surveillance data of TBE in the 27 European countries and in the Far East with risk areas of TBE and in China and Japan are summarised. Therefore the review is a basis for travellers and inhabitants to get background information for their personal risk assessment.

Bartonella henselae in Ixodes ricinus ticks (Acari: Ixodida) removed from humans, Belluno province, Italy

The potential role of ticks as vectors of Bartonella species has recently been suggested. In this study, we investigated the presence of Bartonella species in 271 ticks removed from humans in Belluno Province, Italy. By using primers derived from the 60-kDa heat shock protein gene sequences, Bartonella DNA was amplified and sequenced from four Ixodes ricinus ticks (1.48%). To confirm this finding, we performed amplification and partial sequencing of the pap31 protein and the cell division protein ftsZ encoding genes. This process allowed us to definitively identify B. henselae (genotype Houston-1) DNA in the four ticks. Detection of B. henselae in these ticks might represent a highly sensitive form of xenodiagnosis. B. henselae is the first human-infecting Bartonella identified from Ixodes ricinus, a common European tick and the vector of various tickborne pathogens. The role of ticks in the transmission of bartonellosis should be further investigated.

Molecular evidence of coinfection of Borrelia burgdorferi sensu lato, human granulocytic ehrlichiosis agent, and Babesia microti in ticks from northwestern Poland

To assess the potential risk for tick-borne agents, Ixodes ricinus were collected from 2 sites in northwestern Poland. The ticks were tested by polymerase chain reaction for coinfection with Borrelia burgdorferi sensu lato (s. l.), human granulocytic ehrlichiosis (HGE) agent, and Babesia microti. Of the 533 processed ticks, 16.7% were positive for B. burgdorferi s. l., 13.3% for B. microti, and 4.5% for the HGE agent. Twenty ticks were coinfected with 2 or 3 of the pathogens.

Bartonella strains from ground squirrels are identical to Bartonella washoensis isolated from a human patient

The most likely animal source of a human case of cardiac disease in Washoe County, Nev., was identified by comparison of DNA sequences of three genes (citrate synthase gltA, 60-kDa heat shock protein gene groEL, and 16S rRNA gene) of Bartonella washoensis cultured from the human patient in question and of Bartonella isolates obtained from the following Nevada rodents: Peromyscus maniculatus (17 isolates), Tamias minimus (11 isolates), Spermophilus lateralis (3 isolates), and Spermophilus beecheyi (7 isolates). Sequence analyses of gltA amplicons obtained from Bartonella from the rodents demonstrated considerable heterogeneity and resulted in the identification of 16 genetic variants that were clustered within three groups in phylogenetic analysis. Each of the three groups was associated with a rodent genus, Peromyscus, Tamias, or Spermophilus: The gltA, 16S rRNA gene, and groEL sequences of a Bartonella isolate obtained from a California ground squirrel (S. beecheyi) were completely identical to homologous sequences of B. washoensis, strongly suggesting that these animals were the source of infection in the human case.

Application of broad-range 16S rRNA PCR amplification and DGGE fingerprinting for detection of tick-infecting bacteria

Ticks play an important role in the transmission of arthropod-borne diseases of viral, protozoal and bacterial origin. The present article describes a molecular-biological based method, which facilitated the broad-range analyses of bacterial communities in ixodid ticks (Ixodes ricinus). DNA was extracted both from single ticks and pooled adult ticks. Eubacterial 16S rRNA gene fragments (16S rDNA) were amplified by polymerase chain reaction (PCR) with broad-range ribosomal primers. Sequences spanning the hypervariable V3 region of the 16S rDNA and representing individual bacterial taxons were separated by denaturing gradient gel electrophoresis (DGGE). For phylogenetic identification, DGGE bands were exised, cloned and sequenced. In addition, we set up a 16S rDNA clone library which was screened by DGGE. Sequences were compared with sequences of known bacteria listed in the GenBank database. A number of bacteria were affiliated with the genera Rickettsia, Bartonella, and Borrelia, which are known to be pathogenic and transmitted by ticks. Two sequences were related to the yet to be cultivated Haemobartonella. To our knowledge, Haemobartonella has never been directly detected in I. ricinus. In addition, members of the genera Staphylococcus, Rhodococcus, Pseudomonas, and Moraxella were detected, which have not been identified in ticks so far. Two bacteria were most closely related to a rickettsial endosymbiont of an Acanthamoeba sp., and to an endosymbiont (Legionellaceae, Coxiella group) of the microarthropod Folsomia candida. The results prove that 16S rDNA genotyping in combination with DGGE analysis is a promising approach for the detection and identification of bacteria infecting ticks, regardless of whether these bacteria are fastidious, obligate intracellular or noncultivable.

