Human Monocytotropic Ehrlichiosis

J. E. Dawson; S. A. Ewing; W. R. Davidson; J. E. Childs; S. E. Little; S. M. Standaert

doi:10.1128/9781555816490.ch14

Chapter 14 : Human Monocytotropic Ehrlichiosis

Authors: J. E. Dawson¹, S. A. Ewing², W. R. Davidson³, J. E. Childs⁴, S. E. Little⁵, S. M. Standaert⁶

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Affiliations: 1: Chelan-Douglas Health District, 200 Valley Mall Pkwy., East Wenatchee, WA 98802; 2: 224 Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078; 3: Southeast Cooperative Wildlife Disease Study, College of Veterinary Medicine, University of Georgia, Athens, GA 30602; 4: Department of Biology, 2101 Rollins Basic Science Building, 1510 Clifton Rd. NE, Atlanta, GA 30602; 5: Department of Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602; 6: 3525 Ensign Rd. NE, Suite 02, Olympia, WA 98506

Content Type: Monograph

Publication Year: 2005

Category: Clinical Microbiology

Book DOI: 10.1128/9781555816490

Chapter DOI: 10.1128/9781555816490.ch14

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Abstract:

This chapter first gives a brief history of human monocytotropic ehrlichiosis (HME), which is a zoonotic disease. From this brief history of HME, it is clear that rapid progress in understanding this newly emerged tick-borne zoonosis was facilitated both by its successful cultivation and by experimental studies of ticks linked to field observations. Epidemiological studies were furthered through the use of molecular techniques, and knowledge of HME expanded rapidly in the early to mid-1990s. Next, the chapter talks about biology of the etiologic agent. In the eastern United States, Ehrlichia chaffeensis is maintained in an epizootic cycle involving the lone star tick (Amblyomma americanum) as the principal vector and the white-tailed deer (Odocoileus virginianus) as a major vertebrate reservoir. This critical vector-host association places these two species at the core of E. chaffeensis epizootiology and strongly influences its geographic distribution and seasonality of transmission. HME caused by E. chaffeensis is endemic to the United States, with residents in the southeastern and south-central states at highest risk. The clinical recognition of HME can be difficult, since the spectrum of manifestations is broad and nonspecific, ranging from asymptomatic infection to mild self-limited symptoms to rapidly fatal disease. HME typically presents as an uncomplicated, acute, nonspecific febrile illness that resolves rapidly if treated with doxycycline, characteristic of many rickettsial infections. The chapter ends with a discussion on laboratory diagnosis, treatment and prevention of HME.

Citation: Dawson J, Ewing S, Davidson W, Childs J, Little S, Standaert S. 2005. Human Monocytotropic Ehrlichiosis, p 239-257. In Goodman J, Dennis D, Sonenshine D, Tick-Borne Diseases of Humans. ASM Press, Washington, DC. doi: 10.1128/9781555816490.ch14

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Human Monocytotropic Ehrlichiosis

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Figure 1

Electron micrograph of E. chaffeensis in the cytoplasm of a macrophage. Photograph appears courtesy of Cynthia Goldsmith (CDC).

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10.1128/9781555816490/fig14-1.gif

Figure 1

Electron micrograph of E. chaffeensis in the cytoplasm of a macrophage. Photograph appears courtesy of Cynthia Goldsmith (CDC).

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Figure 2

Average annual incidence of HME through 2001, as derived from states reporting cases. The legend indicates incidence values stratified into quartiles.

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10.1128/9781555816490/fig14-2.gif

Figure 2

Average annual incidence of HME through 2001, as derived from states reporting cases. The legend indicates incidence values stratified into quartiles.

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Figure 3

(a) The average age-specific incidence of HME derived from states reporting cases; (b) month of onset for HME.

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Figure 3

(a) The average age-specific incidence of HME derived from states reporting cases; (b) month of onset for HME.

References

/content/book/10.1128/9781555816490.chap14

1. Allan, S. A., 2001. Ticks (Class Arachnida: Order Acarina), p. 72– 106. In W. M. Samuel,, M. J. Pybus,, and A. A. Kocan (ed.), Parasitic Diseases of Wild Mammals, 2nd ed. Iowa State University Press, Ames, Iowa.

2. Alleman, A. R.,, A. F. Barbet,, M. V. Bowie,, H. L. Sorenson,, S. J. Wong,, and M. Belanger. 2000. Expression of a gene encoding the major antigenic protein 2 homolog of Ehrlichia chaffeensis and potential application for serodiagnosis. J. Clin. Microbiol. 38: 3705– 3709.

3. Anderson, B. E.,, J. E. Dawson,, D. C. Jones,, and K. H. Wilson. 1991. Ehrlichia chaffeensis, a new species associated with human ehrlichiosis. J. Clin. Microbiol. 29: 2838– 2842.

4. Anderson, B. E.,, J. W. Sumner,, J. E. Dawson,, T. Tzianabos,, C. R. Greene,, J. G. Olson,, D. B. Fishbein,, M. Olsen- Rasmussen,, B. P. Holloway,, E. H. George,, and A. F. Azad. 1992. Detection of the etiologic agent of human ehrlichiosis by polymerase chain reaction. J. Clin. Microbiol. 30: 775– 780.

5. Anderson, B. E.,, K. G. Sims,, J. E. Olson,, J. E. Childs,, J. F. Piesman,, C. M. Happ,, G. O. Maupin,, and B. J. B. Johnson. 1993. Amblyomma americanum: a potential vector of human ehrlichiosis. Am. J. Trop. Med. Hyg. 49: 239– 244.

6. Antony, S. J.,, J. S. Dumler,, and E. Hunter. 1995. Human ehrlichiosis in a liver transplant recipient. Transplantation 60: 879– 881.

7. Anziani, O. S.,, S. A. Ewing,, and R. W. Barker. 1990. Experimental transmission of a granulocytic form of the tribe Ehrlichieae by Dermacentor variabilis and Amblyomma americanum to dogs. Am. J. Vet. Res. 51: 929– 931.

8. Arguin, P. M.,, J. Singleton, Jr.,, L. D. Rotz,, E. Marston,, T. A. Treadwell,, K. Slater,, M. Chamberland,, A. Schwartz,, J. G. Olson,, J. E. Childs, and the Transfusion-Associated Tick-Borne Illness Task Force. 1999. An investigation of possible transmission of tick-borne Transfusion 39: 828– 833.

9. Armstrong, R. W. 1992. Ehrlichiosis in a visitor to West Virginia. J. Med. 157: 182– 184.

10. Barbour, A. G.,, G. O. Maupin,, G. J. Teltow,, C. J. Carter,, and J. Piesman. 1996. Identification of an uncultivable Borrelia species in the hard tick Amblyomma americanum: possible agent of a Lyme disease-like illness. J. Infect. Dis. 173: 403– 409.

