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Volume 17, Number 5—May 2011
Dispatch

Rickettsia parkeri in Gulf Coast Ticks, Southeastern Virginia, USA

Author affiliations: Author affiliations: Old Dominion University, Norfolk, Virginia, USA (C.L. Wright, R. Nadolny, D.E. Sonenshine, H.D. Gaff, W.L. Hynes); Naval Medical Research Center, Silver Spring, Maryland, USA (J. Jiang, A.L. Richards)

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Abstract

We report evidence that Amblyomma maculatum tick populations are well established in southeastern Virginia. We found that 43.1% of the adult Gulf Coast ticks collected in the summer of 2010 carried Rickettsia parkeri, suggesting that persons living in or visiting southeastern Virginia are at risk for infection with this pathogen.

Rickettsia parkeri is an obligate intracellular bacterium belonging to the spotted fever group of rickettsiae; this organism has recently been found to be pathogenic to humans (1). Infection with R. parkeri can be considered an emerging infectious disease, referred to as R. parkeri rickettsiosis, American Boutonneuse fever, and Tidewater spotted fever. Two confirmed cases of R. parkeri infections, including the index case in 2002, occurred in southeastern Virginia (13). Since then, 20 R. parkeri infections have been reported, mainly from the southern United States (2). In the United States, Amblyomma maculatum (family Ixodidae) ticks, commonly referred to as Gulf Coast ticks, are the only known natural vector of R. parkeri. A. maculatum ticks have been reported from 12 states: Alabama, Arkansas, Florida, Georgia, Kansas, Kentucky, Mississippi, Oklahoma, South Carolina, Tennessee, Texas (1,4,5), and Virginia (6). Sonenshine et al. reported finding individual A. maculatum ticks in Virginia in 1965 but concluded that populations had not become established (7).

We found large numbers of adult and some nymph A. maculatum ticks in Virginia. This population and the different life stages of the ticks indicate that they are now established in the state. Testing by real-time PCR and sequencing indicated that a high percentage of the ticks contained R. parkeri DNA.

The Study

From May through September 2010, adult questing A. maculatum ticks were collected on flags at 3 locations in southeastern Virginia. Collection sites were selected to produce results that could be compared with those of previous surveys and to provide a comprehensive survey of southeastern Virginia (8). The first study site is 50 km inland and borders the Great Dismal Swamp in Chesapeake, Virginia. The second site, Back Bay National Wildlife Refuge, is <1 km from the Atlantic Ocean in Virginia Beach. The third site, in Portsmouth, borders the Elizabeth River.

The ticks were identified morphologically, and identity was confirmed as needed by molecular methods. DNA was extracted by using the DNeasy Blood and Tissue Kit (QIAGEN, Valencia, CA, USA) according to the manufacturer’s protocol and stored at –20°C until processing.

DNA samples were tested for R. parkeri DNA by real-time PCR with a MiniOpticon Real-Time PCR System (Bio-Rad, Hercules, CA, USA). Testing for R. parkeri DNA was by amplification and detection of a fragment of the ompB gene by using Rpa129F and Rpa224R primers and Rpa188 as the probe (Table 1). Samples negative for R. parkeri DNA were tested for Rickettsia spp. by amplifying a 111-bp fragment of the 17-kDa antigen gene (Table 1).

Three representative A. maculatum samples positive for R. parkeri by real-time PCR were confirmed by sequencing of a 540-bp fragment of the ompA gene. The fragments were amplified on an iCycler (Bio-Rad) by using primers 190-FN1 and 190-RN1 (Table 1). Samples positive for Rickettsia spp. but negative for R. parkeri had their ompB gene amplified and sequenced by using primers RompB11F and RompB1902R (Table 1). All PCR products for sequencing were purified by using Wizard PCR Preps DNA Purification System (Promega, Madison, WI, USA), and sequencing reactions were performed by using the BigDye Terminator v.3.1 Cycle Sequencing Kit (Applied Biosystems, Foster City, CA, USA) as described by the manufacturer and using appropriate primers (Table 1). Sequence similarities were identified by a BLAST search (http://blast.ncbi.nlm.nih.gov).

