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Am. J. Trop. Med. Hyg., 75(4), 2006, pp. 664-668
Copyright © 2006 by The American Society of Tropical Medicine and Hygiene

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NATURAL ANAPLASMA PHAGOCYTOPHILUM INFECTION OF TICKS AND RODENTS FROM A FOREST AREA OF JILIN PROVINCE, CHINA

WU-CHUN CAO*, LIN ZHAN, JING HE, JANET E. FOLEY, SAKE J. DE VLAS, XIAO-MING WU, HONG YANG, JAN. H. RICHARDUS, AND J. DIK F. HABBEMA
Beijing Institute of Microbiology and Epidemiology, State Key Laboratory of Pathogen and Biosecurity, Beijing, People’s Republic of China; Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California; Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands


ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Polymerase chain reaction integrated with sequence analysis was carried out to investigate the natural Anaplasma phagocytophilum infection in ticks and rodents from a forest area of Jilin Province, China. Four (4.0%) of 100 Ixodes persulcatus and 2 (0.7%) of 286 Dermacentor silvarum ticks collected by flagging vegetation were positive. Nine (8.8%) of 102 rodents were infected, as well as 2 (2.8%) of 71 I. persulcatus parasitizing on 25 rodents. The nucleotide sequences of 1442-bp A. phagocytophilum 16S rRNA gene amplified from rodents and ticks were identical to each other and to that previously reported in Heilongjiang Province of China (GenBank accession no. AF205140), but different from those of other countries. The sequences of 357-bp partial citrate synthase gene from the above specimens were homologic, and varied from known A. phagocytophilum agents. These findings add new information on the ecologic features of A. phagocytophilum and indicate the threat of anaplasmosis in the area.


INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium, which encompasses former Ehrlichia phagocytophila, E. equi, and the human granulocytic ehrlichiosis (HGE) agent based on phylogenetic analyses.1 This bacterium has long been recognized as a veterinary agent. Since HGE (now called human granulocytic anaplasmosis), the human infection, was first reported in the United States in 1994,2,3 A. phagocytophilum has been considered as an emerging pathogen of public health importance.4 The disease usually presents as an acute febrile illness characterized by headache, chill, myalgias, arthralgia, malaise, and hematological abnormalities, such as thrombocytopenia, leukopenia, and elevated hepatic aminotransferase levels.5

A. phagocytophilum is thought to be naturally maintained in a tick-rodent cycle, with humans being involved only as incidental "dead-end" hosts.6–10 The agent is usually associated with genus Ixodes ticks, including I. scapularis, I. pacificus, and I. spinipalpis in the United States,8,11,12 I. trianguliceps in the United Kingdom,6,13 I. ricinus in mainland Europe7,9,14–18 and Africa,19 and I. persulcatus in eastern Europe20 and Asia.21–24 Wild rodents have been implicated as natural reservoirs for A. phagocytophilum in the United States, the United Kingdom, and mainland Europe.6,7,9,10

A. phagocytophilum was only documented in I. persulcatus ticks from northeastern China where Lyme disease is endemic.21,22 However, the existence of the agent has not been established in Jilin Province, although its ecological features are similar to the previously mentioned areas. Furthermore, no information is available concerning animal reservoirs of A. phagocytophilum in Asia. Lack of such knowledge has inhibited us to understand the ecology, epidemiology, and potential threats of the pathogens to human health. The objectives of this study were to investigate the presence of A. phagocytophilum in Jilin Province of China, and to determine if rodents, the common hosts of immature stages of ticks, are naturally infected by the agent.


MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Study site. Rodents and actively questing ticks were collected in May 2005 in the hinterland of Changbai Mountains situated at 42°45' north latitude and 130°35' east longitude within Hunchun County, Jilin Province. The terrain consists of forested rolling hills with an average elevation of 825 m. The annual precipitation is about 800 mm, and the relative humidity is around 70%. The temperature ranges from –41.4°C to 33.6°C, with the average of 4.0°C.