11. Belongia, E. A.,, K. D. Reed,, P. D. Mitchell,, C. P. Kolbert,, D. H. Persing,, J. S. Gill,, and J. J. Kazmierczak. 1997. Prevalence of granulocytic Ehrlichia infection among white-tailed deer in Wisconsin. J. Clin. Microbiol. 35: 1465– 1468.

12. Bloemer, S. R.,, E. L. Snoddy,, J. C. Cooney,, and K. Fairbanks. 1986. Influence of deer exclusion on populations of lone star ticks and American dog ticks (Acari:Ixodidae). J. Econ. Entomol. 79: 679– 683.

13. Bloemer, S. R.,, R. H. Zimmerman,, and K. Fairbanks. 1988. Abundance, attachment sites, and density estimators for lone star ticks (Acari: Ixodidae) infesting white-tailed deer. J. Med. Entomol. 25: 295– 300.

14. Brouqui, P.,, and D. Raoult. 1992. In vitro antibiotic susceptibility of the newly recognized agent of ehrlichiosis in humans, Ehrlichia chaffeensis. Antimicrob. Agents Chemother. 36: 2799– 2803.

15. Brouqui, P.,, M. L. Birg,, and D. Raoult. 1994. Cytopathic effect, plaque formation, and lysis of Ehrlichia chaffeensis grown on continuous cell lines. Infect. Immun. 62: 405– 411.

16. Buitrago, M. I.,, J. W. Ijdo,, P. Rinaudo,, H. Simon,, J. Copel,, J. Gadbaw,, R. Heimer,, E. Fikrig,, and F. J. Bia. 1998. Human granulocytic ehrlichiosis during pregnancy treated successfully with rifampin. Clin. Infect. Dis. 27: 213– 215.

17. Buller, R. S.,, M. Arens,, S. P. Hmiel,, C. D. Paddock,, J. W. Sumner,, Y. Rikihisa,, A. Unver,, M. Gaudreault-Keener,, F. A. Manian,, A. M. Liddell,, N. Schmulewitz,, and G. A. Storch. 1999. Ehrlichia ewingii, a newly recognized agent of human ehrlichiosis. N. Engl. J. Med. 341: 148– 155.

18. Burket, C. T.,, C. N. Vann,, R. R. Pinger,, C. L. Chatot,, and F. E. Steiner. 1998. Minimum infection rate of Amblyomma americanum (Acari: Ixodidae) by Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) in southern Indiana. J. Med. Entomol. 35: 653– 659.

19. Carpenter, C. F.,, T. K. Gandhi,, L. K. Kong,, G. R. Corey,, S. M. Chen,, D. H. Walker,, J. S. Dumler,, E. Breitschwerdt,, B. Hegarty,, and D. J. Sexton. 1999. The incidence of ehrlichial and rickettsial infection in patients with unexplained fever and recent history of tick bite in central North Carolina. J. Infect. Dis. 180: 900– 903.

20. Centers for Disease Control and Prevention. 1997. Case definitions for infectious conditions under public health surveillance. Morb. Mortal. Wkly. Rep. 46(RR-10): 46– 47.

21. Centers for Disease Control and Prevention. 2000. Surveillance for Lyme disease—United States, 1992-1998. CDC Surveillance Summaries, April 28, 2000. Morb. Mortal. Wkly. Rep. 49(SS-3): 1– 11.

22. Carpenter, C. F. Centers for Disease Control and Prevention. 2001. Summary of notifiable diseases, United States, 1999. Morb. Mortal. Wkly. Rep. 48: 1– 104.

23. Chen, S.-M.,, V. L. Popov,, H.-M. Feng,, J. Wen,, and D. H. Walker. 1995. Cultivation of Ehrlichia chaffeensis in mouse embryo, Vero, BGM, and L929 cells and study of Ehrlichia-induced cytopathic effect and plaque formation. Infect. Immun. 63: 647– 655.

24. Chen, S.-M.,, X.-J. Yu,, V. L. Popov,, E. L. Westerman,, F. G. Hamilton,, and D. H. Walker. 1997. Genetic and antigenic diversity of Ehrlichia chaffeensis: comparative analysis of a novel human strain from Oklahoma and previously isolated strains. J. Infect. Dis. 175: 856– 863.

25. Childs, J. E.,, J. W. Sumner,, W. L. Nicholson,, R. F. Massung,, S. M. Standaert,, and C. D. Paddock. 1999. Outcome of diagnostic tests using samples from patients with culture-proven human monocytic ehrlichiosis: implications for surveillance. J. Clin. Microbiol. 37: 2997– 3000.

26. Childs, J. E.,, J. H. McQuiston,, J. W. Sumner,, W. L. Nicholson,, J. A. Comer,, R. F. Massung,, S. M. Standaert,, and C. D. Paddock. 1999. Human monocytic ehrlichiosis due to Ehrlichia chaffeensis: how do we count the cases? In D. Raoult and P. Brouqui (ed.), p. 287– 293. Rickettsiae and Rickettsial Diseases at the Turn of the Third Millennium. Elsevier, Paris, France.

27. Childs, J. E.,, and C. D. Paddock. 2002. The ascendancy of Amblyomma americanum as a vector of pathogens affecting humans in the United States. Annu. Rev. Entomol. 48: 307– 337.

28. Comer, J. A.,, W. L. Nicholson,, J. W. Sumner,, J. G. Olson,, and J. E. Childs. 1999. Diagnosis of human ehrlichiosis by PCR assay of acute-phase serum. J. Clin. Microbiol. 37: 31– 34.

29. Comer, J. A.,, W. L. Nicholson,, C. D. Paddock,, J. W. Sumner,, and J. E. Childs. 2000. Detection of antibodies reactive with Ehrlichia chaffeensis in the raccoon. J. Wildlife Dis. 36: 705– 712.

30. Cooley, R. A.,, and G. M. Kohls. 1944. The genus Amblyomma (Ixodidae) in the U. S. J. Parasitol. 30: 77– 111.

31. Dalton, M. J.,, M. J. Clarke,, R. C. Holman,, J. W. Krebs,, D. B. Fishbein,, J. G. Olson,, and J. E. Childs. 1995. National surveillance for Rocky Mountain spotted fever, 1981-1992: epidemiologic summary and evaluation of risk factors for fatal outcome. Am. J. Trop. Med. Hyg. 52: 405– 413.

32. Davidson, W. R.,, D. A. Siefken,, and L. H. Creekmore. 1994. Seasonal and annual abundance of Amblyomma americanum (Acari: Ixodidae) in central Georgia. J. Med. Entomol. 31: 67– 71.

