Amebiasis. Entamoeba Histolytica

Amebiasis ✓ Entamoeba histolytica - Morphology - Life Cycle - Epidemiology - Clinical manifestations & pathogenesis - Diagnosis - Treatment - Prevention & control Pathogenic Free-living Amebae ✓Naegleria ✓Acanthamoeba ✓Balamuthia Amebiasis Entamoeba histolytica Genus: Entamoeba Species: E. histolytica E. dispar E. hartmanni E. polecki E. coli E. gingivalis E. moshkovskii Amebiasis (Amebic dysentery) Epidemiology of Entamoeba histolytica Host: Human Habitat: caecum & sigmoido-rectal region of human. Prevalence The prevalence of E. histolytica is close to 1% worldwide. Mortality Amebiasis is the cause of an estimated 50,000- 100,000 deaths each year. Entamoeba histolytica is the third leading cause of mortality due to parasitic disease in humans after malaria and schistosomiasis. Geographic Distribution Worldwide, with higher incidence of amebiasis in developing countries. Prevalence of amebic infection varies with the level of sanitation (highest prevalence in areas with poor sanitation). In industrialized countries, risk groups include male homosexuals, travelers and recent immigrants, and institutionalized populations. Entamoeba histolytica Trophozoite T: 12-15 µ Minuta Cyst C: 10-15 µ Trophozoites Cysts Hematophage Magnata Life Cycle of Entamoeba histolytica Galactose & N-acetyl-D-galactosamine specific lectin Pathogenesis  Infection with E. histolytica does not necessarily lead to disease. The outcome depends on : ❑ Parasite factors: ▪Adhesion molecules (N- acetyl-D-galactosamine inhibitable lectin Gal/Gal Nac)adhesion to colonic mucins and host cells, to induce contact dependent cytolysis e.g., Cysteine protinase) ▪Strain differences ❑ Host factors’ Contribution: ▪Physico-chemical environment of the gut influenced by bacterial flora, mucus secretion & gut motility ▪Degree of immunological resistance ▪Nutrition status Mode of Transmission The main source of human infection is ingestion of 4-nucleated cysts. ➢ Cyst passers to person (fecal-oral route): ▪Food or drink contaminated with feces containing E. histolytica cysts. ▪Use of human feces (night soil) for soil fertilizer. ▪Contamination of food stuffs by flies, and possibly cockroaches. ➢Fecal-oral self-inoculation ➢Sexual transmission among homosexual males (oral-anal contact). Amebiasis Clinical manifestations vary from no symptoms to severe and fatal symptoms Clinical signs of the disease include: I. Intestinal amebiasis II. Extraintestinal amebiasis 1- Asymptomatic intestinal infection 90% of cases are without clinical symptoms & the infection is cleared without the disease (Self-limiting, asymptomatic infection) parasites in lumen and cysts pass in stool. (healthy cyst passer) 2- Symptomatic intestinal infection 9% of cases: Disease occurs when the amoeba comes in contact with the cells lining the intestine. It then secretes enzymes (e.g., Cysteine proteinases) that destroy cell membranes and proteins. his causes the colitis (is the pain and inflammation of the colon). Clinical manifestations I. Intestinal amebiasis 1- Asymptomatic intestinal infection 2- Symptomatic intestinal infection 9% of cases: After attachment amoebas produce a cytotoxin that kills epithelial cells so they can gain access to deeper tissues. Amebic Colitis (is the pain & inflammation of the colon). This process can lead to penetration and digestion of human tissues, resulting first in flask-shaped ulcers in the intestine. (The lesions are limited to the mucosa & submucosa and tend to spread out laterally, creating the flask-shape amebic ulcer. This Amoebic ulceration initially produce focal and superficial erosions in large intestine with unaffected mucosa in between. Flask-shaped lesion Flask-shaped lesion Amoebic ulceration with unaffected mucosa in between. Honeycomb-shaped lesion 1-2 mm Diffuse ulceration of the mucosa Clinical manifestations I. Intestinal amebiasis 1- Asymptomatic intestinal infection 2- Symptomatic intestinal infection ❑ Amebic Colitis ❑ Dysentery: colitis with diarrhea (sometimes bloody) accompanied by abdominal pain and cramping: numerous bloody stools per day. Clinical manifestations I. Intestinal amebiasis 1- Asymptomatic intestinal infection 2- Symptomatic intestinal infection ❑ Amebic Colitis ❑ Amebic Dysentery ❑ Amoeboma (Amoebic