|
|
||||||||
| ABSTRACT |
|
|
|---|
| INTRODUCTION |
|
|
|---|
| MATERIALS AND METHODS |
|
|
|---|
Laboratory testing. Stool samples were cultured and incubated at 37°C on MacConkey, hektoen, thiosulfate citrate bile sucrose (TCBS), and blood agar plates. Skirrow media incubated at 42°C was used to culture for Campylobacter organisms. Up to five E. colilike colonies were picked and preserved in trypticase soy broth containing 15% glycerol and stored at 70°C until further testing was performed at NAMRU-3. Enterotoxigenic E. coli (ETEC) were identified using previously described criteria.11,12 Enteroaggregative (EAEC) and enteropathogenic (EPEC) E. coli were identified by polymerase chain reaction (PCR) analysis using gene-specific primers after DNA preparation directly from stool.1315 In addition, microscopic examination of preserved stool specimens was conducted at NAMRU-3 by a trained parasitologist to identify any existing ova or parasites.
Statistical analysis.
Descriptive analysis on the self-report health assessment data were conducted using Poisson regression to estimate illness incidence (diarrhea or nausea/vomiting) and evaluate differences in incidence caused by potential predictor variables of country, rank, and calendar month. For the observational study, to test the statistical significance among discrete variables (i.e., proportions), the Mantel-Haenszel
2 or Fisher exact tests were used. For two-group significant testing between continuous variables, either the Student t test (parametric) or the Wilcoxon rank (non-parametric) were used. Where there was more than two group comparison, the Kruskal-Wallis or an ANOVA was used.
All data was double entered into Epi-Info version 6. Stata Version 9 (College Station, TX) and SAS Version 8 (Cary, NC) were used for all analyses. Statistical significance was two-tailed and set at P < 0.05 for each analysis. The health assessment survey description was conducted on de-identified data that was collected solely for health screening purposes by non-study personnel and thus was exempt from the requirement for Institutional Review Board approval. The observational study was conducted under Institutional Review Board reviewed protocol DoD# NAMRU3.2004.0009.
| RESULTS |
|
|
|---|
From the answers on the health assessment survey completed on arrival at the camp, we calculated a diarrhea incidence of 4.9 cases per 100 person-months (95% CI, 4.65.1), with nausea and/or vomiting occurring at a rate of 3.9 cases per 100 person-months (95% CI, 3.54.5). There seemed to be a bimodal distribution of diarrhea incidence during the year, with a primary peak in the summer and a second peak in the fall (Figure 1
). In additional to temporal changes, there were differences based on country of assignment and military rank, with troops from Iraq reporting a higher incidence than those from Afghanistan (5.1 versus 4.1 cases per 100 person-months, IRR = 1.23, P = 0.01). The clinic screening also identified higher military rank to be associated with increased risk of self-reported diarrhea, with junior enlisted (E1E4), mid-level enlisted (E5/E6), senior enlisted (E7E9), and officers reporting rates of 4.1, 5.5, 6.2, and 6.9 episodes per 100 person-months, respectively (P < 0.0001 for trend across ordinal rank). Because country of deployment and rank were both associated with diarrhea and with each other, a multivariate Poisson regression model for the outcomes and covariates of country of deployment and rank were fit. Both covariates remained independent predictors and did not change the univariate effect estimates by > 10% (Iraq versus Afghanistan, unadjusted IRR = 1.23, adjusted IRR = 1.25).
|
|
|
|
|
In addition to symptomology and treatment, those enrolled were asked to describe the individual and operational impact associated with past diarrheal episodes. Of those individuals who experienced a diarrheal episode during their current deployment, a decrease in work performance, for a median of 3 days (IQR, 15) was reported, not including actual days of work lost (Table 4
). Furthermore, among the 24% of individuals who reported missing work because of their illness, a median number of 2 days of work were lost. In addition, 9% of individuals reporting diarrhea required back-up personnel to cover their shift, whereas 3% reported a shift change resulting directly from their illness. Last, a total of 12% of those enrolled reported that operational readiness was impacted because of diarrheal disease.
