Persons with amebiasis may or may not manifest the disease. Symptoms, if any, include flatulence, alternating diarrhea and constipation, and abdominal cramps. In advanced cases, the patient may complain of fever, abdominal tenderness and passage of bloody, mucoid stools (frank dysentery). Dehydration is imminent. The patient is emaciated and possibly anemic from chronic infection and malnutrion. A large mass  (ameboma) may obliterate the intestines. 

Colonies of trophozoites can cause ulcers and perforate the intestinal wall, resulting in severe abdominal pain and peritonitis needing urgent medical intervention.

Extraintestinal amebiasis can cause suppurative infection of the liver parenchyma (abscess), fever, chills, sweating, general debility, nausea, vomiting, and pain in the upper right quadrant. Amebas may spread to other organs, including the lungs or brain, the skin, especially around the buttocks, genitals, or wounds from abdominal surgery or injury.

Complications of amebic colitis include ameboma, toxic megacolon, fulminant or necrotizing colitis, and rectovaginal fistula. Hepatic amebiasis or liver abscess may lead to intrapericardial, intrathoracic, or intraperitoneal rupture, with or without secondary bacterial infection; invasion of the pleural or pericardial cavity; and migration to the brain via blood route and development of brain abscess. Other complications include GI bleeding, bowel perforation, peritonitis, stricture formation, empysema and intussusception [11] [12].

• Fever

  or amoebic liver abscesses (fever, chills, abdominal pain, weight loss, hepatomegaly) that can be fatal if not immediately treated. [orpha.net]

  Abdominal findings range from mild tenderness to frank abdominal pain, with high fevers and toxic systemic symptoms. Abdominal tenderness frequently accompanies amebic colitis. [msdmanuals.com]

  Chronic amoebiasis can present with gastrointestinal symptoms plus fatigue, weight loss and occasional fever. [who.int]

  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. [thirdworldtraveler.com]

  Pain: Types and Pathways, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. [lecturio.com]

• Weight Loss

  loss, hepatomegaly) that can be fatal if not immediately treated. [orpha.net]

  You may experience fatigue, loss of appetite, and some weight loss. The symptoms at this stage are similar to those of giardiasis. [thirdworldtraveler.com]

  Chronic amoebiasis can present with gastrointestinal symptoms plus fatigue, weight loss and occasional fever. [who.int]

  Symptoms include: fever, cough, dull abdominal pain, nausea, diarrhea, ulcers, constipation, gas, hepatomegaly, cough, and weight loss. [web.stanford.edu]

  Chronic amoebiasis, a more serious form of the disease, could take toll on the human body causing fatigue, weight loss and occasional fever. The parasite could also transfer to other organs, known as extraintestinal amoebiasis. According to Dr. [news.abs-cbn.com]

• Malnutrition

  Reviewed here are the associations and interactions of malnutrition, IgA and interferon-gamma, human leukocyte antigen alleles, and parasite genotypes to the outcome of infection. [ncbi.nlm.nih.gov]

  Symptoms of these more severe infections include: anemia appendicitis (inflammation of the appendix) bloody diarrhea fatigue fever gas (flatulence) genital and skin lesions intermittent constipation liver abscesses (can lead to death, if not treated) malnutrition [parasitesinhumans.org]

  Among the risk factors for symptomatic amebiasis include: Pregnancy Use of immunosuppressive drugs The use of corticoids Alcoholism Age of extremes (infants and the elderly) HIV Cancer Malnutrition As already said, more than 90% of patients infected with [tabletsmanual.com]

  […] spread: Through food or water contaminated with stools Through fertilizer made of human waste From person to person, particularly by contact with the mouth or rectal area of an infected person Risk factors for severe amebiasis include: Alcohol use Cancer Malnutrition [nlm.nih.gov]

  […] spread: Through food or water contaminated with stool Through fertilizer made of human waste From person to person, particularly by contact with the mouth or rectal area of an infected person Risk factors for severe amebiasis include: Alcohol use Cancer Malnutrition [medlineplus.gov]