Spatial analysis of Yersinia pestis and Bartonella vinsonii subsp. berkhoffii seroprevalence in California coyotes (Canis latrans)

Zoonotic transmission of sylvatic plague caused by Yersinia pestis occurs in California, USA. Human infections with various Bartonella species have been reported recently. Coyotes (Canis latrans) are ubiquitous throughout California and can become infected with both bacterial agents, making the species useful for surveillance purposes. This study examined the geographic distribution of 863 coyotes tested for Y. pestis and Bartonella vinsonii subsp. berkhoffii serologic status to gain insight into the natural history of B. vinsonii subsp. berkhoffii and to characterize the spatial distribution of the two agents. We found 11.7% of specimens positive to Y. pestis and 35.5% positive to B. vinsonii subsp. berkhoffii. The two pathogens had distinct spatial clusters: Y. pestis was more prevalent in eastern portions of the state and B. vinsonii subsp. berkhoffii in coastal regions. Prevalence of Y. pestis increased with increasing elevation, whereas prevalence of B. vinsonii subsp. berkhoffii decreased with increasing elevation. There were differences in the proportions of positive animals on a yearly basis to both pathogens.

Simultaneous detection of Anaplasma and Ehrlichia species in ruminants and detection of Ehrlichia ruminantium in Amblyomma variegatum ticks by reverse line blot hybridization

The detection of Anaplasma and Ehrlichia species is usually based on species-specific PCR assays, since no assay is yet available which can detect and identify these species simultaneously. To this end, we developed a reverse line blot (RLB) assay for simultaneous detection and identification of Anaplasma and Ehrlichia species in domestic ruminants and ticks. In a PCR the hypervariable V1 region of the 16S ribosomal RNA (rRNA) gene was amplified with a set of primers unique for members of the genera Anaplasma and Ehrlichia [Int. J. Syst. Evol. Microbiol. 51 (2001) 2145]. Amplified PCR products from blood of domestic ruminants or Amblyomma variegatum tick samples were hybridized onto a membrane to which eight species-specific oligonucleotide probes and one Ehrlichia and Anaplasma catch-all oligonucleotide probe were covalently linked. No DNA was amplified from uninfected blood, nor from other hemoparasites such as Theileria annulata, or Babesia bigemina. The species-specific probes did not cross-react with DNA amplified from other species. E. ruminantium, A. ovis and another Ehrlichia were identified by RLB in blood samples collected from small ruminants in Mozambique. Finally, A. variegatum ticks were tested after feeding on E. ruminantium infected sheep. E. ruminantium could be detected in adult ticks even if feeding of nymphs was carried out 3.5 years post-infection. In conclusion, the developed species-specific oligonucleotide probes used in an RLB assay can simultaneously detect and identify several Ehrlichia and Anaplasma species. However, as no quantitative data for the detection limit are available yet, only positive results are interpretable at this stage.

Laboratory diagnosis of Bartonella infections

Bartonella species are pathogens of emerging and reemerging significance, causing a wide array of clinical syndromes. In North America and Europe, they are increasingly recognized as a cause of culture negative endocarditis, neuroretinitis, and disease among homeless, HIV-infected, and other immunosuppressed individuals. In South America, bartonellosis continues to plague those in endemic regions and poses a significant threat to travelers in these areas. As the clinician is increasingly faced with these illnesses, which may be difficult to diagnose, laboratory techniques to confirm or refute the diagnosis are becoming increasingly important. Culture methods have improved over the past decade demonstrating increased sensitivity, but still require prolonged periods before isolation of the organism. Specimen handling, media selection, and growth conditions all may affect results and must be optimized in order to provide the highest likelihood of recovering the organism. Pure culture of the bacteria not only provides morphologic information, but also provides material for further diagnostic testing. Work with liquid media, which may provide a more rapid means of cultivation has shown some promise and should continue to be pursued. Improved blood culture techniques were a primary factor in the discovery of Bartonella endocarditis and continued improvements will likely demonstrate further clinical insights. Serologic testing for B henselae infections has become the cornerstone of clinical diagnosis, replacing the skin test that was poorly standardized and posed a potential risk to the patient. Immunofluorescence assays have been well characterized and validated in clinical trials, however they are not universally available. Vero cell cocultivated antigens appear to provide higher sensitivity and specificity when compared with agar-derived antigens. IFA assays are inherently difficult to perform, requiring significant expertise to provide reproducible results. On the contrary, enzyme immunoassays offer ease of use and a high level of reproducibility, however ideal antigens for use in the diagnosis of Bartonella infections have not been clearly identified. Continued work to define antigenic targets of the human response to infection and incorporation of these into a widely available EIA will provide a cost-effective tool for the clinician and epidemiologist alike. Due to the close phylogenetic relationship of B henselae and B quintana, differentiation between these species by serologic means may prove difficult. Molecular techniques including PCR offer high sensitivity and specificity, rapid availability of information, and the ability to differentiate Bartonella organisms at the highest level. Results of studies to date are promising and as methods are refined it will be important to conduct clinical studies to define the role of these assays. In disseminated Bartonella infections such as bacillary angiomatosis, peliosis, endocarditis, and urban trench fever, PCR currently offers the ability to establish the diagnosis when other tests may be unrevealing. For CSD, this technique should be used as a confirmatory technique when the diagnosis is unclear by other means. PCR analysis of blood specimens offers a minimally invasive approach to diagnosis, but clinical data are scarce and further studies are needed. As DNA microarrays move into the clinical arena, specific hybridization probes may allow improved identification and differentiation of Bartonellae at the molecular level.

