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      Drugs & Diseases > Infectious Diseases

      Amebiasis Treatment & Management

      Updated: Apr 08, 2022
      • Author: Vinod K Dhawan, MD, FACP, FRCPC, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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      Treatment

      Approach Considerations

      Treatment of amebiasis includes pharmacologic therapy, surgical intervention, and preventive measures, as appropriate. Most individuals with amebiasis may be treated on an outpatient basis. Several clinical scenarios may favor inpatient care, as follows:

      • Severe colitis and hypovolemia requiring intravenous (IV) volume replacement

      • Liver abscess that is of uncertain etiology or is not responding to empiric therapy

      • Fulminant colitis requiring surgical evaluation

      • Peritonitis and suspected amebic liver abscess rupture

      Intestinal amebiasis may be mistakenly treated as if it were inflammatory bowel disease (IBD). Accordingly, in all patients with suspected IBD, lower gastrointestinal (GI) endoscopy should be performed before treatment with steroids is initiated.

      The following consultations may be helpful:

      • Infectious disease specialist

      • General surgeon

      • GI specialist

      Follow-up stool examination after therapy completion is recommended to ensure intestinal eradication. No special diet is recommended.

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      Pharmacologic Therapy

      In endemic areas, asymptomatic infections are not treated. In nonendemic areas, however, asymptomatic infection should be treated [80] ; luminal agents that are minimally absorbed by the GI tract (eg, paromomycin, iodoquinol, and diloxanide furoate) are best suited for such therapy. [81, 82] This recommendation is based on two arguments: first, that invasive disease may develop, and second, that shedding of E histolytica cysts in the environment is a public health concern. [4]

      Asymptomatic E dispar infections should not be treated, but because this organism is a marker of fecal-oral contamination, educational efforts should be initiated. [4]

      Metronidazole is the mainstay of therapy for invasive amebiasis. [80, 83, 84] Tinidazole has been approved by the US Food and Drug Administration (FDA) for intestinal or extraintestinal amebiasis. Other nitroimidazoles with longer half-lives (ie, secnidazole and ornidazole) are currently unavailable in the United States.

      Nitroimidazole therapy leads to clinical response in approximately 90% of patients with mild-to-moderate amebic colitis. Because intraluminal parasites are not affected by nitroimidazoles, nitroimidazole therapy for amebic colitis should be followed by treatment with a luminal agent (eg, paromomycin or diloxanide furoate) to prevent a relapse. [4] A 2019 Cochrane Database Review reported that tinidazole may be more effective than metronidazole and is associated with fewer adverse events. [85] Combination drug therapy may be more effective for reducing parasitological failure compared with metronidazole alone. [85]

      Amebic liver abscess of up to 10 cm can be cured with metronidazole without drainage. [86] Drainage is reserved for larger abscesses, for patients who do not exhibit a clinical response to medical therapy by about 72 hours, or for left-lobe abscesses, which could rupture into the pericardium. Resolution of the abscess cavity on serial imaging takes months. [87] Treatment with a luminal agent should also follow. [4]

      Chloroquine has also been used for patients with hepatic amebiasis. Dehydroemetine (available from the Centers for Disease Control and Prevention [CDC] Drug Service [404-639-3670]) has been successfully used but, because of its potential myocardial toxicity, is not preferred.

      Broad-spectrum antibiotics may be added to treat bacterial superinfection in cases of fulminant amebic colitis and suspected perforation. Bacterial coinfection of amebic liver abscess has occasionally been observed (both before and as a complication of drainage), and adding antibiotics to the treatment regimen is reasonable in the absence of a prompt response to nitroimidazole therapy.

      A better understanding of the parasite's metabolic and cellular pathways has been useful in identifying promising drug targets and drug molecules for the treatment of amebiasis. [88]

      Loperamide should be avoided in the treatment of amebic colitis. [89]

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      Surgical and Percutaneous Intervention

      Surgical intervention is required for acute abdomen that is due to any of the following [90] :

      • Perforated amebic colitis

      • Massive GI bleeding

      • Toxic megacolon (rare and typically associated with the use of corticosteroids)

      Surgical intervention is usually indicated in the following clinical scenarios [4] :

      • Uncertain diagnosis (possibility of pyogenic liver abscess)

      • Concern about bacterial suprainfection in amebic liver abscess

      • Failure to respond to metronidazole after 4 days of treatment

      • Empyema after amebic liver abscess rupture

      • Large left-side amebic liver abscess representing risk of rupture in the pericardium

      • Severely ill patient with imminent amebic liver abscess rupture

      Unlike pyogenic liver abscess, uncomplicated amebic liver abscess generally responds to medical therapy alone; drainage is seldom necessary and is usually best avoided. When drainage is necessary, image-guided percutaneous intervention (ie, needle aspiration or catheter drainage [91] ) has replaced surgical intervention as the procedure of choice. The indications for drainage of amebic liver abscess include the following:

      • Presence of a left-lobe abscess more than 10 cm in diameter

      • Impending rupture and abscess that does not respond to medical therapy within 3-5 days

      Percutaneous catheter drainage improves treatment outcomes in amebic empyema and is life-saving in amebic pericarditis. It should be used judiciously in the setting of localized intra-abdominal fluid collections.

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      Prevention

      Amebiasis is prevented by eradicating fecal contamination of food and water through improved sanitation, hygiene, and water treatment. In nonendemic areas, disease transmission can be reduced by early treatment of carriers.

      Amebic cysts are not killed by soap or low concentrations of chlorine or iodine; therefore, water in endemic areas should be boiled for more than 1 minute and vegetables should be washed with a detergent soap and soaked in acetic acid or vinegar for 10-15 minutes before consumption.

      Avoiding sexual practices that involve fecal-oral contact may reduce the risk of sexual transmission of infective cysts. Because reinfection is possible, family members or close contacts of an index case should be screened.

      Household contacts of patients with amebiasis should be screened to prevent spread. [52] Patients with a new diagnosis of inflammatory bowel disease and a history of travel to an endemic area should be screened for amebiasis prior to corticosteroid or other immunosuppressive therapy, as fulminant amebic colitis may result from misdiagnosis. [52]

      In humans, natural E histolytica infection does not seem to result in long-term immunity: individuals with a previous amebic liver abscess are as susceptible to a new infection as other members of the population are. [4]

      Development of a vaccine for invasive amebiasis is still in its infancy. [92, 93, 94] Many components of the ameba are immunogenic and may serve as targets for a future vaccine, including the galactose/N -acetylgalactosamine lectin, the serine-rich E histolytica protein, cysteine proteinases, lipophosphoglycans, amebapores, and the 29-kd protein. Quach et al reviewed current strategies involved in the development of a vaccine against E histolytica. [95]

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