A total of 65 adult and 6 nymph A. maculatum ticks were collected (adults in May–September, nymphs in April). A total of 54 adults were collected from the Chesapeake site, 8 from the Virginia Beach site, and 3 from the Portsmouth site. Of the 6 nymphs collected, 5 were found feeding on a cotton rat at the Chesapeake site in April, and 1 was collected on a flag at the Virginia Beach site in September. Of the 65 total adult ticks tested, 29 (44.6%) were found by real-time PCR to contain Rickettsia spp. DNA, and 28 (43.1%) of the total adults collected contained R. parkeri DNA. Of the 6 nymphs collected, 4 were infected with R. parkeri; all were from the rat at the Chesapeake site. Of the R. parkeri–positive samples sequenced, maximum identity was seen with R. parkeri sequences (GenBank accession no. FJ986616.1). The rate of R. parkeri–infected ticks started out high in May (83% infected) and then decreased to no infected ticks in August (Table 2).

Of the 3 A. maculatum ticks collected from the Portsmouth site, 1 was found by real-time PCR to be positive for Rickettsia spp. but negative for R. parkeri. Sequencing of a fragment of the ompB gene revealed this isolate to contain DNA with a 100% match to Candidatus Rickettsia andeanae isolate T163 (GenBank accession no. GU395297.1), a rickettsiae initially found in Peru (9).

Conclusions

The discovery of such numbers and life stages of A. maculatum ticks in widely dispersed locations indicates that they are now established in southeastern Virginia. Finding adult A. maculatum ticks at the Portsmouth site was unexpected because this is the northernmost site at which we found these ticks and is a peninsula devoid of white-tailed deer, a major host for adult ticks (10,11).

That 43.1% of adult A. maculatum ticks collected from southeastern Virginia contained R. parkeri differs from reported rates of R. parkeri in A. maculatum ticks elsewhere in the United States. For A. maculatum ticks from Florida and Mississippi, R. parkeri infectivity rate is 28% (2); for ticks from Florida, Kentucky, Mississippi, and South Carolina, the average rate is 11.5% (12). For A. maculatum ticks collected from Georgia, an infectivity rate of 5%–11.5% has been reported (13). In Arkansas, only 3 of 207 A. maculatum ticks contained R. parkeri (14). Despite the high percentage of R. parkeri in the southeastern Virginia ticks, 27 of 28 positive samples came from 1 collection site. One explanation could be that R. parkeri is transovarially transmitted. Currently, there is no evidence that R. parkeri is transmitted transovarially by A. maculatum ticks, although transovarial transmission of R. parkeri has been shown in A. americanum ticks in the laboratory (15).

We also found an A. maculatum tick infected with Candidatus Rickettsia andeanae, which has rarely been reported in the United States (2). Whether Candidatus Rickettisa andeanae is pathogenic to humans is unknown, although it has been suspected to cause infections in persons in Peru (9).

Further research is needed to identify the vertebrate host(s) of R. parkeri. This information could be useful for controlling the transmission of R. parkeri to and from the vector, as well as predicting where R. parkeri may be present. Studies relating to transovarial transmission of R. parkeri in A. maculatum ticks would also be useful for predicting the spread of infections. Because R. parkeri is known to cause infection in humans, the presence of this pathogen in southeastern Virginia should be a health concern to persons in this region.

Ms Wright is a PhD student in the Biological Sciences Department at Old Dominion University. Her research interests lie in microbiology, tick-borne pathogens, and infectious diseases.

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Acknowledgments

We thank Brandon Rowan and Ryan Wright for their help with collecting ticks. We also acknowledge the Nature Conservancy, the Back Bay Wildlife Refuge, and Elizabeth River Project for permission to use their land.

The project described was supported by grant no. K25AI067791 (to H.D.G.) from the National Institute of Allergy and Infectious Diseases. This work was supported by the US Department of Defense Global Emerging Infections Surveillance and Response System program (work unit no. 0000188M.0931.001.A0074).

