Encephalitis
Introduction.
Encephalitis refers to inflammation of the brain. This can be caused by many
viral and bacterial pathogens. Many encephalitis viruses are also arboviruses
(arthropod-borne), including West Nile virus, Western Equine Encephalitis virus
(WEE), and Eastern Equine Encephalitis virus (EEE).
Summary
Cause: West Nile Virus (Flavivirus)
- Transmission: arbovirus (mosquito)
- Symptoms: mild flu-like; 20% progress to fever, headache, malaise
(West Nile Fever)
- Pathogenesis: viremia, replication in monocyte/macrophage,
interferon released
- Complications: encephalitis in 1% of cases
- Treatment: supportive
- Vaccine: no
Cause: Alphaviruses (EEE, WEE,VEE)
- Structure: Togaviruses: enveloped ('shrinkwrapped') icosahedral; +ssRNA
- Transmission: arbovirus: mosquito vector
- Reservoir: Birds (EEE, WEE) or horses & rodents (VEE)
- Symptoms: Flu-like (fever, chills, headaches)
- Pathogenesis: viremia, replication in monocyte/macrophage,
interferon released
- Complications: 2nd viremia possible leading to infection of brain,
liver, skin, endothelium
- Treatment: supportive
- Vaccine: available for EEE and WEE
Cause: Other Flaviviruses (St. Louis, Russian spring-summer, Japanese)
- Transmission: arbovirus (mosquitoes & ticks)
- Reservoir: Birds (SLE, RSSE) and pigs (JE)
- Symptoms: Flu-like (fever, chills, headaches)
- Pathogenesis: viremia, replication in monocyte/macrophage,
interferon released
- Complications:2nd viremia possible leading to infection of brain,
liver, skin, endothelium
- Treatment:supportive
- Vaccine: Japanese & Russian spring-summer
Cause: Bunyavirus (California encephalitis, LaCrosse virus)
- Arbovirus transmitted by mosquitoes
- Zoonotic: reservoirs incl. rodents, primates, birds
Cause: Nipah & Hendra virus