Lyme disease

Lyme disease is due to infection with a tick-borne spirochete, Borrelia burgdorferi. Risk for infection is confined to regions that contain the Ixodid tick vector. Characteristic skin, musculoskeletal, cardiac, ocular, and neurologic disorders are associated with the local, early dissemination and late stages of infection. Neurologic involvement can be seen at all stages, and involves both central and peripheral nervous system syndromes. The inability to easily culture B. burgdorferi and the lack of a reliable active infection assay have contributed to controversies in diagnosis and management. Because the vast majority of patients are seropositive, however, antibody testing is helpful to support the diagnosis of Lyme disease. With appropriate antibiotics, most patients do well. This infection provides an important model system to understand how interactions between an organism, vector, and host lead to disease. It also provides a model to study how infectious agents lead to neurologic disease.

Reverse line blot hybridization used to identify hemoprotozoa in Minorcan cattle

Piroplasmosis, a tick-borne protozoal disease, is an important disease affecting domestic and wild animals. We performed PCR-based reverse line blot hybridization (RLB) assays on blood samples obtained from 133 cattle exposed to ticks in field conditions in Minorca (Balearic Islands, Spain) in three different seasons. The oligonucleotides used were those for Theileria annulata, T. buffeli, T. taurotragi, T. velifera, Babesia bigemina, B. bovis, B. divergens, and B. major. The RLB technique allowed the simultaneous identification of T. annulata, T. buffeli, B. bigemina, and B. bovis as the piroplasms present in cattle in Minorca. Of the 133 animals, only 4 were not infected by any of the studied parasites. The results indicated endemic piroplasm infection in cattle in Minorca; especially important was the presence of T. annulata. The RLB was highly sensitive and allowed the simultaneous detection and identification of the Theileria and Babesia species in carrier cattle, which cannot be achieved by classical identification methods.

PCR and molecular detection for differentiating Vibrio species

Vibriosis is an economically important disease of fish, marine invertebrates (particularly penaeid shrimps), and large marine mammals and is responsible for high mortality rates in aquaculture worldwide. Some Vibrio species are also responsible for zoonoses, whereas others are relatively nonpathogenic. Using 16S- and 23S-based PCR reactions, we obtained species-specific patterns and a 470-bp band, respectively. DNA sequences obtained on the 23S rRNA gene allowed us to identify species-specific probes for Vibrio parahaemolyticus, V. alginolyticus, V. anguillarum and for a cluster of taxonomically related species: V. carchariae/harveyi/campbelii. A phylogenetic tree based on the 23S sequences confirmed previous results obtained by Western blotting.

PCR detection of Borrelia burgdorferi sensu lato, tick-borne encephalitis virus, and the human granulocytic ehrlichiosis agent in Ixodes persulcatus ticks from Western Siberia, Russia

PCR assays were used to test adult Ixodes persulcatus ticks from Western Siberia, Russia, for Borrelia burgdorferi sensu lato, tick-borne encephalitis virus (TBEV), and the human granulocytic ehrlichiosis (HGE) agent. Of the 150 ticks that were studied, 38% were infected with B. burgdorferi, 46% were infected with TBEV, and 8% were infected with the HGE agent. These three pathogens were distributed in the ticks independently of one another.

Identification of Anaplasma phagocytophila (formerly Ehrlichia phagocytophila) variants in blood from sheep in Norway

A total of 41 blood samples were collected from 40 Anaplasma phagocytophila-infected sheep in 11 sheep flocks from four different counties of southern Norway. The presence and nature of the Anaplasma species were identified by microscopic detection of morulae, PCR, reverse line blot hybridization, and 16S rRNA gene sequencing. A. phagocytophila was identified in all of the samples, and sequencing of the 16S rRNA gene revealed the presence of four variants of A. phagocytophila. Two of these variants have been described before, but two were newly identified 16S rRNA variants of this species. A. phagocytophila variant 1 was found in nine flocks, A. phagocytophila variant 2 was found in four flocks, the A. phagocytophila prototype was found in two flocks, and A. phagocytophila variant 5 was found in one flock. In two flocks, some sheep were infected with A. phagocytophila variant 1, whereas others were infected with A. phagocytophila variant 2, and in three animals a double infection with two variants was registered. Analyses of the blood samples revealed that blood from sheep infected with A. phagocytophila variant 2 contained nearly twice as many neutrophils and eight times as many Anaplasma-infected neutrophils as blood from sheep infected with the A. phagocytophila variant 1. Furthermore, only 43% of the A. phagocytophila variant 2-infected sheep displayed antibody responses in an immune fluorescence assay, whereas 93% of the sheep with the A. phagocytophila variant 1-infected sheep were seropositive.

