Question

Haemorrhagic nodules in peritoneum of right abdominal flank of equine are produced by the larvae of

• A. Strongylus equinus
• B. Strongylus edentatus
• C. Strongylus vulgaris
• D. Cyathostomum tetracanthum

Hint:

Associate large strongyle migrations with their specific lesions:
*S. vulgaris* $\rightarrow$ Cranial mesenteric artery (colic/aneurysm)
*S. edentatus* $\rightarrow$ Subperitoneal flank (hemorrhagic nodules)
*S. equinus* $\rightarrow$ Pancreas/Liver

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The large strongyles of horses (Strongylus vulgaris, S. edentatus, and S. equinus) undergo extensive and highly species-specific migration through various organs before returning to the large intestine.
Detailed Explanation:
Let us analyze the migration pathways of the three main large strongyles:
(B) Strongylus edentatus:
- After ingestion, L3 larvae penetrate the intestinal mucosa and migrate via the portal system to the liver.
- They undergo molting to L4 larvae in the liver parenchyma.
- From the liver, they migrate through the hepatorenal ligament to the subperitoneal connective tissues of the right abdominal flank and the abdominal wall.
- Their migration in the subperitoneal tissues causes local trauma, inflammation, and focal bleeding, leading to the formation of characteristic hemorrhagic nodules in the peritoneum of the right flank.
- Eventually, they return to the large intestine to mature into adults.
(C) Strongylus vulgaris larvae migrate to the cranial mesenteric artery, causing verminous arteritis and aneurysms.
(A) Strongylus equinus larvae migrate to the liver, peritoneal cavity, and pancreas, but do not produce characteristic subperitoneal nodules in the flank.
(D) Cyathostomum tetracanthum (a small strongyle) does not undergo extra-intestinal somatic migration; its larvae encyst within the mucosa of the large intestine.

Step 2: Final Answer:
The larvae of Strongylus edentatus are responsible for the subperitoneal hemorrhagic nodules in the right flank.