33. Davidson, W. R.,, J. M. Lockhart,, D. E. Stallknecht,, and E. W. Howerth. 1999. Susceptibility of red and gray foxes to infection by Ehrlichia chaffeensis. J. Wildlife Dis. 35: 696– 702.

34. Davidson, W. R.,, J. M. Lockhart,, D. E. Stallknecht,, E. W. Howerth,, J. E. Dawson,, and Y. Rechav. 2001. Persistent Ehrlichia chaffeensis infection in white-tailed deer. J. Wildlife Dis. 37: 538– 546.

35. Dawson, J. E.,, Y. Rikihisa,, S. A. Ewing,, and D. B. Fishbein. 1991. Serologic diagnosis of human ehrlichiosis using two Ehrlichia canis isolates. J. Infect. Dis. 163: 564– 567.

36. Dawson, J. E.,, B. E. Anderson,, D. B. Fishbein,, J. L. Sanchez,, C. S. Goldsmith,, K. H. Wilson,, and C. W. Duntley. 1991. Isolation and characterization of an Ehrlichia sp. from a patient diagnosed with human ehrlichiosis. J. Clin. Microbiol. 29: 2741– 2745.

37. Dawson, J. E.,, and S. A. Ewing. 1992. Susceptibility of dogs to infection with Ehrlichia chaffeensis, causative agent of human ehrlichiosis. Am. J. Vet. Res. 53: 1322– 1327.

38. Dawson, J. E.,, F. J. Candal,, V. G. George,, and E. W. Ades. 1993. Human endothelial cells as an alternative to DH82 cells for isolation of Ehrlichia chaffeensis, E. canis, and Rickettsia rickettsii. Pathobiology 61: 293– 296.

39. Dawson, J. E.,, J. E. Childs,, K. L. Biggie,, C. Moore,, D. E. Stallknecht,, J. Shaddock,, J. Bouseman,, E. Hofmeister,, and J. G. Olson. 1994. White-tailed deer as a potential reservoir of Ehrlichia spp. J. Wildlife Dis. 30: 162– 168.

40. Dawson, J. E.,, D. E. Stallknecht,, E. W. Howerth,, C. Warner,, K. Biggie,, W. R. Davidson,, J. M. Lockhart,, V. F. Nettles,, J. G. Olson,, and J. E. Childs. 1994. Susceptibility of whitetailed deer ( Odocoileus virginianus) to infection with Ehrlichia chaffeensis, the etiologic agent of human ehrlichiosis. J. Clin. Microbiol. 32: 2725– 2728.

41. Dawson, J. E.,, C. K. Warner,, V. Baker,, S. A. Ewing,, D. E. Stallknecht,, W. R. Davidson,, A. A. Kocan,, J. M. Lockhart,, and J. G. Olson. 1996. Ehrlichia-like 16S rDNA sequence from wild white-tailed deer ( Odocoileus virginianus). J. Parasitol. 82: 52– 58.

42. Dawson, J. E.,, K. L. Biggie,, C. K. Warner,, K. Cookson,, S. Jenkins,, J. F. Levine,, and J. G. Olson. 1996. Polymerase chain reaction evidence of Ehrlichia chaffeensis, an etiologic agent of human ehrlichiosis, in dogs from southeast Virginia. Am. J. Vet. Res. 57: 1175– 1179.

43. Dawson, J. E.,, and A. M. Marty,. 1997. Ehrlichiosis, p. 49– 59. In C. R. Horsburgh, Jr.,, and A. M. Nelson (ed.), Pathology of Emerging Infections. American Society for Microbiology, Washington, D.C.

44. Dawson, J. E.,, C. D. Paddock,, C. K. Warner,, P. W. Greer,, J. H. Bartlett,, S. A. Ewing,, U. G. Munderloh,, and S. R. Zaki. 2001. Tissue diagnosis of Ehrlichia chaffeensis in patients with fatal ehrlichiosis by use of immunohistochemistry, in situ hybridization, and polymerase chain reaction. Am. J. Trop. Med. Hyg. 65: 603– 609.

45. Devereaux, C. E. 1997. Human monocytic ehrlichiosis presenting as febrile diarrhea. J. Clin. Gastroenterol. 25: 544– 545.

46. Dobson, A.,, and J. Foufopoulos. 2001. Emerging infectious pathogens of wildlife. Philos. Trans. R. Soc. Lond. B Biol. Sci. 356: 1001– 1012.

47. Dugan, V. G.,, S. E. Little,, D. E. Stallknecht,, and A. D. Beall. 2000. Natural infection of domestic goats with Ehrlichia chaffeensis. J. Clin. Microbiol. 38: 448– 449.

48. Dumler, J. S.,, P. Brouqui,, J. Aronson,, J. P. Taylor,, and D. H. Walker. 1991. Identification of Ehrlichia in human tissue. N. Engl. J. Med. 325: 1109– 1110. (Letter.)

49. Dumler, J. S.,, J. E. Dawson,, and D. H. Walker. 1993. Human ehrlichiosis: hematopathology and immunohistologic detection of Ehrlichia chaffeensis. Hum. Pathol. 24: 391– 396.

50. Dumler, J. S.,, W. L. Sutker,, and D. H. Walker. 1993. Persistent infection with Ehrlichia chaffeensis. Clin. Infect. Dis. 17: 903– 905.

51. Dumler, J. S.,, and D. H. Walker. 2001. Tick-borne ehrlichioses. Lancet Infect. Dis. 6: 21– 28.

52. Dumler, J. S.,, A. F. Barbet,, C. Bekker,, G. A. Dasch,, G. H. Palmer,, S. C. Ray,, Y. Rikihisa,, and F. R. Rurangirwa. 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 designations of Ehrlichia equi and ‘HGE agent’ as subjective synonyms of Ehrlichia phagocytophila. Int. J. Syst. Evol. Microbiol. 51: 2145– 2165.

53. Dunn, B. E.,, T. P. Monson,, J. S. Dumler,, C. C. Morris,, A. B. Westbrook,, J. L. Duncan,, J. E. Dawson,, K. G. Sims,, and B. E. Anderson. 1992. Identification of Ehrlichia chaffeensis morulae in cerebrospinal fluid mononuclear cells. J. Clin. Microbiol. 30: 2207– 2210.

54. Edwards, M. S. 1994. Ehrlichiosis in children. Semin. Ped. Infect. Dis. 5: 143– 147.

55. Eng, T. R.,, J. R. Harkess,, D. B. Fishbein,, J. E. Dawson,, C. N. Greene,, M. A. Redus,, and F. T. Satalowich. 1990. Epidemiologic, clinical, and laboratory findings of human ehrlichiosis in the United States, 1988. JAMA 264: 2251– 2258.

