ENCEPHALITIS SURVEILLANCE PROGRAM
- Two forms of mosquito transmitted encephalitis may occur in Utah:
western equine encephalitis (WEE) and St. Louis encephalitis (SLE).
WEE effects both humans and horses; SLE effects only humans and some
birds (emu's).
- The last outbreak of WEE in humans in Utah was in 1958. There has
never been a human outbreak of SLE in Utah.
- WEE and SLE are characterized in their most severe form by signs and
symptoms of long-term residual neurological damage, which may include
paralysis, memory loss, deterioration of fine motor skills or death.
- The Utah Mosquito Abatement Association (UMAA), Utah State Health
Department (USHD) and the Utah State Agricultural Department (USAD)
has had a cooperative encephalitis surveillance program since 1983.
- The virus that causes WEE or SLE is naturally found in wild bird populations.
The virus does not harm the bird, but multiplies within their blood.
If a Culex tarsalis female mosquito (only female mosquitoes bite) takes
a blood-meal from an infected bird and later take a blood-meal from
a human or horse then those animals may become infected.
- The mosquito that transmits WEE or SLE in Utah is called Culex tarsalis.
This mosquito primarily feeds on birds, but will readily bite man.
- A total of 20 flocks of 20 chickens each are placed in mosquito abatement
districts in the northern 2/3 of the state, as well as in the Moab area.
- Blood samples taken from the chicken flocks, every two weeks, are
tested for the presence of antibodies to WEE and SLE viruses.
- The purpose of the sentinel chicken flocks is to allow early detection
of viral activity in the chickens before man or horses are affected.
- Early detection of encephalitis viral activity will hopefully give
the mosquito abatement districts a chance to concentrate their efforts
in reducing the populations of the mosquito species Culex tarsalis,
which transmits the virus.
For more detailed information on St. Louis Encephalitis, Western Equine
Encephalitis or West Nile Encephalitis,
please go to:
Centers
for Disease Control and Prevention: Arboviral Encephalitis
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