For live animals, scrapie testing uses which tissue types?

For live animals, scrapie testing uses which tissue types?

• A. Uses lymphoid tissue from the third eyelid, rectal mucosa, tonsil, or lymph node
• B. Uses a biopsy of brain tissue
• C. Does not exist
• D. Uses whole blood and a skin biopsy

Answer: (B)

Testing live animals for scrapie relies on detecting the disease-associated prion in tissues where it accumulates early, which are lymphoid tissues that are easy to sample without harming the animal. The practical ante-mortem (live-animal) tests use lymphoid tissues such as the third eyelid (nictitating membrane) with its associated lymphoid tissue, rectal mucosa-associated lymphoid tissue (RAMALT), the tonsil, or lymph nodes. These tissues can harbor PrPSc before the brain is involved, allowing surveillance while the animal is alive. Brain tissue is what’s typically examined to confirm diagnosis, but this requires postmortem sampling or an extremely invasive biopsy in a live animal, which isn’t standard practice for routine testing. That’s why a biopsy of brain tissue is not the accepted method for live-animal scrapie testing. The other options don’t fit because whole blood and skin biopsy aren’t validated routes for scrapie detection in live animals, and saying that no live-animal test exists is false since RAMALT, third eyelid, tonsil, and lymph nodes are commonly used. So the best answer points to lymphoid tissues accessible in living animals—third eyelid, RAMALT, tonsil, or lymph node.

Testing live animals for scrapie relies on detecting the disease-associated prion in tissues where it accumulates early, which are lymphoid tissues that are easy to sample without harming the animal. The practical ante-mortem (live-animal) tests use lymphoid tissues such as the third eyelid (nictitating membrane) with its associated lymphoid tissue, rectal mucosa-associated lymphoid tissue (RAMALT), the tonsil, or lymph nodes. These tissues can harbor PrPSc before the brain is involved, allowing surveillance while the animal is alive.

Brain tissue is what’s typically examined to confirm diagnosis, but this requires postmortem sampling or an extremely invasive biopsy in a live animal, which isn’t standard practice for routine testing. That’s why a biopsy of brain tissue is not the accepted method for live-animal scrapie testing.

The other options don’t fit because whole blood and skin biopsy aren’t validated routes for scrapie detection in live animals, and saying that no live-animal test exists is false since RAMALT, third eyelid, tonsil, and lymph nodes are commonly used.

So the best answer points to lymphoid tissues accessible in living animals—third eyelid, RAMALT, tonsil, or lymph node.