56. Estrada-Peña, A.,, and F. Jongejan. 1999. Ticks feeding on humans: a review of records on human-biting Ixodoidea with special reference to pathogen transmission. Exp. Appl. Acarol. 23: 685– 715.

57. Everett, E. D.,, K. A. Evans,, R. B. Henry,, and G. McDonald. 1994. Human ehrlichiosis in adults after tick exposure; diagnosis using polymerase chain reaction. Ann. Intern. Med. 120: 730– 735.

58. Ewing, S. A.,, E. M. Johnson,, and K. M. Kocan. 1987. Human infection with Ehrlichia canis. N. Engl. J. Med. 317: 899. ( Letter.)

59. Ewing, S. A.,, J. E. Dawson,, A. A. Kocan,, R. W. Barker,, C. K. Warner,, R. J. Panciera,, J. C. Fox,, K. M. Kocan,, and E. F. Blouin. 1995. Experimental transmission of Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) among white-tailed deer by Amblyomma americanum (Acari: Ixodidae). J. Med. Entomol. 32: 368– 374.

60. Felz, M. W.,, and L. A. Durden. 1999. Attachment site of four tick species (Acari: Ixodidae) parasitizing humans in Georgia and South Carolina. J. Med. Entomol. 36: 361– 364.

61. Fichtenbaum, C. J.,, L. R. Peterson,, and G. J. Weil. 1993. Ehrlichiosis presenting as a life-threatening illness with features of the toxic shock syndrome. Am. J. Med. 95: 351– 357.

62.Fishbein D. B., L. A. Sawyer, C. J. Holland, E. B. Hayes, W. Okoroanyanwu, D. Williams, K. Sikes, M. Ristic, and J. E. McDade. 1987. Unexplained febrile illnesses after exposure to ticks. Infection with an Ehrlichia? JAMA 257: 3100– 3104.

63. Fishbein, D. B.,, A. Kemp,, J. E. Dawson,, N. R. Greene,, M. A. Redus,, and D. H. Fields. 1989. Human ehrlichiosis: prospective active surveillance in febrile hospitalized patients. J. Infect. Dis. 160: 803– 809.

64. Fishbein, D. B.,, and J. E. Dawson,. 1991. Ehrlichiae, p. 1054– 1058. In A. Balows,, W. J. Hausler,, K. L. Herrmann,, H. D. Isenberg,, and H. J. Shadomy (ed.), Manual of Clinical Microbiology, 5th ed. American Society for Microbiology, Washington, D.C.

65. Fishbein, D. B.,, J. E. Dawson,, and L. E. Robinson. 1994. Human ehrlichiosis in the United States, 1985 to 1990. Ann. Intern. Med. 120: 736– 743.

66. Gardner, S. L.,, R. C. Holman,, J. W. Krebs,, R. Berkelman,, and J. E. Childs. 2003. National surveillance for the human ehrlichioses in the United States, 1997-2001, and proposed methods for evaluation of data quality. Ann. N. Y. Acad. Sci. 990: 80– 89.

67. Haile, D. G.,, and G. A. Mount. 1987. Computer simulation of population dynamics of the lone star tick, Amblyomma americanum (Acari: Ixodidae). J. Med. Entomol. 24: 356– 369.

68. Harkess, J. R.,, S. A. Ewing,, J. M. Crutcher,, J. Kudlac,, G. McKee,, and G. R. Istre. 1989. Human ehrlichiosis in Oklahoma. J. Infect. Dis. 159: 576– 579.

69. Heo, E. J.,, J. H. Park,, J. R. Koo,, M. S. Park,, M. Y. Park,, J. S. Dumler,, and J. S. Chae. 2002. Serologic and molecular detection of Ehrlichia chaffeensis and Anaplasma phagocytophila (human granulocytic ehrlichiosis agent) in Korean patients. J. Clin. Microbiol. 40: 3082– 3085.

70. Ijdo, J. W.,, C. Wu,, L. A. Magnarelli,, K. C. Stafford III,, J. F. Anderson,, and E. Fikrig. 2000. Detection of Ehrlichia chaffeensis DNA in Amblyomma americanum ticks in Connecticut and Rhode Island. J. Clin. Microbiol. 38: 4655– 4656.

71. Irving, R. P.,, R. R. Pinger,, C. N. Vann,, J. B. Olesen,, and F. E. Steiner. 2000. Distribution of Ehrlichia chaffeensis (Rickettsiales: Rickettsiaeceae) in Amblyomma americanum in southern Indiana and prevalence of E. chaffeensis-reactive antibodies in white-tailed deer in Indiana and Ohio in 1998. J. Med. Entomol. 37: 595– 600.

72. Jackson, L. K.,, D. M. Gaydon,, and J. Goddard. 1996. Seasonal activity and relative abundance of Amblyomma americanum in Mississippi. J. Med. Entomol. 33: 128– 131.

73. Jackson R. T.,, and J. W. Jackson. 1997. Ehrlichiosis with systemic sepsis syndrome. Tenn. Med. 90: 185– 186.

74. James, A. M.,, D. Liveris,, G. P. Wormser,, I. Schwartz,, M. A. Monteclavo,, and B. J. Johnson. 2001. Borrelia lonestari infection after a bite by an Amblyomma americanum tick. J. Infect. Dis. 183: 1810– 1814.

75. Javed, M. Z.,, M. Srivastava,, S. Zhang,, and M. Kandathil. 2001. Concurrent babesiosis and ehrlichiosis in an elderly host. Mayo Clin. Proc. 76: 563– 565.

76. Klein, M. B.,, C. M. Nelson,, and J. L. Goodman. 1997. Antibiotic susceptibility of the newly cultivated agent of human granulocytic ehrlichiosis: promising activity of quinolones and rifamycins. Antimicrob. Agents Chemother. 41: 76– 79.

77. Kocan, A. A.,, S. A. Ewing,, D. Stallknecht,, G. L. Murphy,, S. Little,, L. C. Whitworth,, and R. W. Barker. 2000. Attempted transmission of Ehrlichia chaffeensis among white-tailed deer by Amblyomma maculatum. J. Wildlife Dis. 36: 592– 594.

78. Kocan, A. A.,, G. C. Levesque,, L. C. Whitworth,, G. L. Murphy,, S. A. Ewing,, and R. W. Barker. 2000. Naturally occurring Ehrlichia chaffeensis infection in coyotes from Oklahoma. Emerg. Infect. Dis. 6: 477– 480.