• Chills

  […] manifestations that may range from an asymptomatic state to amoebic colitis (violent abdominal pain, a painful contracted feeling around the anal sphincter, blood and mucus in the stools but without the presence of fever), or amoebic liver abscesses (fever, chills [orpha.net]

  While intestinal disease is often asymptomatic, symptoms may range from acute abdominal pain, fever, chills, and bloody diarrhea to mild abdominal discomfort with diarrhea alternating with constipation. [publichealth.lacounty.gov]

  Sweating, chills, weight loss, and fatigue may also be present. Diagnosis Medical diagnosis of amebiasis is extremely important. [thirdworldtraveler.com]

  […] and mucus • abdominal pain, tenesmus • no fever or moderate fever • possibly signs of dehydration – Amoebic liver abscess • painful hepatomegaly; mild jaundice may be present • anorexia, weight loss, nausea, vomiting • intermittent fever, sweating, chills [medicalguidelines.msf.org]

  Abdominal discomfort Diarrhoea that may include blood or mucus with periods of constipation Nausea Weight loss Fever Chills Treatment of Amoebiasis Consult the Medical Letter or Pediatric Red Book for specific drugs and dosages. [byjus.com]

• Anemia

  People affected may develop anemia.[1][2][3] If the parasite reaches the bloodstream, it can spread through the body and end up in the liver, causing amoebic liver abscesses. Liver abscesses can occur without previous diarrhea. [ncbi.nlm.nih.gov]

  People affected may develop anemia due to loss of blood. [dbpedia.org]

  Symptoms of these more severe infections include: anemia appendicitis (inflammation of the appendix) bloody diarrhea fatigue fever gas (flatulence) genital and skin lesions intermittent constipation liver abscesses (can lead to death, if not treated) [parasitesinhumans.org]

• Dry Cough

  A 53-year-old man presented with a dry cough and mild fever. Chest radiography revealed an abnormal solitary mass lesion in the right upper lung field. The clinical diagnosis was a bacterial lung abscess. [ncbi.nlm.nih.gov]

  Dry cough, chest pain and decreased breath may be due to pleuropulmonary extension of the inflammatory process in the lesions of the superior surface. Hepatomegaly is the most important physical sign in hepatic amebiasis. [scielo.br]

• Diarrhea

  Symptoms range from mild abdominal cramps and watery diarrhea to severe colitis producing bloody diarrhea with mucus. Young people tend to have a more severe disease compared to older individuals. [ncbi.nlm.nih.gov]

  Infection is commonly asymptomatic, but symptoms ranging from mild diarrhea to severe dysentery may occur. Extraintestinal infections include liver abscesses. [msdmanuals.com]

  Almost any cause of diarrhea could mimic amebic diarrhea. If amebic dysentery develops, the differential diagnosis is narrowed to Salmonella, Shigella, and Campylobacter species, and enterohemorrhagic Escherichia coli. [cancertherapyadvisor.com]

  There are mainly two types of amoebiasis:- Intestinal Amoebiasis :- It is frequently asymptomatic and varies from fulminant dysentery with fever, chills, and bloody or mucoid diarrhea to mild abdominal discomfort with diarrhea containing blood or mucus [rnpedia.com]

  It is not uncommon also be fever and dysentery (bloody diarrhea). [tabletsmanual.com]

• Abdominal Pain

  pain, a painful contracted feeling around the anal sphincter, blood and mucus in the stools but without the presence of fever), or amoebic liver abscesses (fever, chills, abdominal pain, weight loss, hepatomegaly) that can be fatal if not immediately [orpha.net]

  Symptomatic patients initially have lower abdominal pain and diarrhoea and later develop dysentery (with blood and mucus in stool). [webhealthcentre.com]

  If abdominal pain symptoms, cramps, and diarrhea persist, a visit to the healthcare provider is recommended. Physicians and nurse practitioners diagnose amebiasis and recommend treatment. [ncbi.nlm.nih.gov]

  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. [thirdworldtraveler.com]

