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Infectious Disease - Amebiasis
Protozoan infection induced by Entamoeba histolytica. Infection by these organisms results in diarrhea, colitis, and occasionally, extra-intestinal symptoms such as liver abscesses.
• Symptomatic illness manifests in fewer than 10% of affected persons. A minimal proportion of individuals with intestinal infections will progress to invasive illness.
Epidemiology
Frequency
Approximately ten percent of the global population is thought to be infected with E. histolytica.
• Prevalence varies from less than 5% in developed nations to 20–30% in tropical regions.
The estimated prevalence in the US is approximately 4%.
The disease manifests across all age groups and affects both genders equally.
RISK FACTORS • Risk factors in endemic regions encompass: – Low socioeconomic status – Inadequate sanitation
– Overcrowding • In nations with low prevalence:
- Immigrants or travelers from endemic areas – Institutionalized individuals – Males engaging in sexual relations with other males
• Risk factors linked to serious disease: - Newborns – Gestation
Corticosteroid treatment; malnutrition.
COMPREHENSIVE PREVENTION
• Humans constitute the sole reservoir of the infection.
Contaminated water or vegetables frequently serve as sources of infection in humans.
Cysts are not eliminated by chlorine; boiling water is essential for decontamination.
• Refrain from consuming polluted water and food. • Ensure that vegetables are thoroughly cleansed with potable water or treated with detergent and immersed in acetic acid or vinegar.
PATHOPHYSIOLOGY
• Infection transmits through the fecal–oral pathway • The organism manifests in two forms:
Trophozoite possessing a singular nucleus, with or without swallowed erythrocytes.
Cyst with four nuclei
The ingestion of the cyst leads to excystation in the small intestine. Trophozoites are generated, infecting the colon and causing symptoms.
• Under adverse conditions, the trophozoite encysts, and the cyst form is excreted in feces.
Cysts persist in a damp environment for several months.
• The majority of individuals infected with the bacterium exhibit minimal invasion of the intestinal mucosa and remain asymptomatic (cyst passers).
Patients exhibiting colonic invasion present with flask-shaped colonic ulcers.
ETIOLOGY • E. histolytica is one of the several Entamoeba species that infect people.
Nonpathogenic species encompass Entamoeba dispar, Entamoeba moshkovskii (both morphologically indistinguishable), Entamoeba hartmanni, and Entamoeba coli.
HISTORY OF DIAGNOSIS
• Patients exhibit symptoms of invasive illness within four weeks following the intake of cysts.
Amebic liver abscess typically requires approximately three months for development.
• Certain patients harbor the germs for extended durations prior to exhibiting notable clinical symptoms. • Intestinal disorder – Asymptomatic infection
— Symptomatic non-invasive infection
- Symptoms are minor; diarrhea is the sole manifestation. - Amebic colitis (dysentery) - Crampy abdominal discomfort - Hemorrhagic, mucoid diarrhea - Rectal hemorrhage may accompany diarrhea, particularly in pediatric patients - Fever is present in one-third of affected individuals – Weight reduction – Anorexia nervosa
• Extra-intestinal disease – Extra-intestinal amebiasis can impact the liver (abscess), spleen, lungs, or brain.
Amebic liver abscess manifests with fever and right upper quadrant pain.
ache in the upper quadrant. Fifty percent of patients with amebic liver abscess exhibit no prior history of colitis.
– Occasionally, the rupture of the abscess may result in peritonitis.
– Rupture of the liver abscess into the pleural cavity results in empyema. Patients exhibit fever, dyspnea, and pleuritic thoracic pain.
Cerebral amebiasis: Nausea, vomiting, cephalalgia, alterations in mental condition
PHYSICAL EXAMINATION
• Colitis – Widespread abdominal pain – Distension, rebound tenderness in severe colitis/perforation • Liver abscess – pain upon palpation of the liver Hepatomegaly - Jaundice is infrequent
DIAGNOSTIC TESTS AND INTERPRETATION
Laboratory
• Stool microscopy and O&P examination may reveal the presence of stool leukocytes.
- Intracytoplasmic erythrocytes within trophozoites (observed)
In E. histolytica and E. dispar, a wet mount for motile trophozoites and formal-ether concentration, followed by an iodine-stained deposit, enhances the probability of finding cysts.
