Viral CNS Infections Flashcards
What clinical signs point to a viral CNS infection over bacterial?
Negative gram stain, increased lymphocyte count in CSF (pleocytosis), high protein/normal glucose levels
What is the epidemiology of viral CNS infections?
Typically acute onset, healthy hosts can be infected but more severe infection in immunocompromised individuals. Frequently occurs as meningo-encephalitis
What 4 viruses commonly cause CNS infections?
Enterovirus, HSV 1,2, Arboviruses, rabies
Describe the characteristics of enteroviruses
(+)ssRNA, non-enveloped, respiratory virus. causes 30-50% of viral meningitis, more severe illness apparent in neonates and immunocompromised people, seasonal outbreaks
How does enteroviral meningitis usually manifest?
Respiratory symptoms with sever headaches. Can be a prolonged illness but long term sequalae
What is the most effective way to diagnose viral CNS infections?
Run a CSF profile (high protein/normal glucose levels) and RT-PCR of the CSF
How are viral CNS infections prevented and treated?
Only vaccine available is for poliovirus. Treated symptoms with pain control and hydration, no effective antiviral available
Describe HSV (AKA human herpes virus) with respect to CNS infections
Causes a much more severe illness than enterovirus (70% mortality rate without treatment), most common cause of sporadic viral encephalitis in north america
Describe the pathogenesis, sypmtoms, diagnosis, treatment and prevention of HSV encephalitis
Rarely caused from the primary exposure to the virus. Usually caused from reactivation by stress of the virus from latency in sensory ganglions
Symptoms: fever, headache, progressive neurological/focal symptoms, seizures, changes in mental status, possibility of long-term sequelae. May be caused by either HHV1 or 2
Diagnosis: CSF profile and PCR only, serology is useless due to cross-reactivity from antigen
Treatment: empiric therapy of acyclovir if HSV infection suspected
Prevention: no vaccine available
Describe the basic mechanism of action of and resistance to acyclovir
Acyclovir inhibits viral DNA synthesis by incorporating in viral DNA. It is triphosphorylated by one viral kinase and two human kinases before being incorporated. Resistance to the drug is through mutations in HSV thymidine kinase or DNA polymerase
What are arboviruses?
Arboviruses are arthropod-borne viruses whose most common vectors are mosquitoes and ticks
Name the 3 important families of arboviruses than cause disease in humans and some examples of viruses in each
Flaviviruses (zika, dengue, yellow fever, (+)ssRNA), togaviruses (equine encephalitis virus, chikungunya (+)ssRNA)
bunyaviruses (-)ssRNA
What are the three diseases caused by arboviruses in humans?
Systemic febrile illness, hemorrhagic fever, encephalitis
If a viral CNS infection is suspected, what two viruses should you look for first?
Enterovirus, herpes virus
Describe rabies virus, its transmission, what tissues and parts of the body it affects
Large, enveloped (-)ssRNA virus. Transmitted through the saliva of infected animals. In north america the most common animals are bats, skunks, raccoons and foxes (rarely dogs/cats). Rabies is a neurotropic virus which means it has affinitiy for nervous tissue. It affects the brain, salivary glands and sensory nerves to skin. It has a very long incubation period (weeks)
