Dalton MJ, Clarke MJ, Holman RC, Krebs JW, Fishbein DB, Olson JG, Childs JE, 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.
Holman RC, Paddock CD, Curns AT, Krebs JW, McQuiston JH, Childs JE, 2001. Analysis of risk factors for fatal Rocky Mountain spotted fever: evidence for superiority of tetracyclines for therapy. J Infect Dis 184: 1437–1444.
Openshaw JJ, Swerdlow DL, Krebs JW, Holman RC, Mandel E, Harvey A, Haberling D, Massung RF, McQuiston JH, 2010. Rocky Mountain spotted fever in the United States, 2000–2007: interpreting contemporary increases in incidence. Am J Trop Med Hyg 83: 174–182.
Centers for Disease Control and Prevention, 2000. Consequences of delayed diagnosis of Rocky Mountain spotted fever in children—West Virginia, Michigan, Tennessee, and Oklahoma, May–July 2000. MMWR 49: 885–888.
Traeger MS, Regan JJ, Humpherys D, Mahoney DL, Martinez M, Emerson GL, Tack DM, Geissler A, Yasmin S, Lawson R, Hamilton C, Williams V, Levy C, Komatsu K, McQuiston JH, Yost DA, 2015. Rocky Mountain spotted fever characterization and comparison to similar illnesses in a highly endemic area—Arizona, 2002–2011. Clin Infect Dis 60: 1650–1658.
Regan JJ, Traeger MS, Humpherys D, Mahoney DL, Martinez M, Emerson GL, Tack DM, Geissler A, Yasmin S, Lawson R, Williams V, Hamilton C, Levy C, Komatsu K, Yost DA, McQuiston JH, 2015. Risk factors for fatal outcome from Rocky Mountain spotted fever in a highly endemic area—Arizona, 2002–2011. Clin Infect Dis 60: 1659–1666.
Centers for Disease Control and Prevention, 2006. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichiosis, and anaplasmosis—United States. MMWR Recomm Rep 55: 1–27.
Drexler N, Dahlgren FS, Nichols Heitman K, Massung RF, Paddock CD, Barton Behravesh C, 2016. National surveillance of spotted fever group rickettsioses in the United States, 2008–2012. Am J Trop Med Hyg 94: 26–34.
Huebner RJ, Jellison WL, Armstrong C, 1947. Rickettsialpox: a newly recognized rickettsial disease: V. Recovery of Rickettsia akari from a house mouse (Mus musculus). Public Health Rep 62: 777–780.
Greenberg M, Pellitteri O, Klein IF, Huebner RJ, 1947. Rickettsialpox—a newly recognized rickettsial disease: II. Clinical observations. J Am Med Assoc 133: 901–906.
Paddock CD, Sumner JW, Comer JA, Zaki SR, Goldsmith CS, Goddard J, McLellan SL, Tamminga CL, Ohl CA, 2004. Rickettsia parkeri: a newly recognized cause of spotted fever rickettsiosis in the United States. Clin Infect Dis 38: 805–811.
Paddock CD, Finley RW, Wright CS, Robinson HN, Schrodt BJ, Lane CC, Ekenna O, Blass MA, Tamminga CL, Ohl CA, McLellan SL, Goddard J, Holman RC, Openshaw JJ, Sumner JW, Zaki SR, Eremeeva ME, 2008. Rickettsia parkeri rickettsiosis and its clinical distinction from Rocky Mountain spotted fever. Clin Infect Dis 47: 1188–1196.
Parker RR, 1939. Observations on an infectious agent from Amblyomma maculatum. Public Health Rep 54: 1482–1484.
Cohen SB, Yabsley MJ, Garrison LE, Freye JD, Dunlap BG, Dunn JR, Mead DG, Jones TF, Moncayo AC, 2009. Rickettsia parkeri in Amblyomma americanum ticks, Tennessee and Georgia, USA. Emerg Infect Dis 15: 1471–1473.
Johnston SH, Glaser CA, Padgett K, Wadford DA, Espinosa A, Espinosa N, Eremeeva ME, Tait K, Hobson B, Shtivelman S, Hsieh C, Messenger SL, 2013. Rickettsia spp. 364D causing a cluster of eschar-associated illness, California. Pediatr Infect Dis J 32: 1036–1039.
