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Volume 22, Number 8—August 2016
Dispatch

Seroconversions for Coxiella and Rickettsial Pathogens among US Marines Deployed to Afghanistan, 2001–2010

Author affiliations: US Naval Medical Research Unit 2, Phnom Penh, Cambodia (C.M. Farris); Naval Medical Research Center, Silver Spring, Maryland, USA (C.M. Farris, T.E. Myers, A.L. Richards); Uniformed Services University of Health Science, Bethesda, Maryland, USA (N. Pho)

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Abstract

We assessed serum samples from 1,000 US Marines deployed to Afghanistan during 2001–2010 to find evidence of 4 rickettsial pathogens. Analysis of predeployment and postdeployment samples showed that 3.4% and 0.5% of the Marines seroconverted for the causative agents of Q fever and spotted fever group rickettsiosis, respectively.

Rickettsial and rickettsial-like diseases have played a considerable role in military activities throughout much of recorded history (1). These diseases, which have worldwide distribution and cause a high number of deaths and illnesses, include the select agents (http://www.selectagents.gov/SelectAgentsandToxinsList.html) Rickettsia prowazekii and Coxiella burnetii, the causative agents of epidemic typhus and Q fever, respectively. Furthermore, outbreaks caused by rickettsial disease pathogens, such as scrub typhus (Orientia tsutsugamushi) in Laos, Vietnam, and Cambodia and African tick-bite fever (Rickettsia africae) in Botswana, have affected military forces in recent history (2,3). O. tsutsugamushi was the leading cause of fever of unknown origin in US soldiers during the Vietnam conflict and caused >16,000 cases of scrub typhus among Allied forces during World War II (1).

The epidemiology of rickettsial pathogens is not well understood in Central Asia, where >100,000 US and allied troops have been engaged in military operations since 2001. Retrospective studies from military personnel deployed during Operation Desert Shield/Desert Storm in 1991 revealed exposures of 9.8% and 5.7% for spotted fever group rickettsiae (SFGR) and typhus group rickettsiae (TGR), respectively; however, no seroconversions were observed (4). Since 2001 in Iraq, >150 cases of Q fever have been confirmed in US troops and civilians (58). An outbreak of Q fever and brucellosis in local residents in the Bamyan province of Afghanistan during 2011 (9) and the historic presence of SFGR and vectors known to carry SFGR (10) highlight the inherent risk of contracting rickettsial-like diseases in Afghanistan. We estimated the risk for rickettsial infections in military personnel deployed to Afghanistan by measuring the rate of seroconversion for SFGR, TGR, scrub typhus group Orientiae (STGO), and C. burnetii among US Marines stationed in Afghanistan during 2001–2010.

The Study

Serum samples from US Marines 18–45 years of age who served >180 days in Afghanistan during 2001–2010 were obtained from the US Department of Defense Serum Repository (DoDSR). Documentation of prior exposure to Q fever or rickettsioses and sample volume <0.5 mL were exclusion criteria. We selected the most recent 1,000 postdeployment specimens that fit the inclusion criteria for our study.

Military service members have blood drawn every 2 years for HIV testing and during postdeployment screenings, and a portion of each sample is stored at the DoDSR. All predeployment samples were collected <1 year before the start of Afghanistan service, and postdeployment samples were collected within ≈1 year after the end of Afghanistan service. Paired predeployment and postdeployment samples were irreversibly stripped of personal identifiers by DoDSR and labeled with an internal DoDSR code. Only DoDSR has access to the key linking the code to personal identifiers. The Naval Medical Research Center Institutional Review Board approved the study.

We screened specimens for antibodies against TGR, SFGR, and STGO by ELISA, as described (11) and determined titers for positive specimens. Seroconversion (i.e., titer <100 in the predeployment sample and titer >400 in the paired postdeployment sample) or a 4-fold rise in titer between the predeployment and paired postdeployment sample was used to determine acute infection.

We tested specimens for antibodies against C. burnetii by using the Q fever Immunodot assay (GenBio, San Diego, CA, USA), according to the manufacturer’s instructions. Specimens were considered positive for acute infection if antibodies against phase I and phase II antigen were present. Seroconversion was defined by the presence of antibodies against phase I antigen in the postdeployment sample but not in the predeployment sample.

