Background. Amebiasis is a parasitic infection disease of the human intestines. It is caused by the protozoan Entamoeba histolytica, or E. histolytica. The protozoan is a single-celled that usually enters the human body when a person ingests cysts through food or water.Entamoeba histolytica is well recognized as a pathogenic ameba, associated with intestinal and extraintestinal infections. The other species are important because they may be confused with E. histolytica in diagnostic investigations.
Epidemiology. E. histolytica has a worldwide distribution. This disease is common in tropical countries with underdeveloped sanitation. It’s most common in the Indian subcontinent, parts of Central and South America, and parts of Africa. It’s relatively rare in the United States. Although it is found in cold areas, the incidence is highest in tropical and subtropical regions that have poor sanitation and contaminated water. About 90% of infections are asymptomatic, and the remaining produce a spectrum of clinical syndrome.
Life cycle.Amoebas primitive unicellular microorganisms with a relatively simple life cycle which can be divided into two stages: (1) Trophozoite–actively motile feeding stage; (2) Cyst-quiescent, resistant infective stage. Their reproduction is through binary fission, e.g. splitting of the trophozoite or through the development of numerous trophozoites within the mature multinucleated cyst. Motility is accomplished by extension of pseudopodia (“false foot”).
Pathogenesis. Trophozoites divide and produce extensive local necrosis in the large intestine. Invasion into the deeper mucosa with extension into the peritoneal cavity may occur. This can lead to secondary involvement of other organs, primarily the liver but also the lungs, brain, and heart.
Treatment. Acute, fulminating amebiasis is treated with metronidazole followed by iodoquinol, and asymptomatic carriage can be eradicated with iodoquinol, diloxanide furoate, or paromomycin. Metronidazole, chloroquine, and diloxanide furoate can be used for the treatment of extra-intestinal amoebiasis.
Prevention. Prevention for this disease can be done in two ways: (1) Introduction of adequate sanitation measures and education about the routes of transmission; (2) Avoid eating raw vegetables grown by sewerage irrigation and night soil.
References:
Centers for Disease Control and Prevention. Parasites – Amebiasis – Entamoeba histolytica[Updated: December 16, 2015]Available from: https://www.cdc.gov/parasites/amebiasis/
Dawit A., Ephrem K., S. Nagesh, Solomon G., Fetene D., Jemal A. Medical Parasitology. USAID collaboration with Ethiopia Public Health Training Initiative, The Carter Center, the Ethiopia Ministry of Health, and the Ethiopia Ministry of Education. 2006.