Shapiro MR, Fritz CL, Tait K, Paddock CD, Nicholson WL, Abramowicz KF, Karpathy SE, Dasch GA, Sumner JW, Adem PV, Scott JJ, Padgett KA, Zaki SR, Eremeeva ME, 2010. Rickettsia 364D: a newly recognized cause of eschar-associated illness in California. Clin Infect Dis 50: 541–548.
Stromdahl EY, Jiang J, Vince M, Richards AL, 2011. Infrequency of Rickettsia rickettsii in Dermacentor variabilis removed from humans, with comments on the role of other human-biting ticks associated with spotted fever group rickettsiae in the United States. Vector Borne Zoonotic Dis 11: 969–977.
McQuiston JH, Zemtsova G, Perniciaro J, Hutson M, Singleton J, Nicholson WL, Levin ML, 2012. Afebrile spotted fever group Rickettsia infection after a bite from a Dermacentor variabilis tick infected with Rickettsia montanensis. Vector Borne Zoonotic Dis 12: 1059–1061.
Apperson CS, Engber B, Nicholson WL, Mead DG, Engel J, Yabsley MJ, Dail K, Johnson J, Watson DW, 2008. Tick-borne diseases in North Carolina: is “Rickettsia amblyommii” a possible cause of rickettsiosis reported as Rocky Mountain spotted fever? Vector Borne Zoonotic Dis 8: 597–606.
Jiang J, Yarina T, Miller MK, Stromdahl EY, Richards AL, 2010. Molecular detection of Rickettsia amblyommii in Amblyomma americanum parasitizing humans. Vector Borne Zoonotic Dis 10: 329–340.
Billeter SA, Blanton HL, Little SE, Levy MG, Breitschwerdt EB, 2007. Detection of Rickettsia amblyommii in association with a tick bite rash. Vector Borne Zoonotic Dis 7: 607–610.
Barrett A, Little SE, Shaw E, 2014. “Rickettsia amblyommii” and R. montanensis infection in dogs following natural exposure to ticks. Vector Borne Zoonotic Dis 14: 20–25.
National Office of Vital Statistics, 1953. Reported incidence of selected notifiable diseases: United States, each division and state, 1920–1950. Vital Statistics. Special Reports 37: 179–243.
Atkinson SF, Sarkar S, Avina A, Schuermann JA, Williamson P, 2012. Modelling spatial concordance between Rocky Mountain spotted fever disease incidence and habitat probability of its vector Dermacentor variabilis (American dog tick). Geospat Health 7: 91–100.
Childs JE, Paddock CD, 2003. The ascendancy of Amblyomma americanum as a vector of pathogens affecting humans in the United States. Annu Rev Entomol 48: 307–337.
Blanton LS, Mendell NL, Walker DH, Bouyer DH, 2014. “Rickettsia amblyommii” induces cross protection against lethal Rocky Mountain spotted fever in a guinea pig model. Vector Borne Zoonotic Dis 14: 557–562.
Springer YP, Eisen L, Beati L, James AM, Eisen RJ, 2014. Spatial distribution of counties in the continental United States with records of occurrence of Amblyomma americanum (Ixodida: Ixodidae). J Med Entomol 51: 342–351.
Wood SN, 2006. Generalized Additive Models: An Introduction with R. Boca Raton, FL: Chapman and Hall/CRC.
Bockman SF, 1989. Generalizing the formula for areas of polygons to moments. Am Math Mon 96: 131–132.
Salvatore M, Meyers BR, 2010. Tetracyclines and chloramphenicol. Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Vol. 1, 7th edition. Philadelphia, PA: Elsevier Churchill Livingstone, 385–402.
Drexler N, Miller M, Gerding J, Todd S, Adams L, Dahlgren FS, Bryant N, Weis E, Herrick K, Francies J, Komatsu K, Piontkowski S, Velascosoltero J, Shelhamer T, Hamilton B, Eribes C, Brock A, Sneezy P, Goseyun C, Bendle H, Hovet R, Williams V, Massung R, McQuiston JH, 2014. Community-based control of the brown dog tick in a region with high rates of Rocky Mountain spotted fever, 2012–2013. PLoS One 9: e112368.
Wood MW, 1896. Spotted fever as reported from Idaho. Report to the Surgeon General of the Army. 60–65.
Cobb JO, 1902. The so-called “spotted fever” of the Rocky Mountains—a new disease in Bitter Root Valley, Mont. Public Health Rep 17: 1868–1870.