Sample collection. Host-seeking ticks were collected by flagging vegetation. Ticks were identified to the species level and the developmental stage, and were stored alive until use. Rodents were captured using box traps with peanuts as baits. Attached feeding ticks were removed by using sterile forceps, identified by species and life stage, and stored in 1.5-mL microcentrifuge tubes in the refrigerator until DNA extraction. After identification of species and sex, the spleen was removed from each rodent and stored at –20°C until tested.

DNA extraction. DNA extraction from ticks was performed as previously described.22 Briefly, each tick was placed into a microtube and mechanically disrupted with sterile scissors in 50 µL DNA extraction buffer (10 mM Tris pH 8.0, 2 mM EDTA, 0.1% sodium dodecyl sulfate, and 500 µg of proteinase K per ml). The sample was incubated for 2 hours at 56°C, and then boiled at 100°C for 10 minutes to inactivate proteinase K. After centrifugation, the supernatant was transferred to fresh sterile microtube and purified by extracting twice with an equal volume of phenol-chloroform before use.

A small piece of spleen (about 500 mg) from individual rodent was used for DNA extraction. Briefly, each spleen specimen was crushed with Trizol (Invitrogen, Carlsband, CA, USA) to separate DNA from RNA after centrifugation. The precipitated DNA were obtained after washing twice in a solution containing 0.1 M sodium citrate in 10% ethanol, then the DNA pellet was suspend in 75% ethanol and kept at room temperature for 10–20 minutes. After centrifuging at 2000 g at 2–8°C for 5 minutes, the DNA was dissolved in weak base by adding a certain quantity of 8 mM NaOH and centrifugated to remove insoluble material. Then the supernatant containing the DNA was transferred to a new tube, adjusted with HEPES to pH 7–8, and stored at 4°C for PCR use.

Polymerase chain reaction amplification. A nested PCR was performed with primers designed to amplify the partial 16S rRNA gene of A. phagocytophilum.21,22 Primers GE9f and GE10r, previously described by Chen and colleagues,3 were applied for the primary amplification. In nested PCR, Ehr5218 and GE10r were used as primers, and expected to yield a 441-bp product. Both primary and nested PCR amplifications were performed in a volume of 30 µL in a Perkin-Elmer model 2400 thermal cycler. Cycling conditions involved an initial 3-minute denaturation at 95°C followed by 35 cycles of 94°C for 15 s, 55°C for 20 s, and 72°C for 15 s, and a final extension at 72°C for 5 minutes. In parallel with each amplification, a positive control (a plasmid containing the 16S rRNA gene of HGE agent, kindly provided by Dr. J. Stephen Dumler at Department of Pathology, The Johns Hopkins Medical Institutions) and a negative control (distilled water) were included.

To further identify the agent in the samples positive for the A. phagocytophilum 16S rRNA gene, another nested PCR was performed to amplify partial sequence of the citrate synthase gene (gltA) of A. phagocytophilum.25 The primers W1 (5'-TGTTTTGGAGTGTGGAGAC-3') and W2 (5'-GGTGAACCAATCTCAGCAA-3') for the initial amplifications, and the primers N1 (5'-ATATAGAAAATCT-GATCGG-3') and N2 (5'-CTCTAAGTTTGCGTCAGC-3) for the nested reactions were designed, and expected to produce a 357-bp fragment. PCR amplifications were conducted in a volume of 30 µL in a Perkin-Elmer model 2400 thermal cycler. The cycling conditions were identical for primary and nested amplifications, which involved 3-minute denaturation at 95°C, followed by 35 cycles of 94°C for 15 seconds, 50°C for 20 seconds, and 70°C for 20 seconds, and a final extension at 70°C for 5 minutes.

All the PCR products were separated by agarose gel electrophoresis, stained with ethidium bromide, and visualized under UV light. To minimize contamination, DNA extraction, the reagent setup, amplification, and agarose gel electrophoresis were performed in separate rooms.