79. Kordick, S. K.,, E. B. Breitschwerdt,, B. C. Hegarty,, K. L. Southwick,, C. M. Colitz,, S. I. Hancock,, J. M. Bradley,, R. Rumbough,, J. T. McPherson,, and J. N. MacCormack. 1999. Coinfection with multiple tick-borne pathogens in a Walker hound kennel in North Carolina. J. Clin. Microbiol. 37: 2631– 2638.

80. Kramer, V. L.,, M. P. Randolph,, L. T. Hui,, W. E. Irwin,, A. G. Gutierrez,, and D. J. Vugia. 1999. Detection of the agents of human ehrlichioses in ixodid ticks from California. Am. J. Trop. Med. Hyg. 60: 62– 65.

81. LaBarre, R.. 1994. Absence of Ehrlichia chaffeensis in West Texas tick vectors and identification of Rickettsia-like organism with shared antigenicity, D-37. Abstr. 94th Gen. Meet. Am. Soc. Microbiol. 1994. American Society for Microbiology, Washington, D.C.

82. Lee, E.,, and Y. Rikihisa. 1996. Lack of tumor necrosis factor alpha, interleukin-6 (IL-6), and granulocyte-macrophage colony-stimulating factor expression but presence of IL-1β, IL-8, and IL-10 expression in human monocytes exposed to viable or killed Ehrlichia chaffeensis. Infect. Immun. 64: 4211– 4219.

83. Lee, E.,, and Y. Rikihisa. 1997. Anti- Ehrlichia chaffeensis antibody induces potent proinflammatory cytokine mRNA expression in human monocytes exposed to E. chaffeensis through sustained reduction of Iĸβ-a and activation of NF-ĸβ. Infect. Immun. 65: 2890– 2897.

84. Liddell, A. M.,, J. W. Sumner,, C. D. Paddock,, Y. Rikihisa,, A. Unver,, R. S. Buller,, and G. A. Storch. 2002. Reinfection with Ehrlichia chaffeensis in a liver transplant recipient. Clin. Infect. Dis. 34: 1644– 1647.

85. Little, S. E.,, J. E. Dawson,, J. M. Lockhart,, D. E. Stallknecht,, C. K. Warner,, and W. R. Davidson. 1997. Development and use of specific polymerase chain reaction for the detection of an Ehrlichia-like organism in white-tailed deer. J. Parasitol. 33: 246– 253.

86. Little, S. E.,, D. E. Stallknecht,, J. M. Lockhart,, J. E. Dawson,, and W. R. Davidson. 1998. Natural co-infection of a white-tailed deer ( Odocoileus virginianus) population with three Ehrlichia spp. J. Parasitol. 84: 897– 901.

87. Little, S. E.,, and E. W. Howerth. 1999. Ehrlichia chaffeensis in archived tissues of a white-tailed deer. J. Wildlife Dis. 35: 596– 599.

88. Lockhart, J. M.,, W. R. Davidson,, J. E. Dawson,, and D. E. Stallknecht. 1995. Temporal association of Amblyomma americanum with the presence of Ehrlichia chaffeensis-reactive antibodies in white-tailed deer. J. Wildlife Dis. 31: 119– 124.

89. Lockhart, J. M.,, W. R. Davidson,, D. E. Stallknecht,, and J. E. Dawson. 1996. Site-specific geographic association between Amblyomma americanum (Acari: Ixodidae) infestations and Ehrlichia chaffeensis-reactive (Rickettsiales: Ehrlichieae) antibodies in white-tailed deer. J. Med. Entomol. 33: 153– 158.

90.Lockhart J. M., W. R. Davidson, D. E. Stallknecht, J. E. Dawson, and S. E. Little. 1997. Natural history of Ehrlichia chaffeensis in the Piedmont physiographic province of Georgia. J. Parasitol. 83: 887– 894.

91. Lockhart, J. M.,, W. R. Davidson,, D. E. Stallknecht,, J. E. Dawson,, and E. W. Howerth. 1997. Isolation of Ehrlichia chaffeensis from white-tailed deer ( Odocoileus virginianus) confirms their role as natural reservoir hosts. J. Clin. Microbiol. 35: 1681– 1686.

92. Lockhart, J. M.,, and W. R. Davidson. 1999. Evaluation of C3H/HeJ mice for xenodiagnosis of infection with Ehrlichia chaffeensis. J. Vet. Diag. Investig. 11: 55– 59.

93. Maeda, K. M.,, M. Markowitz,, R. C. Hawley,, M. Ristic,, D. Cox,, and J. E. McDade. 1987. Human infection with Ehrlichia canis, a leukocytic rickettsia. N. Engl. J. Med. 316: 853– 856.

94. Magnarelli, L. A.,, J. F. Anderson,, K. C. Stafford III,, and J. S. Dumler. 1997. Antibodies to multiple tick-borne pathogens of babesiosis, ehrlichiosis, and Lyme borreliosis in white-footed mice. J. Wildlife Dis. 33: 466– 473.

95. Magnarelli, L. A.,, J. W. Ijdo,, K. C. Stafford III,, and E. Fikrig. 1999. Infections of granulocytic ehrlichiae and Borrelia burgdorferi in white-tailed deer in Connecticut. J. Wildlife Dis. 35: 266– 274.

96. Marshall, G. S.,, R. F. Jacobs,, G. E. Schutze,, H. Paxton,, S. C. Buckinghan,, J. P. Devincenzo,, M. A. Jackson,, V. H. San Joaquin,, S. M. Standaert,, and C. R. Woods. 2002. Ehrlichia chaffeensis seroprevalence among children in the Southeast and south-central regions of the United States. Arch. Pediatr. Adolesc. Med. 156: 166– 170.

97. Martin, G. S.,, B. W. Christman,, and S. M. Standaert. 1999. Rapidly fatal infection with Ehrlichia chaffeensis. N. Engl. J. Med. 341: 763– 764.

98. Marty, A. M.,, J. S. Dumler,, G. Imes,, H. P. Brusman,, L. L. Smrkovski,, and D. M. Frisman. 1995. Ehrlichiosis mimicking thrombotic thrombocytopenic purpura. Case report and pathological correlation. Hum. Pathol. 26: 920– 925.

99. Mathisen, G.,, P. J. Weis,, and C. A. Kennedy. 1993. Pneumonia, aseptic meningitis, and leukopenia in a 28-year-old man. Clin. Infect. Dis. 16: 809– 815.

100. Maurin, M.,, C. Abergel,, and D. Raoult. 2001. DNA gyrasemediated natural resistance to fluoroquinolones in Ehrlichia spp. Antimicrob. Agents Chemother. 45: 2098– 2105.

