Amoebiasis
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Direct answer
Amoebiasis, also called amoebic dysentery, is a protozoan disease of the large intestine caused by Entamoeba histolytica, transmitted through contaminated food and water. The parasites damage the intestinal wall, producing abdominal pain and cramps with stools carrying excess mucus and blood clots. Houseflies act as mechanical carriers, transferring the parasite from the faeces of infected persons to food and drink, so sanitation and fly control are central to prevention.
What you must remember
- Causative organism: Entamoeba histolytica, a protozoan parasite named for its tissue-lysing ability in the gut wall.
- Site of infection: the large intestine, where the trophozoites erode the mucosa and form ulcers.
- Symptoms: constipation alternating with cramps, abdominal pain, and stools with excess mucus and blood clots — the features of amoebic dysentery.
- Transmission: ingestion of food and water contaminated with cysts from the faeces of infected persons.
- Mechanical vector: the housefly, which carries the infective cysts from faeces to human food and drink on its body and legs.
- Prevention: safe drinking water, washing raw vegetables and fruit, proper sewage disposal, protecting food from flies and washing hands before eating.
- Contrast: unlike malaria, spread by a mosquito bite, amoebiasis is faecal-oral and needs no biological vector — the fly is only a mechanical carrier.
Common confusion
Amoebiasis is confused with bacillary dysentery and with other gut protozoan or worm infections. The exam distinction is the trio of Entamoeba histolytica, the large intestine and stools with mucus and blood clots. Note also the housefly's role — mechanical transfer of cysts, not part of the parasite's life cycle — unlike the female Anopheles, inside which Plasmodium genuinely completes part of its cycle.
Exam-focused takeaway
NEET-UG lists amoebiasis among protozoan diseases and pairs it with Entamoeba histolytica, the large intestine and contaminated food and water in match-the-following sets. Statement questions test the mucus-and-blood stool picture and the housefly's mechanical carriage. Assertion-reason items contrast faecal-oral transmission with vector-borne diseases such as malaria and filariasis.
Frequently asked questions
Which organism causes amoebiasis?
The protozoan Entamoeba histolytica, which infects and damages the large intestine.
What are the symptoms of amoebiasis?
Abdominal pain and cramps with constipation, and stools containing excess mucus and blood clots — together called amoebic dysentery.
How is amoebiasis transmitted?
Through food and water contaminated with faecal matter containing the parasite, and via houseflies that mechanically carry cysts from faeces to food.
What is the housefly's role in amoebiasis?
It acts only as a mechanical carrier, transporting Entamoeba cysts from infected faeces to human food and drink.
Which part of the alimentary canal is infected?
The large intestine, whose wall is invaded and ulcerated by the parasite.