Gastroenteritis in Marines during Operation Iraqi Freedom • CID 2005:40 (15 February) • 519
M A J O R A R T I C L E
Gastroenteritis in US Marines
during Operation Iraqi Freedom
Scott A. Thornton,1Sterling S. Sherman,2Tibor Farkas,3Weiming Zhong,3Pete Torres,2and Xi Jiang3
1Navy Environmental and Preventive Medicine Unit No. 6, Pearl Harbor, Hawaii;
San Diego, California; and
2Navy Environmental and Preventive Medicine Unit No. 5,
3Cincinnati Children’s Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio
(See the editorial commentary by Matson et al. on pages 526–7 and the article by Crum et al. on pages 511–8)
Approximately 83,000 US Marines participated in the opening phase of OperationIraqiFreedom
in Spring 2003. A Navy Preventive Medicine laboratory was set up in Ad Diwaniyah, Iraq, to provide clinical
diagnostic support for Marine medical units during a period of repositioning in south-central Iraq.
Specimen collection boxes were sent to 130 primary care medical stations handling 500–900 per-
sonnel each. The laboratory had capability to detect many different disease agents, especially those causing febrile
illness. Diarrheal stool diagnostic evaluation included plating and biochemical identification, antigen serologic
testing, fluorescent antibody antigen detection, disk diffusion antimicrobial susceptibility testing, enzyme immu-
noassay, and reverse-transcriptase polymerase chain reaction for norovirus (NV). Confirmation and sequencing
work for NV was done at Cincinnati Children’s Hospital Medical Center (Ohio).
By far the most common reason for infectious disease sick call visits was gastrointestinal illness; no
other symptoms had equivalent impact. An enteropathogen was detected in 57 (44%) of 129 stool samples, with
NV detected in 30 stool samples (23%) obtained from 14 different battalion or similar-sized units;nextinfrequency
were Shigella flexneri and Shigella sonnei, which were isolated from 26 stool samples (20%) obtained from 15 units.
Sequencing the NV RNA polymerase gene demonstrated that NV strains represented 7 genetic clusters, including
2 strains from genogroup I and 5 from genogroup II. Ciprofloxacin was effective in vitro against most bacterial
agents, but neither doxycyline (which was taken daily as the antimalarial prophylaxis dose) nor trimethoprim-
sulfamethoxazole were effective.
Multiple strains of Shigella species and NV predominated, probably because they do not require
a large inoculum to cause infection. Otherwise, personnel remained free of infectious illness during this phase of
the conflict, because other infectious agents were rare or absent.
Infectious diseases have long been problematic to de-
ployed US military ground forces. During recent op-
erations in theMiddleEast andSomalia,foodandwater
sources were tightly controlled, and medical interven-
tion measures, such as administration of vaccines and
antimicrobial prophylaxis regimens, have been success-
Received 24 June 2004; accepted 14 October 2004; electronically published 20
The views expressed in this 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, or the US Government.
Presented in part: 43rd Navy Occupational Health and Preventive Medicine
Workshop, Chesapeake, Virginia, 18–24 March 2004; and 23rd Annual Meeting
of the American Society for Virology, Montreal, Quebec, Canada, 10–14 July 2004
Reprints or correspondence: LCDR Scott A. Thornton, Head, Microbiology Dept.,
Navy Environmental and Preventive Medicine Unit No. 6, Pearl Harbor, HI 96860
Clinical Infectious Diseases2005;40:519–25
This article is in the public domain, and no copyright is claimed.
fully implemented to reduce disease incidence. When
such measures are not followed, even the preventable
diseases again become an issue [1–3]. Iraq has many
of the diarrheal disease agents typically found in the
Middle East, including Vibrio cholerae in some areas.
Norovirus (NV), a common cause of viral gastroen-
teritis outbreaks in military units, was undocumented
in Iraq but was presumably present, because it was a
cause of outbreaks of infection in the military in nearby
Saudi Arabia during the 1991 Gulf War [4, 5]. Other
disease threats endemic in Iraq include malaria(mostly
due to Plasmodium vivax), arboviruses, brucellosis,
leishmaniasis, leptospirosis, infection with rickettsial
agents, schistosomiasis, Q fever, hepatitis A and B, and
typhoid fever [6, 7].
On 20 March 2003, Operation Iraqi Freedom com-
menced, with US and allied military entering Iraq. The
ground component included ∼83,000 Marines of the
First Marine Expeditionary Force. The Marines quickly
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Gastroenteritis in Marines during Operation Iraqi Freedom • CID 2005:40 (15 February) • 525
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19. Buesa J, Collado B, Lopez-Andujar P, et al. Molecular epidemiology
of caliciviruses causing outbreaks and sporadic cases of acute gastro-
enteritis in Spain. J Clin Microbiol 2002;40:2854–9.
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