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ENCEPHALITIS MOSQUITOES
GENERAL INFORMATION |
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The
Encephalitis
Mosquito (Culex
tarsalis) is one of 53 types of mosquitoes that occur in
California and is found in all California counties. This
species has a prominent white band on its proboscis (beak) and white
bands on its tarsi (feet). It is further characterized
by black scales which form inverted "v's" on the underside of its
blunt-tipped abdomen. The Culex
tarsalis mosquito most closely resembles
Culex stigmatosoma but has a white band that runs down the
length of its hind legs. This species tends to breed in clear,
clean, agricultural, industrial, domestic and natural water sources
during spring, summer and fall months. Example breeding sites
are: poorly maintained swimming pools, ornamental ponds, storm
drains, flood control canals, ditches, waste water ponds,
containers, pastures, seepages, marshes, seasonal wetlands and duck
club ponds. This mosquito is the primary vector of
Western Equine Encephalitis and
St.
Louis Encephalitis (sleeping sickness) in the Western United
States. It is also an excellent vector of
West Nile Virus
a mosquito-borne disease, which is rapidly spreading across the
United States.
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Adult
Daily Activity:
Adults
rest by day in shaded or darkened areas such as animal burrows,
treeholes, hollow logs, under bridges, in eves and entry ways of
residences, brush piles and dense vegetation. Females pass the
winter months in a form of hibernation (diapause) that is not
required, which is triggered by short day length and/or ambient
temperatures. This inactivity usually occurs from December
through February for San Francisco Bay area populations of this
mosquito. Significant alterations in the typical winter
weather pattern can vary the time spent in diapause (hibernation).
Flight activity typically occurs from dusk until dawn with light
intensity determining adult mosquito activity. Male
mating swarms occur shortly before to just after sunset. |
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Adult
Flight Range:
Maximum
known distance traveled is 15.75 miles, with females flying up to
three miles per night. |
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Adult
Feeding:
To
obtain energy adult mosquitoes feed on plant juices. To produce
eggs female mosquitoes take blood meals from other animals.
The preferred hosts are
birds although the host feeding pattern does change with the season
and host availability. Nesting birds are the primary hosts
during spring and early summer with a switch to mammals (e.g.
rabbits, dogs, and humans) during the late summer and fall. |
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Eggs and Larvae:
Clusters of glued
together eggs, also known as egg rafts, are laid directly on the
water. Eggs usually hatch within a few days. Larval
development usually takes one to three weeks depending on weather
conditions, water temperature, and competition for food resources.
Larvae have been found in brackish water with salinities of 10 ppt
(almost 1/3 that of seawater). Females of this species can
produce eggs without a blood meal (known as autogeny) although egg
production is reduced when this happens. |
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DISEASES TRANSMITTED
The
Encephalitis Mosquito is the primary vector of
Western Equine Encephalitis and
St. Louis Encephalitis (sleeping sickness) in California.
Encephalitis Mosquitoes become infected while feeding on birds that
harbor the virus. They can then transmit the virus to other animals.
This species has been identified as a carrier of
West Nile Virus, a
mosquito-borne disease that is rapidly spreading across the United States.
WHAT IS ENCEPHALITIS
AND
HOW DOES IT AFFECT YOU?
Technically, encephalitis means swelling of the brain. Many things
including a bite from a mosquito infected with the
encephalitis virus can cause this serious disease. Clinical symptoms of
mosquito-transmitted encephalitis vary from mild cases showing little or no
symptoms to more severe infections, which show fever, headache, convulsions
and coma. Most people infected with the virus show little or no disease
symptoms. The two most common types of mosquito-borne encephalitis in
California are
Western Equine Encephalitis and
St. Louis Encephalitis. Contact your local
Mosquito Abatement District or the CDC
for more information about encephalitis.
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ENCEPHALITIS MOSQUITO LIFE
CYCLE |
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Encephalitis Mosquitoes have four life
stages: egg, larva, pupa, and adult. The immature stages need
standing water to complete their life cycle.
This mosquito can complete its life cycle in 10 to 23 days. |
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RESIDENTS SHOULD |
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If you have a mosquito problem call your
local Mosquito Abatement District to identify the problem. That
is the first step in identifying what type of mosquito is being
dealt with. |
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Use insect repellents if it is necessary
when in an area where this mosquito is found. Read and follow
the directions carefully! |
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PERSONAL PROTECTION FROM MOSQUITOES |
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FIRST AID FOR MOSQUITO BITES |
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q
Reduce
outdoor activities during peak feeding periods (1 to 2 hours
after dark). |
q
Wash
bite with soap and water. |
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q
Wear
long pants and long sleeved shirts. |
q
Apply
anti-itch medication. |
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q
Apply
insect repellent. |
q
Apply
cold cloth for swelling. |
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q
Watch
for secondary infections. |
For more information on
Encephalitis
Mosquitoes contact:
Napa County Mosquito Abatement District
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