Amebiasis Treatment & Management

Updated: Jul 31, 2018
  • 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 [61] ; luminal agents that are minimally absorbed by the GI tract (eg, paromomycin, iodoquinol, and diloxanide furoate) are best suited for such therapy. [62, 63] This recommendation is based on 2 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. [61, 64, 65] 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]

Amebic liver abscess of up to 10 cm can be cured with metronidazole without drainage. [66] Clinical defervescence should occur during the first 3-4 days of treatment. Failure of metronidazole therapy may be an indication for surgical intervention. 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.

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Surgical and Percutaneous Intervention

Surgical intervention is required for acute abdomen that is due to any of the following [67] :

  • 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 [68] ) 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.

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]

Vaccinations using native and recombinant forms of Gal-lectin have been successful in protecting animals against intestinal amebiasis and amebic liver abscess. Protection against amebic liver abscesses has also been reported by targeting other E histolytica components, including the serine-rich protein and the 29-kDa-reductase antigen. To date, vaccines against the Gal-lectin hold the most promise, but clinical trials are required to validate its efficacy in humans.

Development of a vaccine for invasive amebiasis is still in its infancy. [69, 70, 71] 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 recently reviewed current strategies involved in the development of a vaccine against E histolytica. [72]

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