Question

Given below are two statements:
Statement (I): Summer sores in horses is caused by the deposition of larvae of stomach worms in existing wounds by the visiting infected flies.
Statement (II): The lesions of varying size are seen on legs, withers and sheath, and heal spontaneously in winters.
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:

Cutaneous habronemiasis is called "summer sores" because fly vectors are active only in the summer, and the lesions characteristically regress on their own during the cold winter months.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
"Summer sores," scientifically known as cutaneous habronemiasis, is a seasonal skin disease of horses characterized by chronic, non-healing, granulomatous skin lesions.
It occurs when the larval stages of equine stomach nematodes are deposited in atypical cutaneous locations.

Step 2: Detailed Explanation:
Let us analyze both statements:
- Statement (I): The disease is caused by the larvae of the equine stomach worms Habronema muscae, Habronema majus (formerly microstoma), or Draschia megastoma. The intermediate hosts (houseflies or stable flies) ingest the worm larvae from manure. When these infected flies feed on pre-existing wounds, cuts, or moist areas of the horse's skin, the L3 larvae escape from the fly's mouthparts and are deposited in the wound. This aberrant larval migration triggers a hypersensitivity reaction, leading to summer sores. Thus, Statement (I) is true.
- Statement (II): Summer sore lesions typically occur on body parts prone to wounds or moisture, such as the legs, sheath, medial canthus of the eyes, and withers. These lesions are highly seasonal and active during the warm fly season. When the winter months arrive, fly activity ceases, and the ambient temperature drops, causing the larvae to die. Consequently, the associated inflammatory response subsides, and the lesions typically undergo spontaneous regression or healing in the winter. 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, corresponding to option (A).