– To enhance the efficacy of microscopic diagnosis, many samples must be analyzed. • Antigen detection – Fecal antigen identified with ELISA. More sensitive than O&P, however less effective than PCR. Requires either fresh or frozen specimens.
Applicable in hepatic abscess fluid.
– The TechLab E. histolytica II ELISA differentiates between pathogenic and nonpathogenic amebae• Serology – Beneficial in diagnosing liver abscess and invasive colonic illness – ELISA (most frequently utilized), indirect immunofluorescent assay, indirect hemagglutination assay – False positives in the early stages of the disease – Titers persist at elevated levels for years – In endemic regions, high seropositivity precludes differentiation between active and prior infection.
• Culture is conducted exclusively in research laboratories. • PCR – Real-time PCR is technically intricate yet exhibits more sensitivity than the stool antigen.
- Applicable in hepatic abscess fluid. • Additional laboratory examinations
Leukocytosis absent of eosinophilia is frequently observed in individuals with invasive amebic illness. Elevated alkaline phosphatase levels and moderately increased transaminases are noted in liver abscess cases.
Imaging
Imaging modalities, including ultrasound, CT, and MRI scans, are beneficial in evaluating patients with suspected amebic liver abscess. The amebic abscess is typically situated in the right lobe, specifically in the right upper posterior section of the liver.
Diagnostic Procedures and Additional Methods
• Colonoscopy and biopsy for colonic pathology – Results may appear normal in the first stages of the condition
– Fragile, ulcerated mucosa exhibiting punctate hemorrhages – Lateral infiltration into the submucosal tissues results in the distinctive flask-shaped ulcer associated with amebic colitis – Amebomas manifest as annular lesions
The aspiration of a liver abscess produces dark, odorless, sterile pus, typically referred to as "anchovy paste," which may contain trophozoites. Aspiration of liver abscesses frequently does not yield the organism, as it resides within the abscess walls.
Pathological Observations
Intestinal biopsy specimens obtained from the margins of ulcers must be assessed for motile trophozoites.
• The biopsy reveals mucosal thickening with many distinct ulcers interspersed among areas of normal-appearing mucosa.
DIFFERENTIAL DIAGNOSIS
• Ulcerative colitis • Colorectal carcinoma • Crohn's disease • Diverticulitis • Abdominal abscess • Irritable bowel syndrome • Pyogenic abscess • Hepatoma • Echinococcal liver cyst
MEDICATION FOR TREATMENT
• Asymptomatic disease – Intra-luminal carriage necessitates treatment due to the potential risk of invasive disease.
Paromomycin 500 mg orally three times day for seven days should be used as the first-line treatment.
Diloxanide furoate 500 mg three times daily for 10 days Iodoquinol 650 mg orally three times daily for 20 days
• Colitis – Metronidazole 750 mg orally three times daily for 10 days or tinidazole 1 g orally twice daily for 3 days, followed by one of the subsequent treatments:
Iodoquinol 650 mg orally three times daily for 20 days
Paromomycin 500 mg orally three times daily for seven days • Liver abscess – Administer Metronidazole 750 mg orally or intravenously three times daily for 10 days, followed by Iodoquinol 650 mg orally three times daily for 20 days
CLINICAL INTERVENTIONS/ADDITIONAL PROCEDURES
For a substantial abscess (>3 cm), aspiration and needle intervention
Drainage is warranted. Minor abscesses dissolve with medical intervention.
CONTINUED MANAGEMENT POST-TREATMENT SUGGESTIONS
Patients undergoing treatment for liver abscesses should receive follow-up ultrasounds to confirm cyst clearance, which may require many months.
OUTLOOK
Amebiasis presents significant morbidity and mortality, particularly in underdeveloped nations.
COMPLICATIONS
Fulminant colitis accompanied with toxic megacolon, perforation, and peritonitis is uncommon however thoroughly documented.
Amebomas are mass lesions located in the colon, frequently found in the cecum or ascending colon, resulting from inflammation associated with amebic colitis. Amebomas can lead to blockage and may mimic colon cancer.
• Ruptured liver abscess with diaphragm perforation resulting in pleural or pericardial illness.