• Nausea

  KEYWORDS: Adverse reaction; Amebiasis; Metronidazole; Nausea [ncbi.nlm.nih.gov]

  Minor side effects like nausea and metallic taste in mouth may be observed with these drugs. You may also be prescribed some medications for diarrhoea, if present. [surgerydoor.co.uk]

  The symptoms of intestinal amoebiasis include diarrhoea, abdominal cramps, bowel movements streaked with blood or mucus, nausea or vomiting and occasionally fever. [doctor.ndtv.com]

  But sometimes, it invades the lining of the colon, causing stomachache, cramping, nausea, loss of appetite, bloody diarrhea, or fever. [bimcbali.com]

  Symptoms include pain or discomfort over the liver, which is occasionally referred to the right shoulder, as well as intermittent fever, sweats, chills, nausea, vomiting, weakness, and weight loss. Jaundice is unusual and low grade when present. [msdmanuals.com]

• Abdominal Cramps

  You may generally think that occasional abdominal cramps with some loose motion and gas as a sign of indigestion, but it can also be a more serious condition called amoebiasis (also known as amebiasis or entamobiasis). [homeremediesforall.com]

  These patients may also suffer from abdominal cramps, fatigue, and weight loss. AMEBIC DYSENTERY. [medical-dictionary.thefreedictionary.com]

  Patients with severe colitis pass offensive and bulky stools containing blood and mucus and have fever and lower abdominal cramps. 2. Gross pathology of intestinal amebiasis showing extensive ulceration 3. [slideshare.net]

  Symptoms of Amebiasis Diarrhea, possibly containing blood or mucus Rectal pain during bowel movements (tenesmus) Intestinal gas (excessive flatulence) Severe abdominal cramping and tenderness Excessive gas Loss of weight High fever Fatigue Nausea and [healthcommunities.com]

  A person infected with such condition has abdominal cramps, nauseating feeling, Fatigue etc. Few of the other symptoms include anorexia (Loss of appetite) and intestinal gas/flatulence or bloating. [ayushveda.com]

• Tenesmus

  In 10% of patients with the disease amoeba, the most common symptoms are usually abdominal pain, tenesmus (painful evacuate) and aqueous massive diarrhea with several bowel movements per day, and weight loss. [tabletsmanual.com]

  – Amoebic dysentery • diarrhoea containing red blood and mucus • abdominal pain, tenesmus • no fever or moderate fever • possibly signs of dehydration – Amoebic liver abscess • painful hepatomegaly; mild jaundice may be present • anorexia, weight loss [medicalguidelines.msf.org]

   Abdominal pain and tenderness in the lower abdomen,painful sudden bowel evacuation(tenesmus) with recto-sigmoid involvement and diarrhoea developing over a period of one to several weeks. [slideshare.net]

  Symptoms of Amebiasis Diarrhea, possibly containing blood or mucus Rectal pain during bowel movements (tenesmus) Intestinal gas (excessive flatulence) Severe abdominal cramping and tenderness Excessive gas Loss of weight High fever Fatigue Nausea and [healthcommunities.com]

  Persons with intestinal amebiasis (amebic colitis) generally have 1 to 3 weeks of increasingly severe diarrhea progressing to grossly bloody dysenteric stools with lower abdominal pain and tenesmus. Weight loss and fever may be present. [kflaph.ca]

• Hepatomegaly

  […] asymptomatic state to amoebic colitis (violent abdominal pain, a painful contracted feeling around the anal sphincter, blood and mucus in the stools but without the presence of fever), or amoebic liver abscesses (fever, chills, abdominal pain, weight loss, hepatomegaly [orpha.net]

  Amebiasis should be considered in the differential diagnosis of infants and children with hematochezia or hepatomegaly, especially in endemic areas. [ncbi.nlm.nih.gov]

  – Amoebic dysentery • diarrhoea containing red blood and mucus • abdominal pain, tenesmus • no fever or moderate fever • possibly signs of dehydration – Amoebic liver abscess • painful hepatomegaly; mild jaundice may be present • anorexia, weight loss [medicalguidelines.msf.org]