Sequencing and phylogenetic analyses. All samples positive for both 16S rRNA gene and gltA were re-amplified with the primer set GE9f and GE10r3 and the primer set Ehr5218 and 3–17,26 which could yield 919-bp and 964-bp products, respectively. Consequently, a fragment of 1442-bp of A. phagocytophilum 16S rRNA gene were obtained from each sample, based on overlapping region of sequence.

The PCR products of both 1442-bp 16S rRNA gene and 357-bp gltA of A. phagocytophilum were collected and purified. The nucleotide sequences of positive samples were determined by a dideoxynucleotide cycle sequencing method with an automated DNA sequencer (ABI PRISM 377, Perkin-Elmer, Inc.). The sequences obtained at present study were compared with the previously published sequences deposited in GenBank using BLAST program from the National Center for Biotechnology Information web site.

Multiple sequence alignment was conducted with the Clustal X, version 1.83 (http://www.bio-soft.net/fomat.html). The phylogenetic analyses were performed with PHYLIP (version 3.63).27 The distance matrices for the aligned sequences were calculated by the Kimura 2-parameter method; phylogenetic trees were constructed using the neighbor-joining method. The stability of the tree obtained was estimated by bootstrap analysis with 1,000 replications. Tree figures were generated with the TreeView program (version 1.66).

Statistical analysis. x2 test or Fisher’s exact test (whenever necessary) was used to compare the proportions. A P value < 0.05 was considered statistically significant.

Nucleotide sequencing accession number. The partial nucleotide sequences of A. phagocytophilum 16S rRNA gene and gltA from representative I. persulcatus and Dermacentor silvarum ticks, Apodemus peninsulae, A. agrarius, and Tamias sibiricu rodents in this study were deposited in GenBank under the accession numbers DQ449947, DQ449948, DQ449945, DQ342324, DQ449946, DQ160228, DQ449952, DQ449950, DQ449949, and DQ449951, respectively.


RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
A. phagocytophilum was first detected by a nested PCR specifically targeting the 16S rRNA gene. A total of 386 unfed, host-seeking ticks, including 100 adult I. persulcatus and 286 D. silvarum, were collected on vegetation and individually examined. Infection rates of ticks in light of species, sex, and stage are shown in Table 1Go. The positive rate of A. phagocytophilum in I. persulcatus (4.0%) was significantly higher than that in D. silvarum (0.7%) (Fisher’s exact test, P = 0.041). The male I. persulcatus ticks had significant higher infection rate than females did (Fisher’s exact test, P = 0.011). There was no significant difference in positive rates among male, female, and nymphal D. silvarum ticks (Fisher’s exact test, P = 0.398).


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TABLE 1
Results of nested PCR for the detection of A. phagocytophilum in ticks collected by flagging vegetation from Jilin, China
 
A total of 102 rodents from 7 species were captured and detected for the presence of A. phagocytophilum. Nine rodents from 3 species, including Japanese field mouse (A. peninsulae), black-striped field mouse (A. agrarius), and Siberian chipmunk (T. sibiricu), were found naturally infected, with an overall positive rate of 8.8% (Table 2Go). The difference in infection rates among species was not statistically significant (x2 = 9.82, df = 6, P = 0.132).


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TABLE 2
Results of nested PCR for the detection of A. phagocytophilum in rodents and their parasitizing I. persulcatus ticks collected from Jilin, China
 
Only I. persulcatus ticks were found to be "parasiting" on the captured rodents. Among the 102 rodents, 25 (24.5%) hosted 71 I. persulcatus ticks (see Table 2Go), including 56 larvae and 15 nymphs. Only 2 nymphs were positive for A. phagocytophilum with an overall infection rate of 2.8%. The 2 infected nymphs were respectively from a positive A. peninsulae and a negative A. agrarius (see Table 2Go). The samples positive for the A. phagocytophilum 16S rRNA gene were further tested by another nested-PCR assay targeting gltA, and all showed positive results.

