Amoebic dysentery is caused by the protozoan parasite Entamoeba histolytica
. Invasive intestinal parasitic infection can result in symptoms of fulminant dysentery, such as fever, chills, bloody or mucous diarrhoea, and abdominal discomfort. The dysentery can alternate with periods of constipation or remission. This review focuses on amoebic dysentery only, and includes populations with both suspected and documented disease in endemic areas where levels of infection do not exhibit wide fluctuations through time.
The term "amoebic dysentery" encompasses people described as having symptomatic intestinal amoebiasis, amoebic colitis, amoebic diarrhoea, or invasive intestinal amoebiasis. Extraintestinal amoebiasis (e.g., amoebic liver abscess) and asymptomatic amoebiasis are not covered.
We found no accurate global prevalence data for E histolytica
infection and amoebic dysentery. Estimates on the prevalence of Entamoeba
infection range from 1% to 40% of the population in Central and South America, Africa, and Asia, and from 0.2% to 10.8% in endemic areas of developed countries such as the USA.
However, these estimates are difficult to interpret, mainly because infection can remain asymptomatic or go unreported,
and because many older reports do not distinguish E histolytica
from the non-pathogenic, morphologically identical species Entamoeba dispar
. Development and availability of more sophisticated methods (such as the enzyme-linked immunosorbent assay [ELISA]
-based test) to differentiate the two species might give a more accurate estimate of its global prevalence.
Infection with E histolytica
is a common cause of acute diarrhoea in developing countries. One survey conducted in Egypt found that 38% of people with acute diarrhoea in an outpatient clinic had amoebic dysentery.
Ingestion of cysts from food or water contaminated with faeces is the main route of E histolytica
transmission. Low standards of hygiene and sanitation, particularly those related to crowding, tropical climate, contamination of food and water with faeces, and inadequate disposal of faeces, all account for the high rates of infection seen in developing countries.
In developed countries, risk factors include communal living, oral and anal sex, compromised immune system, and migration or travel from endemic areas.
Amoebic dysentery may progress to amoeboma
, fulminant colitis, toxic megacolon, and colonic ulcers, and may lead to perforation.
Amoeboma may be mistaken for colonic carcinoma or pyogenic abscess. Amoebic dysentery may also result in chronic carriage and the chronic passing of amoebic cysts. Fulminant amoebic dysentery is reported to have 55% to 88% mortality.
It is estimated that more than 500 million people are infected with E histolytica
Between 40,000 and 100,000 will die each year, placing this infection second to malaria in mortality caused by protozoan parasites.
To reduce the infectious period, length of illness, risks of dehydration, risks of transmission to others, and rates of severe illness; to prevent complications and death, with minimal adverse effects.
Mortality; quality of life; hospitalisation: length of hospital stay, rate of hospital admission; complications (i.e., amoeboma, extension to pleural cavity, chronic cyst carriage); treatment effectiveness: therapeutic cure (defined as absence of parasites in stools, disappearance of symptoms, and healing of ulcers); clinical failure (defined as persistence of symptoms), and parasitological failure (defined as persistence of parasites in stools or in other diagnostic tests); and adverse effects of treatment.
Clinical Evidence search and appraisal April 2010. The following databases were used to identify studies for this systematic review: Medline 1966 to April 2010, Embase 1980 to April 2010, and The Cochrane Database of Systematic Reviews 2010, Issue 3 (1966 to date of issue). An additional search within The Cochrane Library was carried out for the Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment (HTA). We also searched for retractions of studies included in the review. Abstracts of the studies retrieved from the initial search were assessed by an information specialist. Selected studies were then sent to the contributor for additional assessment, using pre-determined criteria to identify relevant studies. Study design criteria for inclusion in this review were: published systematic reviews of RCTs and RCTs in any language, including open studies, with no minimum number of participants. There was no minimum length of follow-up required to include studies, and no maximum loss to follow-up. We included systematic reviews of RCTs and RCTs where harms of an included intervention were studied, applying the same study design criteria for inclusion as we did for benefits. In addition we use a regular surveillance protocol to capture harms alerts from organisations such as the FDA and the MHRA, which are added to the reviews as required. To aid readability of the numerical data in our reviews, we round many percentages to the nearest whole number. Readers should be aware of this when relating percentages to summary statistics such as relative risks (RRs) and odds ratios (ORs). We have performed a GRADE evaluation of the quality of evidence for interventions included in this review (). The categorisation of the quality of the evidence (high, moderate, low, or very low) reflects the quality of evidence available for our chosen outcomes in our defined populations of interest. These categorisations are not necessarily a reflection of the overall methodological quality of any individual study, because the Clinical Evidence population and outcome of choice may represent only a small subset of the total outcomes reported, and population included, in any individual trial. For further details of how we perform the GRADE evaluation and the scoring system we use, please see our website (www.clinicalevidence.com).
GRADE Evaluation of interventions for Amoebic dysentery.