Williamson PC, Billingsley PM, Teltow GJ, Seals JP, Turnbough MA, Atkinson SF, 2010. Borrelia, Ehrlichia, and Rickettsia spp. in ticks removed from persons, Texas, USA. Emerg Infect Dis 16: 441–446.
Fornadel CM, Zhang X, Smith JD, Paddock CD, Arias JR, Norris DE, 2011. High rates of Rickettsia parkeri infection in Gulf Coast ticks (Amblyomma maculatum) and identification of “Candidatus Rickettsia andeanae” from Fairfax County, Virginia. Vector Borne Zoonotic Dis 11: 1535–1539.
Fritzen CM, Huang J, Westby K, Freye JD, Dunlap B, Yabsley MJ, Schardein M, Dunn JR, Jones TF, Moncayo AC, 2011. Infection prevalences of common tick-borne pathogens in adult lone star ticks (Amblyomma americanum) and American dog ticks (Dermacentor variabilis) in Kentucky. Am J Trop Med Hyg 85: 718–723.
Moncayo AC, Cohen SB, Fritzen CM, Huang E, Yabsley MJ, Freye JD, Dunlap BG, Huang J, Mead DG, Jones TF, Dunn JR, 2010. Absence of Rickettsia rickettsii and occurrence of other spotted fever group rickettsiae in ticks from Tennessee. Am J Trop Med Hyg 83: 653–657.
Pagac BB, Miller MK, Mazzei MC, Nielsen DH, Jiang J, Richards AL, 2014. Rickettsia parkeri and Rickettsia montanensis, Kentucky and Tennessee, USA. Emerg Infect Dis 20: 1750–1752.
Mixson TR, Campbell SR, Gill JS, Ginsberg HS, Reichard MV, Schulze TL, Dasch GA, 2006. Prevalence of Ehrlichia, Borrelia, and Rickettsial agents in Amblyomma americanum (Acari: Ixodidae) collected from nine states. J Med Entomol 43: 1261–1268.
Castellaw AH, Showers J, Goddard J, Chenney EF, Varela-Stokes AS, 2010. Detection of vector-borne agents in lone star ticks, Amblyomma americanum (Acari: Ixodidae), from Mississippi. J Med Entomol 47: 473–476.
Smith MP, Ponnusamy L, Jiang J, Ayyash LA, Richards AL, Apperson CS, 2010. Bacterial pathogens in ixodid ticks from a Piedmont County in North Carolina: prevalence of rickettsial organisms. Vector Borne Zoonotic Dis 10: 939–952.
Zhang X, Ren X, Norris DE, Rasgon JL, 2012. Distribution and infection frequency of ‘Candidatus Rickettsia amblyommii’ in Maryland populations of the lone star tick (Amblyomma americanum) and culture in an Anopheles gambiae mosquito cell line. Ticks Tick Borne Dis 3: 38–42.
Gaines DN, Operario DJ, Stroup S, Stromdahl E, Wright C, Gaff H, Broyhill J, Smith J, Norris DE, Henning T, Lucas A, Houpt E, 2014. Ehrlichia and spotted fever group Rickettsiae surveillance in Amblyomma americanum in Virginia through use of a novel six-plex real-time PCR assay. Vector Borne Zoonotic Dis 14: 307–316.
Killmaster LF, Loftis AD, Zemtsova GE, Levin ML, 2014. Detection of bacterial agents in Amblyomma americanum (Acari: Ixodidae) from Georgia, USA, and the use of a multiplex assay to differentiate Ehrlichia chaffeensis and Ehrlichia ewingii. J Med Entomol 51: 868–872.
McCall CL, Curns AT, Rotz LD, Singleton JA Jr, Treadwell TA, Comer JA, Nicholson WL, Olson JG, Childs JE, 2001. Fort Chaffee revisited: the epidemiology of tick-borne rickettsial and ehrlichial diseases at a natural focus. Vector Borne Zoonotic Dis 1: 119–127.
Paddock CD, Goddard J, 2015. The evolving medical and veterinary importance of the Gulf Coast tick (Acari: Ixodidae). J Med Entomol 52: 230–252.