101. McCall, C. L.,, A. T. Curns,, J. S. Singleton,, J. A. Comer,, J. G. Olson,, L. D. Rotz,, T. A. Treadwell,, P. Arguin,, and J. E. Childs. 2001. Fort Chaffee revisited; the epidemiology of tick-borne diseases at a persistent focus. Vector Borne Zoonotic Dis. 2: 119– 127.

102. McDade, J. E. 1990. Ehrlichiosis—a disease of animals and humans. J. Infect. Dis. 161: 609– 617.

103. McKechnie, D. B.,, K. S. Slater,, J. E. Childs,, R. F. Massung,, and C. D. Paddock. 2000. Survival of Ehrlichia chaffeensis in refrigerated, ADSOL-treated RBCs. Transfusion 40: 1041– 1047.

104. McQuiston, J. H.,, C. D. Paddock,, R. C. Holman,, and J. E. Childs. 1999. The human ehrlichioses in the United States. Emerg. Infect. Dis. 5: 635– 642.

105. Means, R. G.,, and D. J. White. 1997. New distribution records of Amblyomma americanum (L.) (Acari: Ixodidae) in New York State. J. Vector Ecol. 22: 133– 145.

106. Moore, V. A.,, A. S. Varela,, M. J. Yabsley,, W. R. Davidson,, and S. E. Little. 2003. Detection of Borrelia lonestari, putative agent of STARI (southern tick-associated rash illness), in white-tailed deer ( Odocoileus virginianus) from the southeastern United States. J. Clin. Microbiol. 41: 424– 427.

107. Morris, J. G., Jr.,, and M. Potter. 1997. Emergence of new pathogens as a function of changes in host susceptibility. Emerg. Infect. Dis. 3: 435– 441.

108. Moskovitz, M.,, R. Fadden,, and T. Min. 1991. Human ehrlichiosis: a rickettsial disease associated with severe cholestasis and multisystemic disease. J. Clin. Gastroenterol. 13: 86– 90.

109. Mueller-Anneling, L.,, M. J. Gilchrist,, and P. S. Thorne. 2000. Ehrlichia chaffeensis antibodies in white-tailed deer, Iowa, 1994 and 1996. Emerg. Infect. Dis. 6: 397– 400.

110. Murphy, G. L.,, S. A. Ewing,, L. C. Whitworth,, J. C. Fox,, and A. A. Kocan. 1998. A molecular and serologic survey of Ehrlichia canis, E. chaffeensis, and E. ewingii in dogs and ticks from Oklahoma. Vet. Parasitol. 79: 325– 339.

111. Nutt, A. K.,, and J. Raufman. 1999. Gastrointestinal and hepatic manifestations of human ehrlichiosis: 8 cases and a review of the literature. Dig. Dis. 17: 37– 43.

112. Ohashi, N.,, A. Unver,, N. Zhi,, and Y. Rikihisa. 1998. Cloning and characterization of multigenes encoding the immunodominant 30-kilodalton major outer membrane proteins of Ehrlichia canis and application of the recombinant protein for serodiagnosis. J. Clin. Microbiol. 36: 2671– 2680.

113. Okada, H.,, T. Tajima,, M. Kawahara,, and Y. Rikihisa. 2001. Ehrlichial proliferation and acute hepatocellular necrosis in immunocompetent mice experimentally infected with the HF strain of Ehrlichia, closely related to Ehrlichia chaffeensis. J. Comp. Pathol. 124: 165– 171.

114. Olano, J. P.,, E. Masters,, L. Cullman,, W. Hoegrefe,, X. J. Yu,, and D. H. Walker,. 1999. Human monocytotropic ehrlichiosis (HME): epidemiological, clinical and laboratory diagnosis of a newly emergent infection in the United States, p. 262– 268. In D. Raoult, and P. Brouqui (ed.), Rickettsiae and Rickettsial Diseases at the Turn of the Third Millennium. Elsevier, Paris, France.

115. Olano, J. P.,, and D. H. Walker. 2002. Human ehrlichioses. Med. Clin. North Am. 86: 375– 392.

116. Paddock, C. D.,, J. W. Sumner,, G. M. Shore,, D. C. Bartley,, R. C. Elie,, J. G. McQuade,, C. R. Martin,, C. S. Goldsmith,, and J. E. Childs. 1997. Isolation and characterization of Ehrlichia chaffeensis strains from patients with fatal ehrlichiosis J. Clin. Microbiol. 35: 2496– 2502.

117. Paddock, C. D.,, S. M. Folk,, G. M. Shore,, L. J. Machado,, M. M. Huycke,, L. N. Slater,, A. M. Liddell,, R. S. Buller,, G. A. Storch,, T. P. Monson,, D. Rimland,, J. W. Sumner,, J. Singleton,, K. C. Bloch,, Y. W. Tang,, S. M. Standaert,, and J. E. Childs. 2001. Infections with Ehrlichia chaffeensis and Ehrlichia ewingii in persons coinfected with human immunodeficiency virus. Clin. Infect. Dis. 33: 1586– 1594.

118. Paddock, C. D.,, and J. E. Childs. 2003. Ehrlichia chaffeensis: a prototype emerging pathogen. Clin. Microbiol. Rev. 16: 37– 64.

119. Patel, R. G.,, and M. A. Byrd. 1999. Near fatal acute respiratory distress syndrome in a patient with human ehrlichiosis. South Med. J. 92: 333– 335.

120. Patrick, C. D.,, and J. A. Hair. 1977. Seasonal abundance of lone star ticks on white-tailed deer. Environ. Entomol. 6: 263– 269.

121. Patrick, C. D. 1978. White-tailed deer utilization of three different habitats and its influence on lone star tick populations. J. Parasitol. 64: 1100– 1106.

122. Pearce, C. J.,, M. E. Conrad,, P. E. Nolan,, D. B. Fishbein,, and J. E. Dawson. 1988. Ehrlichiosis: a cause of bone marrow hypoplasia in humans. Am. J. Hematol. 28: 53– 55.

123. Petersen, L. R.,, L. A. Sawyer,, D. B. Fishbein,, P. W. Kelley,, R. J. Thomas,, L. A. Magnarelli,, M. Redus,, and J. E. Dawson. 1989. An outbreak of ehrlichiosis in members of an Army Reserve unit exposed to ticks. J. Infect. Dis. 159: 562– 568.

124. Pick, N.,, I. Potasman,, C. Strenger,, A. Keysary,, and I. Schwartz. 2000. Ehrlichiosis associated vasculitis. J. Intern. Med. 247: 674– 678.

125. Ratnasamy, N.,, E. D. Everett,, W. E. Roland,, G. McDonald,, and C. W. Caldwell. 1996. Central nervous system manifestations of human ehrlichiosis. Clin. Infect. Dis. 23: 314– 319.