All the PCR-positive specimens (i.e., 6 questing ticks, 9 rodents, and 2 parasitizing I. persulcatus) were re-amplified, and a 1442-bp fragment of A. phagocytophilum 16S rRNA gene was obtained from each specimen. The nucleotide sequences amplified from the above positive specimens were identical to each other. The phylogenetic tree based on the alignments of the 16S rRNA gene sequences showed that the agent detected in this study was distinct from the previously reported A. phagocytophilum (Figure 1Go), although they were in the same clade.


Figure 1
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  		    FIGURE 1. Phylogenetic tree based on 1442-bp of the 16S RNA gene using PHYLIP software (version 3.63).25 The distance matrix was calculated by using Kimura 2- parameter method. The tree was obtained by the neighbor-joining method. The numbers at the nodes are the proportions of 1000 bootstrap resamplings that support the topology shown.

 
The sequence analysis of 357-bp partial gltA revealed the nucleotide sequences amplified from the positive ticks and rodents had 100% homology, and varied from all known A. phagocytophilum sequences deposited in GenBank. The gltA-based phylogenetic tree (Figure 2Go) showed more distance than the tree derived from analysis of the 16S rRNA gene. The agent identified in the study appeared to be most closely related to A. phagocytophilum detected in I. persulcatus ticks from Russia (GenBank accession no. AY339602), but genetically far away from A. phagocytophilum agents found in other countries.


Figure 2
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  		    FIGURE 2. Phylogenetic tree based on 357-bp of gltA using PHYLIP software (version 3.63).25 The distance matrix was calculated by using Kimura 2-parameter method. The tree was obtained by the neighbor-joining method. The numbers at the nodes are the proportions of 1000 bootstrap resamplings that support the topology shown.

 

DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
A. phagocytophilum is believed to be naturally maintained in a tick-rodent cycle with Ixodes ticks as vectors. Considering the fact that both A. phagocytophilum and Borrelia burgdorferi agents share the similar ecological system,18,20–22 an investigation on presence of A. phagocytophilum was carried out in a forest area of Jilin Province of northeastern China, where Lyme disease is highly endemic.28 As a result, A. phagocytophilum was firstly identified in the province. The infection rate of the agent in I. persulcatus ticks was 4.0%, which is in agreement with the prevalence of 4.6% in the same tick species previously collected in Inner Mongolia Autonomous Region and Heilongjiang Province, China.22 The infection rate in male I. persulcatus ticks seems higher than that in the female. These diversities could be attributable to geographical and seasonal variations of infected ticks or to different sampling approaches. Further studies using a greater number of tick samples in different seasons, locations, and habitats are required to understand the infection levels. Discrepant infection rates of A. phagocytophilum in ticks have been observed around the world. The prevalence of A. phagocytophilum in I. persulcatus ticks from Korea23 was obviously lower than that in I. persulcatus and I. ovatus ticks from Japan.24 The infection rate could be < 1% in adult I. pacificus from California,29 and in I. ricinus from the United Kingdom15 and Switzerland.17 Higher prevalences were reported in I. scapularis in the United States8 and I. ricinus in the Netherlands18 and Sweden.30

In the study, A. phagocytophilum was first detected in D. silvarum in the world, although the infection rate in this species (0.7%) was significantly lower than that in I. persulcatus (4.0%). A. phagocytophilum is well documented to be associated with Ixodes ticks that may act as vectors; however, the agent has also been reported in Dermacentor ticks such as D. reticulates in Austria31 and D. variabilis in California.32 The presence in alternate ticks may be due to the existence of secondary maintenance cycles, in which A. phagocytophilum circulates between relatively host-specific, usually nonhuman-biting ticks and their hosts.6,33 The additional cycles would possibly buffer the agent from local extinction and assist to re-establish the primary cycles.33 D. silvarum is a 3-host tick well adapted to a broad range of habitats and infests a variety of domestic animals such as scalper, sheep, goat and horse, but has rarely been found to feed on humans in China. The finding of this study provides further evidence to the above. The competency of D. silvarum as a vector for A. phagocytophilum and its significance in veterinary medicine has yet to be demonstrated.