Estrada-Pena A, Venzal JM, Mangold AJ, Cafrune MM, Guglielmone AA, 2005. The Amblyomma maculatum Koch, 1844 (Acari: Ixodidae: Amblyomminae) tick group: diagnostic characters, description of the larva of A. parvitarsum Neumann, 1901, 16S rDNA sequences, distribution and hosts. Syst Parasitol 60: 99–112.
Paddock CD, Denison AM, Dryden MW, Noden BH, Lash RR, Abdelghani SS, Evans AE, Kelly AR, Hecht JA, Karpathy SE, Ganta RR, Little SE, 2015. High prevalence of “Candidatus Rickettsia andeanae” and apparent exclusion of Rickettsia parkeri in adult Amblyomma maculatum (Acari: Ixodidae) from Kansas and Oklahoma. Ticks Tick Borne Dis 6: 297–302.
Dahlgren FS, Mandel EJ, Krebs JW, Massung RF, McQuiston JH, 2011. Increasing incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000–2007. Am J Trop Med Hyg 85: 124–131.
Nichols Heitman K, Dahlgren FS, Drexler N, Massung RF, Barton Behravesh C, 2016. Increasing incidence of ehrlichiosis in the United States: a summary of national surveillance of Ehrlichia chaffeensis and Ehrlichia ewingii infections in the United States, 2008–2012. Am J Trop Med Hyg 94: 52–60.
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Spotted fever group (SFG) Rickettsia species are etiologic agents of a wide range of human infections from asymptomatic or mild infections to severe, life-threatening disease. In the United States, recent passive surveillance for SFG rickettsiosis shows an increased incidence and decreased severity of reported cases. The reasons for this are not well understood; however, we hypothesize that less pathogenic rickettsiae are causing more human infections, while the incidence of disease caused by more pathogenic rickettsiae, particularly Rickettsia rickettsii, is relatively stable. During the same period, the range of Amblyomma americanum has expanded. Amblyomma americanum is frequently infected with “Candidatus Rickettsia amblyommii”, a SFG Rickettsia of unknown pathogenicity. We tested our hypothesis by modeling incidence rates from 1993 to 2013, hospitalization rates from 1981 to 2013, and case fatality rates from 1981 to 2013 regressed against the presence of A. americanum, the decade of onset of symptoms, and the county of residence. Our results support the hypothesis, and we show that the expanding range of A. americanum is associated with changes in epidemiology reported through passive surveillance. We believe epidemiological and acarological data collected on individual cases from enhanced surveillance may further elucidate the reasons for the changing epidemiology of SFG rickettsiosis.
Financial support: This study was supported by the Centers for Disease Control and Prevention.
Authors' addresses: F. Scott Dahlgren, Christopher D. Paddock, and Casey Barton Behravesh, Rickettsial Zoonoses Branch, Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Atlanta, GA, E-mails: iot0@cdc.gov, cdp9@cdc.gov, and dlx9@cdc.gov. Yuri P. Springer and Rebecca J. Eisen, Bacterial Diseases Branch, Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, CO, E-mails: yurispringer@gmail.com and dyn2@cdc.gov.
Dalton MJ, Clarke MJ, Holman RC, Krebs JW, Fishbein DB, Olson JG, Childs JE, 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.
Holman RC, Paddock CD, Curns AT, Krebs JW, McQuiston JH, Childs JE, 2001. Analysis of risk factors for fatal Rocky Mountain spotted fever: evidence for superiority of tetracyclines for therapy. J Infect Dis 184: 1437–1444.
Openshaw JJ, Swerdlow DL, Krebs JW, Holman RC, Mandel E, Harvey A, Haberling D, Massung RF, McQuiston JH, 2010. Rocky Mountain spotted fever in the United States, 2000–2007: interpreting contemporary increases in incidence. Am J Trop Med Hyg 83: 174–182.
Centers for Disease Control and Prevention, 2000. Consequences of delayed diagnosis of Rocky Mountain spotted fever in children—West Virginia, Michigan, Tennessee, and Oklahoma, May–July 2000. MMWR 49: 885–888.
Traeger MS, Regan JJ, Humpherys D, Mahoney DL, Martinez M, Emerson GL, Tack DM, Geissler A, Yasmin S, Lawson R, Hamilton C, Williams V, Levy C, Komatsu K, McQuiston JH, Yost DA, 2015. Rocky Mountain spotted fever characterization and comparison to similar illnesses in a highly endemic area—Arizona, 2002–2011. Clin Infect Dis 60: 1650–1658.
