PM2ch37.pdf

Diseases Transmitted by Food, Water, and Soil

Chapter 37

DISEASES TRANSMITTED BY FOOD,

WATER, AND SOIL

DAVID N. TAYLOR, MD

SHARON L. LUDWIG, MD, MPH

LEONARD N. BINN, P H D

JAMES FLECKENSTEIN, MD

JOSE L. SANCHEZ, MD, MPH

WILLIAM A. PETRI, JR., MD, P H D

JOANNA M. SCHAENMAN, P H D

CHARLES W. HOGE, MD

JOHN H. CROSS, P H D

W. PATRICK CARNEY, MPH, P H D

NAOMI E. ARONSON, MD

DUANE R. HOSPENTHAL, MD, P H D

MAY-ANN LEE, P H D

ERIC P. H. YAP, MBBS, DP HIL

DIARRHEA CAUSED BY ESCHERICHIA COLI

CAMPYLOBACTER ENTERITIS

VIRAL GASTROENTERITIS

TYPHOID FEVER

NONTYPHOIDAL SALMONELLOSIS

SHIGELLOSIS

CHOLERA

AMEBIASIS

GIARDIASIS

ENTERIC COCCIDIA INFECTIONS

HELMINTHS

SCHISTOSOMIASIS

COCCIDIOIDOMYCOSIS

HISTOPLASMOSIS

MELIOIDOSIS

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Military Preventive Medicine: Mobilization and Deployment, Volume 2

D.N. Taylor , MD, Colonel, Medical Corps, US Army (Retired); Department of International Health, Johns Hopkins University

Bloomberg School of Public Health, 624 North Broadway, Baltimore, MD 21205; Formerly, Research Coordinator for Prevention of

Diarrheal Disease, Division of Communicable Diseases and Immunology, Walter Reed Army Institute of Research, Silver Spring,

Maryland

S.L. Ludwig , MD, MPH, Commander, US Public Health Service, Operational Preventive Medicine/Epidemiology Staff Officer, US

Coast Guard Commandant (G-WKH-1), 2100 Second Street SW, Washington DC 20593

L.N. Binn , PhD; Supervisory Research Microbiologist, Department of Virus Diseases, Division of Communicable Diseases and

Immunology, Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500

J. Fleckenstein , MD; Assistant Professor of Medicine, Departments of Medicine and Molecular Sciences, Infectious Disease Divi-

sion, University of Tennessee Health Science Center and Veterans Affairs, 1030 Jefferson Avenue, Memphis, TN 38104; Formerly:

Lieutenant Colonel, Medical Corps, US Army; Infectious Disease Service, Walter Reed Army Medical Center, Washington, DC

20307

J.L. Sanche z, MD, MPH, Colonel, Medical Corps, US Army; Medical Epidemiologist and Military Chief, Global Epidemiology and

Threat Assessment, HIV Research Program, Walter Reed Army Institute of Research, 13 Taft Court, Rockville, MD 20850

W.A. Petri, Jr ., MD, PhD; Professor of Medicine, Microbiology, and Pathology, Division of Infectious Diseases, Room 2115, MR4

Building, University of Virginia Health Sciences Center, Charlottesville VA 22908

J.M. Schaenman , PhD; Chief Resident, Department of Internal Medicine, Stanford University School of Medicine, 300 Pasteur

Drive, Stanford, CA 94305

C.W . Hoge , MD, Colonel, Medical Corps, US Army; Chief, Department of Psychiatry and Behavioral Sciences, Division of Neurop-

sychiatry, Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500; Formerly, Principal Investigator, Department of

Enteric Infections, Division of Communicable Diseases and Immunology, Walter Reed Army Institute of Research

J.H. Cross , PhD; Professor of Tropical Public Health, Uniformed Services University of the Health Sciences, 4301 Jones Bridge

Road, Bethesda MD 20814-4799

W.P. Carney , MPH, PhD, Captain, MSC, US Navy (Ret.); Professor, Department of Preventive Medicine and Biometrics, Uniformed

Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814-4799

N.E. Aronson , MD, Colonel, Medical Corps, US Army; Director, Infectious Diseases Division, Room A3058, Uniformed Services

University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814

D.R. Hospenthal , MD, PhD, Lieutenant Colonel, Medical Corps, US Army; Chief, Infectious Disease Service, Brooke Army Medical

Center, 3851 Roger Brooke Drive, Fort Sam Houston, TX 78234-6200

M-A. Lee , PhD; Programme Head, Defence Medical and Environmental Research Institute, @DSO National Laboratories, 27 Medi-

cal Drive, Singapore 119597

E.P.H. Yap , MBBS, DPhil; Programme Head, Defence Medical and Environmental Research Institute, @DSO National Laboratories,

27 Medical Drive, Singapore 119597

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Diseases Transmitted by Food, Water, and Soil

DIARRHEA CAUSED BY ESCHERICHIA COLI

Escherichia coli is a gram-negative, facultatively

anaerobic, rod-shaped bacterium that is generally

a normal, nonpathogenic inhabitant of the intestine

of mammals. It is a member of the large family of

bacteria known as the Enterobacteriaceae, which

also includes salmonellae and shigellae. E coli that

compose the normal intestinal flora may become

pathogenic when seeded outside the intestine, as a

cause of sepsis, focal infections, or wound infec-

tions. E coli may acquire virulence factors that ren-

der them pathogenic to humans in the gut. These

virulence factors are usually stabile genetic charac-

teristics that are passed on from generation to gen-

eration resulting in a stable clone or strain.

Four general categories of E coli have been rec-

ognized as enteric pathogens: 1 Enterotoxigenic E coli

(ETEC), enterohemorrhagic E coli (EHEC), entero-

invasive E coli (EIEC), and enteropathogenic E coli

(EPEC). EPEC organisms are part of a larger group

generally referred to as enteroadherent E coli .

disease has accompanied military campaigns for

centuries, 6 but traveler’s diarrhea was only de-

scribed as a clinical syndrome after World War II

when travel to exotic locations by air became more

feasible. 7 It was not until the early 1970s that ETEC

was recognized as an enteric pathogen in both hu-

mans and animals. 8 One of the first known ETEC

outbreaks occurred in British troops stationed in

Aden in the Persian Gulf region in the 1960s. 9 Rowe

identified a single E coli serotype (O148:H28) as the

cause of illnesses that occurred in the first few

weeks of the deployment. These strains of E coli, as

well as others (O6:H16) from US military forces

serving in Vietnam, were shown to be pathogenic

in volunteers and were subsequently found to pro-

duce enterotoxins. 10 Ever since, ETEC has been

found to be an important cause of diarrhea during

many deployments in the developing world, most

notably the Middle East and Africa (Table 37-1). Di-

arrheal disease was a major problem during the

Persian Gulf War, 11 and ETEC and Shigella organisms

caused the majority of these illnesses (Table 37-2).

Enterotoxigenic Escherichia coli

Introduction and Military Relevance

Description of the Pathogen

ETEC is one of the most common causes of diar-

rheal diseases among children in developing coun-

tries 2,3 and is the most common cause of traveler’s

diarrhea acquired in those countries. 4,5 Diarrheal

ETEC produces either a heat-labile toxin (LT), a

heat-stable toxin (ST), or both toxins (LT/ST). The

isolation rates of ETEC producing these toxins from

persons with diarrhea varies from survey to sur-

TABLE 37-1

ISOLATION RATES OF ENTEROTOXIGENIC ESCHERICHIA COLI AMONG PERSONNEL ON

MILITARY DEPLOYMENTS (1987–1993)

Number

Percentage

Exercise (Country)

Year

cultured

ETEC

Reference

Operation Restore Hope (Somalia)

1992-1993

113

Operation Desert Shield (Saudi Arabia)

1990

432

Operation Bright Star (Egypt)

