Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R:
Assertion A : Oesophagostomum columbinum is a serious pathogen of sheep and 200-300 adult worms can cause a severe disease.
Reason R : Adult worms are voracious blood suckers and cause severe anaemia.
In light of the above statements, choose the correct answer from the options given below:

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

To distinguish these parasites, remember: Haemonchus and Bunostomum are blood suckers (causing anemia), whereas Oesophagostomum causes nodule formation (resulting in "pimply gut", diarrhea, and protein loss).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Oesophagostomum columbinum, commonly known as the nodular worm of sheep and goats, is a highly pathogenic nematode inhabiting the large intestine.
Understanding the specific pathogenesis of the different life cycle stages is essential to differentiate its clinical manifestations from those of other gastrointestinal nematodes.

Step 2: Detailed Explanation:
Let us analyze the Assertion and the Reason individually:
1. Assertion A: Oesophagostomum columbinum is a serious pathogen of sheep and 200-300 adult worms can cause a severe disease.
This statement is correct.
Oesophagostomum columbinum is indeed a major pathogen in sheep.
Even a relatively small burden of 200-300 adult worms can cause severe clinical disease.
This is due to the marked inflammatory and granulomatous reactions (nodule formation) triggered by the larvae in the intestinal wall, leading to gut dysfunction, intussusception, and "pimply gut".
Therefore, Assertion A is true.
2. Reason R: Adult worms are voracious blood suckers and cause severe anaemia.
This statement is incorrect.
Adults of Oesophagostomum columbinum are not blood suckers.
They reside in the lumen of the colon and feed on mucus, inflammatory exudates, and ingesta.
The severe anemia observed in sheep grazing on infected pastures is typically caused by abomasal parasites like Haemonchus contortus, which are true blood suckers.
The pathogenesis of Oesophagostomum centers around severe protein-losing enteropathy, malabsorption, diarrhea, and emaciation, but not direct hematophagy.
Therefore, Reason R is false.

Step 3: Final Answer:
Assertion A is true, but Reason R is false because Oesophagostomum adults are not blood-feeding parasites.
Therefore, the correct answer is option (C).