Entamoeba histolytica Life Cycle

Entamoeba histolytica life cycle has two main stages, the trophozoite and the cyst stage. Infection begins with the ingestion of mature cysts, usually through contaminated food or water. Once inside the host’s intestine, the cysts release trophozoites, which can either colonize the intestinal lining, causing disease or transform back into cysts for excretion in feces, completing the cycle and facilitating transmission. In this article, we will study the life cycle of Entamoeba histolytica, the diseases caused by it, its symptoms, and treatment.

Entamoeba histolytica Classification

Entamoeba histolytica is a protozoan parasite that belongs to the following classifications:

Kingdom	Protista
Subkingdom	Protozoa
Phylum	Sarcomastigophora
Class	Lobosea
Order	Euamoebida
Genus	Entamoeba
Species	histolytica

Entamoeba histolytica Life Cycle

Entamoeba histolytica is a protozoan that causes infections in humans. It is a unicellular organism characterized by a simple cell structure and belongs to the phylum Protozoa, the class Sarcodina, and the order Lobosa. Entamoeba possesses a single nucleus and lacks typical organelles such as mitochondria and a Golgi apparatus. This parasitic amoeba has a life cycle that involves both cyst and trophozoite stages. The trophozoites are responsible for causing infection in the host’s intestines, leading to amoebiasis. Entamoeba histolytica is more common in people who live in tropical areas with poor sanitary conditions.

Entamoeba histolytica Life Cycle Diagram

The diagram shows the stages of Entamoeba histolytica life cycle as follows:

Stages of Entamoeba histolytica Life Cycle

The life cycle of Entamoeba histolytica has two main stages: the trophozoite and the cyst stage. The cyst is the infectious agent and is transmitted through contaminated food or water. Detailed description of each stage is as follows:

Cyst – Stage 1

The cyst stage is the first and infective stage of the life cycle of Entamoeba histolytica.

• The cyst is the infectious agent and is transmitted through the oral fecal route via contaminated food or water.
• Cysts are spherical and can measure 10–20 µm. Immature cysts may have one to three, while mature cysts have four nuclei.
• They have a protective wall that enables them to withstand external conditions. Cysts can survive days to weeks in the external environment and remain infectious.
• Infection is caused by ingestion of mature cysts through fecally contaminated food or water.

Excystation – Stage 2

Excystation is the process by which cysts transform into trophozoites. It occurs in the small intestine.

• Excystation involves the breaking of the cyst wall and the release of the active form of the parasite, known as trophozoites
• Each cyst releases two trophozoites through excystation. The trophozoites then feed off and absorb nutrients from the infected person.
• The trophozoites, now in the active and motile form, are capable of colonizing the large intestine and initiating the disease process.

Trophozoite – Stage 3

The trophozoite is an invasive stage, where trophozoites attach to the intestinal epithelium and multiply by binary division.

• Trophozoites are unicellular parasites that measure 14 to 18 mm in diameter.
• They are the active, motile, and feeding forms of Entamoeba histolytica.
• Trophozoites feed on bacteria, debris, and other particles present in the intestinal lumen by extending and retracting pseudopodia.
• Trophozoites are responsible for the invasive and pathogenic nature of Entamoeba histolytica. They can penetrate the intestinal mucosa, leading to tissue damage and causing symptoms such as dysentery (inflammatory diarrhea).
• The trophozoites can be passed out of the host’s body in feces. They are rapidly destroyed once outside the body.++

Morphology

Entamoeba histolytica is a parasite that has three stages: trophozoite, precyst, and cyst. Morphology of Entamoeba histolytica includes:

Trophozoites

Trophozoites are spherical or oval shaped and have a diameter of 15–20 µm. It is enclosed by thin cell membrane and contains a central endosome, peripheral chromatin, a single nucleus and radial achromatic fibrils. In the host it move towards the colon using finger-like pseudopods.