Of the 1,000 postdeployment serum samples screened for SFGR, TGR, and STGO, only 879 were screened for Q fever because the volume of 121 samples was depleted from earlier testing. The screening assays showed that 87, 18, and 1 samples were positive for antibodies against C. burnetii, SFGR, and STGO, respectively, before deployment. No antibodies against TGR were detectable in any samples. Seroconversions to C. burnetii and SFGR occurred in 3.4% and 0.5% of the paired serum samples, respectively (Table). C. burnetii infection was most prevalent among the agents tested both before deployment (n = 87) and during deployment (n = 30). Of 879 specimens, 117 (13.3%) were positive.

Figure

Thumbnail of Serum samples assessed for evidence of seroconversion for Coxiella burnetii among US Marines deployed to Afghanistan, by year deployment began, 2001–2010. A) Number of Coxiella burnetii seroconversions (n = 30). B) Total number of samples assessed for antibodies against Coxiella burnetii (n = 879).

Figure. Serum samples assessed for evidence of seroconversion for Coxiella burnetii among US Marines deployed to Afghanistan, by year deployment began, 2001–2010. A) Number of Coxiella burnetii seroconversions (n = 30). B)...

Most of the 30 C. burnetii seroconversions occurred in Marines who began deployment in 2008 (n = 12) and 2009 (n = 8) (Figure, panel A). However, most (634/879 [72.1%]) of the sample population were deployed during this period (Figure, panel B), so higher rates for these years likely do not indicate higher risk. With the exception of 1 fixed-wing pilot, all C. burnetii and SFGR seroconversions occurred in general infantrymen, who represented 93.1% of C. burnetii–positive samples and 92.6% of total samples.

Range of deployment time was 180–450 days, and average length of deployment was 271 (SD 104.49) days. Average length of deployment for those who seroconverted for C. burnetii or SFGR was 286.2 (SD 112.01) and 342.4 (SD 131.65) days, respectively. Analysis by t-test showed no correlation between length of deployment and seroconversion for either C. burnetii (p = 0.98) or SFGR (p = 1.0).

Predeployment serum samples were collected 3–364 (mean 183, SD 111.07) days before deployment, and postdeployment samples were collected <443 (mean 61.3, SD 111.02) days after return. Samples showing seroconversions for C. burnetii and SFGR were collected an average of 179.3 (SD 93.94) and 151.6 (SD 126.76) days, respectively, predeployment and 76.9 (SD 87.64) and 129.8 (SD 127.85) days, respectively, postdeployment.

Conclusions

Acute febrile illness can be difficult to diagnose because many infections have similar symptoms and signs and are difficult to differentiate without appropriate diagnostic tools. The rate of C. burnetii seroconversions (3.4%) in Marines in our study is similar to that reported in United Kingdom military personnel deployed to Afghanistan during 2008–2011 (7); the study from the United Kingdom also confirms the presence of rickettsiae in the region. The rate of C. burnetii seropositivity in the United States is ≈3% but ranges dramatically; nearby Nova Scotia, Canada, has rates >14% (8,12). With proper treatment of infections, the case-fatality rate for Q fever and rickettsial infections is <2%. However, rates can be >30%; among hospitalized Mediterranean spotted fever patients in Portugal in 1997, the case-fatality rate was 32.5% (13).

In our study, gaps between dates of blood draws and start and end dates of deployment provided an opportunity for exposure to agents of Q fever and SFGR outside the deployment period. The nature of retrospective, blinded studies prevents follow-up with participants to ascertain additional information, including whether symptoms developed or treatment was sought. This limitation is especially true for studies of military populations, for whom routine blood draws are typically used, rather than samples being specifically collected for research studies. However, results from these studies provide valuable information, and in our study, this limitation does not discount the documented prevalence of Q fever in Iraq and Afghanistan (410,14) or the inherent risk to deployed US military personnel. Our results highlight the risk of contracting Q fever and the need for Q fever diagnostics in military engagements in Central Asia.

Dr. Farris is a Lieutenant in the United States Navy and is currently stationed at the Naval Medical Research Unit 2 detachment in Phnom Penh, Cambodia. Her research interests include intracellular bacteria and vectorborne diseases.

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Acknowledgments

This work was supported by Global Emerging Infections Surveillance section of the Armed Forces Health Surveillance Branch (work unit # P0413).

The views in this are article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the US Government. The authors are employees of the US Government. This work was prepared as part of their official duties. Title 17 USC paragraph 105 provides that “Copyright protection under this title is not available for any work of the United States Government.” Title 17 USC defines a US Government work as work prepared by a military service member or employee of the US Government as part of that person’s official duties.

