Entamoeba Histolytica

ENTAMOEBA HISTOLYTICA
Entamoeba histolytica is an anaerobic parasitic amoebozoan, part of the genus Entamoeba. Predominantly infecting humans and other primates causing amoebiasis, E. histolytica is estimated to infect about 35-50 million people worldwide.

CLASSIFICATION

DISEASE OF ENTAMOBEA
Entamoeba histolytica is an ameba that feeds on cells in the human colon. It is the cause of amebic dysentery (bloody diarrhea) as well as colonic ulcerations. The infection is also referred to as amebiasis.

GEOGRAPHICAL DISTRIBUTION
COSMOPOLITIAN
The prevalence of Entamoeba infection is as high as 50% in areas of Central and South America, Africa, and Asia. E histolytica seroprevalence studies in Mexico revealed that more than 8% of the population were positive

MORPHOLOGY
. Trophic:
The trophic forms vary in size from 15-40 micro average being 25 micro. The cell body is divisible into two distinct portions—ectoplasm and endoplasm. The ectoplasm is clear and translucent while the endoplasm is granular

Cysts vary in diameter from 10-20 micro. The cysts are spherical. The cyst wall is double and the cytoplasm usually bears four nuclei. The cytoplasm is clear and often contains black rod-like chromatoid bar or bodies.

LIFECYCLE
When the cyst of E.histolytica reaches caecum or lower part of ileum excystation occurs and an amoeba with four nuclei emerges and that divides by binary fission to form eight trophozoites.
Trophozoites migrate to the large intestine and lodge into the submucosal tissue.
Trophozoites grow and multiply by binary fission in the large intestine (Trophozoite phase of the life cycle is responsible for producing characteristics lesion of amoebiasis).
Certain numbers of trophozoites are discharged into the lumen of the bowel and are transformed into cystic forms.
The cysts thus formed are unable to develop in the same host and therefore necessitate a transference to another susceptible host. The cysts are passed in the feces.

PATHOGENECITY
E. histolytica, as its name suggests (histo–lytic = tissue destroying), is pathogenic; infection can be asymptomatic or can lead to amoebic dysentery or amoebic liver abscess. Symptoms can include fulminating dysentery, bloody diarrhea, weight loss, fatigue, abdominal pain, and amoeboma

SYMPTOMS
On average, about one in 10 people who are infected with E. histolytica becomes sick from the infection. The symptoms often are quite mild and can include loose stools, stomach pain, and stomach cramping. Amebic dysentery is a severe form of amebiasis associated with stomach pain, bloody stools, and fever

DIAGNOSIS
A single stool examination has a low sensitivity of detecting the parasite (129). The best diagnostic method is detection of E. histolytica antigen or DNA in stool (78, 79). Clinical diagnosis of amebiasis is difficult because of the nonspecific nature of symptoms

TREATMENT
Current U.S. treatment guidelines recommend as first line either metronidazole 750 mg PO tid for 7-10 days (35-50 mg/kg/d in children) OR tinidazole 2 g once PO daily for 5 days (50 mg/kg/day in children 3 years of age or older). Luminal agents used are paromomycin, iodoquinol, and diloxanide furoate.

PREVENTION AND CONTROL
Improved sanitation will help to reduce the liklihood of transmission. Travelers to endemic areas can reduce the risk of infection by drinking bottled water, not using ice cubes in drinks, and washing fruits and vegetables with clean water (or by peeling them yourself).

Reference
https://youtu.be/wBPh9svlU9Q
https://youtu.be/gfCunkjxkMo
https://youtu.be/VRMv_lzhMZc