Seroprevalence of Babesia infections in humans exposed to ticks in midwestern Germany

Babesiosis is considered to be an emerging tick-borne disease in humans worldwide. However, most studies on the epidemiology of human babesiosis to date have been carried out in North America, and there is little knowledge on the prevalence of infection and frequency of disease in other areas. The aim of this study was to investigate the prevalence of Babesia infections in a human population in Germany. A total of 467 sera collected between May and October 1999 from individuals living in the Rhein-Main area were tested for the presence of immunoglobulin G (IgG) and IgM antibodies to antigens of Babesia microti and Babesia divergens by indirect fluorescent-antibody (IFA) tests. These sera were derived from 84 Lyme borreliosis patients suffering from erythema migrans, 60 asymptomatic individuals with positive borreliosis serology, and 81 individuals with a history of tick bite. Cutoff values for discrimination between seronegative and seropositive results in the IFA tests were determined using sera from 120 healthy blood donors and 122 patients suffering from conditions other than tick-borne diseases (malaria, n = 40; toxoplasmosis, n = 22; syphilis, n = 20; Epstein-Barr virus infection, n = 20; and presence of antinuclear antibodies, n = 20). The overall specificities of the IFA tests for B. microti and B. divergens were estimated to be >or=97.5%. Positive IgG reactivity against B. microti antigen (titer, >or=1:64) or B. divergens antigen (titer, >or=1:128) was detected significantly more often (P < 0.05) in the group of patients exposed to ticks (26 of 225 individuals; 11.5%) than in the group of healthy blood donors (2 of 120 individuals; 1.7%). IgG antibody titers of >or=1:256 against at least one of the babesial antigens were found significantly more often (P < 0.05) in patients exposed to ticks (9 of 225) than in the control groups (1 of 242). In the human population investigated here, the overall seroprevalences for B. microti and B. divergens were 5.4% (25 of 467) and 3.6% (17 of 467), respectively. The results obtained here provide evidence for concurrent infections with Borrelia burgdorferi and Babesia species in humans exposed to ticks in midwestern Germany. They also suggest that infections with Babesia species in the German human population are more frequent than believed previously and should be considered in the differential diagnosis of febrile illness occurring after exposure to ticks or blood transfusions, in particular in immunocompromised patients.

Genetic variants of Ehrlichia phagocytophila, Rhode Island and Connecticut

Primers were used to amplify a 561-bp region of the 16S rRNA gene of Ehrlichia phagocytophila from Ixodes scapularis ticks and small mammals collected in Rhode Island and Connecticut. DNA sequences for all 50 E. phagocytophila-positive samples collected from 1996 through 1998 in southwestern Connecticut were identical to the sequence reported for E. phagocytophila DNA from confirmed human cases. In contrast, the sequences from 92 of 123 E. phagocytophila-positive Rhode Island samples collected from 1996 through 1999 included several variants differing by 1-2 nucleotides from that in the agent infecting humans. While 11.9% of 67 E. phagocytophila-positive ticks collected during 1997 in Rhode Island harbored ehrlichiae with sequences identical to that of the human agent, 79.1% had a variant sequence not previously described. The low incidence of human ehrlichiosis in Rhode Island may in part result from interference by these variant ehrlichiae with maintenance and transmission of the true agent of human disease.

Low prevalence of Bartonella henselae infections in Norwegian domestic and feral cats

Bartonella henselae is the causative agent of cat scratch disease (CSD). This clinical entity is very rarely encountered in human medical practice in Norway. B. henselae infections including bacteraemia in cats have been frequently reported. The objective of the present study was to investigate the seroprevalence rate and the degree of B. henselae bacteraemia in Norwegian domestic and feral cats. One hundred cats investigated at a small animal veterinary practice in the middle of Norway were included in the study. Blood collected in Isolator blood-lysis tubes and lysates of erythrocytes after freezing and thawing were cultured. PCR analysis of whole blood was also performed. Serology was performed by indirect fluorescence assay (IFA) and enzyme immunoassay (EIA) using immobilised B. henselae Houston-1 strain as antigen. None of the 100 cats investigated was found to be bacteraemic. All 100 cats were seronegative when analysed by IFA; one cat was positive by EIA. The discrepancy between IFA and EIA of this particular cat is probably due to cross-reactive antibodies. Contrary to findings reported from several geographic regions, B. henselae infections in Norwegian cats appear to be virtually absent. This in turn may explain why CSD has not been reported in human medical practice in Norway.

PCR detection and serological evidence of granulocytic ehrlichial infection in roe deer (Capreolus capreolus) and chamois (Rupicapra rupicapra)

The role of wild mammals, such as roe deer (Capreolus capreolus) and chamois (Rupicapra rupicapra), in the epidemiology of granulocytic ehrlichiae in Switzerland was investigated. We tested blood samples for Ehrlichia phagocytophila genogroup 16S rRNA gene sequences by PCR and for immunoglobulin G antibodies against granulocytic ehrlichiae by indirect fluorescent-antibody assay (IFA). Overall means of 60.9% of 133 roe deer serum samples and 28.2% of 39 chamois serum samples were seroreactive by IFA. PCR results were positive for 18.4% of 103 roe deer serum samples as well. None of the 24 chamois blood samples tested were positive by PCR. Partial 16S rRNA gene and groESL heat shock operon sequences of three roe deer samples tested showed strong degrees of homology (> or =99.7 and > or =98.6%, respectively) with the sequences of granulocytic ehrlichiae isolated from humans. These results confirm that chamois, and particularly roe deer, are commonly infected with granulocytic ehrlichiae and provide evidence that these wild mammals are potential reservoirs for granulocytic ehrlichiae in Switzerland.

