Amoebiasis is a parasitic infection caused by Entamoeba histolytica. It is usually contracted by ingesting water or food contaminated with amoebic cysts. Amoebiasis is an intestinal infection that may or may not be symptomatic. When symptoms are present it is generally known as invasive amoebiasis.
Transmission:
Amoebiasis is usually transmitted by contamination of drinking water and foods with feces, but it can also be transmitted indirectly through contact with dirty hands or objects as well as by anal-oral contact.
Symptoms:
Infections can sometimes last for years. Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks. Symptoms can range from mild diarrhea to dysentery with blood and mucus. The blood comes from amoebae invading the lining of the intestine. In about 10% of invasive cases the amoebae enter the bloodstream and may travel to other organs in the body. Most commonly this means the liver, as this is where blood from the intestine reaches first, but they can end up almost anywhere.
Diagnosis:
Asymptomatic human infections are usually diagnosed by finding cysts shed in the stool. Various flotation or sedimentation procedures have been developed to recover the cysts from fecal matter and stains help to visualize the isolated cysts for microscopic examination. Since cysts are not shed constantly, a minimum of three stools should be examined. In symptomatic infections, the motile form (the trophozoite) can often be seen in fresh feces. Serological tests exist and most individuals (whether with symptoms or not) will test positive for the presence of antibodies. The levels of antibody are much higher in individuals with liver abscesses. Serology only becomes positive about two weeks after infection. More recent developments include a kit that detects the presence of ameba proteins in the feces and another that detects ameba DNA in feces. These tests are not in widespread use due to their expense.
Treatment:
For amebic dysentery a multi-prong approach must be used, starting with one of:
* Metronidazole 500-750mg three times a day for 5-10 days
* Tinidazole 2g once a day for 3 days is an alternative to metronidazole
In addition to the above, one of the following luminal amebicides should be prescribed as an adjunctive treatment, either concurrently or sequentially, to destroy E. histolytica in the colon:
* Paromomycin 500mg three times a day for 10 days
* Diloxanide Furoate 500mg three times a day for 10 days
* Iodoquinol 650mg three times a day for 20 days
For amebic liver abscess:
* Metronidazole 400mg three times a day for 10 days
* Tinidazole 2g once a day for 6 days is an alternative to metronidazole
* Diloxanide furoate 500mg three times a day for 10 days (or one of the other lumenal amebicides above) must always be given afterwards
Doses for children are calculated by body weight and a pharmacist should be consulted for help.
Transmission:
Amoebiasis is usually transmitted by contamination of drinking water and foods with feces, but it can also be transmitted indirectly through contact with dirty hands or objects as well as by anal-oral contact.
Symptoms:
Infections can sometimes last for years. Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks. Symptoms can range from mild diarrhea to dysentery with blood and mucus. The blood comes from amoebae invading the lining of the intestine. In about 10% of invasive cases the amoebae enter the bloodstream and may travel to other organs in the body. Most commonly this means the liver, as this is where blood from the intestine reaches first, but they can end up almost anywhere.
Diagnosis:
Asymptomatic human infections are usually diagnosed by finding cysts shed in the stool. Various flotation or sedimentation procedures have been developed to recover the cysts from fecal matter and stains help to visualize the isolated cysts for microscopic examination. Since cysts are not shed constantly, a minimum of three stools should be examined. In symptomatic infections, the motile form (the trophozoite) can often be seen in fresh feces. Serological tests exist and most individuals (whether with symptoms or not) will test positive for the presence of antibodies. The levels of antibody are much higher in individuals with liver abscesses. Serology only becomes positive about two weeks after infection. More recent developments include a kit that detects the presence of ameba proteins in the feces and another that detects ameba DNA in feces. These tests are not in widespread use due to their expense.
Treatment:
For amebic dysentery a multi-prong approach must be used, starting with one of:
* Metronidazole 500-750mg three times a day for 5-10 days
* Tinidazole 2g once a day for 3 days is an alternative to metronidazole
In addition to the above, one of the following luminal amebicides should be prescribed as an adjunctive treatment, either concurrently or sequentially, to destroy E. histolytica in the colon:
* Paromomycin 500mg three times a day for 10 days
* Diloxanide Furoate 500mg three times a day for 10 days
* Iodoquinol 650mg three times a day for 20 days
For amebic liver abscess:
* Metronidazole 400mg three times a day for 10 days
* Tinidazole 2g once a day for 6 days is an alternative to metronidazole
* Diloxanide furoate 500mg three times a day for 10 days (or one of the other lumenal amebicides above) must always be given afterwards
Doses for children are calculated by body weight and a pharmacist should be consulted for help.
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