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References

  1. Paddock  CD, Sumner  JW, Comer  JA, Zaki  SR, Goldsmith  CS, Goddard  J, Rickettsia parkeri: a newly recognized cause of spotted fever rickettsiosis in the United States. Clin Infect Dis. 2004;38:80511. DOIPubMedGoogle Scholar
  2. Paddock  CD, Fournier  PE, Sumner  JW, Goddard  J, Elshenawy  Y, Metcalfe  MG, Isolation of Rickettsia parkeri and identification of a novel spotted fever group Rickettsia sp. from Gulf Coast ticks (Amblyomma maculatum) in the United States. Appl Environ Microbiol. 2010;76:268996. DOIPubMedGoogle Scholar
  3. Whitman  TJ, Richards  AL, Paddock  CD, Tamminga  CL, Sniezek  PJ, Jiang  J, Rickettsia parkeri infection after tick bite, Virginia. Emerg Infect Dis. 2007;13:3346. DOIPubMedGoogle Scholar
  4. Merten  HA, Durden  LA. A state-by-state survey of ticks recorded from humans in the United States. J Vector Ecol. 2000;25:10213.PubMedGoogle Scholar
  5. Goddard  J, Norment  B. Notes on the geographical distribution of the Gulf Coast tick, Amblyomma maculatum (Koch) [Acari: Ixodidae]. Entomological News (USA). 1983;94:1034.
  6. Levine  JF, Sonenshine  DE, Nicholson  WL, Turner  RT. Borrelia burgdorferi in ticks (Acari: Ixodidae) from coastal Virginia. J Med Entomol. 1991;28:66874.PubMedGoogle Scholar
  7. Sonenshine  D, Lamb  J Jr, Anastos  G. The distribution, hosts and seasonal activity of Virginia ticks. Va J Sci. 1965;16:2691.
  8. Sonenshine  DE, Ratzlaff  RE, Troyer  J, Demmerle  S, Demmerle  ER, Austin  WE, Borrelia burgdorferi in eastern Virginia: comparison between a coastal and inland locality. Am J Trop Med Hyg. 1995;53:12333.PubMedGoogle Scholar
  9. Jiang  J, Blair  PJ, Felices  V, Moron  C, Cespedes  M, Anaya  E, Phylogenetic analysis of a novel molecular isolate of spotted fever group Rickettsiae from northern Peru: Candidatus Rickettsia andeanae. Ann N Y Acad Sci. 2005;1063:33742. DOIPubMedGoogle Scholar
  10. Scifres  C, Oldham  T, Teel  P, Drawe  D. Gulf coast tick (Amblyomma maculatum) populations and responses to burning of coastal prairie habitats. Southwest Nat. 1988;33:5564. DOIGoogle Scholar
  11. Barker  RW, Kocan  AA, Ewing  SA, Wettemann  RP, Payton  ME. Occurrence of the Gulf Coast tick (Acari: Ixodidae) on wild and domestic mammals in north-central Oklahoma. J Med Entomol. 2004;41:1708. DOIPubMedGoogle Scholar
  12. Sumner  JW, Durden  LA, Goddard  J, Stromdahl  EY, Clark  KL, Reeves  WK, Gulf Coast ticks (Amblyomma maculatum) and Rickettsia parkeri, United States. Emerg Infect Dis. 2007;13:7513.PubMedGoogle Scholar
  13. Cohen  SB, Yabsley  MJ, Garrison  LE, Freye  JD, Dunlap  BG, Dunn  JR, Rickettsia parkeri in Amblyomma americanum ticks, Tennessee and Georgia, USA. Emerg Infect Dis. 2009;15:14713. DOIPubMedGoogle Scholar
  14. Trout  R, Steelman  CD, Szalanski  AL, Williamson  PC. Rickettsiae in Gulf Coast ticks, Arkansas, USA. Emerg Infect Dis. 2010;16:8302.PubMedGoogle Scholar
  15. Goddard  J. Experimental infection of lone star ticks, Amblyomma americanum (L.), with Rickettsia parkeri and exposure of guinea pigs to the agent. J Med Entomol. 2003;40:6869. DOIPubMedGoogle Scholar

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DOI: 10.3201/eid1705.101836

Table of Contents – Volume 17, Number 5—May 2011

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Wayne L. Hynes, Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA

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Page created: August 14, 2011
Page updated: August 14, 2011
Page reviewed: August 14, 2011
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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