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encephalitis

encephalitis

introduction

  • inflammation of the brain parenchyma which may or may not be associated with meningitis
  • the most common cause in in immunocompetent adults in Western society is caused by herpes simplex virus, while varicella may be life threatening in immunocompromised patients and thus patients with suspected encephalitis should generally by started on high dose iv antivirals ASAP.

aetiology

  • varicella-zoster virus (chickenpox/shingles) - mainly in immunocompromised patients (eg. AIDS, immunosuppressants)
  • cytomegalovirus (CMV) - HIV-associated CMV encephalitis
  • arboviruses (generally account for ~10% of cases but can be much higher in an epidemic):
    • California Encephalitis due to La Crosse virus
    • CBRNE–Venezuelan Equine Encephalitis
    • Eastern Equine Encephalitis (EEE)
    • Japanese Encephalitis
      • caused by JEV, a flavivirus;
      • the most significant etiology of arboviral encephalitis worldwide
      • mainly rural Asia including Indonesia and PNG
      • may cause Guillain-Barré syndrome
    • St. Louis Encephalitis
    • Venezuelan Equine Encephalitis - togavirus
    • West Nile Encephalitis (WNE)
    • Western Equine Encephalitis (WEE)
    • in Australia:
      • Kunjin virus - rarely symptomatic
      • Murray Valley encephalitis virus
        • Murray Valley encephalitis virus - north-western Victoria and other states, particularly after floods (eg. La Nina years such as 1951, 1974, 2011) as host is water birds.
        • high subclinical rate with only 1 in 500 becoming ill.
        • some people may experience a mild form of the disease with symptoms such as fever, headaches, neck stiffness, photophobia, nausea and vomiting
        • only a very small number of these cases go on to develop MVE
        • incubation period thought to be 1-4wks
        • Dx via serologic testing
        • no specific Rx
      • NB. Barmah Forest virus and Ross River virus generally cause a polyarthritis rather than encephalitis although usually cause fever and headaches
  • other zoonoses:
    • Henipavirus encephalitis (Hendra virus (HeV) / Nipah virus (NiV))
      • generally spread by urine of flying foxes and mortality rate of horses is 75% and humans 60%
      • outbreaks in north-eastern Australia
      • post-exposure Rx is available for humans
    • rabies
  • toxins:
    • Chamki Bukhar - encephalitis in children associated with hypoglycaemia from eating lychees in India, thought to be due to a toxin in the fruit
encephalitis.txt · Last modified: 2019/06/13 15:10 by gary1