Neurologic aspects of Lyme disease

Lyme disease has emerged as a major infection with frequent neurologic manifestations. These manifestations probably reflect several predominantly indirect pathogenetic mechanisms and involve host, vector, and organism factors. With early diagnosis and appropriate antibiotic treatment, patients do well. Because culture is not reliable, diagnosis has relied on positive serology to document exposure. Serology should improve as second-generation assays become available. Although there is a preventive vaccine based on the lipoprotein OspA, newer vaccines in development may prove more desirable. Lyme disease provides a valuable model to study how infectious pathogens cause neurologic disease.

Subacute bartonella infection in Swedish orienteers succumbing to sudden unexpected cardiac death or having malignant arrhythmias

During the period 1979-92, an increasing number of sudden unexpected cardiac deaths (SUCD) occurred in young, Swedish, male elite orienteers. Myocarditis was the most common diagnosis in the 16 victims, and in 4 cases was also associated with fatty infiltration mimicking arrhythmogenic right ventricular cardiomyopathy (ARVC). Tissues from autopsies of 5 orienteers were tested for Bartonella by PCR targeting the gltA (citrate-synthase) gene. The products were then sequenced. Antibodies to B. henselae, B. quintana and B. elizabethae were measured by indirect fluorescence antibody assay. Bartonella spp. DNA was detected in the hearts of 4 deceased orienteers, and in the lung of a fifth deceased case. The sequences were close to B. quintana in 2 cases and identical to B. henselae in 3. Four of these 5 cases, as well as 2 additional cases of elite orienteers with ARVC, indicated antibodies to Bartonella. It is suggested that Bartonella-induced silent subacute myocarditis, eventually leading to electric instability, caused the increased SUCD rate among the Swedish orienteers. It is further suggested that Bartonella infection may be a major pathogenetic factor in the development of ARVC-like disease. Although the mode of transmission is unknown, both zoonotic/vector-borne and parenteral person-to-person transmission may be involved.

High prevalence of granulocytic Ehrlichiae and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks from Bulgaria

Bulgarian Ixodes ricinus ticks were examined for Ehrlichia and Borrelia coinfection: 34 and 32% of adult ticks and at least 2 and 10% of nymphs were positive for these infections, respectively. Coinfections and dual or triple Borrelia infections were frequent, although Ehrlichia phagocytophila heterogeneity was minimal. Multiple tick-borne bacteria coexist in I. ricinus ticks in southeastern Europe.

Distinct combinations of Borrelia burgdorferi sensu lato genospecies found in individual questing ticks from Europe

The genetic diversity of Borrelia burgdorferi sensu lato was assessed in individual adult Ixodes ricinus ticks from Europe by direct PCR amplification of spirochetal DNA followed by genospecies-specific hybridization. Analysis of mixed infections in the ticks showed that B. garinii and B. valaisiana segregate from B. afzelii. This and previous findings suggest that host complement interacts with spirochetes in the tick, thereby playing an important role in the ecology of Lyme borreliosis.

Borrelia burgdorferi sensu lato and Ehrlichia spp. in Ixodes ticks from southern Norway

We report the results of a study of the prevalence of Ehrlichia and Borrelia species in 341 questing Ixodes ricinus ticks from two locations in southern Norway. The prevalences of Borrelia burgdorferi sensu lato and Ehrlichia spp. were, respectively, 16 and 11.5% at site 1 and 17 and 6% at site 2. Prevalence and species composition of Borrelia and Ehrlichia varied with location and date of collection. The dominant Borrelia species at both sites was Borrelia afzelii, followed by Borrelia burgdorferi sensu stricto. Borrelia garinii was found in only a single tick. The dominant member of the Ehrlichia group was a recently described Ehrlichia-like organism related to the monocytic ehrlichiae. Variants of Ehrlichia phagocytophila and the agent of human granulocytic ehrlichiosis were also found. The highest prevalences for B. afzelii, B. burgdorferi sensu stricto, and the Ehrlichia-like organism were observed in May. B. afzelii was most prevalent in females, less prevalent in nymphs, and least prevalent in males, while the prevalence of Ehrlichia was highest in nymphs, lower in females, and least in males. Double infections with B. afzelii and B. burgdorferi sensu stricto and with B. afzelii and the Ehrlichia-like organism were significantly overrepresented. Tick densities were highest in May, when densities of more than 200 ticks/100 m2 were observed, and declined during the summer months to densities as low as 20 ticks/100 m2. We conclude that estimates of the prevalence of tick-borne bacteria are sensitive to the choice of date and site for collection of ticks. This is the first study of tick-borne Borrelia and Ehrlichia in Norway and the lowest reported B. garinii prevalence in Northern Europe. The prevalence of the Ehrlichia-like organism is described for the first time in questing ticks.