  Physical findings:  Hepatomegaly  Localised tenderness  Rales,rhonchi  Localised intercostal tenderness  Jaundice  Epigastric tenderness 4. [slideshare.net]

• Back Pain

  pain Liver: hepatomegaly Kidney: kidney stone (nephrolithiasis), complicated urinary tract infection Left low back pain Spleen Kidney: kidney stone (nephrolithiasis), complicated urinary tract infection Low back pain kidney pain (kidney stone, kidney [en.wikipedia.org]

  A gradual onset of lower abdominal pain and mild diarrhea is followed by malaise, weight loss, and diffuse lower abdominal or back pain. Cecal involvement may mimic acute appendicitis. [accessmedicine.mhmedical.com]

The diagnosis of amebiasis requires collection of fecal sample from the patient for subsequent tests [13]. Microscopic examination may not always reveal the presence of the amebas (trophozoites and/or cysts). Two methods are currently available:

1. In vitro reaction of parasite protein (antigen) with specific antibody and
2. Polymerase chain reaction (PCR)

Molecular diagnostic technique to identify ameba's genetic material. PCR amplifies the ameba's genetic material when present and makes detection possible even with minute quantities of reagents. Both tests are sensitive and specific. Routine microscopy examination may require three to six repeat ed stool examinations and differential diagnosis of ameba species is difficult based on gross morphology.

Colonoscopy can reveal the presence of ulcers or other signs of infection in the large intestine. Tissue samples may be obtained for further evaluation.

Parasites may not be found in the stool in extraintestinal amebiasis. Appropriate diagnostic methods are ultrasonography, CT scan, or MRI, with serological test for anti-ameba antibodies to confirm liver abscess or infection in other sites. Given a strong index of suspicion, the physician may initiate treatment with an amebicidal drug and if the patient responds well, the disease is presumed to be amebiasis. 

• Hypoalbuminemia

  Development of such fulminant course is found to be associated with various factors including male gender, age over 60 years, associated liver abscess, progressive abdominal pain, and signs of peritonitis, leukocytosis, hyponatremia, hypokalemia, and hypoalbuminemia [casesjournal.biomedcentral.com]

  The right pleural effusion was at first impression attributed to hypoalbuminemia secondary to liver insufficiency. In fact this is a relatively common pulmonary complication of invasive amebiasis, seen in as much as 20% of all cases 4. [scielo.mec.pt]

  A moderate elevation of alkaline phosphatase, as well as hypoalbuminemia and transaminases, would suggest the possibility of a large abscess [22]. [scielo.br]

• Hyponatremia

  Development of such fulminant course is found to be associated with various factors including male gender, age over 60 years, associated liver abscess, progressive abdominal pain, and signs of peritonitis, leukocytosis, hyponatremia, hypokalemia, and [casesjournal.biomedcentral.com]

• Neutrophilia

  In patients with multiple abscesses, or bacterial infection, the leukocytosis may be severe, accompanied by neutrophilia, with an increased percentage of immature forms similar to a leukemoid reaction [21]. [scielo.br]

• Leukopenia

  Elevated levels of mevalonic acid in the urine; associated with a deficiency of mevalonate kinase. (05 Mar 2000) orotic aciduria A rare disorder of pyrimidine metabolism characterised by hypochromic anaemia with megaloblastic changes in bone marrow, leukopenia [kmle.co.kr]

• Entamoeba Histolytica

  Life cycle of Entamoeba histolytica Warning: do not confuse the Entamoeba histolytica with other harmless amoeba like dispar Entamoeba, Entamoeba moshkovskii, Endolimax nails or Entamoeba coli. [tabletsmanual.com]

  Homepage Rare diseases Search Search for a rare disease Amoebiasis due to Entamoeba histolytica Disease definition Amebiasis due to Entamoeba histolytica is a parasitic disease caused by the protozoa, Entamoeba histolytica, mainly occurring in tropical [orpha.net]