Among the 7 rodent species trapped in the study, A. peninsulae, A. agrarius, and T. sibiricu were found positive for A. phagocytophilum. The overall infection rate of 102 rodents was 8.8%. As far as we know, this is the first observation of A. phagocytophilum infection in wild animals from China. In the forest areas of northeastern China, Apodemus mice and Clethrionomys voles are dominant rodents and important hosts for larval and nymphal I. persulcatus ticks. This was confirmed by our study. It is unknown if A. phagocytophilum, as some other tick-borne agents, is maintained through transovarial transmission in ticks.10 A 2-year longitudinal study carried out in a woodland area in northwest England indicated a seasonal variation in rodent infections, which appears to be associated with seasonal increases in the abundance of I. trianguliceps nymphs and adults, but not larvae.6 This finding further testifies the transstadial, but not transovarial, maintenance of A. phagocytophilum by ixodid ticks. Although the A. phagocytophilum infection in rodents could be low because they would receive few bites from infected ticks, a rodent-tick cycle of infection was verified. In the United States, molecular and serological studies indicate that the white-footed mouse (P. leucopus) is the main host for immature I. scapularis ticks, and is apparently the reservoir for A. phagocytophilum.10,34,35 Antibodies against A. phagocytophilum were also detected in Tamias striatus, Clethrionomys gapperi,34 Neotoma spp., and other Peromyscus spp.36

About a quarter of rodents (24.5%) in our study were being parasitized with ticks, all of which were I. persulcatus. Most of the ticks collected on rodents were larvae (78.9%), and the others were nymphs. Two nymphs were found positive, but no larvae were infected. The role of rodents in transmission and maintenance of A. phagocytophilum in China requires further investigations.

In the study, spleen specimens were used to identify the natural infection of A. phagocytophilum in rodents with reference to previously reported results. Experimental studies on monkeys infected with A. phagocytophilum showed that the spleen harbors the organism for the longest period of time and is the best source for the diagnosis of carrier state by PCR.37 In mice that were experimentally infected with the HGE agent, splenic infection was obvious and persistent.38 A field investigation indicates that spleens from wild small animals are most often infected over other samples such as blood, livers, and ears.7

The nucleotide sequences of partial 16S rRNA gene amplified from rodents as well as questing and parasitizing ticks were identical to each other and to those previously published in China.21,22 To further classify and determine the agents, DNA of gltA (357-bp) was amplified and sequenced. The gltA sequence analyses indicate that the agent detected in the study is closely related to A. phagocytophilum identified in Russian I. persulcatus (GenBank accession no. AY339602), with 2-bp difference (99.4% similarity) at nucleotide level and 1-position difference (99.1% similarity) at amino acid level. The nucleotide sequence of the agent has only 87–93% homology with other A. phagocytophilum strains. Sequences of gltA exhibit higher variation than the 16S rRNA gene, therefore allowing better discrimination among Rickettsia species.23 In conclusion, the agent discovered in this study is unique and worthy of studying its public health and veterinary significances.

Received February 1, 2006. Accepted for publication May 16, 2006.

Acknowledgments: We are grateful to Dr. Rong-man Xu for identification of ticks and reading the manuscript and to Ms. Hai-nan Huang for assistance in tick collection.

Financial support: This study was carried out with financial support from the National Key Technology R & D Program of China (2003BA712a05-01), National Natural Science Foundation of China (No. 39970655), and the Commission of the European Community, as part of the project "Effective and Acceptable Strategies for the Control of SARS and New Emerging Infections in China and Europe" (Contract No. 003824).

