Question

Given below are two statements:
Statement (I): Self cure phenomenon is a highly species-specific phenomenon and occurs when a larval population of a particular nematode is superimposed on an existing adult worm population of the same nematode.
Statement (II): The self-cure phenomenon is a Type-I hypersensitivity reaction and can be eliminated by administration of antihistaminic drug.
In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

Self-cure is essentially an allergic reaction of the gut to new worm larvae, which expels the old worms. Since histamine mediates this Type-I hypersensitivity, antihistamines will block this protective expulsion.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The self-cure phenomenon is a naturally occurring immunological reaction observed in livestock (originally discovered in sheep infected with Haemonchus contortus), where an established adult nematode population is suddenly expelled from the gastrointestinal tract.

Step 2: Detailed Explanation:
Let us evaluate the immunological and physiological aspects of both statements:
- Statement (I): Self-cure is a highly species-specific protective immune response. It occurs when a sheep harboring an established adult population of a specific nematode (e.g., Haemonchus contortus) ingests a fresh, challenging dose of infective L3 larvae of the same nematode species. The superimposition of this new larval population triggers the sudden expulsion of the adult worms. Thus, Statement (I) is true.
- Statement (II): Immunologically, self-cure is a localized Type-I (immediate) hypersensitivity reaction. The antigens from the newly ingested larvae react with IgE antibodies bound to mucosal mast cells in the abomasal or intestinal wall. This triggers mast cell degranulation, releasing vasoactive amines like histamine. The resulting histamine release causes mucosal edema, increased vascular permeability, and smooth muscle contractions, which wash out and expel the adult worms. Research has demonstrated that administering antihistaminic drugs blocks this histamine-mediated pathway, thereby eliminating or preventing the self-cure response. Thus, Statement (II) is true.
Therefore, both Statement (I) and Statement (II) are true.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are true, which corresponds to option (A).