  Entamoeba histolytica is a protozoan parasite responsible for a disease called amoebiasis. [parasitesinhumans.org]

  Touching, and bringing to your mouth, cysts (eggs) picked up from surfaces that are contaminated with entamoeba histolytica. [rnpedia.com]

  See Amebic abscess, Amebic dystentery. a·me·bi·a·sis ( am'ē-bī'ă-sis ) Infection with Entamoeba histolytica or other pathogenic amebae. [ ameba + G. [medical-dictionary.thefreedictionary.com]

• Colitis

  The organisms infect the... read more, or ulcerative colitis Ulcerative Colitis Ulcerative colitis is a chronic inflammatory and ulcerative disease arising in the colonic mucosa, characterized most often by bloody diarrhea. [msdmanuals.com]

  Symptoms range from mild abdominal cramps and watery diarrhea to severe colitis producing bloody diarrhea with mucus. Young people tend to have a more severe disease compared to older individuals. [ncbi.nlm.nih.gov]

  Imaging studies are not helpful in diagnosing amebic colitis. Amebic liver abscess is best diagnosed by an imaging study of the liver (ultrasonography, CT, or MRI). [cancertherapyadvisor.com]

• Colonic Ulcer

  In spite of absence of cyst and trophozoites in pus, stool, and biopsy of colon diagnosis of amoebic ulcers with amoebic liver abscess was kept due positive serology and response to metronidazole. [atmph.org]

  Gross features: Amebic lesions begin as small foci of necrosis that progress to ulcers. In the early stages the colonic ulcers have a narrow neck and thus appear as small nodules with a minute surface opening (5 mm in diameter). [histopathology-india.net]

  Ulcers. 61 Premkumar M...Joshi YK 31304698 2019 35 Biliary Peritonitis due to a Ruptured Amebic Liver Abscess Mimicking a Periampullary Tumor and Liver Metastases with the Elevation of CA 19-9 and CA 125: A Case Report. 61 Marin-Leiva J...Damian Bello [malacards.org]

  ulcerations, abdominal pain, diarrhea, or bloody diarrhea.[5][2] Complications can include inflammation and ulceration of the colon with tissue death or perforation, which may result in peritonitis.[2] Anemia may develop due to prolonged gastric bleeding [en.wikipedia.org]

• Leukocytosis

  The usual laboratory findings are leukocytosis, elevated alkaline phosphatase, and elevated ESR with typical symptoms of fever, RUQ pain, and liver tenderness. [journals.lww.com]

  High fever, leukocytosis and high CRP were associated with extraluminal amebic diseases. [ncbi.nlm.nih.gov]

  […] fever, cough, and dull, achy right upper quadrant pain that may also include referred pain in the right chest or shoulder Only 1/3 have gastrointestinal symptoms Symptoms usually develop over two to four weeks The liver is usually enlarged and tender Leukocytosis [pathologyoutlines.com]

  Results of diagnostic tests reveal leukocytosis, elevated serum alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels, and frequently also elevated serum C-reactive protein (CRP) levels. [empendium.com]

The current drug of choice for amebiasis is metronidazole or tinidazole [14], which kills the trophozoites in the intestine and other organs. Metronidazole is taken daily for several days, whereas tinidazole is given as a single large dose, with fewer side effects. Dehydrated patients are given fluids. Alcoholic drink is contraindicated since it may cause nausea, vomiting, flushing and headaches. These drugs are not to be taken by pregnant women.

Metronidazole and tinidazole do not kill ameba cysts that are in the large intestine. A second drug (such as diloxanide, paromomycin, or iodoquinol) is prescribed to eliminate the cysts, thus prevent a relapse. These drugs may be taken by asymptomatic individuals who are positive for cysts both for prophylaxis and for eliminating the source of contamination of the environment with the infective stage of the parasite.

Amebiasis is among the leading causes of morbidity in developing countries. Susceptibility to infection and fatality rates vary with age, nutritional status, immune status , and involvement of extraintestinal foci. Severity of amebiasis is more pronounced in young children, especially neonates; malnourished individuals; pregnant and postpartum women; those on corticosteroids and those with immune deficiencies and/or malignancies.

