Microbiology-Prions and Viral CNS Infections Flashcards
What would EM of the microbe causing this condition look like?
Rabies is a bullet-shaped rhabdovirus. The microscopic image is of a Negri body.
What are the majority of rabies exposures in the US related to?
1/2 come from bats, rodent bites are not generally considered potentially rabid. 1/2 come from traveling outside of the US and returning.
How long does it typically take for rabies symptoms to manifest?
2 weeks to one year (typically 20-60 days)
How far is the progression of disease in someone who has rabies and is exhibiting behavioral changes and salivating?
The limbic lobe, hippocampus and cerebellum are all commonly affected sites in rabies, however, once it gets to the limbic lobe you really start to see behavioral changes. It then travels outside of the CNS to the salivary glands.
An outbreak was seen in the hospital that affected patients with HIV, organ transplants and on chronic steroids. Early on they presented with personality changes, symptoms progressed to motor deficits, visual deficits, ataxia, aphasia, dementia, coma and death. On biopsy, many of their brains appeared the same as the brain below. What caused them to die?
JC virus is latent in 60-80% of adults, but when people become immunocompromised it infects oligodendrocytes, leading to demyelination and progressive multifocal leukencephalopathy.
How do you treat someone with PMLE?
Antivirals. If you don’t treat them they die within 3-5 months.
A 37 year old male presents with dementia, aphasia, myoclonus, extrapyramidal signs, and vision loss. These symptoms have developed over the last two months. No infective substances are found in labs. What would you expect histology of his brain to look like?
This sounds like CJD (prion disease), characterized by spongiform encephalopathy.
Human prion-related diseases
Creutzfeldt-Jakob disease, Kuru, Gerstmann-Streussler-Shanker disease and fatal familial insomnia.
How are prions infectious?
Normal PrPc forms a dimer with abnormal PrPsc and converts to PrPsc. The body thinks PrPc is deficient, makes more and thus more PrPsc is increased. PrPsc has a high percentage of beta-pleated sheet that prevents its degradation by proteases.
Bovine spongiforme encephalopathy that causes human disease
Prion disease in cattle is not inactivated by heat. People eat burgers and start developing PrP amyloid plaques in the brain. Incubation period is about 8 years.
How is PrPsc transmitted in the hospital?
It is highly resistant to inactivation and can be transmitted by dural grafts, corneal transplants, electrodes etc.
Familial CJD
PrP mutation that predisposes people to PrPsc development
Idiopathic CJD
Spontaneous PrPc to PrPsc mutation
Transmissible CJD
Iatrogenic (Intraneuronal introduction from surgical procedures)
Kuru CJD
Dermal introduction of PrPsc from canibalism