Detection of haemoparasites in cattle by reverse line blot hybridisation with a note on the distribution of ticks in Sicily

A reverse line blot hybridisation (RLB) of 21 oligonucleotides with polymerase chain reaction (PCR) amplified regions of 16S rRNA (Ehrlichia/Anaplasma group) or 18S rRNA (Babesia/Theileria group) genes of haemoparasites detected Theileria annulata, T. buffeli/orientalis, Babesia bovis, B. bigemina, B. divergens, Ehrlichia bovis, Anaplasma marginale, A. centrale and unknown species within the Rickettsia tribe.A very high prevalence of mixed infections was detected, which indicated that animals infected with Babesia spp. were also infected with Theileria spp. and/or Anaplasma spp. The tick distribution appeared to be seasonal with Hyalomma marginatum as the most frequently observed tick and Boophilus annulatus and Ixodes ricinus as the least frequently observed ticks. Other species identified in the 818 ticks collected during the five sampling periods between April 1998 and November 1999 included H. lusitanicum, Rhipicephalus sanguineus group, R. bursa, Dermacentor marginatus, Haemaphysalis punctata, B. annulatus and I. ricinus.

Identification of Ehrlichia spp. and Borrelia burgdorferi in Ixodes ticks in the Baltic regions of Russia

The presence and distribution of Ehrlichia spp. and Borrelia burgdorferi sensu lato was demonstrated among ixodid ticks collected in the Baltic regions of Russia, where Lyme borreliosis is endemic. A total of 3,426 Ixodes ricinus and 1,267 Ixodes persulcatus specimens were collected, and dark-field microscopy showed that 265 (11.5%) I. ricinus and 333 (26.3%) I. persulcatus ticks were positive. From these samples, 472 dark-field-positive and 159 dark-field-negative ticks were subjected to PCR and subsequent reverse line blot hybridization. Fifty-four ticks (8.6%) carried Ehrlichia species, and 4 (0.6%) carried ehrlichiae belonging to the Ehrlichia phagocytophila complex, which includes the human granulocytic ehrlichiosis agent. The E. phagocytophila complex and an Ehrlichia-like species were detected only in I. ricinus whereas Ehrlichia muris was found exclusively in I. persulcatus, indicating a possible vector-specific infection. Borrelia garinii was found predominantly in I. persulcatus, but Borrelia afzelii was evenly distributed among the two tick species. Only two I. ricinus ticks carried B. burgdorferi sensu stricto, while Borrelia valaisiana and a newly identified B. afzelii-like species were found in 1.7 and 2.5% of all ticks, respectively. Of the dark-field-positive ticks, only 64.8% yielded a Borrelia PCR product, indicating that dark-field microscopy may detect organisms other than B. burgdorferi sensu lato. These observations show that the agent of human granulocytic ehrlichiosis may be present in ticks in the Baltic regions of Russia and that clinicians should be aware of this agent as a cause of febrile disease.

Molecular evidence of Bartonella spp. in questing adult Ixodes pacificus ticks in California

Ticks are the vectors of many zoonotic diseases in the United States, including Lyme disease, human monocytic and granulocytic ehrlichioses, and Rocky Mountain spotted fever. Most known Bartonella species are arthropod borne. Therefore, it is important to determine if some Bartonella species, which are emerging pathogens, could be carried or transmitted by ticks. In this study, adult Ixodes pacificus ticks were collected by flagging vegetation in three sites in Santa Clara County, Calif. PCR-restriction fragment length polymorphism and partial sequencing of 273 bp of the gltA gene were applied for Bartonella identification. Twenty-nine (19.2%) of 151 individually tested ticks were PCR positive for Bartonella. Male ticks were more likely to be infected with Bartonella than female ticks (26 versus 12%, P = 0.05). None of the nine ticks collected at Baird Ranch was PCR positive for Bartonella. However, 7 (50%) of 14 ticks from Red Fern Ranch and 22 (17%) of 128 ticks from the Windy Hill Open Space Reserve were infected with Bartonella. In these infected ticks, molecular analysis showed a variety of Bartonella strains, which were closely related to a cattle Bartonella strain and to several known human-pathogenic Bartonella species and subspecies: Bartonella henselae, B. quintana, B. washoensis, and B. vinsonii subsp. berkhoffii. These findings indicate that I. pacificus ticks may play an important role in Bartonella transmission among animals and humans.

Assessing the association between the geographic distribution of deer ticks and seropositivity rates to various tick-transmitted disease organisms in dogs

OBJECTIVE

To determine whether the geographic distribution of deer ticks (Ixodes scapularis) was associated with the distribution of dogs seropositive for various tick-transmitted disease organisms (ie, Borrelia burgdorferi, Rickettsia rickettsii, the human granulocytic ehrlichiosis [HGE] agent, Ehrlichia canis, and Bartonella vinsonii subsp berkhoffii).

DESIGN

Serologic survey.

SAMPLE POPULATION

Serum samples from 277 dogs in animal shelters and veterinary hospitals in Rhode Island.

