GASTROINTESTINAL DISORDERS - Medicine for Mountaineering and Other Wilderness Activities - page 257

Cryptosporidiosis
Cryptosporidia were discovered in laboratory mice in 1907 and have been known to
produce diarrheal disease in a variety of animals including domestic animals. They were
not thought to infect humans until 1976 when the first human infection was diagnosed.
In the subsequent decade, infections by the parasite were recognized mostly in immuno-
compromised individuals, primarily persons with acquired immune deficiency syndrome
(AIDS) or malnutrition. Since the early 1980s, cryptosporidiosis been recognized as a ma-
jor worldwide cause of diarrhea in otherwise healthy individuals.
Cryptosporidia are ubiquitous. The organisms have been found in up to 97 percent of
the large streams, lakes, and reservoirs in the United States. Infections occur on every con-
tinent but Antarctica and cause up to 20 percent of the cases of diarrhea severe enough
for individuals to seek medical attention. These microorganisms are commonly found in
swimmingpoolsbecausetheyareresistanttothechlorineusedtodisinfectthewater.Some
pools do not allow babies in diapers because they are a common source of Cryptosporidia .
Cryptosporidia present a particular problem in wilderness situations because the organ-
isms resist iodine and chlorine disinfectants and must be eliminated from water by boil-
ing, filtration, or ultraviolet light. Hypochlorous acid and chlorine dioxide do destroy these
parasites but require four hours.
After ingestion, the organisms implant in the cells lining the small intestine. Mature or-
ganisms are released into the intestinal lumen as thick-walled (80 percent) or thin-walled
(20 percent) cysts. The thick-walled cysts are excreted, but the thin-walled cysts can reim-
plant and maintain the infestation.
Inimmunocompetent hoststheincubationperiodistwotofourteendays.Typicalsymp-
toms are watery diarrhea, crampy pain, anorexia, malaise, and flatulence. Approximately
10to15percentofinfectedindividualsareasymptomatic.Othersmayhavemorethansev-
entystoolsaday.Thevolumeofdiarrhealfluidmayexceedtwenty-fivelitersaday,mostly
in immunocompromised individuals. Obviously, dehydration is common and often severe.
Eating aggravates the diarrhea and pain, so many individuals do not eat and lose weight.
Eradication of the infection is dependent on the development of immunity by the host.
Immunocompromised individuals rid themselves of the organisms slowly—or not at all.
For persons with HIV infection or receiving chemotherapy that suppresses their immune
system, infestation may prove fatal. Malnourished children have impaired cellular immu-
nity and also are prone to severe cryptosporidiosis.
Theonlydrugfoundtobeeffectiveforimmunocompetentpeopleisnitazoxanide(Alini-
a®), but this agent is not effective for immunocompromised persons. The drug is more ef-
fective when taken with food. This agent is also effective for Giardia infestations but is
more expensive than metronidazole (Flagyl®).
Fluid replacement is a vital aspect of therapy and can be accomplished with bouillon,
Gatorade®, or other oral rehydration fluids. The disorder lasts from two days to a month,