Male homosexuals, particularly those with several or
many partners.
People who swim in or boat on rivers, lakes, streams,
or other bodies of water liable to contamination by
fecal matter. The greatest risk of infection comes
from accidentally swallowing a mouthful of water
while swimming, diving, rafting, or water skiing.
People who depend on well water for their household
drinking supply.
Some people are at increased risk of a severe case
of giardiasis because they have other health problems:
An impaired immune system.
Crohn’s disease, cystic fibrosis, or other diseases that
weaken the intestines.
Malnutrition.
Recent surgery on the stomach or taking medications
to lower stomach acid secretion (stomach acid kills
G. lamblia).
Treatment
Most people with giardiasis can be diagnosed and
treated by their primary care physician. Diagnosis is
usually done by examining stool samples under a
microscope for the characteristic cysts and tropho-
zoites ofG. lamblia(both forms of the organism may
appear in the stool); by enzyme-linked immunosorb-
ent assay (ELISA) tests; or by an Entero-test. The
Entero-test, also called the string test, consists of a
gelatin capsule containing a nylon string attached to
a weight. The patient tapes one end of the string to the
inside of the cheek and swallows the capsule. The
string is left in place for 4 to 6 hours or overnight
while the patient is fasting; it is then removed and the
mucus on the string is examined for trophozoites.
Patients suspected of having chronic giardiasis
may be referred to a gastroenterologist, who is a doc-
tor with special training in digestive disorders. In some
cases, the doctor may need to examine the patient’s
small intestine through an endoscope or remove a
sample of tissue from the lining of the patient’s intes-
tine to make sure that the patient’s symptoms are
caused by a parasite and not by some other disorder.
Medications
Giardiasis is most commonly treated with one of
the following drugs, which cause the death of the dis-
ease organisms:
Metronidazole (Flagyl). The most common drug
given to treat giardiasis. Adults are usually given
three doses per day over a 5-day period, while chil-
dren are usually given a 10-day course.
Furazolidone (Furoxone). Some doctors prefer to
treat children with this drug because it is available
in a liquid form.
Nitazoxanide (Alinia). This drug is also preferred for
treating children because it causes fewer adverse
effects in younger patients.
Tinidazole (Tindamax). Tinidazole is a relatively
new anti-infective drug; it was approved by the
Food and Drug Administration (FDA) only in- It has the advantage of requiring only one
dose of 2000 mg for treatment of giardiasis rather
than several days of repeated doses.
Paramomycin (Humatin). Paramomycin is the only
drug effective againstG. lambliathat is considered
safe to give pregnant women.
Some herbalists and naturopaths recommend bar-
berry (Berberis vulgaris) as an anti-infective agent in
treating giardiasis.
Children or adults who are carrying cysts are some-
times given anti-infective drugs even if they are not
symptomatic, in order to lower the risk of transmission
to other children in a daycare center or other family
members.
Dietary treatment
People with mild cases of giardiasis may not need
any special dietary therapy after they have started
taking medications to kill the parasites.
Children and adults who have become dehydrated
because of severe diarrhea may be given a rehydration
drink (Lytren, Rehydralyte, or Pedialyte) to sip.
Adults should drink 1 cup of water or rehydration
drink for each large passage of watery stool. Children
should be given 1/2 to 1 cup of rehydration fluid (or
Pedialyte frozen pops) per hour, asdehydrationis
more dangerous to them than to adults. Children
should not be given undiluted sports drinks, soda
pop, or fruit juice, as these contain too much sugar
and not enoughelectrolytes. If a commercial rehydra-
tion drink is not available and the diarrhea does not
stop within 24 hours, the World Health Organization
(WHO) formula for oral rehydration can be used. To
make the WHO formula at home, combine 1 quart of
boiled or purified water with 2 teaspoons table sugar,
1/2 teaspoon salt, and 1/2 teaspoon of baking soda
(sodiumbicarbonate).
Dietary therapy for adults recovering from giar-
diasis includes the following:
Take clear liquids only (beef broth, soda, vegetable
or chicken bouillon, etc.) for the first 24 hours of
acute symptoms; do not try to eat solid foods.Giardiasis