RESULTS

Overall, 143 (52%) dogs were seropositive for B burgdorferi, 59 (21.3%) were seropositive for R rickettsii, 40 (14.4%) were seropositive for the HGE agent, 8 (2.9%) were seropositive for E canis, and 6 (2.2%) were seropositive for B vinsonii. Regression analysis indicated that the natural logarithm of nymphal deer tick abundance was correlated with rate of seropositivity to the HGE agent and to B burgdorferi but not to rate of seropositivity to R rickettsii, E canis, or B vinsonii. Percentages of samples seropositive for B burgdorferi, R rickettsii, the HGE agent, and E canis were significantly higher for samples from the southwestern part of the state where ticks in general and deer ticks in particular are abundant than for samples from the northern and eastern portions of the state, where ticks are relatively rare.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that all 5 disease agents are in Rhode Island and pose a risk to dogs and humans. Knowledge concerning tick distributions may be useful in predicting the pattern of disease associated with particular tick species and may aid diagnostic, prevention, and control efforts.

Ticks and tickborne bacterial diseases in humans: an emerging infectious threat

Ticks are currently considered to be second only to mosquitoes as vectors of human infectious diseases in the world. Each tick species has preferred environmental conditions and biotopes that determine the geographic distribution of the ticks and, consequently, the risk areas for tickborne diseases. This is particularly the case when ticks are vectors and reservoirs of the pathogens. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 15 ixodid-borne bacterial pathogens have been described throughout the world, including 8 rickettsiae, 3 ehrlichiae, and 4 species of the Borrelia burgdorferi complex. This article reviews and illustrate various aspects of the biology of ticks and the tickborne bacterial diseases (rickettsioses, ehrlichioses, Lyme disease, relapsing fever borrelioses, tularemia, Q fever), particularly those regarded as emerging diseases. Methods are described for the detection and isolation of bacteria from ticks and advice is given on how tick bites may be prevented and how clinicians should deal with patients who have been bitten by ticks.

Tick-borne bacterial diseases emerging in Europe

Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 11 tick-borne human bacterial pathogens have been described throughout Europe. These include five spotted fever rickettsiae, the agent of human granulocytic ehrlichiosis, four species of the B. burgdorferi complex and a new relapsing fever borrelia. We present these emerging diseases and focus on the factors that play a role in the recognition of new tick-borne diseases.

Tick-borne infectious diseases of dogs

Tick-transmitted infections are an emerging problem in dogs. In addition to causing serious disease in traditional tropical and semi-tropical regions, they are now increasingly recognized as a cause of disease in dogs in temperate climates and urban environments. Furthermore, subclinically infected companion animals could provide a reservoir for human tick-transmitted infectious agents, such as Ehrlichia chaffeensis, Ehrlichia ewingll, the Ehrlichia phagocytophila group and Rickettsia conorii. Here, we discuss the emergence of new canine tick-transmitted diseases, which results from several factors, including the expansion of the tick range into urban and semi-urban areas worldwide, the movement of infected dogs into previously non-endemic areas, and the advent of novel molecular techniques for diagnosis and pathogen identification.

Granulocytic Ehrlichiae in Ixodes persulcatus ticks from an area in China where Lyme disease is endemic

A total of 372 adult Ixodes persulcatus ticks were collected from vegetation in a forest area of Heilongjiang Province in northeastern China, where Lyme disease is known to be endemic. The ticks were examined for the presence of granulocytic ehrlichiae by heminested PCR with primers derived from the 16S rRNA gene. Of 310 ticks obtained from the Dahe forestry farm, two pools (each containing 5 ticks) were found positive, with a minimum infection rate of 0.6%. Ehrlichial DNA was also detected in one female (1.6%) of 62 ticks collected from the Yulin forestry farm. The overall minimum infection rate of the 372 I. persulcatus adults was 0.8%. The nucleotide sequences of 919-bp PCR products from the three positive tick specimens were identical to each other and very closely related to the members of the Ehrlichia phagocytophila genogroup. This is the first identification of granulocytic ehrlichiae in ticks in Asia and the first report of infection in I. persulcatus anywhere.

Bartonella infection in animals: carriership, reservoir potential, pathogenicity, and zoonotic potential for human infection

Recent observations have begun to support a role for Bartonella spp. as animal as well as human pathogens. Bartonella spp. are vector-transmitted, blood-borne, intracellular, gram-negative bacteria that can induce prolonged infection in the host. Persistent infections in domestic and wild animals result in a substantial reservoir of Bartonella organisms in nature that can serve as a source for inadvertent human infection. The prevalence of bacteremia can range from 50 to 95% in selected rodent, cat, deer, and cattle populations. Dogs infected with Bartonella spp. can develop lameness, endocarditis, granulomatous lymphadenitis, and peliosis hepatis, lesions that have also been reported in association with human infection. Understanding the role of Bartonella spp. as pathogens in cats and other wild or domestic animals awaits the results of additional studies. Considering the extensive animal reservoirs and the large number of insects that have been implicated in the transmission of Bartonella spp., both animal and human exposure to these organisms may be more substantial than is currently believed.

Bartonella infection in animals: carriership, reservoir potential, pathogenicity, and zoonotic potential for human infection

Recent observations have begun to support a role for Bartonella spp. as animal as well as human pathogens. Bartonella spp. are vector-transmitted, blood-borne, intracellular, gram-negative bacteria that can induce prolonged infection in the host. Persistent infections in domestic and wild animals result in a substantial reservoir of Bartonella organisms in nature that can serve as a source for inadvertent human infection. The prevalence of bacteremia can range from 50 to 95% in selected rodent, cat, deer, and cattle populations. Dogs infected with Bartonella spp. can develop lameness, endocarditis, granulomatous lymphadenitis, and peliosis hepatis, lesions that have also been reported in association with human infection. Understanding the role of Bartonella spp. as pathogens in cats and other wild or domestic animals awaits the results of additional studies. Considering the extensive animal reservoirs and the large number of insects that have been implicated in the transmission of Bartonella spp., both animal and human exposure to these organisms may be more substantial than is currently believed.