* Address correspondence to Wu-chun Cao, Beijing Institute of Microbiology and Epidemiology, State Key Laboratory of Pathogen and Biosecurity, Beijing, People’s Republic of China. E-mail: caowc{at}nic.bmi.ac.cn Back

Authors’ addresses: Wu-Chun Cao, Lin Zhan, Jing He, Xiao-Ming Wu, and Hong Yang, Beijing Institute of Microbiology and Epidemiology, State Key Laboratory of Pathogen and Biosecurity, 20 Dong-Da Street, Fengtai District, Beijing 100071, P. R. China. Janet E. Foley, Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616. Sake J. de Vlas, Jan H. Richardus, and J. Dik F. Habbema, Department of Public Health, Faculty of Medicine and Health Sciences, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.

Reprint requests: Dr. Wu-Chun Cao, Beijing Institute of Microbiology and Epidemiology, State Key Laboratory of Pathogen and Biosecurity, 20 Dong-Da Street, Fengtai District, Beijing 100071, P. R. China, Telephone: (+86) 10-63896082, Fax: (+86) 10-63896082, E-mail: caowc{at}nic.bmi.ac.cn or caowc2000{at}yahoo.com.cn.


REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Dumler JS, Barbet AF, Bekker CP, Dasch GA, Palmer GH, Ray SC, Rikihisa Y, Rurangirwa FR, 2001. Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales: unification of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia and Ehrlichia with Neorickettsia, descriptions of six new species combinations and designation of Ehrlichia equi and "HGE agent" as subjective synonyms of Ehrlichia phagocytophila. Int J Syst Evol Microbiol 51: 2145–2165.[Abstract]
  2. Bakken JS, Dumler JS, Chen S-M, Eckman MR, Van Etta LL, Walker DH, 1994. Human granulocytic ehrlichiosis in the upper midwest United States, a new species emerging? JAMA 272: 212–218.[Abstract/Free Full Text]
  3. Chen S-M, Dumler JS, Bakken JS, Walker DH, 1994. Identification of a granulocytotropic Ehrlichia species as the etiologic agent of human diseases. J Clin Microbiol 32: 589–595.[Abstract/Free Full Text]
  4. Walker DH, Dumler JS, 1996. Emergence of the ehrlichioses as human health problems. Emerg Infect Dis 2: 18–29.[Web of Science][Medline]
  5. Bakken JS, Krueth J, Wilson-Nordskog C, Tilden RL, Asanovich K, Dumler JS, 1996. Clinical and laboratory characteristics of human granulocytic ehrlichiosis. JAMA 275: 199–205.[Abstract/Free Full Text]
  6. Bown KJ, Begon M, Bennett M, Woldehiwet Z, Ogden NH, 2003. Seasonal dynamics of Anaplasma phagocytophila in a rodenttick (Ixodes trianguliceps) system, United Kingdom. Emerg Infect Dis 9: 63–70.[Web of Science][Medline]
  7. Liz JS, Anderes L, Sumner JW, Massung RF, Gern L, Rutti B, Brossard M, 2000. PCR detection of granulocytic ehrlichiae in Ixodes ricinus ticks and wild small mammals in western Switzerland. J Clin Microbiol 38: 1002–1007.[Abstract/Free Full Text]
  8. Pancholi P, Kolbert CP, Mitchell PD, Reed KD Jr, Dumler JS, Bakken JS, Telford SR, Persing DH, 1995. Ixodes dammini as a potential vector of human granulocytic ehrlichiosis. J Infect Dis 172: 1007–1012.[Web of Science][Medline]
  9. Polin H, Hufnagl P, Haunschmid R, Gruber F, Ladurner G, 2004. Molecular evidence of Anaplasma phagocytophilum in Ixodes ricinus ticks and wild animals in Austria. J Clin Microbiol 42: 2285–2286.[Abstract/Free Full Text]