Regan JJ, Traeger MS, Humpherys D, Mahoney DL, Martinez M, Emerson GL, Tack DM, Geissler A, Yasmin S, Lawson R, Williams V, Hamilton C, Levy C, Komatsu K, Yost DA, McQuiston JH, 2015. Risk factors for fatal outcome from Rocky Mountain spotted fever in a highly endemic area—Arizona, 2002–2011. Clin Infect Dis 60: 1659–1666.
Centers for Disease Control and Prevention, 2006. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichiosis, and anaplasmosis—United States. MMWR Recomm Rep 55: 1–27.
Drexler N, Dahlgren FS, Nichols Heitman K, Massung RF, Paddock CD, Barton Behravesh C, 2016. National surveillance of spotted fever group rickettsioses in the United States, 2008–2012. Am J Trop Med Hyg 94: 26–34.
Huebner RJ, Jellison WL, Armstrong C, 1947. Rickettsialpox: a newly recognized rickettsial disease: V. Recovery of Rickettsia akari from a house mouse (Mus musculus). Public Health Rep 62: 777–780.
Greenberg M, Pellitteri O, Klein IF, Huebner RJ, 1947. Rickettsialpox—a newly recognized rickettsial disease: II. Clinical observations. J Am Med Assoc 133: 901–906.
Paddock CD, Sumner JW, Comer JA, Zaki SR, Goldsmith CS, Goddard J, McLellan SL, Tamminga CL, Ohl CA, 2004. Rickettsia parkeri: a newly recognized cause of spotted fever rickettsiosis in the United States. Clin Infect Dis 38: 805–811.
Paddock CD, Finley RW, Wright CS, Robinson HN, Schrodt BJ, Lane CC, Ekenna O, Blass MA, Tamminga CL, Ohl CA, McLellan SL, Goddard J, Holman RC, Openshaw JJ, Sumner JW, Zaki SR, Eremeeva ME, 2008. Rickettsia parkeri rickettsiosis and its clinical distinction from Rocky Mountain spotted fever. Clin Infect Dis 47: 1188–1196.
Parker RR, 1939. Observations on an infectious agent from Amblyomma maculatum. Public Health Rep 54: 1482–1484.
Cohen SB, Yabsley MJ, Garrison LE, Freye JD, Dunlap BG, Dunn JR, Mead DG, Jones TF, Moncayo AC, 2009. Rickettsia parkeri in Amblyomma americanum ticks, Tennessee and Georgia, USA. Emerg Infect Dis 15: 1471–1473.
Johnston SH, Glaser CA, Padgett K, Wadford DA, Espinosa A, Espinosa N, Eremeeva ME, Tait K, Hobson B, Shtivelman S, Hsieh C, Messenger SL, 2013. Rickettsia spp. 364D causing a cluster of eschar-associated illness, California. Pediatr Infect Dis J 32: 1036–1039.
Shapiro MR, Fritz CL, Tait K, Paddock CD, Nicholson WL, Abramowicz KF, Karpathy SE, Dasch GA, Sumner JW, Adem PV, Scott JJ, Padgett KA, Zaki SR, Eremeeva ME, 2010. Rickettsia 364D: a newly recognized cause of eschar-associated illness in California. Clin Infect Dis 50: 541–548.
Stromdahl EY, Jiang J, Vince M, Richards AL, 2011. Infrequency of Rickettsia rickettsii in Dermacentor variabilis removed from humans, with comments on the role of other human-biting ticks associated with spotted fever group rickettsiae in the United States. Vector Borne Zoonotic Dis 11: 969–977.
McQuiston JH, Zemtsova G, Perniciaro J, Hutson M, Singleton J, Nicholson WL, Levin ML, 2012. Afebrile spotted fever group Rickettsia infection after a bite from a Dermacentor variabilis tick infected with Rickettsia montanensis. Vector Borne Zoonotic Dis 12: 1059–1061.
Apperson CS, Engber B, Nicholson WL, Mead DG, Engel J, Yabsley MJ, Dail K, Johnson J, Watson DW, 2008. Tick-borne diseases in North Carolina: is “Rickettsia amblyommii” a possible cause of rickettsiosis reported as Rocky Mountain spotted fever? Vector Borne Zoonotic Dis 8: 597–606.