Protozoan infection induced by Entamoeba histolytica. Infection by these organisms results in diarrhea, colitis, and occasionally, extra-intestinal symptoms such as liver abscesses.
• Symptomatic illness manifests in fewer than 10% of affected persons. A minimal proportion of individuals with intestinal infections will progress to invasive illness.
Epidemiology
Frequency
Approximately ten percent of the global population is thought to be infected with E. histolytica.
• Prevalence varies from less than 5% in developed nations to 20–30% in tropical regions.
The estimated prevalence in the US is approximately 4%.
The disease manifests across all age groups and affects both genders equally.
RISK FACTORS • Risk factors in endemic regions encompass: – Low socioeconomic status – Inadequate sanitation
– Overcrowding • In nations with low prevalence:
- Immigrants or travelers from endemic areas – Institutionalized individuals – Males engaging in sexual relations with other males
• Risk factors linked to serious disease: - Newborns – Gestation
Corticosteroid treatment; malnutrition.
COMPREHENSIVE PREVENTION
• Humans constitute the sole reservoir of the infection.
Contaminated water or vegetables frequently serve as sources of infection in humans.
Cysts are not eliminated by chlorine; boiling water is essential for decontamination.
• Refrain from consuming polluted water and food. • Ensure that vegetables are thoroughly cleansed with potable water or treated with detergent and immersed in acetic acid or vinegar.
PATHOPHYSIOLOGY
• Infection transmits through the fecal–oral pathway • The organism manifests in two forms:
Trophozoite possessing a singular nucleus, with or without swallowed erythrocytes.
Cyst with four nuclei
The ingestion of the cyst leads to excystation in the small intestine. Trophozoites are generated, infecting the colon and causing symptoms.
• Under adverse conditions, the trophozoite encysts, and the cyst form is excreted in feces.
Cysts persist in a damp environment for several months.
• The majority of individuals infected with the bacterium exhibit minimal invasion of the intestinal mucosa and remain asymptomatic (cyst passers).
Patients exhibiting colonic invasion present with flask-shaped colonic ulcers.
ETIOLOGY • E. histolytica is one of the several Entamoeba species that infect people.
Nonpathogenic species encompass Entamoeba dispar, Entamoeba moshkovskii (both morphologically indistinguishable), Entamoeba hartmanni, and Entamoeba coli.
HISTORY OF DIAGNOSIS
• Patients exhibit symptoms of invasive illness within four weeks following the intake of cysts.
Amebic liver abscess typically requires approximately three months for development.
• Certain patients harbor the germs for extended durations prior to exhibiting notable clinical symptoms. • Intestinal disorder – Asymptomatic infection
— Symptomatic non-invasive infection
- Symptoms are minor; diarrhea is the sole manifestation. - Amebic colitis (dysentery) - Crampy abdominal discomfort - Hemorrhagic, mucoid diarrhea - Rectal hemorrhage may accompany diarrhea, particularly in pediatric patients - Fever is present in one-third of affected individuals – Weight reduction – Anorexia nervosa
• Extra-intestinal disease – Extra-intestinal amebiasis can impact the liver (abscess), spleen, lungs, or brain.
Amebic liver abscess manifests with fever and right upper quadrant pain.
ache in the upper quadrant. Fifty percent of patients with amebic liver abscess exhibit no prior history of colitis.
– Occasionally, the rupture of the abscess may result in peritonitis.
– Rupture of the liver abscess into the pleural cavity results in empyema. Patients exhibit fever, dyspnea, and pleuritic thoracic pain.
Cerebral amebiasis: Nausea, vomiting, cephalalgia, alterations in mental condition
PHYSICAL EXAMINATION
• Colitis – Widespread abdominal pain – Distension, rebound tenderness in severe colitis/perforation • Liver abscess – pain upon palpation of the liver Hepatomegaly - Jaundice is infrequent
DIAGNOSTIC TESTS AND INTERPRETATION
Laboratory
• Stool microscopy and O&P examination may reveal the presence of stool leukocytes.
- Intracytoplasmic erythrocytes within trophozoites (observed)
In E. histolytica and E. dispar, a wet mount for motile trophozoites and formal-ether concentration, followed by an iodine-stained deposit, enhances the probability of finding cysts.
