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La Crosse Encephalitis (LACV)

Pathogens & Vectors

  • La Crosse virus is a California serogroup virus

    • Genus: Bunyavirus

    • Family: Bunyaviridae 

  • Members of the family Bunyaviridae have three segments of single-stranded RNA; the virus particles are spherical or oval, enveloped, and are 90-100 nm in diameter

  • Arboviruses (Arthropod Borne disease) by the eastern treehole mosquito Aedes triseriatus

 

Symptoms (Incubation period ranges from 5 to 15 days)

  • Fever (usually lasting 2-3 days)

  • Headache

  • Nausea

  • Vomiting

  • Fatigue

  • Lethargy

  • Severe neuroinvasive disease occurs most in children under the age of 16. Although seizures during the acute illness are common, fatal cases are rare (less than one percent) and most patients seem to recover completely

  • Neurologic sequelae (conditions resulting from the initial disease) have been reported in some cases. These may include recurrent seizures, hemiparesis (partial paralysis of one side of the body), and cognitive and neurobehavioral abnormalities

 

Treatment

  • No vaccine against LACV infection or specific antiviral treatment for clinical LACV infection is available

  • Patients with suspected LAC encephalitis should be hospitalized, appropriate serologic and other diagnostic tests ordered, and supportive treatment provided

     

     

     

     

     

     

     

La Crosse virus neuroinvasive disease cases reported by state, 2004- 2013

La Crosse encephalitis is a rare disease that is caused by a virus spread by infected mosquitoes. La Crosse encephalitis virus (LACV) is one of a group of mosquito-transmitted viruses that can cause inflammation of the brain which is encephalitis. This disease is known to be in Virginia now.

 

Historical Data

  • Discovered in La Crosse, Wisconsin in 1963

  • Affects Midwestern and Mid-Atlantic states

  • 1996 - First case in Virginia

  • 10 cases in Virginia between 2004 to 2013

 

Transmission

  • Cycle between the mosquito Aedes triseriatus and vertebrate hosts, such as chipmunks and squirrels, in deciduous forest habitats, where tree lose their leaves

  • Humans can become infected with LACV from the bite of an infected mosquito

  • Humans considered "dead-end" or incidental hosts for LACV due to not having a big enough concentration of the virus in our blood to infect feeding mosquitos

  • Ae. triseriatus lays its eggs in pools of water accumulated in tree holes, but can also lay eggs in man-made water holding containers

  • LACV is passed from the female mosquito to the eggs laid

  • The virus can survive in dormant eggs through the winter and develop into infected, flying mosquitoes in the spring

Information gathered by Harper H.
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