Gastroenteritis in US Marines during Operation Iraqi Freedom

Abstract

Background: Approximately 83,000 US Marines participated in the opening phase of Operation Iraqi Freedom 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.

Methods: Specimen collection boxes were sent to >30 primary care medical stations handling 500-900 personnel 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 immunoassay, 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).

Results: 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; next in frequency 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.

Conclusions: 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.