Treatment of intestinal amebiasis with appropriate drugs is straightforward but there is no immunity following previous infections nor guarantee against reinfections. Complete elimination of the intestinal forms can prevent the occurrence of extraintestinal amebiasis. Ninety percent (90%) of persons with intestinal amebiasis are asymptomatic and only 4-10% of them developed colitis or extraintestinal amebiasis after a one year follow-up period. 

Effective treatment with amebicidal drugs has kept mortality rates below 1% for patients with uncomplicated liver abscess. On the other hand, hepatic amebiasis can be complicated by intraperitoneal rupture in 2-7% of patients and higher mortality rates can result from this [2].

Amebiasis is infection with the protozoan parasite, Entamoeba histolytica, which has two clinical manifestations i.e., intestinal amebiasis  (colitis. diarrhea, dysentery) and extraintestinal amebiasis (liver abscess, pleuropulmonary, cardiac, and cerebral involvement).

Other species of Entamoeba are: E coli, E dispar, E moshkovskii, E polecki, E coli, and E hartmanni. These too reside in the human intestinal lumen as commensals (non-pathogenic) and should be differentiated from E histolytica as the only potentially pathogenic species. E dispar and E moshkovskii have been recovered from patients with gastrointestinal (GI) symptoms; however, their role in the pathogenesis of amebiasis remains to be verified.

E dispar and E histolytica are indistinguishable from each other by light microscopy. Molecular techniques have shown them as two different species, with E dispar being the commensal (as in patients with HIV infection) and E histolytica, the pathogenic species.

Co-infections with E histolytica and E dispar have been reported in many individuals, with E dispar being 10 times more common than E histolytica. In Brazil and Egypt, E dispar and E histolytica infections are equally prevalent [2]. In Western countries, E dispar has been isolated from 20%-30% of MSM (men having sex with other men).

Transmission of E histolytica is primarily through the ingestion of fecally contaminated food and water containing cysts, or through the hands of food handlers. Sexual transmission occurs via oral-anal practices (anilingus). Malnutrition, resulting in immune deficiency , is a risk factor in amebiasis [3].

Amebiasis in the United States is approximately 4% of the total population. Of these, only 10% of E histolytica infections are invasive, and only 1% of those positive for E histolytica by stool examination actually develop symptomatic amebiasis. Asymptomatic E dispar infection is 10 times more prevalent than E histolytica.

About 50 million cases of amebiasis due to E histolytica are reported each year, with 100,000 deaths worldwide. This is presumed to be an underestimation, representing as it is, the so-called tip of the iceberg, since only 10%-20% of infected individuals become symptomatic [4] [5]. Amebiasis is among the leading causes of morbidity in developing countries [6].

Infection with the protozoan parasite E histolytica is associated with  proteolysis, tissue damage and host-cell apoptosis in humans and presumably nonhuman primates. Ingested E histolytica cysts from contaminated food and water or oral-anal sex undergo excystation in the terminal ileum or colon. Each mature cyst can give rise to four highly motile trophozoites which will colonize the intestinal mucosa, causing tissue lysis and ulcerations. Meanwhile,  trophozoites may find their way in the bloodstream and migrate to the liver, lung, and other sites, causing further damage thereat. With physiological changes in conditions in the intestinal lumen, the amebas may transform into cysts that are excreted in the feces. Excreted cysts when ingested by the next susceptible host will initiate a new infectious cycle.

The trophozoite's ability to invade the colonic epithelium is facilitated by a 260-kd surface protein, galactose/N -acetylgalactosamine (GAL/GalNAc)–specific lectin, containing a 170-kd subunit and a 35-kd subunit [7] [8]. IgA antibody binds to this lectin receptor, killing the ameba thus, preventing reinfection [9].