1989

104

USS Kennedy (Alexandria, Egypt * )

1988

118

Operation Bright Star (Egypt)

1987

183

* port visit

References: (1) Sharp TW, Thornton SA, Wallace MR, et al. Diarrheal disease among military personnel during Operation Restore

Hope, Somalia, 1992-1993. Am J Trop Med Hyg . 1995;52:188–193. (2) Hyams KC, Bourgeois AL, Merrell BR, et al. Diarrheal disease

during Operation Desert Shield. N Engl J Med . 1991;325:1423–1428. (3) Taylor DN, Sanchez JL, Candler W, Thornton S, McQueen C,

Echeverria P. Treatment of travelers’ diarrhea: Ciprofloxacin plus loperamide compared with ciprofloxacin alone; a placebo-

controlled, randomized trial. Ann Intern Med . 1991;114:731–734. (4) Scott DA, Haberberger RL, Thornton SA, Hyams KC. Norfloxacin

for the prophylaxis of travelers’ diarrhea in U.S. military personnel. Am J Trop Med Hyg . 1990;42:160–164. (5) Haberberger RL Jr,

Mikhail IA, Burans JP, et al. Traveler’s diarrhea during joint American–Egyptian armed forces exercises in Cairo, Egypt. Mil Med .

1991;156:27–30.

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Military Preventive Medicine: Mobilization and Deployment, Volume 2

TABLE 37-2

nated with human feces used as fertilizer or with

untreated sewage. During the Persian Gulf War,

vegetables acquired from local markets were an

important source of contamination. Decontamina-

tion of salad vegetables in chlorinated water was

unsuccessful because the volume of food required

was too great to allow for the proper contact time. 15

Geographic Distribution . In tropical climates,

disease caused by ETEC occurs year-round; in more

temperate climates, disease is more common in the

warmer summer months. In the developed world,

ETEC is a rare cause of diarrhea, and almost all of

the epidemiologic data that are available is from

foodborne or waterborne outbreaks. 16–18

Incidence . Diarrhea caused by ETEC is a major

health problem for infants and children in the de-

veloping world and is the major cause of traveler’s

diarrhea in those traveling to the developing world.

Studies in areas of the developing world where

hygiene is poor suggest that exposure to ETEC is

nearly constant. Under these circumstances, the level

of immunity is the key factor in determining suscep-

tibility to disease. Infants and newly arriving travel-

ers have the least immunity and more frequently

develop severe diarrhea when infected. After repeated

exposure, illnesses become less severe or less symp-

tomatic. Because ETEC is endemic in developing

countries, outbreaks are rare except in new arriv-

als, such as travelers. During the build-up stages

of the Persian Gulf War (August to October 1990),

diarrhea affected as many as 5% of the service mem-

ber strength per week (Figure 37-1).

BACTERIAL ENTEROPATHOGENS IDENTIFIED

IN STOOL SAMPLES FROM 432 US MILITARY

PERSONNEL WITH ACUTE GASTROENTERITIS

DURING OPERATION DESERT SHIELD

Isolation Rate

Enteropathogen

Number Percent

ETEC *

Heat-labile toxin

3.5

Heat-stable toxin

10.2

Heat-labile and heat-stable toxin

14.8

Mixed ETEC infection

0.5

Total of ETEC

125

28.9

Shigella organisms

S dysenteriae

0.9

S flexneri

2.8

S boydii

1.9

S sonnei

20.6

Total of Shigella organisms

113

26.2

EIEC †

0.7

Salmonella

1.6

Campylobacter

0.5

* Enterotoxigenic E coli

† Enteroinvasive E coli

Reprinted from: Hyams KC, Bourgeois AL, Merrell BR, et al.

Diarrheal disease during Operation Desert Shield. N Engl J Med .