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References

  1. Kelly  DJ, Richards  AL, Temenak  J, Strickman  D, Dasch  GA. The past and present threat of rickettsial diseases to military medicine and international public health. Clin Infect Dis. 2002;34(Suppl 4):S14569. DOIPubMedGoogle Scholar
  2. Corwin  A, Soderquist  R, Suwanabun  N, Sattabongkot  J, Martin  L, Kelly  D, Scrub typhus and military operations in Indochina. Clin Infect Dis. 1999;29:9401. DOIPubMedGoogle Scholar
  3. Smoak  BL, McClain  JB, Brundage  JF, Broadhurst  L, Kelly  DJ, Dasch  GA, An outbreak of spotted fever rickettsiosis in U.S. Army troops deployed to Botswana. Emerg Infect Dis. 1996;2:21721. DOIPubMedGoogle Scholar
  4. Richards  AL, Malone  JD, Sheris  S, Weddle  JR, Rossi  CA, Ksiazek  TG, Arbovirus and rickettsial infections among combat troops during Operation Desert Shield/Desert Storm. J Infect Dis. 1993;168:10801. DOIPubMedGoogle Scholar
  5. Faix  DJ, Harrison  DJ, Riddle  MS, Vaughn  AF, Yingst  SL, Earhart  K, Outbreak of Q fever among US military in western Iraq, June–July 2005. Clin Infect Dis. 2008;46:e658. DOIPubMedGoogle Scholar
  6. Newman  EN, Johnstone  P, Bridge  H, Wright  D, Jameson  L, Bosworth  A, Seroconversion for infectious pathogens among UK military personnel deployed to Afghanistan, 2008–2011. Emerg Infect Dis. 2014;20:201522. DOIPubMedGoogle Scholar
  7. White  B, Brooks  T, Seaton  RA. Q fever in military and paramilitary personnel in conflict zones: case report and review. Travel Med Infect Dis. 2013;11:1347. DOIPubMedGoogle Scholar
  8. Gutiérrez  RL, Hartzell  JD. Fever, dyspnea, and hepatitis in an Iraq veteran. Cleve Clin J Med. 2012;79:62330. DOIPubMedGoogle Scholar
  9. Saeed  KMI, Ansari  J, Asghar  RJ, Ahadi  J. Concurrent brucellosis and Q fever infection: a case control study in Bamyan Province, Afghanistan in 2011. Int J Infect Dis. 2012;16(Suppl 1):e37 .DOIGoogle Scholar
  10. Wallace  MR, Hale  BR, Utz  GC, Olson  PE, Earhart  KC, Thornton  SA, Endemic infectious diseases of Afghanistan. Clin Infect Dis. 2002;34(Suppl 5):S171207. DOIPubMedGoogle Scholar
  11. Jiang  J, Myers  TE, Rozmajzl  PJ, Graf  PC, Chretien  JP, Gaydos  JC, Seroconversions to rickettsiae in US military personnel in South Korea. Emerg Infect Dis. 2015;21:10734. DOIPubMedGoogle Scholar
  12. Marrie  TJ, Pollak  PT. Seroepidemiology of Q fever in Nova Scotia: evidence for age dependent cohorts and geographical distribution. Eur J Epidemiol. 1995;11:4754. DOIPubMedGoogle Scholar
  13. de Sousa  R, Nóbrega  SD, Bacellar  F, Torgal  J. Mediterranean spotted fever in Portugal: risk factors for fatal outcome in 105 hospitalized patients. Ann N Y Acad Sci. 2003;990:28594. DOIPubMedGoogle Scholar
  14. Anderson  AD, Baker  TR, Littrell  AC, Mott  RL, Niebuhr  DW, Smoak  BL. Seroepidemiologic survey for Coxiella burnetii among hospitalized US troops deployed to Iraq. Zoonoses Public Health. 2011;58:27683. DOIPubMedGoogle Scholar

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Cite This Article

DOI: 10.3201/eid2208.160221

Table of Contents – Volume 22, Number 8—August 2016

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Christina M. Farris, Naval Medical Research Unit 2 Detachment Phnom Penh, Unit 8166 Box P, APO, AP 96546, USA

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Page created: July 15, 2016
Page updated: July 15, 2016
Page reviewed: July 15, 2016
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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