St. Louis encephalitis pathophysiology

Jump to navigation Jump to search

St. Louis encephalitis Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating St. Louis encephalitis from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

X Ray

CT

MRI

Echocardiography or Ultrasound

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

St. Louis encephalitis pathophysiology On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of St. Louis encephalitis pathophysiology

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on St. Louis encephalitis pathophysiology

CDC on St. Louis encephalitis pathophysiology

St. Louis encephalitis pathophysiology in the news

Blogs on St. Louis encephalitis pathophysiology

Directions to Hospitals Treating St. Louis encephalitis

Risk calculators and risk factors for St. Louis encephalitis pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Vishnu Vardhan Serla M.B.B.S. [2]; Anthony Gallo, B.S. [3]

Overview

St. Louis encephalitis virus is usually transmitted via mosquitos to the human host. St. Louis encephalitis virus contains positive-sense viral RNA; this RNA has its genome directly utilized as if it were mRNA, producing a single protein which is modified by host and viral proteins to form the various proteins needed for replication. Transmission to humans requires mosquito species capable of creating a "bridge" between infected animals and uninfected humans. The incubation period is 5-15 days.[1] Humans are dead-end hosts for the virus, meaning there is an insufficient amount of Japanese encephalitis virus in the blood stream to infect a mosquito; there is also no evidence of person to person spread.[2]


Pathophysiology

St. Louis encephalitis virus is usually transmitted via mosquitos to the human host. St. Louis encephalitis virus contains positive-sense viral RNA; this RNA has its genome directly utilized as if it were mRNA, producing a single protein which is modified by host and viral proteins to form the various proteins needed for replication. The following table is a summary of the St. Louis encephalitis virus:[3][4]

Characteristic Data
Nucleic acid RNA
Sense ssRNA(+)
Virion Enveloped
Capsid Spherical
Symmetry Yes; T=3-like organization; icosahedral-like
Capsid monomers Unknown
Envelope length (diameter) 50 nm
Additional envelope information Mature virons contain 2 virus-encoded membrane proteins (M and E); immature virons contain a protein precursor
Genome shape Linear
Genome length 10-11 kb
Nucleotide cap Yes
Polyadenylated tail No; a loop structure is formed instead
Incubation period 5-15 days

St. Louis encephalitis is contracted by the bite of an infected mosquito, primarily Culex pipiens, Culex tarsalis, and Culex nigripalpus. Japanese encephalitis virus circulates between a mosquito vector and birds in the United States and South America.[5] Transmission to humans requires mosquito species capable of creating a "bridge" between infected animals and uninfected humans; this occurs when humans become part of the enzootic cycle. The incubation period is 5-15 days.[1] Humans are dead-end hosts for the virus, meaning there is an insufficient amount of Japanese encephalitis virus in the blood stream to infect a mosquito; there is also no evidence of person to person spread.[2]

St. Louis encephalitis virus is transmitted in the following pattern:[3]

  1. Attachment of the viral envelope protein E to host receptors mediates internalization into the host cell by clathrin-mediated endocytosis, or by apoptotic mimicry.
  2. Fusion of virus membrane with host endosomal membrane. RNA genome is released into the cytoplasm.
  3. The positive-sense ssRNA virus is translated into a polyprotein, which is cleaved into all structural and non-structural proteins necessary for RNA synthesis (replication and transcription).
  4. Replication takes place at the surface of endoplasmic reticulum in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
  5. The dsRNA genome is transcribed/replicated, thereby providing viral mRNAs/new ssRNA(+) genomes.
  6. Virus assembly occurs at the endoplasmic reticulum. The virion buds via the host endosomal sorting complexes required for transport (ESCRT), and is sent to the Golgi apparatus.
  7. The prM protein is cleaved in the Golgi, thereby maturing the virion which is fusion competent.
  8. New virions are released by exocytosis.

On microscopic histopathological analysis, the enveloped, spherical, and icosahedral-like virion shape are characteristic findings of St. Louis encephalitis.

Image:CULEXT1.jpg|left|Image of culex tarsalis Image:Sle_transmission_cycle_450px.jpg|left|Transmission cycle

Gallery

References

  1. 1.0 1.1 Saint Louis Encephalitis. Centers for Disease Control and Prevention (CDC), National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. (2010) http://www.cdc.gov/sle/general/qa.html Accessed on May 3, 2016.
  2. 2.0 2.1 Saint Louis Encephalitis Transmission. Centers for Disease Control and Prevention (CDC), National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases. (2010) http://www.cdc.gov/sle/technical/transmission.html Accessed on May 3, 2016.
  3. 3.0 3.1 Flavivirus. SIB Swiss Institute of Bioinformatics. (2015) http://viralzone.expasy.org/viralzone/all_by_species/24.html Accessed on April 12, 2016
  4. Japanese encephalitis - Frequently Asked Questions. CDC Centers for Disease Control and Prevention. (2015) http://www.cdc.gov/japaneseencephalitis/qa/index.html Accessed on April 12, 2016
  5. The Management of Encephalitis: Clinical Practice Guidelines by the Infectious Diseases Society of America. http://www.idsociety.org/uploadedFiles/IDSA/Guidelines-Patient_Care/PDF_Library/Encephalitis.pdf Accessed on May 3, 2016.
  6. 6.0 6.1 "Public Health Image Library (PHIL)".