Pathogenesis and Clinical Findings

vey, but in most studies the isolation rates of each

toxin type are approximately equal. 12 Strains pro-

ducing ST or LT/ST are more pathogenic than

strains producing only LT and belong to a small

number of O:H serotypes; most have recognized

intestinal cell adherence or colonization factors. 1

Strains producing only heat-labile toxin belong to

a much larger number of O:H serotypes and often

do not possess known colonization factors. 12

ETEC can cause a severe watery diarrhea similar

to cholera. ETEC must adhere to the small intesti-

nal mucosa to cause disease. ETEC adherence is

mediated by fimbriae on the surface of the organ-

ism. These fimbriae, called colonization factor an-

tigens, are encoded by plasmids that usually encode

heat stable toxin and often heat labile toxin. 1 The

pathophysiology of diarrhea caused by ETEC is

primarily determined by the production of these

enterotoxins. Similar to cholera toxin, heat labile toxin

is composed of one A subunit and 5 B subunits that

bind to ganglioside GM1 on eucaryotic cell surfaces.

The A subunit undergoes proteolytic cleavage that

produces two fragments designated A1 and A2. The

A1 fragment activates adenylcyclase and increases

cyclic adenosine monophosphate through adenos-

ine diphosphate ribosylation of the cell membrane,

which causes fluid secretion by inhibiting sodium

and chloride absorption and chloride secretion.

Epidemiology

Transmission . Most epidemiologic studies have

implicated contaminated foods as the main source

of ETEC. The human reservoir is large, and fecal

spread to food via hands is probably the main

method of contamination. 13,14 ETEC can also be iso-

lated from domestic animals, and contamination of

meats with intestinal contents may be another im-

portant source in food. Vegetables can be contami-

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Diseases Transmitted by Food, Water, and Soil

ETEC causes a secretory diarrhea with fluid and

electrolyte loss without evidence of inflammation.

The amount of diarrhea may be mild or massive,

cholera-like purging. Generally, an inoculum of

about 10 8 organisms is required to infect 50% of

persons exposed. 10 Disease severity increases with

inoculum size and may also be associated with the

quantity of toxin produced by the organism. In trav-

elers, disease occurs most commonly in the first

weeks of travel. The incubation period ranges from

12 to 48 hours and shortens with higher inoculum

size. Symptoms that accompany ETEC diarrhea are

malaise, anorexia, abdominal cramping, nausea,

vomiting in 25%, and low-grade fever in 30%. Un-

treated the illness lasts 1 to 5 days but can last as

long as 2 weeks. Stool frequency is usually around

10 episodes per day for 1 or 2 days. 7,19 Complica-

tions are usually associated with dehydration.

These include lethargy, muscle cramping, loss of

consciousness, renal failure, and death. Infants and

children may have a decreased absorptive capacity

of the small bowel for several weeks after the ill-

ness, which can lead to malnutrition.

Diagnostic Approaches

E coli is a gram-negative rod that grows readily

on routine culture media under aerobic conditions.

E coli is identified on MacConkey agar as a lactose-

fermenter. E coli can be isolated after several days

from fecal specimens preserved in Cary-Blair trans-

port media. There is no biochemical or serological

4.0

Fresh fruits and

vegetables banned

3.0

2.0

1.0

0.0

26 2 9 16 23 30 7 14 21 28 4 11 18 25 2 9 16 23 30 6 13 20 27 3 10 17 24 3 10 17 24 31

Aug Sep

Oct

Nov

Dec

Jan

Feb

Mar

Weekly reporting date

Fig. 37-1 . This graph shows the weekly rates of gastroenteritis among 40,000 Marine Corps ground troops stationed

in northeast Saudi Arabia in 1990 and 1991. The arrow indicates when fresh produce was removed from their diet,

which was followed by a sharp decrease in the diarrheal disease incidence.

Reprinted with permission from: Hyams KC, Hanson K, Wignall FS, Escamilla J, Oldfield EC III. The impact of

infectious diseases on the health of US troops deployed to the Persian Gulf during Operations Desert Shield and

Desert Storm. Clin Infect Dis . 1995;20:1497–1504.

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