Amebapores, which are peptides capable of forming pores in bimolecular lipid layers of cell membranes are responsible for cytolysis and apoptosis of the parasite. Trophozoite-induced apoptosis in liver abscess was observed with a non-Fas and non–tumor necrosis factor (TNF)-α1 receptor pathway in experimental animal models [10]. Amebapores can also induce apoptosis at sublytic concentrations.

Cysteine proteinases are involved in colonization of the gut and may amplify interleukin (IL)-1–mediated inflammation just as human IL-1–converting enzyme would cleave IL-1 precursor to its active form [11]. The anaphylatoxins C3a and C5a and immunoglobulins, IgA and IgG are likewise cleaved and inactivated by cysteine proteinases [12].

E histolytica is equipped with 100 putative transmembrane kinases (TMKs), of which there are 9 subgroups. EhTMKB1-9 is found in proliferating trophozoites and is induced by serum. This was shown to be involved in phagocytosis and virulence of E histolytica in amebic colitis. Thus, TMKs such as EhTMKB1-9 may serve as potential targets for future drug development.

• The only lasting control of amebiasis is in breaking the cycle of transmission through sanitary human waste disposal, keeping food and water free from contamination with infective cysts, and good personal hygiene practices especially among food handlers. Treat all infected persons with amebicidal drugs for both trophozoite and cystic forms of the parasite.
• Amebiasis vaccine is in the developmental stage, with prospective candidates in the pipeline, expected to be available soon.
• The choice of vaccine material and its efficacy in ensuring long-term protective immunity are important considerations both for clinical and public health applications [15].

Amebiasis is an infectious disease of the large intestine, liver and other organs that is caused by the protozoan parasite, Entamoeba histolytica [1]. The parasite undergoes two developmental stages, namely:

1. A motile, vegetative, and tissue-invasive form, trophozoite and
2. A dormant, infective form, cyst.

The infective stage or cyst is transmitted directly from one person to another, or through food and water. The trophozoite or vegetative stage invades the intestinal mucosa, causing diarrhea or fulminant dysentery in intestinal amebiasis. Involvement of the liver and other organs such as the skin or brain is called extra-intestinal amebiasis.

Affected persons may be asymptomatic or may experience a variety of clinical manifestations such as alternate diarrhea and constipation, abdominal tenderness, cramps, malaise, and fever. Asymptomatic persons may be cyst-passers that is, cysts are found in their stools. Cyst is the infective stage to man. Trophozoites are found in the stools of patients with diarrhea or dysentery. These are motile amebas, usually seen with ingested red blood cells under the microscope.

Diagnosis is by routine microscopic examination of fecal smears or liver aspirate, and if needed, colonoscopy or ultrasonography, and blood tests. Oral anti-trophozoite drugs are taken by patients with diarrhea or dysentery, with another amebicide to eliminate the cysts.

Amebiasis is common in areas where fecal contamination of food and water is rampant due to poor sanitation. These are in Africa, the Indian subcontinent, parts of Central and South America, and Asia. In the United States, there are cases among immigrants and sometimes in travelers who might have acquired the infection from developing countries.

Amebiasis is an infectious disease primarily of the intestines caused by the protozoan parasite, Entamoeba histolytica. The ameba can reside in the large intestine (colon) with other species of amebas as commensals without causing disease. When conditions permit as when the innate immunity of the human host is impaired, the parasite may invade the intestinal wall, cause ulcers or perforations, and manifest clinically as colitis, chronic diarrhea, or at its worst, acute dysentery.  

From the intestines the amebas can migrate via the blood route to the liver, causing liver abscess. In severe cases the lungs, brain, skin and other organs may become involved.

Infection with Entamoeba histolytica cysts is acquired from ingestion of ameba cysts from contaminated food or water, through the unwashed hands of food handlers, through oral-anal sex, or in some places, when human waste is used as fertilizer.  