General behavioral risks and attitudes were assessed for both cases and asymptomatic individuals, and no significant differences were found between the two groups. Few individuals in either group reported "always or frequently" eating cooked meals off-base (10% cases versus 4% asymptomatics), eating raw vegetables off-base (5% cases versus 2% asymptomatics), or consuming drinks from the local community that contain ice (19% cases versus 15% asymptomatics). Reported adherence to handwashing recommendations after eating (73% cases versus 65% asymptomatics) and after using the latrine (78% cases versus 68% asymptomatics) were equivalent among cases and asymptomatic individuals.
| DISCUSSION |
|
|
|---|
Overall, we identified a relatively low incidence of self-reported diarrheal illness compared with previous studies on similar populations deployed in the region. Estimates of diarrhea incidence ranged from 4.9 cases per 100 person-months based on data collected from the health assessment survey to 12.2 cases per 100 person-months using data collected from participants in the clinic based observational study. In contrast, in a previous study conducted by our group evaluating illness among troops serving in Iraq and Afghanistan, the incidence of diarrhea was estimated to be 29 per 100 person-months.8 The reasons for the different estimates on diarrhea incidence are not certain but may be related to a number of factors. The initial study was performed using questionnaires with a total focus on diarrhea, whereas in this study, the health assessment survey contained questions about numerous conditions with only two questions focused directly on diarrhea. Additionally, the initial survey collected data from troops who were in the region before, during, and after combat operations, whereas this study involved individuals who only were involved in post-combat operations. We previously showed a decline in reported diarrhea after the combat phase of the war compared with pre- and during combat periods. This decline was thought to be caused by improved public health during non-combat operations.13 Alternatively, multiple deployments to the region by the same individuals may have resulted in a level of limited immunity or changes in risk behaviors as a result of prior experiences. It is also possible that, in this study, subjects were less likely to answer affirmatively to any of the health screening questions because they may have perceived that this would require them to make an appointment with the Troop Medical Clinic and thus interfere with R&R activities. Last, the estimate of incidence from the health prospective observation study should be considered a minimum incidence estimate (did not account for multiple episodes) and likely underestimates the true burden of disease. Further studies of the temporal changes in incidence are needed.
In concordance with our previous studies, the incidence of diarrhea among troops stationed in Iraq was significantly higher than among those stationed in Afghanistan.5,8 We again found the incidence of diarrhea was higher among the senior enlisted and officer ranks compared with the lower enlisted ranks. The reasons for the differences in incidence of diarrhea by geographic region or military rank are beyond the scope of this study; however, potential causes may include regional differences in infrastructure, host behavior, and infectious agent exposures. These factors may include differences in preventive medicine assets and function in Iraq compared with Afghanistan caused in part by increased insurgent activities in Iraq, different preventive medicine efforts (i.e., verbal training) being focused on the more junior troops, and senior enlisted and officers having more opportunities to eat at local establishments. Further research should be focused on better understanding of the impact each of these factors have on the risk of diarrheal illness.
In this study, ETEC was the most prevalent pathogen identified (32%). These data support other studies that have shown ETEC to be the most common cause of diarrhea among deployed troops. Recently, a systematic review among studies published between 1990 and 2005 reporting on diarrhea in US military and similar traveler populations described a 28% prevalence (99% CI, 2136%) of ETEC among 13 studies of traveler populations to the Middle East region.17 However, results of this study are in contrast to a previous report of diarrhea among troops stationed in Iraq that implicated norovirus (23%) and Shigella spp. (20%) as the predominant etiological agents of diarrhea.14 A major limitation of that particular study was the sampling strategy used. Laboratory supplies were distributed to more than 30 Battalion Aid Stations throughout the area, and specimens were collected from only acute individuals. Furthermore, combat operations in the area significantly increased the duration of time necessary between collection and plating. These methods likely resulted in a bias toward sampling of pathogens commonly associated with epidemic diarrhea rather than sporadic diarrhea in deployed settings.18 Last, only four stool samples were tested for ETEC, making it impossible for the study to know the impact of ETEC on the incidence of diarrhea. In this study, focus was on bacterial and parasitic agents, but stool was collected and archived to allow us to test in the future for viral pathogens associated with diarrhea. Because a pathogen was not identified in nearly 50% of the stool samples in this study, it is possible that viral agents could be pathogens in a significant portion of these cases. An additional commensal finding of interest was the relatively frequent finding of protozoa. While not recognized as pathogens, they do seem to be a good surrogate marker for exposure.
Overall, 60% of individuals in this study that completed the health assessment survey reported having had an episode of diarrhea and/or vomiting during their deployment, 30% of individuals reported seeking care for their episode, 12% reported receiving intravenous fluid rehydration, and 2% were hospitalized. These findings are consistent with previous estimates reported in this deployed population.7,8 If these rates are expanded to the > 180,000 troops currently deployed in the region, a considerable health care burden of illness is identified. However, more important than the health careassociated burden of disease is the probable human performance and mission readiness impact of these illnesses on troops. One of five individuals who became ill with diarrhea while deployed reported not being able to work because of their illness (missing on average 2 days), and an additional two of these five reported that their work performance was decreased because of their illness. With multiple episodes of diarrhea during deployment, this equates to a large number of lost and impacted duty days of the war-fighter and is cause for concern.
