Amebiasis, which is caused by a protozoan parasite, occurs
worldwide, especially in regions with poor sanitation. High-risk
areas (where up to 50% of the population carry the parasite) are
Mexico, South America, India, and West and Southern Africa.
This potentially serious illness is caused by parasites that
invade the wall of the large intestine, causing either acute dysentery
or chronic diarrhea of variable severity. The parasites can also
infect the liver, causing inflammation and liver abscess. In the
carrier state, which is common, parasites live in the intestine
without causing symptoms.
Transmission occurs through ingestion of fecally contaminated
food or water. Flies can serve as carriers of the amebic cysts.
Infected food handlers can spread the disease. Person-to-person
contact is important in transmission; household members and sexual
partners can easily become infected.
Signs and Symptoms
Symptoms of amebiasis are variable. You may be carrying the
parasites and have no symptoms whatsoever. Mild illness causes
crampy abdominal pain, little or no fever, and semiformed, foul-smelling
stools. Mucus may be present but usually without blood. Soft stools
or diarrhea may alternate with constipation. You may experience
fatigue, loss of appetite, and some weight loss. The symptoms
at this stage are similar to those of giardiasis.
More severe illness (amebic dysentery) is characterized by
fever, bloody diarrhea, generalized abdominal tenderness, vomiting,
and much greater toxicity. Illness at this stage represents a
medical emergency and requires urgent care.
Travelers who develop amebic liver abscess usually don't have
diarrhea or other intestinal symptoms. Instead, they may note
fever, upper abdominal pain, and an enlarged, tender liver. Sweating,
chills, weight loss, and fatigue may also be present.
Medical diagnosis of amebiasis is extremely important. Amebic
dysentery must be distinguished from other infections causing
bloody diarrhea (e.g., those due to Shigella, Campylobacter, Clostridium
difflcile, and Yersinia). Reglonal enteritis and ulcerative colitis
must be considered in the younger patient. In older persons, surgical
conditions such as diverficulitis can mimic amebiasis.
Amebiasis is treated with Flagyl (metronidazole). Treatment
eliminates cysts from the stool, thus preventing transmission
of the disease to close contacts such as family members.