Symptoms

The symptoms of amebiasis range from mild to severe. Mild symptoms are:

• Diarrhea: Passage of 3 to 8 semiformed stools per day, or passage of soft stools with mucus and occasional blood
• Abdominal cramps
• Fatigue
• Flatulence
• Painful and unproductive bowel movement (tenesmus)
• Weight loss

Severe symptoms include:

• Dysentery: Passage of bloody, mucoid stools more than 10 times a day
• Abdominal tenderness
• Vomiting
• Fever
• Emaciation
• Dehydration

Diagnosis

• Microscopic examination of Direct Fecal Smears for trophozoites and/or cysts, repeated over several days
• Serological examinations for ameba antigens using specific antibody especially for extraintestinal amebiasis
• Colonoscopy or sigmoidoscopy (internal examination of the lower large intestine) 
• Microscopic examinatiion of tissues from infected organs such as liver aspirate

Treatment

• Amebicidal drug, metronidazole (kills the trophozoites) for symptomatic case; other amebicide such as diloxanide, for asymptomatic case or cyst-passer 
• Supportive treatment and drugs to control  vomiting
• Drink plenty of fluids, water for dehydrated patients
• Antibiotics (if co-existing bacterial infection is suspected)

1. Pritt BS, Clark CG. Amebiasis. Mayo Clin Proc. 2008 Oct; 83(10):1154-9; quiz 1159-60.
2. Stanley SL Jr. Amoebiasis. Lancet. 2003 Mar 22; 361(9362):1025-34.
3. Verkerke HP, Petri WA Jr, Marie CS. The dynamic interdependence of amebiasis, innate immunity, and undernutrition. Semin Immunopathol. 2012 Nov; 34(6):771-85.

4. Valenzuela O, Morán P, Gómez A, et al. Epidemiology of amoebic liver abscess in Mexico: the case of Sonora. Ann Trop Med Parasitol. 2007 Sep; 101(6):533-8.

5. Van Hal SJ, Stark DJ, Fotedar R, et al. Amoebiasis: current status in Australia. Med J Aust. 2007 Apr 16; 186(8):412-6.

6. Stauffer W, Abd-Alla M, Ravdin JI. Prevalence and incidence of Entamoeba histolytica infection in South Africa and Egypt. Arch Med Res. 2006 Feb; 37(2):266-9.

7. Ravdin JI, Stanley P, Murphy CF, et al. Characterization of cell surface carbohydrate receptors for Entamoeba histolytica adherence lectin. Infect Immun. 1989 Jul; 57(7):2179-86.

8. Ximénez C, Cerritos R, Rojas L, et al. Human amebiasis: breaking the paradigm?. Int J Environ Res Public Health. 2010 Mar; 7(3):1105-20.

9. Haque R, Mondal D, Duggal P, et al. Entamoeba histolytica infection in children and protection from subsequent amebiasis. Infect Immun. 2006 Feb; 74(2):904-9.

10. Seydel KB, Stanley SL Jr. Entamoeba histolytica induces host cell death in amebic liver abscess by a non-Fas-dependent, non-tumor necrosis factor alpha-dependent pathway of apoptosis. Infect Immun. 1998 Jun; 66(6):2980-3.

11. Rao S, Solaymani-Mohammadi S, Petri WA Jr, et al. Hepatic amebiasis: a reminder of the complications. Curr Opin Pediatr. 2009 Feb; 21(1):145-9.

12. Sodhi KS, Ojili V, Sakhuja V, et al. Hepatic and inferior vena caval thrombosis: vascular complication of amebic liver abscess. J Emerg Med. 2008 Feb; 34(2):155-7.
13. Abd-Alla MD, Jackson TF, Gathiram V, et al. Differentiation of pathogenic Entamoeba histolytica infections from nonpathogenic infections by detection of galactose-inhibitable adherence protein antigen in sera and feces. J Clin Microbiol. 1993 Nov; 31(11):2845-50.
14. Kimura M, Nakamura T, Nawa Y. Experience with intravenous metronidazole to treat moderate-to-severe amebiasis in Japan. Am J Trop Med Hyg. 2007 Aug; 77(2):381-5.
15. Parija SC. Progress in the research on diagnosis and vaccines in amebiasis. Trop Parasitol. 2011 Jan; 1(1):4-8.