– To enhance the efficacy of microscopic diagnosis, many samples must be analyzed. • Antigen detection – Fecal antigen identified with ELISA. More sensitive than O&P, however less effective than PCR. Requires either fresh or frozen specimens.
Applicable in hepatic abscess fluid.
– The TechLab E. histolytica II ELISA differentiates between pathogenic and nonpathogenic amebae• Serology – Beneficial in diagnosing liver abscess and invasive colonic illness – ELISA (most frequently utilized), indirect immunofluorescent assay, indirect hemagglutination assay – False positives in the early stages of the disease – Titers persist at elevated levels for years – In endemic regions, high seropositivity precludes differentiation between active and prior infection.
• Culture is conducted exclusively in research laboratories. • PCR – Real-time PCR is technically intricate yet exhibits more sensitivity than the stool antigen.
- Applicable in hepatic abscess fluid. • Additional laboratory examinations
Leukocytosis absent of eosinophilia is frequently observed in individuals with invasive amebic illness. Elevated alkaline phosphatase levels and moderately increased transaminases are noted in liver abscess cases.
Imaging
Imaging modalities, including ultrasound, CT, and MRI scans, are beneficial in evaluating patients with suspected amebic liver abscess. The amebic abscess is typically situated in the right lobe, specifically in the right upper posterior section of the liver.
Diagnostic Procedures and Additional Methods
• Colonoscopy and biopsy for colonic pathology – Results may appear normal in the first stages of the condition
– Fragile, ulcerated mucosa exhibiting punctate hemorrhages – Lateral infiltration into the submucosal tissues results in the distinctive flask-shaped ulcer associated with amebic colitis – Amebomas manifest as annular lesions
The aspiration of a liver abscess produces dark, odorless, sterile pus, typically referred to as "anchovy paste," which may contain trophozoites. Aspiration of liver abscesses frequently does not yield the organism, as it resides within the abscess walls.
Pathological Observations
Intestinal biopsy specimens obtained from the margins of ulcers must be assessed for motile trophozoites.
• The biopsy reveals mucosal thickening with many distinct ulcers interspersed among areas of normal-appearing mucosa.
DIFFERENTIAL DIAGNOSIS
• Ulcerative colitis • Colorectal carcinoma • Crohn's disease • Diverticulitis • Abdominal abscess • Irritable bowel syndrome • Pyogenic abscess • Hepatoma • Echinococcal liver cyst
MEDICATION FOR TREATMENT
• Asymptomatic disease – Intra-luminal carriage necessitates treatment due to the potential risk of invasive disease.
Paromomycin 500 mg orally three times day for seven days should be used as the first-line treatment.
Diloxanide furoate 500 mg three times daily for 10 days Iodoquinol 650 mg orally three times daily for 20 days
• Colitis – Metronidazole 750 mg orally three times daily for 10 days or tinidazole 1 g orally twice daily for 3 days, followed by one of the subsequent treatments:
Iodoquinol 650 mg orally three times daily for 20 days
Paromomycin 500 mg orally three times daily for seven days • Liver abscess – Administer Metronidazole 750 mg orally or intravenously three times daily for 10 days, followed by Iodoquinol 650 mg orally three times daily for 20 days
CLINICAL INTERVENTIONS/ADDITIONAL PROCEDURES
For a substantial abscess (>3 cm), aspiration and needle intervention
Drainage is warranted. Minor abscesses dissolve with medical intervention.
CONTINUED MANAGEMENT POST-TREATMENT SUGGESTIONS
Patients undergoing treatment for liver abscesses should receive follow-up ultrasounds to confirm cyst clearance, which may require many months.
OUTLOOK
Amebiasis presents significant morbidity and mortality, particularly in underdeveloped nations.
COMPLICATIONS
Fulminant colitis accompanied with toxic megacolon, perforation, and peritonitis is uncommon however thoroughly documented.
Amebomas are mass lesions located in the colon, frequently found in the cecum or ascending colon, resulting from inflammation associated with amebic colitis. Amebomas can lead to blockage and may mimic colon cancer.
• Ruptured liver abscess with diaphragm perforation resulting in pleural or pericardial illness.
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