Jiang J, Yarina T, Miller MK, Stromdahl EY, Richards AL, 2010. Molecular detection of Rickettsia amblyommii in Amblyomma americanum parasitizing humans. Vector Borne Zoonotic Dis 10: 329–340.
Billeter SA, Blanton HL, Little SE, Levy MG, Breitschwerdt EB, 2007. Detection of Rickettsia amblyommii in association with a tick bite rash. Vector Borne Zoonotic Dis 7: 607–610.
Barrett A, Little SE, Shaw E, 2014. “Rickettsia amblyommii” and R. montanensis infection in dogs following natural exposure to ticks. Vector Borne Zoonotic Dis 14: 20–25.
National Office of Vital Statistics, 1953. Reported incidence of selected notifiable diseases: United States, each division and state, 1920–1950. Vital Statistics. Special Reports 37: 179–243.
Atkinson SF, Sarkar S, Avina A, Schuermann JA, Williamson P, 2012. Modelling spatial concordance between Rocky Mountain spotted fever disease incidence and habitat probability of its vector Dermacentor variabilis (American dog tick). Geospat Health 7: 91–100.
Childs JE, Paddock CD, 2003. The ascendancy of Amblyomma americanum as a vector of pathogens affecting humans in the United States. Annu Rev Entomol 48: 307–337.
Blanton LS, Mendell NL, Walker DH, Bouyer DH, 2014. “Rickettsia amblyommii” induces cross protection against lethal Rocky Mountain spotted fever in a guinea pig model. Vector Borne Zoonotic Dis 14: 557–562.
Springer YP, Eisen L, Beati L, James AM, Eisen RJ, 2014. Spatial distribution of counties in the continental United States with records of occurrence of Amblyomma americanum (Ixodida: Ixodidae). J Med Entomol 51: 342–351.
Wood SN, 2006. Generalized Additive Models: An Introduction with R. Boca Raton, FL: Chapman and Hall/CRC.
Bockman SF, 1989. Generalizing the formula for areas of polygons to moments. Am Math Mon 96: 131–132.
Salvatore M, Meyers BR, 2010. Tetracyclines and chloramphenicol. Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Vol. 1, 7th edition. Philadelphia, PA: Elsevier Churchill Livingstone, 385–402.
Drexler N, Miller M, Gerding J, Todd S, Adams L, Dahlgren FS, Bryant N, Weis E, Herrick K, Francies J, Komatsu K, Piontkowski S, Velascosoltero J, Shelhamer T, Hamilton B, Eribes C, Brock A, Sneezy P, Goseyun C, Bendle H, Hovet R, Williams V, Massung R, McQuiston JH, 2014. Community-based control of the brown dog tick in a region with high rates of Rocky Mountain spotted fever, 2012–2013. PLoS One 9: e112368.
Wood MW, 1896. Spotted fever as reported from Idaho. Report to the Surgeon General of the Army. 60–65.
Cobb JO, 1902. The so-called “spotted fever” of the Rocky Mountains—a new disease in Bitter Root Valley, Mont. Public Health Rep 17: 1868–1870.
Williamson PC, Billingsley PM, Teltow GJ, Seals JP, Turnbough MA, Atkinson SF, 2010. Borrelia, Ehrlichia, and Rickettsia spp. in ticks removed from persons, Texas, USA. Emerg Infect Dis 16: 441–446.
Fornadel CM, Zhang X, Smith JD, Paddock CD, Arias JR, Norris DE, 2011. High rates of Rickettsia parkeri infection in Gulf Coast ticks (Amblyomma maculatum) and identification of “Candidatus Rickettsia andeanae” from Fairfax County, Virginia. Vector Borne Zoonotic Dis 11: 1535–1539.
Fritzen CM, Huang J, Westby K, Freye JD, Dunlap B, Yabsley MJ, Schardein M, Dunn JR, Jones TF, Moncayo AC, 2011. Infection prevalences of common tick-borne pathogens in adult lone star ticks (Amblyomma americanum) and American dog ticks (Dermacentor variabilis) in Kentucky. Am J Trop Med Hyg 85: 718–723.
Moncayo AC, Cohen SB, Fritzen CM, Huang E, Yabsley MJ, Freye JD, Dunlap BG, Huang J, Mead DG, Jones TF, Dunn JR, 2010. Absence of Rickettsia rickettsii and occurrence of other spotted fever group rickettsiae in ticks from Tennessee. Am J Trop Med Hyg 83: 653–657.