This clinic-based observational study and health screening assessment survey contributes to our expanding knowledge of the incidence, impact, and pathogens responsible for causing diarrhea among deployed troops. Enteropathogenic E. coli are again identified as primary pathogens of concern, and based on the high rates of illness and parasites recovered, it seems that environmental control of diarrheal infection remains a challenge. We feel these data provide continued support for the robust research program in the Department of Defense and private sectors to identify primary interventions for the prevention of diarrheal disease.
Received March 15, 2006. Accepted for publication June 30, 2006.
Acknowledgments: We thank Army Central Command and the Camp As Sayliyah Troop Medical Clinic for assistance with this research project. Furthermore, we thank Dr. Hind Shaheen and Marilou Salamat for laboratory technical assistance. Lastly, we thank Dr. Anne Marie Svennerholm for providing reagents used to detect enterotoxigenic E. coli toxins.
Financial support: This project was funded by the Military Infectious Disease Research Program work unit 6000.RAD1.DE0301.
Disclaimer: 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.
* Address correspondence to Marshall R. Monteville, NAMRU-3 PSC 452 Box 5000, FPO AE, 09835. E-mail: montevillem{at}namru3.med.navy.mil ![]()
Copyright assignment statement: Some of the authors are military service members (or employees of the US Government). This work was prepared as part of their official duties. Title 17 U.S.C.
105 provides that "Copyright protection under this title is not available for any work of the United States Government." Title 17 U.S.C.
101 defines a US Government work as a work prepared by a military service member or employee of the US Government as part of that persons official duties.
Authors addresses: Marshall R. Monteville, NAMRU-3 PSC 452 Box 5000, FPO AE, 09835, Telephone: 011-202-342-1375 ext. 379, E-mail: montevillem{at}namru3.med.navy.mil. Mark S. Riddle, NAMRU-3 PSC 452 Box 5000, FPO AE, 09835, Telephone: 011-202-342-1375 ext. 451, E-mail: riddlem{at}namru3.med.navy.mil. Usha Baht, ASG QA, ATTN TMC/508, APO AE 09898, Telephone: 009-74-438-4251, E-mail: ubhatuk{at}yahoo.co.uk. Shannon D. Putnam, NAMRU-2, Box 3 Unit 8132, FPO AP 96520, E-mail: putnam{at}namru2.org. Robert W. Frenck, Jr. UCLA Center for Vaccine Research, 1124 W. Carson St., Torrance, CA 90502, Telephone: 310-781-3636, E-mail: rfrenck{at}uclacvr.labiomed.org. Kenneth S. Brooks, ASG QA, ATTN TMC/508, APO AE 09898, E-mail: Kenneth.s.brooks{at}us.army.mil. Manal Moustafa, NAMRU-3 PSC 452 Box 5000, FPO AE, 09835, E-mail: manalm{at}namru3.med.navy.mil. Jaime Bland, ASG QA, ATTN TMC/508, APO AE 09898, Telephone: 009-74-460-8333, E-mail: Jaime.Bland{at}qatar.army.mil. John W. Sanders, NAMRU-3 PSC 452 Box 5000, FPO AE, 09835, E-mail: jwsanders{at}Bethesda.med.navy.mil.
Reprint requests: Marshall R. Monteville, NAMRU-3 PSC 452 Box 5000, FPO AE, 09835. E-mail: montevillem{at}namru3.med.navy.mil.
| REFERENCES |
|
|
|---|
This article has been cited by other articles:
![]() |
C. K. Porter, H. El Mohammady, S. Baqar, D. M. Rockabrand, S. D. Putnam, D. R. Tribble, M. S. Riddle, R. W. Frenck, P. Rozmajzl, E. Kilbane, et al. Case Series Study of Traveler's Diarrhea in U.S. Military Personnel at Incirlik Air Base, Turkey Clin. Vaccine Immunol., December 1, 2008; 15(12): 1884 - 1887. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. S. Riddle, D. R. Tribble, S. D. Putnam, M. Mostafa, T. R. Brown, A. Letizia, A. W. Armstrong, and J. W. Sanders Past Trends and Current Status of Self-Reported Incidence and Impact of Disease and Nonbattle Injury in Military Operations in Southwest Asia and the Middle East Am J Public Health, December 1, 2008; 98(12): 2199 - 2206. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |