Current Diagnosis and Treatment of Amebiasis
Treatment of Amebiasis
Drug therapy of invasive amebiasis is different from that of non-invasive infection, and is summarized in Table 1. Asymptomatic infection should be treated because of its potential to progress to invasive disease. Luminal agents—such as paromomycin, iodoquinol, or diloxanide furoate—that are not absorbed are best suited for such a therapy.
Metronidazole, a nitroimidazole, is the mainstay of therapy for invasive amebiasis.34 Tinidazole has also recently been approved by the US Food and Drug Administration (FDA) for intestinal or extraintestinal amebiasis. Other nitroimidazoles with longer half-lives—i.e. secnidazole and ornidazole— are currently unavailable in the US. Nitroimidazole therapy leads to clinical response in ~90% of patients with mild to moderate amebic colitis. Nitroimidazole therapy does not eradicate the intraluminal parasites, and should be followed by treatment with a luminal agent such as paromomycin or diloxanide furoate to prevent a relapse. Dehydroemetine has been used successfully, but is not preferred due to its potential myocardial toxicity.
Broad-spectrum antibiotics may be added to treat bacterial superinfection in cases of fulminant amebic colitis and suspected perforation. Bacterial co-infection of amebic liver abscess has occasionally been observed (both before and as a complication of drainage), and it is reasonable to add antibiotics to the treatment regimen in the absence of a prompt response to nitroimidazole therapy.
Surgical intervention is required for acute abdominal pain due to perforated amebic colitis, massive gastrointestinal bleeding, or toxic megacolon. Toxic megacolon is rare, and is typically associated with the use of corticosteroids. Surgical attempts to correct amebic bowel perforation or peritonitis should be avoided, although some patients may benefit from peritoneal lavage.35 Unlike pyogenic liver abscess, amebic liver abscess generally responds to medical therapy alone, and drainage is seldom necessary. The indications for drainage of amebic liver abscess include presence of left-lobe abscess, size >10cm in diameter, impending rupture, and abscess that does not respond to medical therapy within three to five days. Imaging-guided percutaneous treatment (needle aspiration or catheter drainage) has replaced surgical intervention as the procedure of choice for reducing the size of an abscess.36
Preventive Strategies in Amebiasis
Improved sanitation is critical to preventing fecal–oral transmission of organisms such as E. histolytica. Travelers to developing countries should be advised to avoid consumption of unsafe food and water and sexual practices that may lead to fecal–oral transmission.
Development of a vaccine for invasive amebiasis is still in its infancy. Many components of the ameba are immunogenic and may serve as targets for a future vaccine, including the (Gal/GalNAc) lectin, the serinerich E. histolytica protein, cysteine proteinases, lipophosphoglycans, amebapores, and the 29kDa protein.37 Progress in vaccine development has been facilitated by new animal models that allow better testing of potential vaccine candidates and by the application of recombinant technology to vaccine design. Oral vaccines utilizing amebic antigens— either co-administered with some form of cholera toxin or expressed in attenuated strains of Salmonella or Vibrio cholera—have been developed and tested in animals for mucosal immunogenicity.38 ■
- Petri WJ, Singh U, Enteric Amoebiasis. In: Guerrant RL,Walker DH, Weller PF, (eds), Tropical Infectious Diseases: Principles, Pathogens & Practice, 2nd edn, Elsevier Churchill Livingstone, 2006;967–83.
- Diamond LS, Clark CG, A redescription of Entamoeba histolytica Schaudinn, 1903 (amended Walker, 1911) separating it from Entamoeba dispar Brumpt, 1925, J Eukaryot Microbiol, 1993;40: 340–44.
- Haque R, Huston CD, Hughes M, et al., Amebiasis, N Engl J Med, 2003;348:1565–73.
- Fotedar R, Stark D, Beebe N, et al., PCR detection of Entamoeba histolytica, Entamoeba dispar, and Entamoeba moshkovskii in stool samples from Sydney, Australia, J Clin Microbiol, 2007;45:1035–7.
- Haque R, Mollah NU, Ali IK, et al., Diagnosis of amebic liver abscess and intestinal infection with the TechLab Entamoeba histolytica II antigen detection and antibody tests, J Clin Microbiol, 2000;38:3235–9.
- Helmy MM, Rashed LA, Abdel-Fattah HS, Detection and differentiation of Entamoeba histolytica and Entamoeba dispar isolates in clinical samples by PCR, J Egypt Soc Parasitol, 2007;37:257–74.
- Khairnar K, Parija SC, A novel nested multiplex polymerase chain reaction (PCR) assay for differential detection of Entamoeba histolytica, E. moshkovskii and E. dispar DNA in stool samples, BMC Microbiol, 2007;7:47.
- Stanley SL, Amoebiasis, Lancet, 2003;361:1025–34.
- Haque R, Mondal D, Duggal P, et al., Entamoeba histolytica infection in children and protection from subsequent amebiasis, Infect Immun, 2006;74:904–9.
- Blessmann J, Van Linh P, Nu PA, et al., Epidemiology of amebiasis in a region of high incidence of amebic liver abscess in central Vietnam, Am J Trop Med Hyg, 2002;66:578–83.
- World Health Organization, Amoebiasis: Weekly Epidemiologic Record, 1997;72:97–100.
- Ravdin JI, Stauffer WM, Entamoeba histolytica (amoebiasis). In: Mandell GL, Bennett JE, Dolin R (eds), Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, 6th edn, Churchill Livingstone, 2005;3097–3111.
- Freedman DO,Weld LH, Kozarsky PE, et al., Spectrum of disease and relation to place of exposure among ill returned travelers, N Engl J Med, 2006;354:119–30.
- Jessurun J, Barron-Rodriguez LP, Fernandez-Tinoco G, et al., The prevalence of invasive amebiasis is not increased in patients with AIDS, AIDS, 1992;6:307–9.
- Hung CC, Chen PJ, Hsieh SM, et al., Invasive amoebiasis: an emerging parasitic disease in patients infected with HIV in an area endemic for amoebic infection, AIDS, 1999;13:2421–8.
- Park WB, Choe PG, Jo JH, et al., Amebic liver abscess in HIVinfected patients, Republic of Korea, Emerg Infect Dis, 2007;13: 516–17.
- Carrero JC, Cervantes-Rebolledo C, Aguilar-Diaz H, et al., The role of the secretory immune response in the infection by Entamoeba histolytica, Parasite Immunol, 2007;29:331–8.
- Heymann DL, Amoebiasis: Control of communicable diseases, America Public Health Association, 2004:11–15.
- Stauffer W, Abd-Alla M, Ravdin JI, Prevalence and incidence of Entamoeba histolytica infection in South Africa and Egypt, Arch Med Res, 2006;37:266–9.
- Monga NK, Sood S, Kaushik SP, et al., Amebic peritonitis, Am J Gastroenterol, 1976;66:366–73.
- Adams EB, MacLeod IN, Invasive amebiasis. II. Amebic liver abscess and its complications, Medicine (Baltimore), 1977;56:325–34.
- Haque R, Ali IK, Akther S, et al., Comparison of PCR, isoenzyme analysis, and antigen detection for diagnosis of Entamoeba histolytica infection, J Clin Microbiol, 1998;36:449–52.
- Katzenstein D, Rickerson V, Braude A, New concepts of amebic liver abscess derived from hepatic imaging, serodiagnosis, and hepatic enzymes in 67 consecutive cases in San Diego, Medicine (Baltimore), 1982;61:237–46.
- Sharma MP, Dasarathy S, Sushma S, et al., Variants of amebic liver abscess, Arch Med Res, 1997;28 Spec No:272–3.
- Wells CD, Arguedas M, Amebic liver abscess, South Med J, 2004; 97:673–82.
- Dhawan VK, Malik SK, Acute pneumonia in the right lower lobe, Chest, 1975;67:346–7.
- Adams EB, MacLeod IN, Invasive amebiasis. I. Amebic dysentery and its complications, Medicine (Baltimore), 1977;56:315–23.
- Tanyuksel M, Petri WA, Laboratory diagnosis of amebiasis, Clin Microbiol Rev, 2003;16:713–29.
- Evangelopoulos A, Legakis N, Vakalis N, Microscopy, PCR and ELISA applied to the epidemiology of amoebiasis in Greece, Parasitol Int, 2001;50:185–9.
- McCarthy JS, Peacock D, Trown KP, et al., Endemic invasive amoebiasis in northern Australia, Med J Aust, 2002;177:570.
- Conter RL, Pitt HA, Tompkins RK, et al., Differentiation of pyogenic from amebic hepatic abscesses, Surg Gynecol Obstet, 1986;162: 114–20.
- 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;31:2845–50.
- Jelinek T, Peyerl G, Loscher T, et al., Evaluation of an antigencapture enzyme immunoassay for detection of Entamoeba histolytica in stool samples, Eur J Clin Microbiol Infect Dis, 1996;15:752–5.
- Powell SJ, MacLeod I, Wilmot AJ, et al., Metronidazole in amoebic dysentery and amoebic liver abscess, Lancet, 1966;2:1329–31.
- Kapoor OP, Joshi VR, Multiple amoebic liver abscesses, A study of 56 cases, J Trop Med Hyg, 1972;75:4–6.
- van Sonnenberg E, Mueller PR, Schiffman HR, et al., Intrahepatic amebic abscesses: indications for and results of percutaneous catheter drainage, Radiology, 1985;156:631–5.
- Chaudhry OA, Petri WA, Vaccine prospects for amebiasis, Expert Rev Vaccines, 2005;4:657–68.
- Snow MJ, Stanley SL, Recent progress in vaccines for amebiasis, Arch Med Res, 2006;37:280–87.