Genetic diversity of Borrelia burgdorferi sensu lato in ticks from mainland Portugal

To date Borrelia lusitaniae is the only genospecies of Borrelia burgdorferi sensu lato isolated from Ixodes ricinus ticks collected in Portugal and Tunisia. This suggests that the genospecies diversity of B. burgdorferi sensu lato decreases toward the southwestern margin of its Old World subtropical range. In order to further explore the genetic diversity of B. burgdorferi sensu lato from this region, 55 I. ricinus and 27 Hyalomma marginatum questing adults, collected during the spring of 1998 from a sylvatic habitat south of Lisbon, Portugal, were analyzed. Infection prevalences of 75% in I. ricinus ticks and 7% in H. marginatum ticks were detected by a nested PCR that targets the rrf (5S)-rrl (23S) spacer of B. burgdorferi sensu lato. Restriction fragment length polymorphism (RFLP) analysis of the I. ricinus-derived amplicons showed that the sequences in the majority of samples were similar to those of B. lusitaniae type strains (76% for strain PotiB1, 5% for strain PotiB3). Two novel RFLP patterns were obtained from 12% of the samples. The remaining 7% of samples gave mixed RFLP patterns. Phylogenetic analysis of rrf-rrl spacer sequences revealed a diverse population of B. lusitaniae in questing adult I. ricinus ticks (the sequences did not cluster with those of any other genospecies). This population consisted of 10 distinct sequence types, suggesting that multiple strains of B. lusitaniae were present in the local I. ricinus population. We hypothesize that B. lusitaniae has a narrow ecological niche that involves host species restricted to the Mediterranean Basin.

PCR detection of granulocytic ehrlichiae in Ixodes ricinus ticks and wild small mammals in western Switzerland

The presence of granulocytic ehrlichiae was demonstrated by PCR in Ixodes ricinus ticks and wild small mammals in Switzerland in two areas of endemicity for bovine ehrlichiosis. Six ticks (three females and three nymphs) (1.4%) of 417 I. ricinus ticks collected by flagging vegetation contained ehrlichial DNA. A total of 201 small mammals from five species, wood mouse (Apodemus sylvaticus), yellow-necked mouse (Apodemus flavicollis), earth vole (Pitymys subterraneus), bank vole (Clethrionomys glareolus), and common shrew (Sorex araneus), were trapped. The analysis of I. ricinus ticks [corrected] collected on 116 small mammals showed that nine C. glareolus voles and two A. sylvaticus mice hosted infected tick larvae. In these rodents, granulocytic ehrlichia infection was also detected in blood, spleen, liver, and ear samples. Further examinations of 190 small mammals without ticks or with noninfected ticks showed the presence of ehrlichial DNA in spleen and other tissues from six additional C. glareolus, three A. flavicollis, and one S. araneus mammals. This study suggests that A. sylvaticus, A. flavicollis, S. araneus, and particularly C. glareolus are likely to be natural reservoirs for granulocytic ehrlichiae. Partial 16S rRNA gene sequences of granulocytic ehrlichiae from ticks and rodents showed a high degree of homology (99 to 100%) with granulocytic ehrlichiae isolated from humans. In contrast, groESL heat shock operon sequence analysis showed a strong divergence (approximately 5%) between the sequences in samples derived from rodents and those derived from samples from questing ticks or from other published ehrlichia sequences. Dual infections with granulocytic ehrlichia and Borrelia burgdorferi were found in ticks and small mammals.

Bartonella spp. isolated from wild and domestic ruminants in North America

Bartonella species were isolated from 49% of 128 cattle from California and Oklahoma, 90% of 42 mule deer from California, and 15% of 100 elk from California and Oregon. Isolates from all 63 cattle, 14 deer, and 1 elk had the same polymerase chain reaction/restriction fragment length polymorphism profiles. Our findings indicate potential for inter- and intraspecies transmission among ruminants, as well as risk that these Bartonella spp. could act as zoonotic agents.

Molecular detection of pathogen DNA in ticks (Acari: Ixodidae): a review

Ticks play an important role in human and veterinary medicine, in particular due to their ability to transmit a wide spectrum of pathogenic micro-organisms of protozoal, rickettsial, bacterial and viral origin. Pathogens in ticks can be identified by conventional methods such as indirect immunofluorescence, isolation in cell culture or by using histological staining techniques. However, the advent of the polymerase chain reaction (PCR) has resulted in tremendous improvements in the specific and sensitive detection of pathogen DNA in ticks. In this paper, literature on DNA extraction methods, PCR protocols, primers and probes, which are in use for the successful detection and identification of pathogens in ticks, are critically reviewed. Some recommendations are also given towards the end of this review.