The causative agent for the disease scrapie belongs to the category of:

ESIC Nursing Officer -2019 (Shift -1)

Applied Microbiology & Infection control

Easy

Appeared in: ESIC Nursing Officer -2019 (Shift -1)

Explanation

Scrapie is a fatal neurodegenerative disease affecting the central nervous system of sheep and goats.
The causative agent is a prion, which is an abnormal, misfolded version of a normal cellular protein (PrP).
Prions are unique as infectious agents because they are composed solely of protein and lack any genetic material (DNA or RNA).
They propagate by inducing normally folded proteins to convert into the misfolded, disease-causing form, leading to brain damage and a characteristic 'spongy' appearance.

Option B: Bacteria are single-celled prokaryotic organisms with their own genetic material and cellular machinery. They cause diseases through infection and toxin production, which is a different mechanism from the protein misfolding seen in scrapie.
Option C: Viruses are infectious agents that contain a nucleic acid core (DNA or RNA) and require a host cell to replicate. Scrapie is caused by a protein-only agent, not a virus.
Option D: Protozoans are single-celled eukaryotic organisms, which are structurally far more complex than prions. They cause diseases like malaria and giardiasis, which have completely different pathologies from spongiform encephalopathies.

Visual 1: Diagram: Prion Propagation. A visual showing a misfolded prion protein (PrPsc) interacting with a normal protein (PrPc) and causing it to misfold, initiating a chain reaction of protein aggregation.

Clinical Relevance

Nursing practice connection: Knowing Pathogen classification and prion diseases helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding prions is crucial as they cause fatal, untreatable neurodegenerative diseases in both animals (Scrapie, Bovine Spongiform Encephalopathy - BSE) and humans (Creutzfeldt-Jakob Disease - CJD).
Prions are highly resistant to conventional sterilization methods like heat, chemicals, and radiation. This poses a significant infection control challenge in healthcare, especially concerning neurosurgical instruments that may have been exposed to prion-infected tissue.
The transmission of prion diseases across species (e.g., from cattle with BSE to humans, causing variant CJD) highlights the importance of public health surveillance and food safety regulations.

How to Approach the Question

First, identify the key term in the question stem: 'scrapie'.
This is a factual recall question that tests your knowledge of different categories of infectious agents.
Recall or deduce the nature of scrapie. It is a classic example of a transmissible spongiform encephalopathy (TSE), a group of neurodegenerative diseases.
Connect the disease category (TSE) with its specific causative agent. All TSEs are known to be caused by prions.
Evaluate the given options. Bacteria, viruses, and protozoans are fundamentally different types of pathogens. Prions are unique as they are infectious proteins without any genetic material.
Select the option that correctly identifies the agent responsible for scrapie and other TSEs.

Concept Tested & Keywords

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