DIARRHEAL DISEASES
In developing countries
of the world, infectious diarrhea kills about 4 million people per year. In the
United States, it is esti-mated that children younger than 5 years of age
experience more than 20 million episodes of diarrheal diseases each year, with
about 400 deaths per year attributed to such episodes. Dehydra-tion is the most
important factor for the morbidity and mortality associated with diarrheal
disease. Dehydration is largely control-lable by using rehydration therapy
(Guerrant & Steiner, 2000).
The portal of entry of
all diarrheal pathogens is oral ingestion. Although the food we eat is far from
sterile, the high acidity of the stomach and the antibody-producing cells of
the small bowel generally serve to decrease the potential of pathogens. If the
num-ber of organisms is large enough, or if the food neutralizes the acidic
environment, infection can occur. Decreased gastric acidity
with disruption of normal bowel flora (as occurs after surgery), use of
antimicrobial agents, and the immune dysfunction of AIDS all decrease
intestinal defenses.
There are many viral,
bacterial, and parasitic causes for diarrheal diseases. Rotavirus is the most
significant viral cause of diarrhea in young children. Common causes of
bacterial infection in-clude Escherichia
coli and Salmonella, Shigella,
Campylobacter, and Yersinia
species. Parasitic infections of importance include Giardia and Cryptosporidium species
and Entamoeba histolytica.
E. coli is
the most common aerobic organism colonizing the largebowel. When E. coli organisms are cultured from
fecal specimens, the results seldom suggest pathology, but rather reflect
normal flora. However, certain strains of E.
coli with increased virulence
(ie, degree of pathogenicity of an organism) have been responsible for
significant outbreaks in recent years. These stronger patho-logic strains are
subgrouped as enterotoxigenic E. coli
(ETEC) be-cause of their production of enterotoxins. ETEC strains often cause
cholera-like disease, with rapid, severe dehydration and an increased risk of
death.
Recent outbreaks of an E. coli species, 0157:H7, have often
been linked to the ingestion of undercooked beef. This bacterium lives in the intestines
of cattle and can be introduced into meat at the time of slaughter. Prevention
of disease from this strain of E. coli is
aimed at teaching the public to cook ground beef thor-oughly (ie, until the
meat is no longer pink and the juices run clear).
Salmonella is
a gram-negative bacillus with many species, includ-ing the very pathogenic Salmonella typhi (ie, typhoid fever). Of
the nontyphi species, most organisms are prevalent in animal food sources. It
is estimated that Salmonella species
contaminate more than 50% of commercially available chicken products and are
fre-quently found in eggs (intact and with broken shells), in raw milk, and
occasionally in beef (Crump et al., 2002). Approxi-mately 40% of the deaths
caused by Salmonellaoccur in nursing
home residents. The high mortality rate reflects the seriousness of the
infection in the elderly, who often have weakened immune systems (CDC, 2000a).
There is great
variability of symptoms associated with Salmo-nella
species infection, including an asymptomatic carrier state,gastroenteritis,
and systemic infection. Diarrhea with gastro-enteritis is common. Disseminated
disease and bacteremia, whether accompanied by diarrhea or not, is less common.
The person with Salmonella-caused diarrhea can be a
source for transmission to others. The importance of good hygiene should be
emphasized, and health care workers should use special care when handling
bedpans, stool specimens, or other objects that may have fecal contamination.
Hand washing is imperative after any con-tact with a person with Salmonella diarrhea. Patients with
gastro-enteritis generally are not treated with antibiotics because antibiotic
use may increase the period of time that the patient carries the bac-teria
while not improving the clinical outcome. However, those with systemic
salmonellosis require antimicrobial therapy.
The Shigella species is a gram-negative organism that invades the lumen
of the intestine and causes disease and severe watery (possibly bloody)
diarrhea. Shigella species spread
through the fecal-oral route, with easy transmission from one person to
another. Small numbers of organisms are needed to cause disease. Because
transmission occurs easily with improper hygiene, it is not sur-prising that Shigella organisms disproportionately
affect pediatric populations. Disease in the very young may infrequently be
com-plicated by pulmonary or neurologic symptoms.