126. Rawlings, J. 1996. Human ehrlichiosis in Texas. J. Spir. Tick-borne Dis. 3: 94– 97.

127. Reddy, G. R.,, and C. P. Streck. 1999. Variability in the 28-kDa surface antigenic protein multigene locus of isolates of the emerging disease agent Ehrlichia chaffeensis suggest that it plays a role in immune invasion. Mol. Cell. Biol. Res. Commun. 1: 167– 175.

128. Rikihisa, Y. 1991. The tribe Ehrlichieae and ehrlichial diseases. Clin. Microbiol. Rev. 4: 286– 308.

129. Rikihisa, Y. 1999. Clinical and biological aspects of infection caused by Ehrlichia chaffeensis. Microbes Infect. 1: 367– 376.

130. Ristic, M,. 1986. Pertinent characteristics of leukocytic rickettsiae of humans and animals, p. 182– 187. In L. Leive (ed.), Microbiology- 1986. American Society for Microbiology, Washington, D.C.

131. Ristic, M.,, and D. L. Huxsoll,. 1984. Ehrlichiae, p. 704– 709. In N. R. Krieg, and J. G. Holt (ed.), Bergey’s Manual of Systematic Bacteriology, vol. 1. The Williams & Wilkins Co., Baltimore, Md.

132. Rohrbach, B. W.,, J. R. Harkess,, and J. Kudlac. 1987. Human ehrlichiosis: a cause of “Oklahoma Tick Fever”? Okla. St. Dep. Health Commun. Dis. Bull. 87: 1.

133. Rohrbach, B. W.,, J. R. Harkess,, S. A. Ewing,, J. Kudlac,, G. L. McKee,, and G. R. Istre. 1990. Epidemiologic and clinical characteristics of persons with serologic evidence of E. canis infection. Am. J. Public Health 80: 442– 445.

134. Roland, W. E.,, E. D. Everett,, T. L. Cyr,, S. Z. Hasan,, C. B. Dommarju,, and G. A. McDonald. 1998. Ehrlichia chaffeensis in Missouri ticks. Am. J. Trop. Med. Hyg. 59: 641– 643.

135. Rydkina, E.,, V. Roux,, and D. Raoult. 1999. Determination of the genome size of Ehrlichia spp., using pulsed field gel electrophoresis. FEMS Microbiol. Lett. 176: 73– 78.

136. Rynkiewicz, D.,, and L. X. Liu. 1994. Human ehrlichiosis in New England. N. Engl. J. Med. 330: 292. ( Letter.)

137. Safdar, N.,, R. B. Love,, and D. G. Maki. 2002. Severe Ehrlichia chaffeensis infection in a lung transplant recipient: a review of ehrlichiosis in the immunocompromised patient. Emerg. Infect. Dis. 8: 320– 323.

138. Semnter, P. J.,, J. R. Saurer,, and J. A. Hair. 1973. The ecology and behavior of the lone star tick (Acarina: Ixodidae). IV. Abundance and seasonal distribution in different habitat types. J. Med. Entomol. 10: 618– 628.

139. Sexton, D. J.,, G. R. Corey,, C. Carpenter,, L. Q. Kong,, T. Gandhi,, E. Breitschwerdt,, B. Hegarty,, S. M. Chen,, H. M. Feng,, X. J. Yu,, J. Olano,, D. H. Walker,, and J. S. Dumler. 1998. Dual infection with Ehrlichia chaffeensis and a spotted fever group rickettsia: a case report. Emerg. Infect. Dis. 4: 311– 316.

140. Shea, K. W.,, A. J. Calio,, N. C. Klein,, and B. A. Cunha. 1995. Rhabdomyolysis associated with Ehrlichia chaffeensis infection. Clin. Infect. Dis. 21: 1056– 1057.

141. Shibata, S.-I.,, M. Y. Kawahara,, Y. Rikihisa,, H. Fujita,, Y. Watanabe,, C. Suto,, and T. Ito. 2000. New ehrlichia species closely related to Ehrlichia chaffeensis isolated from Ixodes ovatus ticks in Japan. J. Clin. Microbiol. 38: 1331– 1338.

142. Smith, S.,, A. E. Sehdev,, P. S. Sehdev,, R. Jacobs,, and J. S. Dumler. 2002. Human monocytic ehrlichiosis presenting as acute appendicitis during pregnancy. Clin. Infect. Dis. 35: 99– 102.

143. Sonenshine, D. E.,, and G. J. Levy. 1971. The ecology of the lone star tick Amblyomma americanum (L.) in two contrasting habitats in Virginia (Acari: Ixodidae). J. Med. Entomol. 8: 623– 635.

144. Sotomayor, E. A.,, V. L. Popov,, H. Feng,, D. H. Walker,, and J. P. Olano. 2001. Animal model of fatal human monocytotropic ehrlichiosis. Am. J. Pathol. 158: 757– 769.

145. Standaert, S. M.,, J. E. Dawson,, W. Schaffner,, J. E. Childs,, K. L. Biggie,, J. Singleton, Jr.,, R. R. Gerhardt, M. L. Knight, and R. H. Hutcheson. 1995. Ehrlichiosis in a golf-oriented retirement community. N. Engl. J. Med. 333: 420– 425.

146. Standaert, S. M.,, L. A. Clough,, W. Schaffner,, J. S. Adams,, and K. M. Neuzil. 1998. Neurologic manifestations of human monocytic ehrlichiosis. Infect. Dis. Clin. Pract. 7: 358– 362.

147. Standaert, S. M.,, T. Yu,, M. A. Scott,, J. E. Childs,, C. D. Paddock,, W. Nicholson,, J. Singleton,, and M. J. Blaser. 2000. Primary isolation of Ehrlichia chaffeensis from patients with febrile illnesses: clinical and molecular characteristics. J. Infect. Dis. 181: 1082– 1088.

148. Steiner, F. E.,, R. R. Pinger,, and C. N. Vann. 1999. Infection rates of Amblyomma americanum (Acari: Ixodidae) by Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) and prevalence of E. chaffeensis-reactive antibodies in white-tailed deer in southern Indiana, 1997. J. Med. Entomol. 36: 715– 719.

149. Stromdahl, E. Y.,, S. R. Evans,, J. J. O’Brien,, and A. G. Guttierez. 2001. Prevalence of infection in ticks submitted to the human tick test kit program of the U.S. Army Center for Health Promotion and Preventive Medicine. J. Med. Entomol. 38: 67– 74.

150. Sumner, J. W.,, W. L. Nicholson,, and R. F. Massung. 1997. PCR amplification and comparison of nucleotide sequences from the groESL heat shock operon of Ehrlichia species. J. Clin. Microbiol. 35: 2087– 2092.