Pagac BB, Miller MK, Mazzei MC, Nielsen DH, Jiang J, Richards AL, 2014. Rickettsia parkeri and Rickettsia montanensis, Kentucky and Tennessee, USA. Emerg Infect Dis 20: 1750–1752.
Mixson TR, Campbell SR, Gill JS, Ginsberg HS, Reichard MV, Schulze TL, Dasch GA, 2006. Prevalence of Ehrlichia, Borrelia, and Rickettsial agents in Amblyomma americanum (Acari: Ixodidae) collected from nine states. J Med Entomol 43: 1261–1268.
Castellaw AH, Showers J, Goddard J, Chenney EF, Varela-Stokes AS, 2010. Detection of vector-borne agents in lone star ticks, Amblyomma americanum (Acari: Ixodidae), from Mississippi. J Med Entomol 47: 473–476.
Smith MP, Ponnusamy L, Jiang J, Ayyash LA, Richards AL, Apperson CS, 2010. Bacterial pathogens in ixodid ticks from a Piedmont County in North Carolina: prevalence of rickettsial organisms. Vector Borne Zoonotic Dis 10: 939–952.
Zhang X, Ren X, Norris DE, Rasgon JL, 2012. Distribution and infection frequency of ‘Candidatus Rickettsia amblyommii’ in Maryland populations of the lone star tick (Amblyomma americanum) and culture in an Anopheles gambiae mosquito cell line. Ticks Tick Borne Dis 3: 38–42.
Gaines DN, Operario DJ, Stroup S, Stromdahl E, Wright C, Gaff H, Broyhill J, Smith J, Norris DE, Henning T, Lucas A, Houpt E, 2014. Ehrlichia and spotted fever group Rickettsiae surveillance in Amblyomma americanum in Virginia through use of a novel six-plex real-time PCR assay. Vector Borne Zoonotic Dis 14: 307–316.
Killmaster LF, Loftis AD, Zemtsova GE, Levin ML, 2014. Detection of bacterial agents in Amblyomma americanum (Acari: Ixodidae) from Georgia, USA, and the use of a multiplex assay to differentiate Ehrlichia chaffeensis and Ehrlichia ewingii. J Med Entomol 51: 868–872.
McCall CL, Curns AT, Rotz LD, Singleton JA Jr, Treadwell TA, Comer JA, Nicholson WL, Olson JG, Childs JE, 2001. Fort Chaffee revisited: the epidemiology of tick-borne rickettsial and ehrlichial diseases at a natural focus. Vector Borne Zoonotic Dis 1: 119–127.
Paddock CD, Goddard J, 2015. The evolving medical and veterinary importance of the Gulf Coast tick (Acari: Ixodidae). J Med Entomol 52: 230–252.
Estrada-Pena A, Venzal JM, Mangold AJ, Cafrune MM, Guglielmone AA, 2005. The Amblyomma maculatum Koch, 1844 (Acari: Ixodidae: Amblyomminae) tick group: diagnostic characters, description of the larva of A. parvitarsum Neumann, 1901, 16S rDNA sequences, distribution and hosts. Syst Parasitol 60: 99–112.
Paddock CD, Denison AM, Dryden MW, Noden BH, Lash RR, Abdelghani SS, Evans AE, Kelly AR, Hecht JA, Karpathy SE, Ganta RR, Little SE, 2015. High prevalence of “Candidatus Rickettsia andeanae” and apparent exclusion of Rickettsia parkeri in adult Amblyomma maculatum (Acari: Ixodidae) from Kansas and Oklahoma. Ticks Tick Borne Dis 6: 297–302.
Dahlgren FS, Mandel EJ, Krebs JW, Massung RF, McQuiston JH, 2011. Increasing incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000–2007. Am J Trop Med Hyg 85: 124–131.
Nichols Heitman K, Dahlgren FS, Drexler N, Massung RF, Barton Behravesh C, 2016. Increasing incidence of ehrlichiosis in the United States: a summary of national surveillance of Ehrlichia chaffeensis and Ehrlichia ewingii infections in the United States, 2008–2012. Am J Trop Med Hyg 94: 52–60.
Past two years | Past Year | Past 30 Days | |
---|---|---|---|
Abstract Views | 1851 | 1616 | 53 |
Full Text Views | 609 | 23 | 1 |
PDF Downloads | 310 | 27 | 2 |