granuloma) An inflammatory thickening of the intestinal wall, due to repeated invasion of colon by E. histolytica. Localized granulomatous mass misdiagnosed with carcinoma. ❑ Amoebic Appendicitis the appendix becomes inflamed and painful. Clinical manifestations I. Intestinal amebiasis 2- Symptomatic intestinal infection ❑ Amebic Colitis ❑ Amebic Dysentery ❑ Amoeboma (Amoebic granuloma) ❑ Amoebic Appendicitis Intestinal amebiasis complications ❑ Amoebic peritonitis Trophozoites penetrate the muscle and serous layers leading to intestinal perforations -rare but fatal, more than 80% of amebiasis death related to it. ❑ Hemorrhage Rarely involvement of blood vessels at the base of the ulcer may produce profuse bleeding. ❑ Stricture of colon (narrowness) secondary to fibrosis and inflammation Amoeboma Stricture of colon (narrowness) Clinical manifestations I. Intestinal amebiasis II. Extra-intestinal amebiasis 1% of cases: If the parasites gain access to damaged blood vessels, they could be carried to various extra-intestinal sites in the body, most frequently, the liver (where the amoeba causes hepatic amoebiasis) 1- Hepatic amoebiasis (amoebic liver abscesses) 1% of cases: The high incidence of extra-intestinal infection occurs in the liver (88%), and of this number, a majority develop in the right lobe (80%). Trophozoites are carried to the liver right lobe through the portal venous circulation. Signs & symptoms: hepatomegaly, liver tenderness, pain in the upper abdomen, high fever and anorexia, weight loss, vomiting, fatigue. The smallest of amoebic liver abscesses may be only a few millimeters in diameters, solid and whitish, but it soon increases in diameters, with yellowish-gelatinous content and later a cavity filled with liver-colored fluid and cellular debris. Two abscesses in the right lobe and one abscess in the left lobe in a patient with amebic liver abscess Abdominal computed tomography in a patient with amebic liver abscess shows one abscess in the right lobe and one abscess in the left lobe The most typical presentation of amebic liver abscess is fever, right upper quadrant pain, and tenderness. Involvement of the diaphragmatic surface of the liver may lead to right-side pleuritic pain or referred shoulder pain. A posteroanterior (left-hand side) and lateral (right-hand side) chest radiograph in a patient with amebic liver abscess Liver aspiration is indicated only if abscesses are large (> 12 cm), abscess rupture is imminent, medical therapy has failed, or abscesses are present in the left lobe. Typical aspirate: ✓ chocolate syrup ✓ Trophozoites are attached to the margin of the abscess wall ✓ Trophozoites may be found in the last portions of aspirated material Entamoeba histolytica in liver aspirate, trichrome stain. Clinical manifestations II. Extra-intestinal amebiasis 1- Hepatic amebiasis (amoebic liver abscess) 2- Pleuropulmonary amebiasis (amebic lung abscess) Amebic lung abscess is most commonly the result of contiguous spread from a liver abscess rupturing through the right hemidiaphragm. However, amebic lung abscess acquired through hematogenous spread has been reported. Signs & symptoms: cough, pleuritic pain, and dyspnea. The trophozoites of E. histolytica may be found in the sputum sample. Clinical manifestations II. Extra-intestinal amebiasis 1- Hepatic amebiasis (amoebic liver abscess) 2- Pleuropulmonary amebiasis (amebic lung abscess) 3- Cerebral amebiasis (amebic brain abscess) Amebic brain abscesses resulting from hematogenous spread or amebic liver abscess. Signs & symptoms: the abrupt onsets of nausea, vomiting, headache, and mental status changes. Progression can be very rapid, sometimes leading to death within 12-72 hours. Ameba are shown in a sample of brain tissue Computed tomography (CT) reveals irregular lesions without a surrounding capsule or enhancement. A tissue biopsy sample reveals trophozoites. Clinical manifestations II. Extra-intestinal amebiasis 1- Hepatic amebiasis (amoebic liver abscess) 2- Pleuropulmonary amebiasis (amebic lung abscess) 3- Cerebral amebiasis (amebic brain abscess) 4- Cutaneous amebiasis Cutaneous amebiasis can also occur in skin around sites of colostomy wound, perianal region, region overlying visceral lesion and at the site of drainage of liver abscess. Cutaneous