  10. Telford SR, Dawson JE, Katavlos P, Warner CK, Kolbert CP, Persing DH, 1996. Perpetuation of the agent of human granulocytic ehrlichiosis in a deer tick-rodent cycle. Proc Natl Acad Sci U S A 93: 6209–6214.[Abstract/Free Full Text]
  11. Burkot TR, Maupin GO, Schneider BS, Denatale C, Happ CM, Rutherford JS, 2001. Use of a sentinel host system to study the questing behavior of Ixodes spinipalpis and its role in the transmission of Borrelia bissettii, human granulocytic ehrlichiosis, and Babesia microti. Am J Trop Med Hyg 65: 293–299.[Abstract]
  12. Richter PJ, Kimsey RB, Madigan JE, Barlough JE, Dumler JS, Brooks DL, 1996. Ixodes pacificus (Acari: Ixodidae) as a vector of Ehrlichia equi (Rickettsiales: Ehrlichieae). J Med Entomol 33: 1–5.[Web of Science][Medline]
  13. Ogden NH, Bown K, Horrocks BK, Woldehiwet Z, Bennett M, 1998. Granulocytic Ehrlichia infection in ixodid ticks and mammals in woodlands and uplands of the U.K. Med Vet Entomol 12: 423–429.[Web of Science][Medline]
  14. Cinco M, Padovan D, Murgia R, Maroli M, Frusteri L, Heldtander M, 1997. Coexistence of Ehrlichia phagocytophila and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks from Italy as determined by 16S rRNA gene sequencing. J Clin Microbiol 35: 3365–3366.[Web of Science][Medline]
  15. Guy E, Tasker S, Joynson DH, 1998. Detection of the agent of human granulocytic ehrlichiosis (HGE) in UK ticks using polymerase chain reaction. Epidemiol Infect 121: 681–683.[Medline]
  16. Oteo JA, Gil H, Barral M, Pérez A, Jimenez S, Blanco JR, 2001. Presence of granulocytic ehrlichia in ticks and serological evidence of human infection in La Rioja, Spain. Epidemiol Infect 127: 353–358.[Medline]
  17. Pusterla N, Leutenegger CM, Huder JB, Weber R, Braun U, Lutz H, 1999. Evidence of the human granulocytic ehrlichiosis agent in Ixodes ricinus ticks in Switzerland. J Clin Microbiol 37: 1332–1334.[Abstract/Free Full Text]
  18. Schouls LM, Van de Pol I, Rijpkema SGT, Schot CS, 1999. Detection and identification of Ehrlichia, Borrelia burgdorferi sensu lato and Bartonella species in Dutch Ixodes ricinus ticks. J Clin Microbiol 37: 2215–2222.[Abstract/Free Full Text]
  19. Sarih M, Ghirbi YM, Bouattour A, Gern L, Baranton G, Postic D, 2005. Detection and identification of Ehrlichia spp. in ticks collected in Tunisia and Morocco. J Clin Microbiol 43: 1127–1132.[Abstract/Free Full Text]
  20. Alekseev AN, Dubinina HV, Van De Pol I, Schouls LM, 2001. Identification of Ehrlichia spp. and Borrelia burgdorferi in Ixodes ticks in the Baltic regions of Russia. J Clin Microbiol 39: 2237–2242.[Abstract/Free Full Text]
  21. Cao WC, Zhao QM, Zhang PH, Dumler JS, Zhang XT, Fang LQ, Yang H, 2000. Granulocytic Ehrlichiae in Ixodes persulcatus ticks from an area in China where Lyme disease is endemic. J Clin Microbiol 38: 4208–4210.[Abstract/Free Full Text]
  22. Cao WC, Zhao QM, Zhang PH, Yang H, Wu XM, Wen BH, Zhang XT, Habbema JDF, 2003. Prevalence of Anplasma phagocytophila and Borrelia burgdorferi in Ixodes persulcatus ticks from northeastern China. Am J Trop Med Hyg 68: 547–550.[Abstract/Free Full Text]
  23. Kim CM, Kim MS, Park MS, Park JH, Chae JS, 2003. Identification of Ehrlichia chaffeensis, Anaplasma phagocytophilum, and A. bovis in Haemaphysalis longicornis and Ixodes persulcatus ticks from Korea. Vector Borne Zoonotic Dis 3: 17–26.[Web of Science][Medline]