Cysts

Cyst are round or oval in shape, with a diameter of 12–15 µm. They are surrounded by a cyst wall, which is a highly retractile membrane that resists digestion by gastric juice in the human stomach. Cysts contain 1–4 nuclei, and young cysts usually have chromatoid bodies that appear as elongated bars with rounded ends.

Entamoeba histolytica Characteristics

Protozoa Entamoeba histolytica is responsibl for disease amebiasis. The characteristics of entamoeba are as follows:

• Entamoeba histolytica is a eukaryotic organism and lacks organelles like mitochondria, rough endoplasmic reticulum, and the Golgi apparatus.
• Morphologically Entamoeba’s trophozoite is a small pear shaped cell that ranges in size from 15–20 µm.
• It has a single nucleus with a centrally located karyosome.
• For feeding and movement it possess pseudopodia.
• Life cycle alternates between cyst stage and the trophozoite stages.
• It resides in the large intestine of the host.
• Reproduction is through binary fission.
• Entamoeba histolytica causes amoebiasis, a disease that can lead to dysentery and liver abscesses.
• It is more prevalent in areas with poor sanitation and is endemic in some tropical and subtropical regions.

Mode of Transmission

Entamoeba histolytica can be transmitted through the fecal-oral route. This means that a person can become infected by:

• Ingesting food or water that has been contaminated with feces containing E. histolytica cysts.
• Indirect hand contamination from contaminated surfaces.
• Inadequate sanitation and hygiene contribute to the spread.
• Person-to-person transmission through direct contact with infected feces.
• Oral anal sexual contact with a chronically ill or asymptomatic carrier.

Conclusion – Entamoeba histolytica Life Cycle

Entamoeba histolytica exhibits a life cycle characterized by alternating trophozoite and cyst stages. Trophozoites resides the large intestine and causes amoebic dysentery. When conditions become unfavorable, trophozoites transform into cysts, which are excreted in feces. Upon ingestion by a new host, cysts undergo excystation in the small intestine, releasing active trophozoites. These trophozoites then multiplies in the large intestine and causes the infection. Transmission primarily occurs through contaminated food or water. Understanding the life cycle is important for diagnosing and managing amoebiasis caused by Entamoeba histolytica.

FAQs -Entamoeba histolytica Life Cycle

What are the Life Cycle Stages of Entamoeba histolytica?

The life cycle of the parasite Entamoeba histolytica has two main stages: the trophozoite and the cyst stage. 

What are the Symptoms of Entamoeba histolytica?

The symptoms of Entamoeba histolytica are generally mild and can include loose feces, weight loss, fever, stomach pain, and stomach cramping.

What is Entamoeba histolytica?

Entamoeba histolytica is a parasitic protozoan that causes intestinal amebiasis. It’s a pathogenic amoeba that lives in the human gastrointestinal tract.

Which Organ is Infected by Entamoeba histolytica?

Entamoeba histolytica is a parasite that lives in the upper part of the large intestine. It can also affect the liver, respiratory tract, heart, and brain.

Which Disease is Caused by Entamoeba histolytica?

The parasite Entamoeba histolytica causes the disease amebiasis, also known as amoebic dysentery. It’s a microscopic parasite that spreads through human feces.

What is the Diagnostic Stage of Entamoeba histolytica?

The common method for diagnosing pathogenic Entamoeba species is microscopic identification of cysts and trophozoites in the stool.

What are the First Signs of Amoeba?

The first signs of amebiasis, also known as amoebic dysentery, include: Nausea, Diarrhea, Weight loss, Stomach tenderness, Occasional fever.

What is the Prevention of Entamoeba histolytica?

Prevention of Entamoeba histolytica involves maintaining good hygiene practices, including proper handwashing and the consumption of safe, clean water and food.

Who is the Host of Entamoeba histolytica?

Humans are the main host of Entamoeba histolytica but dogs, cats and rodents can also be infected sometimes.