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Section 3. Summaries of Infectious Diseases
Giardia intestinalis Infections
(Giardiasis)
Clinical Manifestations
Etiology
Epidemiology
Diagnostic Tests
Treatment
Isolation of the Hospitalized Patient
Control Measures
CLINICAL MANIFESTATIONS: Symptomatic infection causes a broad
spectrum of clinical manifestations. Children can have occasional
days of acute watery diarrhea with abdominal pain, or they may
experience a protracted, intermittent, often debilitating disease,
which is characterized by passage of foul-smelling stools associated
with flatulence, abdominal distention, and anorexia. Anorexia
combined with malabsorption can lead to significant weight loss,
failure to thrive, and anemia. Asymptomatic infection is common.
ETIOLOGY: Giardia intestinalis is a flagellate protozoan that
exists in trophozoite and cyst forms; the infective form is
the cyst. Infection is limited to the small intestine and biliary
tract.
EPIDEMIOLOGY: Giardiasis has a worldwide distribution. Humans
are the principal reservoir of infection, but
Giardia organisms
can infect dogs, cats, beavers, and other animals.
1 These animals
can contaminate water with feces containing cysts that are infectious
for humans. People become infected directly (by hand-to-mouth
transfer of cysts from feces of an infected person) or indirectly
(by ingestion of fecally contaminated water or food). Many people
who become infected with
G intestinalis remain asymptomatic.
Most community-wide epidemics have resulted from a contaminated
water supply. Epidemics resulting from person-to-person transmission
occur in child care centers and in institutions for people with
developmental disabilities. Staff and family members in contact
with people in these settings occasionally become infected.
Humoral immunodeficiencies predispose to chronic symptomatic
G intestinalis infections. Surveys conducted in the United States
have demonstrated prevalence rates of
Giardia organisms in stool
specimens that range from 1% to 20%, depending on geographic
location and age. Duration of cyst excretion is variable but
can be months. The disease is communicable for as long as the
infected person excretes cysts.
The incubation period . . . [Go to Full Text]
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Red Book 2006 2006: 130.
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