Antimicrobial therapy should be instituted early.
Frequently, initial therapy choices must be altered when final microbiologic
testing reveals the organism’s sensitivity.
In the United States,
diarrheal disease attributed to Campylobacter
species surpasses that recorded for Salmonella
and Shigella species. The organism is
found abundantly in animal food sources. It is especially common in poultry but
can also be found in beef and pork. Transmission appears to be almost entirely
by the fecal-oral route, with food sources representing the reservoir of
organism. Direct person-to-person transmission appears to be less common than
for other enteric pathogens, such as Shigella.
Cooking and storing food at appropriate temperatures
pro-tects against Campylobacter. It
is important that kitchen utensils used in meat preparation be kept away from
other food to prevent Campylobacter transmission.
After a person is
infected, the organism directly attacks the lumen of the intestine and may
cause disease through enterotoxin release. Symptoms can range from mild
abdominal cramping and minimal diarrhea to severe disease with profuse watery
bloody di-arrhea and debilitating abdominal cramping. Antimicrobial ther-apy is
recommended only for those who are seriously ill.
Giardia lamblia is
a protozoan. Transmission occurs when foodor drink is contaminated with viable
cysts of the organism. People often become infected while traveling to endemic
areas in in-dustrialized and nonindustrialized countries of the world or by
drinking contaminated water from mountain streams within the United States. The
organism can be transmitted by close contact, as occurs in day care settings.
Transmission by sexual contact has also been documented.
Frequently, the infection goes unnoticed. Infection is
often recognized more easily in children than in adults. In extreme cases, the
patient may experience abdominal pain and chronic di-arrhea, usually described
as containing mucus and fat but not blood. Microscopic examination of stool
specimens reveals the trophozoite or cyst stages of the parasitic life cycle.
Metronidazole (Flagyl)
is commonly used to treat Giardia,
but success rates for this and alternative therapies are inconsistent. Patients
with Giardia infections should be
instructed that the or-ganism can be easily transmitted in family or group
settings. Per-sonal hygiene measures should be reinforced, and those who travel
or camp where water is not treated and filtered should be ad-vised to avoid
local water supplies unless water is purified before drinking or used in
cooking.
Although reported cases
of cholera have been rare in the United States in recent decades, no discussion
of infectious diarrhea is complete without mention of this very serious
infectious disease. Historically, epidemics of cholera have influenced all
aspects of life—from medical to political—and infection rates have been
significant enough to destroy governments and armies. Cholera is always a
concern when wars or natural disasters result in inad-equately processed
wastewater. Vibrio cholera also may
be found naturally in brackish rivers and coastal waters.
The V. cholera
organism is a gram-negative organism with sev-eral different serotypes. The
type usually associated with epidemics is toxigenic V. cholera 01. The organism is transmitted by contam-inated food or
water. Most recent cases in the United States have been from contaminated
shellfish found in the Gulf of Mexico or by visitors who have brought
contaminated shellfish into the United States.
Cholera causes disease with a very rapid onset of copious
di-arrhea in which up to 1 L of fluid per hour can be lost. Dehydra-tion, with
subsequent cardiopulmonary collapse may cause rapid progression from onset of
signs and symptoms to death. The principal therapy is rehydration. Rehydration
efforts should be vigorous and sustained. If oral rehydration cannot be
accom-plished, the patient should be hospitalized for intravenous ther-apy
support.
In the United States,
cholera should be suspected in patients who have watery diarrhea after eating
shellfish harvested from the Gulf of Mexico. Confirmation of the causative
organism can be made by stool culture. It is imperative that all cases are
reported to local and state public health authorities. People traveling to
areas where cholera occurs regularly should remember the simple rule of thumb:
“boil it, cook it, peel it, or forget it”.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2024 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.