amebiasis at the site of drainage of liver abscess. A patient with amebiasis liver abscess, with perforation of abscess through the abdominal skin. Cutaneous amebiasis occur in skin around sites of colostomy wound. Cutaneous amebiasis occur in skin around sites of colostomy wound. Cutaneous amebiasis occur in perianal region. perianal ulceration: A 15-month-old boy three perianal ulcers ranging from 1 to 3 cm with irregular borders and a necrotic yellowish dirty base with purulent exudates. The ulcer was surrounded by a reddish, wine-like inflammatory halo and was very painful. Cutaneous amebiasis occur in perianal region. Clinical manifestations II. Extra-intestinal amebiasis 1- Hepatic amebiasis (amoebic liver abscess) 2- Pleuropulmonary amebiasis (amebic lung abscess) 3- Cerebral amebiasis (amebic brain abscess) 4- Cutaneous amebiasis 5- Genitourinary amebiasis Genitourinary involvement may cause painful genital ulcers or fallopian tube amebiasis. Genitourinary amebiasis: Penis amebiasis Diagnosis Parasitological diagnosis Cysts and trophozoites are passed in feces. Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool. Microscopy diagnosis E. histolytica is morphologically identical with E. dispar and E. moshkovskii. Immunodiagnosis 1. Antibody Detection ELISA 2. Antigen Detection ELISA Molecular diagnosis PCR Treatment ❑ Asymptomatic intestinal infection ✓ Paromomycin ✓ Diloxanide furoate (Furamide) ✓ Metronidazole (Flagyl) ❑ Symptomatic intestinal infection & Extra-intestinal amebiasis ✓ Metronidazole ✓ Tinidazole Prevention of amoebiasis ❑ Cysts of Entamoeba can survive for up to a month in soil or for up to 45 minutes under fingernails. ❑ Prevention of amoebiasis is by: ▪ separating food and water from feces ▪ proper sanitation measures ▪ Treatment of patients. ▪ Examination and treatment of food handlers. ▪ Environmental sanitation. ▪ Personal prophylaxis. ▪ Human feces should not be used as fertilizers. Pathogenic Free-living Amebae Naegleria Acanthamoeba Balamuthia Naegleria fowleri Primary Amebic Meningoencephalitis (PAM) Acute and usually fatal disease of the central nervous system. In healthy humans primary amebic meingoencephalitis (PAM) a brain infection that leads to the destruction of brain tissue. In its early stages, symptoms of PAM may be similar to symptoms of bacterial meningitis. Initial symptoms of PAM start about 5 days (range 1 to 9 days) after infection. The initial symptoms may include headache, fever, nausea, or vomiting. Later symptoms can include stiff neck, confusion, lack of attention to people and surroundings, loss of balance, seizures, and hallucinations. After the start of symptoms, the disease progresses rapidly and usually causes death within about 5 days (range 1 to 12 days). a brain-eating amoeba Naegleria fowleri trophozoites are found in cerebrospinal fluid (CSF) and tissue. Cysts are not seen in brain tissue. Flagellated forms are occasionally found in CSF. Acanthamoeba spp Acanthamoeba can cause rare, but severe infections of the eye, skin, and central nervous system. The ameba is found worldwide in the environment in water and soil. The ameba can be spread to the eyes through contact lens use, cuts, or skin wounds or by being inhaled into the lungs. Most people will be exposed to Acanthamoeba during their lifetime, but very few will become sick from this exposure. The three diseases caused by Acanthamoeba are: Acanthamoeba keratitis: An infection of the eye that typically occurs in healthy persons and can result in permanent visual impairment or blindness. Granulomatous Amebic Encephalitis (GAE): A serious infection of the brain and spinal cord that typically occurs in persons with a compromised immune system. Disseminated infection A widespread infection that can affect the skin, sinuses, lungs, and other organs. It is also more common in persons with a compromised immune system. Acanthamoeba keratitis Acanthamoeba sp. Keratitis Cyst with a characteristic shape, in corneal scraping. Corneal biopsy showing a trophozoite Balamuthia mandrillaris Encephalitis Balamuthia amebic encephalitis (BAE) =granulomatous amebic encephalitis (GAE) Balamuthia mandrillaris trophozoites in brain tissue Balamuthia mandrillaris skin lesions Balamuthia mandrillaris infection with important skin lesion.