Entamoeba histolytica, the causative agent of intestinal amoebiasis, is responsible for approximately 100,000
deaths per year around the world. This organism is 1 of the leading causes of deaths by a protozoan
parasite. Also causes illness known as Amoebic dysentery. Being that it is capable of thriving in a
cosmopolitan environment such as those found in developed countries, it prevails among homosexual men,
mental institutions, and among overseas travelers.
It is not uncommon to have intestinal infection with no symptoms. In asymptomatic infections, it is still critical to
diagnose the disease and to initiate anti-amoebic therapy in order to eliminate the carrier state which can
spread the infection to other members in the community. It usually takes about 1 to 4 weeks for symptoms to
show but sometimes more quickly or more slowly.
Some patients may only experience vague, nonspecific symptoms. E. histolytica is also capable of invading
the large intestine and causing severe amoebic dysentery. Approximately 10% of those infected develop an
invasive E. histolytica infection, while the majority (90%) remain asymptomatic. The most common signs and
symptoms of this dysentery include diarrhea, nausea, abdominal pain, weight loss, and cramping. This
corresponds to invasion of the intestine when active trophozoites invade and penetrate the intestinal muscular
wall and simultaneously feed on red blood cells. Amoebic dysentery ensues when trophozoites continue to
erode the intestinal epithelium, leading to the formation of flask-shaped ulcers. Rarely (in about 1% of cases),
E. histolytica can spread through the blood to other organs in the body, causing amoebic abscesses.
A historical examination of the epidemiology of both organisms reveals that E. histolytica infects 50 million
people. It may be more accurate to say that 90% of infections or 450 million people with amoebic infections
are due to E. dispar (dispar = different) and 10% of infections are due to E. histolytica. The isoenzyme
technique helped to establish E. histolytica as the true etiologic agent of amoebic dysentery. Isoenzyme
electrophoresis analysis was critical in establishing the epidemiology of E. histolytica and E. dispar, and
confirming the theory that 2 distinct species with almost entirely identical morphologies existed.
E. histolytica, E. dispar, and E. moshkovskii are hard to distinguish from each other because they are
morphologically similar. Therefore, relying on microscopy alone in order to distinguish these 3 species of
amoebas is ineffective. A number of diagnostic tools, including antigen detection, antibody detection,
isoenzyme electrophoresis analysis, and PCR technology can be used to differentiate between the 3 species.
Enzyme immunoassay (EIA) kits and enzyme linked immunosorbent assay (ELISA) kits are available as
diagnostic tools that aid in the detection of E. histolytica and should be used in addition to microscopy,
particularly antigen detection kits. Thus, serology is primarily used to detect amoebic liver abscess.
Amoebae with ingested erythrocytes, although seen rarely, are a key diagnostic feature of E. histolytica when
found in the stool of a person experiencing amoebic dysentery. Patients may be asked to submit several stool
samples from several different days. If you have been told that you are infected with E. histolytica but you are
feeling fine, you might be infected with E. dispar instead. However, until further testing is done- it is safer to
assume the parasite is E. histolytica. One problem is that the blood test may still be positive if you had
amebiasis in the past, even if you are no longer infected now.
How to Become Infected:
• By putting anything into your mouth that has touched the stool of a person who is infected with E. histolytica.
• By swallowing something, such as water or food, that is contaminated with E. histolytica.
• By touching and bringing to your mouth cysts (eggs) picked up from surfaces that are contaminated with E.
Amoebiasis infection occurs worldwide. In developing countries with poor sanitary conditions, warmer climates
and/ or crowded living nearly 50% of the people are infected.
How to Avoid Entameoba Hystolytica While Traveling or Living in Risk:
• Drink only bottled or boiled (for 1 minute) water or carbonated (bubbly) drinks in cans or bottles. Do not
drink fountain drinks or any drinks with ice cubes. Another way to make water safe is by filtering it through an
"absolute 1 micron or less" filter and dissolving iodine tablets in the filtered water. "Absolute 1 micron" filters
can be found in camping/outdoor supply stores. Or treat the water with iodine tablets.
• Do not eat fresh fruit or vegetables that you did not peel yourself.
• Do not eat lettuce that may be washed with tap water
• Do not eat or drink milk, cheese, or dairy products that may not have been pasteurized.
• Do not eat or drink anything sold by street vendors.
• Avoid sexual practices that allow fecal-oral contact.
• Clean bathrooms and toilets often; pay particular attention to toilet seats and taps.
Metronidazole, or a related drug such a tinidazole, is used to destroy amebae that have invaded tissue. It is
rapidly absorbed into the bloodstream and transported to the site of infection. Antibiotics are necessary, and
are given for 5 days for amoebic dysentery and for 10-14 days if there is a liver abscess or extraintestinal
spread. Large abcesses in the liver may require drainage, using an ultrasound scan to localize the abscess
accurately and position the drainage needle.
Treatment may include:
• An anti-diarrheal medication may also be prescribed. Metronidazole can produce a metallic taste in the
mouth and may give rise to nausea.
• If amoebiasis causes an abscess on your liver or other organs and the abscess does not respond to
antibiotics, it may need to be drained surgically.