⬅ Home
5# Ticks & Prions
1. The fundamental feature that distinguishes prions from all other infectious agents is:
Lack of cellular tropism
Absence of nucleic acids
Inability to induce immune response
Resistance to antibiotics
Explanation:
Prions are proteinaceous infectious particles that completely lack nucleic acids.
2. The normal cellular prion protein (PrPC) is characterized by all EXCEPT:
Extended structure
Protease sensitivity
High β-sheet content
Cell surface localization
Explanation:
High β-sheet content is a feature of the abnormal prion protein (PrPSc), not PrPC.
3. Conversion of PrPC into PrPSc is primarily driven by:
Change in secondary and tertiary structure
Alteration in primary amino acid sequence
RNA-mediated transcription
Host immune response
Explanation:
PrPC and PrPSc share the same primary structure but differ in folding (α-helix → β-sheet).
4. Which mechanism best explains transmissible prion diseases?
Horizontal gene transfer
Immune-mediated cross-reactivity
Spontaneous protein degradation
Template-assisted misfolding of PrPC
Explanation:
PrPSc acts as a template, inducing misfolding of normal PrPC into abnormal PrPSc.
5. The characteristic spongiform appearance in prion diseases is due to:
Demyelination
Neuronal vacuolation and extracellular deposits
Lymphocytic infiltration
Ischemic necrosis
Explanation:
Accumulation of PrPSc leads to neuronal vacuolation and amyloid plaque formation.
6. A defining histopathologic feature of prion diseases is:
Granuloma formation
Marked inflammatory infiltrate
Absence of inflammatory response
Demyelinating plaques
Explanation:
Despite extensive neuronal damage, prion diseases lack inflammatory or immune responses.
7. Kuru was historically transmitted through:
Cannibalism
Tick bites
Blood transfusion
Respiratory droplets
Explanation:
Kuru spread via ritualistic cannibalism involving consumption of brain tissue.
8. Variant Creutzfeldt-Jakob disease (vCJD) is MOST strongly associated with:
Improperly sterilized neurosurgical instruments
PRNP gene mutation
Spontaneous PrPC misfolding
Consumption of BSE-contaminated beef
Explanation:
vCJD results from dietary transmission of BSE prions crossing the species barrier.
9. Early manifestations of variant CJD are predominantly:
Cerebellar ataxia
Psychiatric and behavioral symptoms
Visual disturbances
Lower motor neuron weakness
Explanation:
vCJD typically presents first with psychiatric and behavioral changes.
10. The MOST common route of iatrogenic CJD transmission is:
Blood transfusion
Organ transplantation
Improperly sterilized neurosurgical equipment
Vaccination
Explanation:
Prions resist routine sterilization, allowing transmission via surgical instruments.
11. A prominent early clinical feature of Gerstmann-Sträussler-Scheinker (GSS) disease is:
Ataxia
Psychosis
Sleep disturbance
Visual hallucinations
Explanation:
GSS is slowly progressive with cerebellar ataxia as an early dominant feature.
12. Fatal familial insomnia primarily presents with early:
Dementia
Ataxia
Psychiatric symptoms
Sleep disturbances
Explanation:
Sleep disturbance is the hallmark early feature of fatal familial insomnia.
13. CSF findings in prion diseases typically include:
Pleocytosis and low glucose
Normal cell count and glucose
Marked lymphocytosis
Hypoglycorrhachia
Explanation:
CSF is usually normal except for possible elevated protein levels.
14. RT-QuIC assay is based on detection of:
PRNP gene mutation
Antibodies against PrPSc
Induced misfolding of recombinant prion protein
Neuronal degeneration markers
Explanation:
RT-QuIC detects PrPSc by inducing conformational change in recombinant prion protein.
15. Which method is MOST effective for prion inactivation?
1N sodium hydroxide with extended autoclaving
Formaldehyde
Ultraviolet irradiation
70% alcohol
Explanation:
Prions resist standard sterilization and require NaOH or hypochlorite plus prolonged autoclaving.
16. Tick paralysis is caused by:
Direct nerve invasion
Injection of neurotoxins during feeding
Immune-mediated demyelination
Bacterial superinfection
Explanation:
Ticks inject neurotoxins that cause acute ascending flaccid paralysis.
17. A key feature distinguishing tick paralysis from Guillain-Barré syndrome is:
Ascending paralysis
Respiratory involvement
Autonomic dysfunction
Rapid resolution after tick removal
Explanation:
Tick paralysis resolves quickly and completely once the tick is removed.
18. Hard ticks are identified by:
Presence of a dorsal scutum
Ventrally visible mouthparts
Soft leathery body
Absence of legs in larval stage
Explanation:
Hard ticks have a scutum and mouthparts visible from above.
19. The MOST appropriate method for tick removal is:
Twisting the tick clockwise
Crushing the tick before removal
Steady traction with forceps close to the skin
Applying chemical irritants
Explanation:
Steady traction minimizes toxin injection and prevents retained mouthparts.
20. In the tick life cycle, transformation between stages occurs:
Only inside the host
Outside the host’s body
Only during blood feeding
Only in the larval stage
Explanation:
Molting between stages (larva, nymph, adult) occurs outside the host.