Question

Assertion: Symptoms of amoebic dysentery include stool with blood and mucus, abdominal pain and constipation.
Reason: Amoebic dysentery is caused by Shigella sp.

• A. Both assertion and reason are true and the reason is the correct explanation for the assertion
• B. Both assertion and reason are true but the reason is not the correct explanation for the assertion
• C. Assertion is true but the reason is false
• D. Both the assertion and the reason are false

Answer 1

The correct option is C Assertion is true but the reason is false

Amoebiasis or amoebic dysentery is an infectious intestinal disease which is caused by the protozoan Entamoeba histolytica. The pathogen enters the body through food or water contaminated with cysts (hard resistant protective structures) of Entamoeba histolytica (faecal-oral transmission).

Once ingested, rupturing of cysts occurs in the small intestine and trophozoites (a feeding stage in the life cycles of the protozoan) are released which travel to the large intestine. The trophozoites multiply by binary fission (cell divided into equal halves) and produce more cysts which are passed out of the body along with trophozoites, through the fecal route. Being resistant structures, the cysts can survive upto few weeks outside the human body but the trophozoites perish.

The symptoms of this infection include abdominal cramps, discharge of stool with excess mucus and blood, mild diarrhoea alternating with constipation etc.

Shigella sp. is the causative agent for bacillary dysentery (shigellosis) which manifests symptoms similar to that of amoebic dysentery.

Thus the assertion is true but the reason is false.