VIOLIN: Vaccine Investigation and Online Information Network

Pathogen Page

Entamoeba histolytica

I. General Information

1. NCBI Taxonomy ID:

2. Disease:

Amoebiasis

3. Introduction

Entamoeba histolytica is an anaerobic parasitic protozoan, part of the genus Entamoeba. Predominantly infecting humans and other primates, E. histolytica is estimated to infect about 50 million people worldwide. Many older textbooks state that 10% of the world population is infected, but these figures predate the recognition that at least 90% of these infections were due to a second species, E. dispar. Mammals such as dogs and cats can become infected transiently, but are not thought to contribute significantly to transmission.

The active (trophozoite) stage exists only in the host and in fresh loose faeces; cysts survive outside the host in water, soils and on foods, especially under moist conditions on the latter. The cysts are readily killed by heat and by freezing temperatures, and survive for only a few months outside of the host. When cysts are swallowed they cause infections by excysting (releasing the trophozoite stage) in the digestive tract. The trophozoite stage is readily killed in the environment and cannot survive passage through the acidic stomach to cause infection. Symptoms can include fulminating dysentery, bloody diarrhea, weight loss, fatigue, abdominal pain, and amoeboma (Wiki: Entamoeba histolytica).

4. Microbial Pathogenesis

The amoeba can actually 'bore' into the intestinal wall, causing lesions and intestinal symptoms, and it may reach the blood stream. From there, it can reach different vital organs of the human body, usually the liver, but sometimes the lungs, brain, spleen, etc. A common outcome of this invasion of tissues is a liver abscess, which can be fatal if untreated. Ingested red blood cells are sometimes seen in the amoeba cell cytoplasm (Wiki: Entamoeba histolytica).

5. Host Ranges and Animal Models

Other than infecting humans, mammals such as dogs and cats can become infected transiently, but are not thought to contribute significantly to transmission (Wiki: Entamoeba histolytica).

6. Host Protective Immunity

It has been shown that amoeba-specific sIgA antibodies are capable of blocking parasite adherence to target cells, preventing cytotoxic activity (Carrero et al., 2010).

Loading Pathogen Genes...

Loading Host Genes...

Loading Vaccines...

Loading References...

Table of Contents