GASTROINTESTINAL DISORDERS - Medicine for Mountaineering and Other Wilderness Activities - page 256

Filtration removes the organisms. Iodine in a concentration of eight parts per million
effectively kills parasites and cysts within ten minutes (twenty minutes if the water is
cold—32°F to 40°F or 0°C to 5°C). Bringing water to a boil and chlorine compounds also
can kill Giardia .
Symptoms of Giardiasis vary widely. Clearly, most infested individuals have no symp-
toms at all. In an incident carefully studied by the Centers for Disease Control and Preven-
tion(CDC),disruptioninonecity'swaterdisinfectionsystemallowedtheentirepopulation
toconsume water heavily contaminated with Giardia .Only11percent oftheexposed pop-
ulation developed symptomatic disease, although 46 percent had organisms in their stools.
In the same study, 8.5 percent of the population of a neighboring city was found to have
totally asymptomatic Giardia infestations.
Characteristic symptoms, when they occur, are mild to moderate abdominal discomfort,
abdominal distention due to increased intestinal gas (“rotten egg burps” that smell like
hydrogen sulfide are typical), and mild to moderate diarrhea. Stools are soft, may be
liquid, and are bulky and foul smelling; they do not contain blood, mucus, or pus. Two to
four bowel movements a day are typical. A few individuals have more severe symptoms.
Cramps may occur. Mild to moderate generalized symptoms of illness—weakness, loss
of appetite or even nausea, and chilly sensations—may appear. Without treatment infesta-
tion lasts seven to ten days; because symptoms and the organisms disappear and recurrent
symptomatic infestations are rare, apparently most people develop some type of immunity
after that time.
Rare individuals, less than 1 percent of those with infestations, fail to rid themselves
of the organisms and develop chronic infestations that can cause malabsorption, loss of
weight, ulcerlike stomach pain, and other chronic disturbances. Such prolonged infesta-
tions may result from mild immunologic deficiencies but can occur in otherwise healthy
individuals.
Sometimes Giardiasis is associated with the explosive onset of voluminous diarrhea
like traveler's diarrhea, and travelers, including physicians, often overdiagnose Giardiasis .
However, if a laboratory is not available and typical symptoms persisting for six to seven
dayshavenotbeenrelievedbymeasureseffectivefortraveler'sdiarrhea,atherapeutictrial
of one of the drugs effective against this parasite may be justified.
Several drugs are effective. Metronidazole (Flagyl®) for five to ten days is the most
commonandeffective therapyintheUnitedStates.Cureshavebeenobtainedwithasingle
largedoseofthisdrug.Ifalcoholisconsumedwhiletakingmetronidazole,severevomiting
results.Therefore,alcoholmustbeavoidedduringandforthreedaysaftertakingthisdrug.
Tinidazole (Tindamax®) is an agent similar to metronidazole. The advantage of Tin-
damax® is its ease of administration—with all tablets taken at the same time. As with
Flagyl®, alcohol must be avoided during and for three days after taking the drug. Tindam-
ax® is more expensive than Flagyl®.