151. Sumner, J. W.,, J. E. Childs,, and C. D. Paddock. 1999. Molecular cloning and characterization of the Ehrlichia chaffeensis variable-length PCR target: an antigen-expressing gene that exhibits interstrain variation. J. Clin. Microbiol. 37: 1447– 1453.

152. Sumner, J. W.,, G. A. Storch,, R. S. Buller,, A. M. Liddell,, S. L. Stockham,, Y. Rikihisa,, S. Messenger,, and C. D. Paddock. 2000. PCR amplification and phylogenetic analysis of groESL operon sequences from Ehrlichia ewingii and Ehrlichia muris. J. Clin. Microbiol. 38: 2746– 2749.

153. Telford, S. R. III, and J. E. Dawson. 1996. Persistent infection of C3H/HeJ mice by Ehrlichia chaffeensis. Vet. Microbiol. 52: 103– 112.

154. Thompson, C.,, A. Spielman,, and P. J. Krause. 2001. Coinfecting deer-associated zoonoses: Lyme disease, babesiosis, and ehrlichiosis. Clin. Infect. Dis. 33: 676– 685.

155. Uhaa, I. J.,, J. D. Maclean,, C. R. Green,, and D. B. Fishbein. 1992. A case of human ehrlichiosis acquired in Mali: clinical and laboratory findings. Am. J. Trop. Med. Hyg. 46: 161– 164.

156. Unver, A.,, S. Felek,, C. D. Paddock,, N. Zhi,, H. W. Horowitz,, G. P. Wormser,, L. C. Cullman,, and Y. Rikihisa. 2001. Western blot analysis of sera reactive to human monocytic ehrlichiosis and human granulocytic ehrlichiosis agents. J. Clin. Microbiol. 39: 3982– 3986.

157. U.S. Census Bureau. 2001. Profiles of general demographic characteristics; 2000 census of population and housing, United States. U.S. Department of Commerce, Washington D.C.

158. Walls, J. J.,, K. M. Asanovich,, J. S. Bakken,, and J. S. Dumler. 1998. Serologic evidence of a natural infection of whitetailed deer with the agent of human granulocytic ehrlichiosis in Wisconsin and Maryland. Clin. Diag. Lab. Immunol. 5: 762– 765.

159. Walker, D. H.,, A. G. Barbour,, J. H. Oliver,, R. S. Lane,, J. S. Dumler,, D. T. Dennis,, D. H. Persing,, A. F. Azad,, and E. Mc- Sweegan. 1996. Emerging bacterial zoonotic and vector-borne diseases: ecological and epidemiological factors. JAMA 275: 463– 469.

160. Walker, D. H., and the Task Force on Consensus Approach for Ehrlichiosis (CAFÉ). 2000. Diagnosing human ehrlichioses: current status and recommendations. ASM News 66: 287– 290.

161. Weaver, R. A.,, G. Virella,, and A. Weaver. 1999. Ehrlichiosis with severe pulmonary manifestations despite early treatment. South Med. J. 92: 336– 339.

162. Whitlock, J. E.,, Q. Q. Fang,, L. A. Durden,, and J. H. Oliver, Jr. 2000. Prevalence of Ehrlichia chaffeensis (Rickettsiales: Rickettsiaceae) in Amblyomma americanum (Acari: Ixodidae) from the Georgia coast and barrier islands. J. Med. Entomol. 37: 276– 280.

163. Williams, J. D.,, R. M. Snow,, and J. G. Arciniegas. 1995. Myocardial involvement in a patient with human ehrlichiosis. Am. J. Med. 98: 414– 415.

164. Winslow, G. M.,, E. Yager,, K. Shilo,, D. N. Collins,, and F. K. Chu. 1998. Mechanisms of immunity to Ehrlichia chaffeensis. Infect. Immun. 66: 3892– 3899.

165. Wolf, L.,, T. McPherson,, B. Harrison,, B. Engber,, A. Anderson,, and P. Whitt. 2000 . Prevalence of Ehrlichia ewingii in Amblyomma americanum in North Carolina. J. Clin. Microbiol. 38: 2795. ( Letter.)

166. Wong, S. J.,, G. S. Brady,, and J. S. Dumler. 1997. Serological responses to Ehrlichia equi, Ehrlichia chaffeensis, and Borrelia burgdorferi in patients from New York State. J. Clin. Microbiol. 35: 2198– 2205.

167. Yabsley, M. J.,, A. S. Varela,, C. M. Tate,, V. G. Dugan,, D. E. Stallknecht,, S. E. Little,, and W. R. Davidson. 2002. Ehrlichia ewingii infection in white-tailed deer ( Odocoileus virginianus). Emerg. Infect. Dis. 8: 668– 671.

168. Yabsley, M. J.,, V. G. Dugan,, D. E. Stallknecht,, S. E. Little,, J. M. Lockhart,, J. E. Dawson,, and W. R. Davidson. 2003. Evaluation of a prototype Ehrlichia chaffeensis surveillance system using white-tailed deer ( Odocoileus virginianus) as natural sentinels. Vector Borne Zoonotic Dis. 3: 195– 207.

169. Yabsley, M. J.,, S. E. Little,, E. J. Sims,, V. G. Dugan,, D. E. Stallknecht,, and W. R. Davidson. 2003. Molecular variation in the variable-length PCR target and 120-kilodalton antigen genes of Ehrlichia chaffeensis from white-tailed deer ( Odocoileus virginianus). J. Clin. Microbiol. 41: 5202– 5206.

170. Yevich, S. J.,, J. L. Sanchez,, R. F. Defraites,, C. C. Rives,, J. E. Dawson,, I. J. Uhaa,, B. J. Johnson,, and D. B. Fishbein. 1995. Seroepidemiology of infections due to spotted fever group rickettsiae and Ehrlichia species in military personnel exposed in areas of the United States where such infections are endemic. J. Infect. Dis. 171: 1266– 1273.

171. Yu, X.,, P. Brouqui,, J. S. Dumler,, and D. Raoult. 1993. Detection of Ehrlichia chaffeensis in human tissue by using a species-specific monoclonal antibody. J. Clin. Microbiol. 31: 3284– 3288.

172. Yu, X. J.,, P. Crocquet-Valdes,, L. C. Cullman,, and D. H. Walker. 1996. The recombinant 120-kilodalton protein of Ehrlichia chaffeensis, a potential diagnostic tool. J. Clin. Microbiol. 34: 2853– 2855.

173. Yu, X. J.,, J. W. McBride,, and D. H. Walker. 1999. Genetic diversity of the 28-kilodalton outer membrane protein gene in human isolates of Ehrlichia chaffeensis. J. Clin. Microbiol. 37: 1137– 1143.