CNS Infections- Rabies Virus Flashcards
Rabies Dx is an acute, fulminant, fatal, _________ due to infection of brain and spinal column. This virus can infect nearly all mammals and is transmitted between them by ________ and is fatal to virtually all humans and nearly all mammals. Human survivors are very rare.
focal encephalitis and myelitis
infected secretions, usually saliva
Rabies description
- a neurotrophic virus
- Rhabdoviridae group, a Lyssavirus
- a (-) ssRNA, bullet–shaped virus (enveloped with helical symmetry)
- Single serotype (one major surface antigen)
- Each virus possess many copies of a single glycoprotein peplomer which is specific for the brain, alter one amino acid in the glycoprotein results in an attenuated strain
Virus replicates in the cytoplasm, forming _________ consisting of viral nucleoprotein
(Negri bodies)
eosinophilic cytoplasmic inclusions
Transmitted by
Animal bites or scratches, contact with animal saliva or excretions
- Inhalation of aerosols, e.g., bat droppings
- Transplants (Corneal, others) is rare
Control of human rabies is contingent on control of __________
dog and cat rabies
Worldwide, infected dogs are the most important source of infection for humans
most common source of rabies today in US
Bats
Pathogenesis: Virus is injected/passes through the epidermis (at the bite or lick site) and initially replicates in __________. When the virus titer is high enough, it enters the ________ at unmyelinated sensory terminals and neuromuscular junctions where it is ___________
the adjacent striated skeletal muscle
peripheral nervous system (PNS)
sequestered from the immune system
Pathogenesis: Virus travels slowly (mm per day) by retrograde axoplasmic flow (like polio and herpes viruses) up the nerves to the _____________________. The slow axoplasmic flow accounts, in part, for the long incubation period for person with a bite which occurred at a site far from the brain/CNS.
CNS where it disseminates via transynaptic spread first to the spinal chord and then rapidly to the brain.
Pathogenesis: The virus predominates in the _______, but localizes in the _________, and also infects neurons in almost all brain areas.
Virus then travels back down the autonomic nerves to the _________ (6 locations)
Gray matter
limbic region (focal symptoms)
salivary glands, cornea, lungs, adrenal medulla,
kidneys, bite site
The patient is considered to be potentially infectious during the period from ____ before onset of symptoms (when humans can begin to shed rabies virus in saliva and tears) until his/her death.
2 weeks
The moment the virus enters sensory terminals & neuromuscular junctions, the pt. _________, because the virus is sequestered from ________. Explains importance of post-exposure prophylaxis - it can prevent an infected person from developing rabies!
will eventually die
rabies-specific Ab (and the immune system)
The virus can spread throughout the body, but is never isolated from _________.
the blood
Prodrome is nonspecific flu-like illness lasting 2→4 d and includes:
fever, headache, malaise, nausea and vomiting, loss of appetite/anorexia, anxiety, pain, itching, paresthesias at bite site, if one exists
Describe disease
- usually 5 → 6 days and is always fatal.
- Highly variable presentation: One person may present with paralytic symptoms, another may present with all stages from prodrome to paralytic, while another may lack one or more stages.
Paralytic/Dumb rabies form S/S:
- Less common manifestation (20%)
- S/S are indistinguishable from viral encephalitis
- Patient manifests with paralysis starting at extremities and then spreads to the trunk.
- Paralysis leads to hypoventilation (inhibition of the pharyngeal and respiratory center of brain causes respiratory paralysis), hypotension (cardiac failure), eventually coma and death