  24. Ohashi N, Inayoshi M, Kitamura K, Kawamori F, Kawaguchi D, Nishimura Y, Naitou H, Hiroi M, Masuzawa T, 2005. Anaplasma phagocytophilum–infected ticks, Japan. Emerg Infect Dis 11: 1780–1783.[Web of Science][Medline]
  25. Inokuma H, Brouqui P, Drancourt M, Raoult D, 2001. Citrate synthase gene sequence: a new tool for phylogenetic analysis and identification of Ehrlichia. J Clin Microbiol 39: 3031–3039.[Abstract/Free Full Text]
  26. Wen B, Jian R, Zhang Y, Chen R, 2002. Simultaneous detection of Anaplasma marginale and a new Ehrlichia species closely related to Ehrlichia chaffeensis by sequence analyses of 16S ribosomal DNA in Boophilus microplus ticks from Tibet. J Clin Microbiol 40: 3286–3290.[Abstract/Free Full Text]
  27. Retief JD, 2000. Phylogenetic analysis using PHYLIP. Methods Mol Biol 132: 243–258.[Medline]
  28. Takada N, Fubito I, Fajita H, Wang H-P, Wang J-C, Masuzawa T, 1998. Lyme disease spirochetes in ticks from northeastern China. J Parasitol 84: 499–504.[Medline]
  29. Barlough JE, Madigan JE, Kramer VL, Clover JR, Hui LT, Webb JP, Vredevoe LK, 1997. Ehrlichia phagocytophila geno-group rickettsiae in ixodid ticks from California collected in 1995 and 1996. J Clin Microbiol 35: 2018–2021.[Abstract]
  30. Von Stedingk LV, Gürtelschmid M, Hanson HS, Gustafson R, Dotevall L, Engvall EO, Granström M, 1997. The human granulocytic ehrlichiosis (HGE) agent in Swedish ticks. Clin Microbiol Infect 3: 573–574.[Medline]
  31. Sixl W, Petrovec M, Marth E, Wust G, Stunzner D, Schweiger R, 2003. Investigation of Anaplasma phagocytophila infections in Ixodes ricinus and Dermacentor reticulatus ticks in Austria. Ann N Y Acad Sci 990: 94–97.[Web of Science][Medline]
  32. Holden K, Boothby JT, Anand S, Massung RF, 2003. Detection of Borrelia burgdorferi, Ehrlichia chaffeensis, and Anaplasma phagocytophilum in ticks (Acari: Ixodidae) from a coastal region of California. J Med Entomol 40: 534–539.[Web of Science][Medline]
  33. Goethert HK, Telford SR 3rd, 2003. Enzootic transmission of the agent of human granulocytic ehrlichiosis among cottontail rabbits. Am J Trop Med Hyg 68: 633–637.[Abstract/Free Full Text]
  34. Walls JJ, Greig B, Neitzel DF, Dumler JS, 1997. Natural infection of small mammal species in Minnesota with the agent of human granulocytic ehrlichiosis. J Clin Microbiol 35: 853–855.[Abstract]
  35. Yeh MT, Mather TN, Coughlin RT, Gingrich-Baker C, Sumner JW, Massung RF, 1997. Serologic and molecular detection of granulocytic ehrlichiosis in Rhode Island. J Clin Microbiol 35: 944–947.[Abstract]
  36. Nicholson WL, Muir S, Sumner JW, Childs JE, 1998. Serologic evidence of infection with Ehrlichia spp. in wild rodents (Muridae: Sigmodontinae) in the United States. J Clin Microbiol 36: 695–700.[Abstract/Free Full Text]
  37. Foley JE, Lerche NW, Dumler JS, Madigan JE, 1999. A simian model of human granulocytic ehrlichiosis. Am J Trop Med Hyg 60: 987–993.[Abstract]
  38. Bunnell JE, Trigiani ER, Srinivas SR, Dumler JS, 1999. Development and distribution of pathologic lesions are related to immune status and tissue deposition of human granulocytic ehrlichiosis agent-infected cells in a murine model system. J Infect Dis 180: 546–550.[Web of Science][Medline]



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